GUIDELINE FOR FIELD TESTING OF GAS TURBINE AND CENTRIFUGAL COMPRESSOR PERFORMANCE

GUIDELINE FOR FIELD TESTING OF GAS TURBINE AND CENTRIFUGAL COMPRESSOR PERFORMANCE RELEASE.0 Augut 006 Ga Machinery Reearch Council Southwet Reearch Intitute

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GUIDELINE FOR FIELD TESTING OF GAS TURBINE AND CENTRIFUGAL COMPRESSOR PERFORMANCE RELEASE.0 Author: Klau Brun, Ph.D., SwRI Marybeth G. Nored, SwRI Indutry Adviory Committee: Rainer Kurz, Solar Turbine Principal John Platt, BP Robert Arnold, Duke Energy Don Cruan, Columbia Ga Tranmiion William Couch, El Pao Corporation

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Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance RELEASE.0 Foreword Field teting of ga turbine and compreor ha become increaingly common due to the need to verify efficiency, power, fuel flow, capacity and head of the ga turbine package upon delivery. The performance tet of the ga turbine and compreor in the field i often neceary to aure that the manufacturer meet performance prediction and guarantee a cutomer return on invetment. Economic conideration demand that the performance and efficiency of a ga turbine compreor package be verified at the actual field ite. The field environment i not ideal and meaurement uncertaintie are neceary to characterize the validity of a performance tet. A the working field environment hift further from the ideal cae, the uncertaintie increae. Previou field tet have hown that the compreor efficiency uncertainty can be unacceptably high when ome baic rule for proper tet procedure and tandard are violated. Thi guideline applie to a typical ga turbine and centrifugal compreor. The motivation for conducting a field tet i baed on one of the following objective: The manufacturer i required to verify performance of the ga turbine and compreor to the cutomer. To the manufacturer, the field tet provide a baeline for the ga turbine and compreor at the ite of delivery to compare to the factory performance tet, although the field tet accuracy may be inherently lower. In addition, the field performance tet i the final validation from the manufacturer to the cutomer of the guaranteed performance. The uer need to verify performance of the ga turbine and compreor. Baeline performance data i obtained from the initial field performance tet. The baeline tet can be ued for comparing and monitoring the health of the ga turbine-driven compreor package in the future. The uer or manufacturer need to ae performance of the ga turbine or compreor becaue of degradation concern. Baed on the field tet reult, a performance recovery program may be initiated. The uer require calibration of an intalled hitorical trend monitoring ytem. The field tet i ued to provide initial calibration of the ytem baed on the firt performance of the ga turbine and compreor. The uer need to determine the operating range of the intalled equipment after an upgrade, retage, or phyical ytem change. In thi cae, the urge point may alo need to be re-aeed. The following guideline i a uggeted bet practice for field teting of ga turbine and centrifugal compreor. Specific conideration at a field ite may require deviation from thi guideline in order to meet afety requirement, improve efficiency, or comply with tation operating philoophy. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page i

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Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance RELEASE.0 TABLE OF CONTENTS 1. Purpoe and Application... 1. Performance Parameter... 1.1 Centrifugal Compreor Flow/Flow Coefficient... 3. Centrifugal Compreor Head/Head Coefficient... 4.3 Centrifugal Compreor Efficiency... 6.4 Ga Turbine Power... 7.5 Centrifugal Compreor Aborbed Power (Ga Turbine Power Output)... 7.6 Ga Turbine Heat Rate and Efficiency... 7.7 Ga Turbine Exhaut Heat Rate... 8.8 Turbocompreor Package Efficiency... 8.9 Equation of State... 9.10 Determination of Surge Point and Turndown... 10.11 Similarity Condition... 1 3. Tet Preparation... 15 3.1 Pre-Tet Meeting... 15 3. Pre-Tet Operation and Intrumentation Checkout... 15 3.3 Pre-Tet Equipment Checkout... 16 3.4 Pre-Tet Information... 16 3.5 Tet Stability... 17 3.6 Safety Conideration... 19 4. Meaurement and Intrumentation... 19 4.1 Meaurement of Preure... 0 4. Meaurement of Temperature... 1 4.3 Meaurement of Flow... 4 4.4 Meaurement of Ga Compoition... 8 4.5 Meaurement of Rotational Speed... 30 4.6 Meaurement of Torque... 30 4.7 Meaurement of Generator Power... 30 5. Tet Uncertainty... 31 5.1 Ideal Field Tet Condition For Reducing Uncertaintie... 33 5. Effect of Non-Ideal Intallation on Uncertainty... 37 6. Interpretation of Tet Data... 39 6.1 Data Reduction and Checking Uncertaintie... 39 6. Generation of Performance Curve from Recorded Data Point... 40 Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page iii

6.3 Standardized Uncertainty Limit... 40 6.4 Uing Redundancy to Check Tet Meaurement and Uncertainty... 40 6.5 Effect of Fouling on Tet Reult... 41 6.6 Analyi of Meaured Reult... 41 7. Other Field Teting Conideration... 41 7.1 Determination of Influential Tet Parameter... 4 7. Field Teting of Compreor Under Wet Ga Condition... 4 8. Reference... 43 APPENDICES APPENDIX A Determination of Ga Turbine Power... 45 APPENDIX B Equation of State Model... 49 APPENDIX C Uncertainty Analyi for Independent Variable Meaurement... 57 APPENDIX D Similiarity Calculation for Wet Ga Condition... 67 APPENDIX E Equation of State Model Comparion of Predicted Performance Data... 71 APPENDIX F Application of Compreor Equation for Side Stream Analyi... 77 Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page iv

LIST OF FIGURES Figure 1. Location of Tet Intrumentation for Centrifugal Compreor... Figure. Location of Tet Intrumentation for Ga Turbine... Figure 3. Enthalpy/Preure Change During Compreion and Expanion Proce (Edmiter and Lee, 1984)...6 Figure 4. Typical Compreor Surge Line on Compreor Performance Map...11 Figure 5. ASME PTC 10 Recommended Intallation Configuration for Preure and Temperature Meaurement... Figure 6. Short-Coupled Intallation for a Turbine Meter (AGA-7, Rev. 3)...6 Figure 7. Cloe-Coupled Intallation for a Turbine Meter (AGA-7, Rev. 3)...7 Figure 8. Sampling Method with Pigtail a Recommended in API MPMS Chapter 14.1...9 Figure 9. Example of Tet Uncertainty Range...41 Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page v

LIST OF TABLES Table 1 Table Suggeted Application for Equation of Stage Uage...10 ASME PTC 10 Acceptable Deviation in Tet Parameter for Similarity Condition...13 Table 3 Aement of Stability of Compreor During Pre-Tet Criteria 1...18 Table 4 Aement of Stability of Compreor During Pre-Tet Criteria...18 Table 5 Aement of Stability of Ga Turbine During Pre-Tet...18 Table 6 Typical Uncertaintie in Preure Meaurement (hown a percent of full cale)...1 Table 7 Recommended Depth of Thermowell...3 Table 8 Table 9 Table 10 Typical Uncertaintie in Temperature Meaurement (hown a percent of full cale)...4 ISO 5167 Recommended Intallation Length for Orifice Flow Meter...5 In-Practice Achieveable Uncertainty for Meaured Tet Parameter...3 Table 11a Example of Total Uncertainty Calculation for Compreor in Near Ideal Cae SI Unit...35 Table 11b Example of Total Uncertainty Calculation for Compreor in "Near Ideal" Cae Englih Unit...35 Table 1a Table 1b Ideal Intallation for Ga Turbine Total Uncertainty Calculation SI Unit...36 Ideal Intallation for Ga Turbine Total Uncertainty Calculation Englih Unit...36 Table 13 Effect of Non-Ideal Temperature or Preure Meaurement...38 Table 14 Table 15 Non-Ideal Intallation Effect on Compreor Uncertainty...38 Non-Ideal Intallation Effect on Ga Turbine Uncertainty...39 Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page vi

Definition of Symbol: A = cro-ectional area of pipe C = dicharge coefficient for orifice flow meter D tip = tip diameter of compreor E = velocity of approach factor EHR = exhaut heat rate H = head for compreor, either actual or ientropic HR = ga turbine heat rate LHV = fuel ga heating value, a determined through thermodynamic analyi Ma = Machine Mach number N = haft peed in rpm [ω = πn / 60] P = haft power P = total (tagnation) preure of ga at uction or dicharge ide P tat = tatic preure at uction or dicharge ide Q = volumetric flow rate on uction or dicharge ide of compreor SM% = urge margin of compreor a % of deign flow rate for fixed peed T = temperature of ga at uction or dicharge ide TD% = turndown of compreor a % of deign flow rate for contant head U = velocity of ga W = ma flow through the compreor Z = compreibility of ga at uction or dicharge condition c p = pecific heat at contant preure d = bore diameter of orifice meter f = Schultz correction factor for real ga behavior h = enthalpy of ga at uction, dicharge or ientropic condition k = ientropic exponent Δp = differential preure meaured acro orifice plate η = efficiency ϕ = flow coefficient γ = ratio of pecific heat ρ = denity of ga determined at uction or dicharge condition τ = meaured torque from the turbine haft v = pecific volume of ga at uction, dicharge or ientropic condition ψ = head coefficient ω = haft peed in radian per econd [rad/ec] Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page vii

Subcript: m = mechanical efficiency = ientropic condition P = polytropic condition C = compreor GT = ga turbine TC = turbocompreor package FG = fuel ga propertie = uction ga d = dicharge ga di = dicharge ga, ientropic condition in = input to ga turbine out = output to ga turbine/input to compreor A = denity of air E = exhaut air temperature f = fuel flow to the ga turbine GT = volume flow of air at ga turbine exhaut tip = tip diameter or tip peed for compreor blade tat = tatic Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page viii

Definition 1 : 1. Abolute Preure: The preure meaured above a perfect vacuum.. Gage Preure: The preure meaured with the exiting barometric preure a the zero bae reference. 3. Differential Preure: The difference between any two preure meaured with repect to a common reference (i.e., the difference between two gage preure.) 4. Total (Stagnation) Preure: An abolute or gage preure that would exit when a moving fluid i brought to ret, and it kinetic energy i converted to an enthalpy rie by an ientropic proce from the flow condition to the tagnation condition. In a tationary body of fluid, the tatic and total preure are equal. 5. Abolute Temperature: The temperature above abolute zero, tated in degree Rankine or Kelvin. Rankine temperature i the Fahrenheit temperature plu 459.67 degree; Kelvin i the Celiu temperature plu 73.15 degree. 6. Total (Stagnation) Temperature: The temperature that would exit when a moving fluid i brought to ret, and it kinetic energy i converted to an enthalpy rie by an ientropic proce from the flow condition to the tagnation condition. In a tationary body of fluid, the tatic and total temperature are equal. 7. Denity: The ma of ga per unit volume, equal to the reciprocal of the pecific volume. The denity i a thermodynamic property determined from the abolute total preure and temperature at a point in the fluid uing an equation of tate. 8. Capacity: The rate of flow, determined by delivered ma flow rate divided by inlet ga denity. 9. Preure Ratio: The ratio of abolute total dicharge preure to abolute total uction preure. 10. Machine Mach Number: The ratio of the blade tip velocity at the firt impeller diameter to the acoutic velocity of the ga at the uction condition. 11. Stage: A ingle impeller and it aociated tationary flow paage. 1. Compreor Surge Point: The capacity below which the compreor operation become aerodynamically untable. 13. Ientropic Compreion: A reverible, adiabatic compreion proce. 14. Polytropic Compreion: A reverible, non-adiabatic compreion proce between the total uction preure and temperature and the total dicharge preure and temperature. 15. Ga Power: The power tranmitted to the ga in a compreor, equal to the product of the ma flow rate compreed and the ga work. 16. Shaft Power: The power delivered to the compreor haft by the ga turbine, alo known a brake power. Shaft power i equal to ga power plu mechanical loe. 17. Mechanical Loe: The total power conumed by frictional loe in integral gearing, bearing and eal. 18. Equation of State: An equation or erie of equation that functionally relate the ga thermodynamic propertie, uch a preure, temperature, denity, compreibility, and pecific heat. 1 Definition for referenced term in Field Tet Guideline are baed upon ASME Performance Tet Code (PTC) 10-1997, Performance Tet Code on Compreor and Exhauter. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page ix

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Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance RELEASE.0 1. PURPOSE AND APPLICATION The following guideline i intended to erve a a reference for field teting of ga turbine and centrifugal compreor performance. Thi guideline applie to any party conducting a field tet of a ga turbine or centrifugal compreor (manufacturer, uer company, or third-party). It i intended to provide the mot technically ound, yet practical procedure for all apect of conducting field performance tet of ga turbine and centrifugal compreor. The condition at the field ite often cannot be a cloely controlled a in a factory environment. The pecific ite condition of a particular tet may dictate that the tet procedure deviate from thi guideline or the ideal intallation decribed. Thi doe not preclude a field ite tet. Nonethele, when a particular tet deviate from the intallation requirement or other tet procedure, the deviation will affect the tet uncertainty and hould be accounted for in the uncertainty analyi, a recommended in thi guideline. The tandard that are ued a reference for thi guideline are ASME PTC 10-1997, Performance Tet Code on Compreor and Exhauter, ASME PTC -1997, Performance Tet Code on Ga Turbine, ISO 314, Ga Turbine Acceptance Tet, and ISO 5389, Turbocompreor Performance Tet Code.. PERFORMANCE PARAMETERS The following even performance parameter generally decribe the performance of a ga turbine and centrifugal compreor. Thee parameter are commonly ued in acceptance teting, teting to determine degradation of the machine, and operational range teting. The primary meaurement required in order to calculate thee parameter are dicued in Section 4.0. The uncertainty calculation are dicued in Section 5.0. Accounting for the effect of non-ideal intallation on uncertainty i alo dicued in Section 5.0. Performance Parameter: 1. Centrifugal Compreor Flow/Flow Coefficient. Centrifugal Compreor Head/Head Coefficient 3. Centrifugal Compreor Efficiency 4. Centrifugal Compreor Power Aborbed 5. Ga Turbine Full Load Output Power 6. Ga Turbine Heat Rate (thermal efficiency) 7. Ga Turbine Exhaut Heat Rate The following tet data mut be meaured to determine the above performance parameter. Figure 1 and how the general meaurement arrangement for the required tet intrumentation on the compreor and ga turbine. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 1

Ambient Air - Patm Preure at Meter Q Pm Tm Suction Preure Suction Temperature P T Centrifugal Compreor Pd Dicharge Preure Dicharge Temp Td Flow Rate* Temperature at Meter Sample Line / Ga Chromatograph* Speed of Rotation * Flow Rate Meaurement and Ga Sample may be on uction or dicharge ide. Suction ide i recommended. Figure 1. Location of Tet Intrumentation for Centrifugal Compreor Ambient Air: - Temperature -Atmopheric Preure - Relative Humidity Exhaut Ga Outlet P out Preure H in T in P in Burner Ga Turbine Inlet Air Relative Humidity Inlet Air Temp Inlet Preure Fuel Flow Fuel Ga Compoition Shaft Speed Fuel Figure. Location of Tet Intrumentation for Ga Turbine Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page

Centrifugal Compreor Tet Meaurement : Suction Temperature Suction Preure Dicharge Temperature Dicharge Preure Flow Through Compreor (*Preure, temperature alo required at the flow meaurement point) Suction or Dicharge Ga Compoition Barometric Preure Speed of Rotation Impeller Diameter Uptream and Downtream Piping arrangement Pipe Diameter (uptream and downtream) Ga Turbine Tet Meaurement: Engine Inlet and Ambient Temperature Barometric Preure Power Turbine Speed Ga Generator Speed Fuel Flow (*Preure, temperature alo required at flow meaurement point for fuel ga) Fuel Ga Compoition Inlet and Exhaut Preure Lo Relative Humidity of Inlet Air Water/Steam Injection Rate Important Note: For the remainder of thi document, all preure and temperature ued for performance and uncertainty calculation are abolute total (tagnation) value unle otherwie noted..1 Centrifugal Compreor Flow/Flow Coefficient The actual flow through the centrifugal compreor (Q) hould be meaured by a flow-meauring device, uch a a volumetric flow meter (ultraonic, turbine, etc.), a differential preure device (orifice meter, annubar, etc.), or a nozzle. If an orifice meter i ued (typical of many intallation), the ma flow rate equation i: W π = CE d Δpρ 4 (.1) * Note the dicharge coefficient, C, i determined from the RG equation (a tated in AGA Report No. 3). The dicharge coefficient i dependent on the flow meter Reynold Number. The actual uction volumetric flow i given by: Q W = (.) ρ The requirement apply to each compreor or each compreor ection in a compreor train. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 3

The flow coefficient ued for imilarity comparion i: Q Q ϕ = = (.3) π π 3 Dtip U tip Dtip ω 4 4 * Note the flow coefficient ue the actual volumetric flow rate through the compreor at uction condition. * For a multi-tage compreor, the tip diameter may be defined a the firt impeller diameter or a geometric average for all tage diameter. When comparing flow coefficient for multi-tage machine, the definition of tip diameter hould be verified.. Centrifugal Compreor Head/Head Coefficient Compreor head and efficiency are commonly defined baed on either ientropic or polytropic ideal procee. Both definition are appropriate for performance comparion a they provide a ratio of the actual enthalpy difference (head) to the ideal (ientropic or polytropic) enthalpy difference acro the compreor. The ientropic proce aume a reverible adiabatic proce without loe (i.e., no change in entropy). The polytropic proce i alo a reverible proce, but it i not adiabatic. It i defined by an infinite number of mall ientropic tep followed by heat exchange. Both procee are ideal, reference procee. The compreor actual head (H), ientropic head (H*), and polytropic head (H P ) are determined from the meaurement of preure and temperature on the uction and dicharge ide and the calculation of enthalpy and pecific volume uing an equation of tate (EOS) model. The head are calculated from the enthalpie aociated with each tate from the EOS a follow: Ientropic head: H* hd h = h( pd, ) h( p, T ) = (.4) Actual head: H = h h = h p, T ) h( p, T ) (.5) d ( d d * Note that h d * i the enthalpy aociated with the dicharge preure at the uction entropy,, becaue the entropy change i zero in an ientropic proce. All enthalpie hould be directly determined from the EOS. Ientropic enthalpy can alo be for etimation purpoe (auming ideal ga behavior): h d k 1 k P d c p Td = c p T P (.6) Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 4

Similarly, Polytropic head i determined from: S S n n S d P P P P f P P n n H P P ν = 1 1 1 (.7) The polytropic exponent, n P, i defined a: d S d P P P n ν ν ln ln = (.8) The ientropic exponent, k, i defined a: * ln ln d d P P k ν ν = (.9) For equation (.7), the Schultz Polytropic Head Correction Factor, f, i defined a: [ ] d d d P P k k h h f ν ν = 1 (.10) For performance comparion, it i beneficial to ue non-dimenional head and flow coefficient (ϕ from equation (.3) and from equation.11.13) rather than actual head and flow. P ψ ψ ψ,, Ientropic head coefficient: * * * = = ω ψ D tip H U H (.11) Actual head coefficient: = = ω ψ D tip H U H (.1) Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 5

Polytropic head coefficient: ψ P = P P H H = U Dtip ω (.13).3 Centrifugal Compreor Efficiency The ientropic efficiency i calculated from the ientropic and actual head: H * ψ * η* = = H ψ (.14) The polytropic efficiency i calculated baed upon the polytropic head and the polytropic exponent, n P, a defined in equation (.8): η P = P H H P n Pd P n ( 1) P = h d n P n P h 1 1 f Pν (.15) The compreion proce for a typical centrifugal compreor and the aociated enthalpy change are hown on a P-h diagram in Figure 3 for 100% methane ga mixture. An actual proce i compared to the ientropic tate. METHANE Preure-Enthalpy Diagram Ientropic compreion Actual compreion Preure Enthalpy Figure 3. Enthalpy/Preure Change During Compreion and Expanion Proce (Edmiter and Lee, 1984) Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 6

.4 Ga Turbine Power Four method exit for determining ga turbine power. Thee are: 1. Direct torque coupling meaurement. Direct generator power meaurement 3. Indirect driven centrifugal compreor haft power meaurement 4. Indirect ga turbine heat balance meaurement The direct meaurement method (1) and () either uing a torque-meauring coupling (ee Section 4.6) or the input power from the generator (ee Section 4.7) will normally yield the lowet uncertainty. Uing the driven centrifugal compreor haft power to determine ga turbine haft output power will uually yield a higher uncertainty but i a widely ued and acceptable method, if properly performed. The ga turbine heat balance method yield the highet meaurement uncertainty and i generally not recommended. See Appendix A for a complete dicuion of the indirect approache. If the torque (τ) i meaured uing a torque coupling, then the haft power (P) developed by the ga turbine i calculated a: P = τ ( πn ) (.16) If ga turbine power i determined for an electric power generation application, the ga turbine haft output power can be imply determined from the meaured electric power at the generator terminal, the generator efficiency, and the gearbox efficiency (ee Section 4.7). Indirect method are more complex and are decribed in ection.5 and Appendix A..5 Centrifugal Compreor Aborbed Power (Ga Turbine Power Output) The aborbed power for the compreor (P c ) can be directly ued to determine the ga turbine haft output power, if no gearbox i preent. Otherwie, the gearbox power loe mut be included to determine ga turbine haft output power. Compreor aborbed power i calculated uing the compreor uction ga condition and the actual head (enthalpy change) a follow: P C = P η = ρ Q H (.17) out m If the driven compreor i rated for le power than the ga turbine output power, the full load power of the ga turbine cannot be determined uing thi approach..6 Ga Turbine Heat Rate and Efficiency If the ga turbine haft output power i known (or determined from the driven equipment or heat balance method), then the ga turbine efficiency i determined by dividing the ga turbine haft output power by the fuel energy flow rate. Pout η GT = (.18) W (LHV) f Similarly, the ga turbine heat rate i imply the reciprocal of the efficiency, or: Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 7

W f ( LHV ) HR = (.19) P out A heat rate i often expreed in mixed unit, the appropriate unit converion may need to be applied. The actual fuel ga compoition hould be ued to determine the lower heating value (LHV) of the fuel. If the fuel ga temperature i greater than 0ºC (36ºF) above the ambient temperature, the fuel ga enible heat hould be added to the equation above a uch: Pout η GT = (.0) W LHV + ( ρ c T) ) f ( P FG W f ( LHV + ( ρ cp T) HR = P out FG ) (.1) Senible heat repreent the energy introduced into the combutor in the form of thermal heat contained in the fuel..7 Ga Turbine Exhaut Heat Rate The ga turbine exhaut heat rate i often important for combined cycle or cogeneration application. Exhaut heat rate i the remaining energy in the exhaut flow of the ga turbine, or: GT ( he hr EHR = W ) (.) In equation. h R i a mutually agreed reference enthalpy. Direct meaurement of the ma flow i not recommended to determine the ga turbine exhaut heat rate becaue of the difficulty of accurately performing thi meaurement without a large preure differential. In addition, tet uncertaintie will be high due to the flow meaurement and temperature meaurement uncertaintie. An energy balance of the ytem may be ued to etimate the ga turbine exhaut heat rate, a decribed in Appendix A under method 4..8 Turbocompreor Package Efficiency The turbocompreor package efficiency (η TC ) may be calculated baed upon the previou value. Namely, the total package efficiency i the product of the ga turbine, gearbox, and compreor efficiencie: η = η η η η (.3) TC c GB GT M, compreor Note the compreor efficiency, η C, may be defined a either the ientropic or polytropic efficiency. For compreor drive, the package efficiency may alo be calculated a the compreor ientropic ga power divided by the fuel energy rate into the ga turbine: ρ Q H * η TC = (.4) W LHV f Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 8

Note that equation (.4) doe not work for the calculation of efficiency if polytropic head i ued intead of ientropic head. If equation (.4) i ued to define the package efficiency, an agreement about the treatment of recirculation and leakage loe mut be made to aure that thee loe are addreed properly in the turbocompreor package efficiency..9 Equation of State In the field performance tet of the compreor and turbine, the correct determination of the thermodynamic propertie of the ga (uch a enthalpy, entropy, and denity) play a critical role. The meaured quantitie (uch a preure, temperature, and compoition) are ued a input to an equation of tate (EOS) to determine thermodynamic propertie. The enthalpy change i ued to determine the head and the ientropic or polytropic efficiency of a compreor. The choice of the EOS ued in calculating enthalpy and denity affect the accuracy of the reult and need to be conidered in the uncertainty calculation. The poible equation of tate commonly ued in the ga indutry are: Redlich-Kwong (RK), Soave- Redlich-Kwong (SRK), Peng-Robinon (PR), Benedict-Webb-Rubin (BWR), Benedict-Webb-Rubin- Starling (BWRS), and Lee-Keler-Plocker (LKP), and AGA-10. The final election of the equation of tate to be ued in the field tet hould depend on the applicability of the particular equation of tate model to the ga and temperature encountered along with the proce of interet. Equation of tate model accuracy may depend upon the application range and the ga mixture at the ite (Sandberg, 005; Kumar et al., 1999). The conitent application of the equation of tate throughout the planning, teting, and analyi phae of the field tet i imperative. The choice of which EOS to ue mut be agreed upon before the tet. It i recommended to ue the EOS for tet data reduction that wa alo ued for the performance prediction. Thi procedure i alo recommended in ISO 5389 to avoid additional tet uncertaintie. The election of a particular EOS can have an important effect on the apparent efficiency and aborbed ga power. An added uncertainty of 1 to % can be incurred on the performance reult if the EOS i inconitently applied (Kumar et al., 1999). The formulation of the variou EOS i given in Appendix B..9.1 Application of Equation of State Generally, it i not poible to elect a mot accurate EOS to predict ga propertie, ince there i generally no calibration norm to tet againt for typical hydrocarbon mixture. All the frequently ued EOS model (RK, BWR, BWRS, LKP, SRK, PR) can predict the propertie of hydrocarbon mixture accurately below 0 MPa for common natural ga mixture. Outide thi preure range, deviation between the EOS model of 0.5 to.5% in compreibility factor Z are common, epecially if the natural ga contain ignificant amount of diluent. Becaue derivative of the compreibility factor (Z) mut be ued to calculate the enthalpy difference (i.e., head), the head deviation can be larger than the compreibility factor for different EOS. Table 1 provide uage uggetion for the variou EOS model baed on application. For normal hydrocarbon ga mixture (uch a pipeline quality ga) with diluent content (combined CO and N ) below 10%, all equation of tate hown in Table 1 provide accurate reult. Beyond thi range, Table 1 provide ome general recommendation on the mot applicable EOS. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 9

Table 1. Suggeted Application for Equation of Stage Uage Type of Application Typical hydrocarbon ga mixture, tandard preure and temperature, low CO and N diluent (< 6% total). Air mixture. High-preure application (>3000 pi). High CO and N diluent (10-30%) and/or high hydrogen content gae. High hydrogen content gae (>80% H ) Non-hydrocarbon mixture: ethylene, glycol, carbon dioxide mixture, refrigerant, hydrocarbon vapor, etc. Typically Ued EOS Model All EOS Model may be ued for thi application: Redlich-Kwong (RK), Soave-Redlich-Kwong (SRK), Peng Robinon (PR), Benedict-Webb-Rubin-Starling (BWRS), Benedict-Webb-Rubin (BWR), Lee-Keler- Plocker (LKP), AGA-10 BWRS, BWR, LKP BWRS, LKP PR, LKP, SRK Specific EOS model deigned for particular application or chemical mixture will reult in greater accuracy. The literature hould be conulted for the particular ga and application. A further comparion of the variou EOS model i provided in Appendix E. The calculated enthalpie for variou EOS model at different tate are ued to calculate ientropic efficiency and compreor power for two compreor operating cae..10 Determination of Surge Point and Turndown The low limit flow on a compreor i the urge point. Oftentime, rotating diffuer tall can further limit the compreor operating range due to aerodynamically induced vibration. The urge point i cutomarily ued a the lower flow limit for turndown determination. During a urge event, the flow field within the compreor collape, and the compreor head and flow rate drop uddenly. Surge i uually a udden and ometime catatrophic event and full urge hould be avoided. The turndown of a centrifugal compreor i the allowable operating range between the deign point and the urge line at any given peed for a fixed compreor head. It i determined from the difference between deign flow rate and the minimum flow rate at which the compreor i aerodynamically table a a percentage of the deign point flow rate at the ame head, a follow: TD % = 100 ( Q Q ) / Q Head = contant (.5) deign urge deign The urge margin i defined a the difference between deign flow rate and minimum flow rate a a percentage of the deign flow rate, for a fixed peed (N), a follow: SM % = 100 ( Q Q )/ Q Speed = contant (.6) deign urge deign The determination of the compreor urge point hould be conducted with extreme caution at relatively low preure differential and operating preure (i.e., low energy ) condition. Thu, urge point teting hould be at operating condition that correpond to low energy condition. If incipient urge tet mut Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 10

be performed at high head condition, thee tet hould be preceded by tet at low energy condition in order to characterize the compreor behavior and intrument output of incipient urge. Prior review of the compreor dynamic tet report to identify limiting vibration level may alo be valuable to avoid damaging compreor internal during the tet. Surge point teting conducted on a factory tet tand will often produce different reult than teting at a field intallation becaue the piping configuration and other intallation detail do affect the minimum table flow. Significant ga compoition change will alter the performance map of the compreor and lead to erroneou prediction of head and flow. Thu, urge teting can be important to etablih the correct urge line in the field. An example of a typical compreor urge line at variou compreor peed i hown in Figure 4 a the lower operational boundary of the compreor. 1.3 Compreor Curve - Surge Line and Operational Boundarie MAX SPEED Preure Ratio 1.8 1.4 SURGE LINE 100% RPM 95% RPM 90% RPM 85% RPM Surge Line Surge Control MINIMUM SPEED LIMIT STONEWALL LIMIT 1. 15 30 45 60 Inlet Volume Flow Figure 4. Typical Compreor Surge Line on Compreor Performance Map There are a number of intrument reading that can provide an indication that the compreor i approaching it urge point; however, for each compreor geometry and operating condition, thee indication may be of varying magnitude or ometime may not occur at all. Thu, it i difficult to identify a ingular intrument reading that hould be utilized for the identification of incipient urge. In general practice, there are five indication that hould be monitored: 1. A marked increae in flow fluctuation in the uction and dicharge piping. An increae in uction or dicharge preure pulation 3. An increae in haft vibration (both axial and radial direction) 4. A decreae in head a flow i decreaed 5. An audible indication from the compreor of a ignificant operating change A urge i a udden and ignificant event, identifying the urge from the compreor operating noie can be dangerou, a the compreor may already be in full urge. Uing increaed vibration a the criterion to determine the urge point will be coniderably more inaccurate than other method (Kurz and Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 11

Brun, 005) due to variation in the mechanical reponivene of different compreor ytem. However, the increaed vibration can be due to the onet of talled flow rather than full urge. Alo, not all compreor have their urge point correponding to the maximum head for a fixed peed line. A good method to determine the urge line i by meauring flow and preure fluctuation on the compreor uction and dicharge piping. A thee fluctuation occur at a higher frequency range, preure tranducer and flow meter with a good dynamic repone mut be utilized (linear to at leat 100 Hz). If the dynamic tranducer are intalled at a ditance uptream or downtream from the compreor, the ignal may be delayed. Thu, the urge line hould alway be approached lowly, by carefully throttling uction or dicharge flow while maintaining compreor peed. It i recommended that the urge line i determined for a minimum of three different compreor peed line..11 Similarity Condition Generally, available field tet condition will deviate from pecified tet condition ued in the factory tet or previou teting of the ga turbine/compreor package. Thu, imilarity condition are ued to adjut for difference in the tet condition in order to match the flow characteritic for the machine under different tet condition. The imilarity variable that mut be calculated are provided in Section.11.1 and.11. to follow..11.1 For the Centrifugal Compreor To compare performance data for a centrifugal compreor between predicted performance and actual tet data, the non-dimenional parameter for head and flow mut be ued. Namely, predicted performance, factory tet data, and field tet reult hould be normalized uing the head coefficient (Ψ) and the flow coefficient (ϕ) that were given previouly in Section.1 and.. By matching thee coefficient, the data can then be directly compared (a long a the Machine Mach number, ientropic exponent, and volume flow ratio are imilar a dicued below). Thi comparion of non-dimenional head and flow eliminate the requirement to tet the compreor at the identical peed a the factory tet (or other baeline tet of the unit) during the field tet. To vary ϕ and ψ during the tet, the compreor peed and actual head mut be adjuted. In addition to the head and flow coefficient for thermodynamic imilarity, the machine Mach number, ientropic exponent, and volume/flow ratio hould be maintained a cloely a poible to the comparion tet value to maintain aerodynamic imilarity. Machine Mach number: Ma = k U Z RT = π D tip k Z N RT (.7) Ientropic exponent: vδp k = pδv (.8) Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 1

Volume Flow Ratio: Q Q d Tet Q = Q d Actual (.9) In general, ingle- and two-tage compreor may allow deviation up to 10% from the Machine Mach number and ientropic exponent. For machine with multiple tage or high Machine Mach number (> 0.8), a 10% deviation in the Machine Mach number or ientropic exponent may lead to unacceptable deviation in the data et. Thu, a direct comparion between data et hould not be made unle the Machine Mach number and ientropic exponent are the ame, in uch cae. If the tet data how unexplainable deviation from the predicted performance, a deviation in the Machine Mach number may be the caue. An alternative approach to matching compreor performance data i provided by ASME PTC 10 but i generally written for factory teting rather than field teting. ASME PTC 10 allow deviation in the tet and deign cae for inlet preure, inlet temperature, pecific gravity, peed, capacity, and inlet ga denity (ee Table ). Namely, if the flow coefficient and head coefficient remain the ame a in the comparative (factory) tet, the velocity triangle at the inlet and outlet of each tage of the compreor will remain the ame. Thi i alo known a the Fan Law. Deviation in the tet within the limit given in Table will require only a correction uing the Fan Law. The volume ratio hown in equation (.9) hould alo remain the ame. The volume ratio may be kept contant by maintaining the Mach number and ientropic exponent (within 10%) over the machine. Table. ASME PTC 10 Acceptable Deviation in Tet Parameter for Similarity Condition Condition Acceptable Deviation (%) Inlet Preure 5 Inlet Temperature 8 Specific Gravity Speed Capacity 4 Inlet Ga Denity 8 If the intent i to compare identical compreor, ψ and ϕ can be implified to Q/N and H/N a hown by the Fan Law Proportionality below. Fan Law Proportionality: Q N ; H N ; 3 P N, where: Q = actual volumetric flow rate, acfm N = rotational peed, rpm H = head, ft-lb/lb P = power, ft-lb/min However, if the tet condition are coniderably different and outide the limit of ASME PTC 10 (Table ) or the Mach number difference or ientropic exponent difference i outide the acceptable range (a dicued above), the Fan Law Proportionality i no longer valid. It i recommended in thi cae that Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 13

the compreor manufacturer deign oftware be ued to recalculate compreor performance a well a the head and flow coefficient curve at the changed condition. Both the actual head and flow and/or the head coefficient and flow coefficient can be utilized to verify compreor performance. The compreor manufacturer hould inform the uer of the EOS model ued in recalculating the compreor performance..11. For the Ga Turbine For the ga turbine, the mot important parameter affecting the performance are engine inlet temperature, ga turbine peed and ambient preure. To a leer extent, fuel ga compoition and relative humidity may alo influence the performance characteritic. The achievement of imilarity condition for the ga turbine i more difficult than for the ga compreor becaue of the ga turbine enitivity to ambient condition. ASME PTC (1997) recommend that actual ga turbine performance curve hould be ued to correct the actual tet data. However, thee curve are often not available, particularly for older machine..11..1 Full Load Operation The recommended method of correcting the meaured performance of the turbine i to ue ISO tandard or actual performance curve or the manufacturer oftware. In addition, the teting partie hould agree on the acceptable departure limit for the ga turbine parameter under tet prior to the actual field teting. The procedure for correcting the ga turbine to imilarity condition i a follow: 1. Determine full load power and heat rate for actual ambient condition and turbine peed.. Ue the map or the performance program to calculate the performance of a nominal engine at the ame condition a in (1). 3. Calculate the percent difference between the tet reult in (1) and () above, for power and heat rate. 4. Ue the map or the performance program to calculate the performance of the nominal engine under deired new condition. 5. Apply the percent difference for power and heat rate calculated under (3) to reference value in (4) to yield engine performance under deired new condition..11.. Part Load Operation The following procedure for correcting the ga turbine to imilarity condition at part load operation applie: 1. Determine part load heat rate for defined ambient condition and turbine peed.. Ue the map (if available for part load operation) or the performance program to calculate the performance of a nominal engine at the ame condition a in (1). 3. Calculate the percent difference between the tet reult in (1) and () above for heat rate. 4. Ue the map (if available for part load operation) or the performance program to calculate the performance of the nominal engine under deired new condition. 5. Apply the percent difference for heat rate calculated under (3) to reference value in (4) to yield engine performance under deired new condition. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 14

3. TEST PREPARATION A field tet agenda or plan hould be prepared prior to the tet a thi i an eential part of tet preparation. The plan hould include field condition and equipment layout, intrument to be ued and their location, method of operation, tet afety conideration, and the preure, temperature and flow limit of the facility. Piping and tation layout hould be made available. Any deviation from normal operation that may be neceary to conduct the tet hould alo be provided. The field tet agenda hould include a dicuion of the following: 1. The method of data reduction.. The elected approach for determining the tet uncertainty. 3. The acceptance criteria (pecified in term of maximal uncertainty allowable). 4. The equation of tate to be ued for all calculation in the tet. 5. The ue of ientropic or polytropic calculation (either may be ued for accurate thermodynamic performance characterization.). Tet preparation hould alo include a dicuion on poible operating condition and operational limitation. In many cae, a pecified operating point can only be maintained for a limited period of time (for example, becaue the pipeline operation depend upon the teted package) or at fixed ambient condition (if the neceary ga turbine power i only available on cold day). Becaue intrumentation i part of the overall tation deign, the requirement for intallation of tet intrumentation need to be communicated early. The election and calibration of the tet intrumentation i important. Generally, the intrument upplied for monitoring and protection of the package are not accurate enough to meet the tringent requirement neceary for a field tet (redundant meaurement requirement, mall uncertainty margin, detailed enor location placement, and the effect of improper flow meaurement). Whenever poible, calibrated laboratory quality intrumentation hould be intalled for the tet. (Refer to Section 4.0.) The accuracy of the intrument and the calibration procedure hould be uch that the meaurement uncertainty i reduced to the bet attainable uncertainty under ideal condition (ee Section 5.1). 3.1 Pre-Tet Meeting A meeting between the tet engineer, the partie involved (upplier, operator, etc.) and the cutomer to dicu tet procedure and the ituation on ite hould be conducted in advance of the performance tet. The ite P&ID, Site Layout and Mechanical Intallation Drawing diagram hould be obtained (if available) and ued in preparation for the performance tet. During the pre-tet meeting, the partie hould reach an agreement on the tet purpoe, tet procedure, afety requirement, reponibilitie during the tet, availability of neceary operating condition, and acceptance condition. 3. Pre-Tet Operation and Intrumentation Checkout The following item hould be checked during the pre-tet checkout: A. The tet engineer hould verify that the unit ha been proven uitable for continuou operation. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 15

B. The tet engineer hould note if a ga compreor tart-up trainer i intalled in the inlet pipe. If o, the trainer hould be checked for cleanline, either by ue of a differential preure gauge, direct inpection, or by borecope inpection. C. Sufficient ga hould be available for proper operation of the ga compreor. D. All intrumentation hould be calibrated in the range in which it will be operated during the tet. Check all intrument reading for temperature, preure, flow, torque, and peed to aure that the enor are functioning properly. Verify data acquiition ytem operation prior to tarting the field performance tet. E. All RTD or thermocouple ued in the tet hould ue pring load type fitting, or when neceary, the thermowell will be erviced with oil or other approved heat tranfer material. F. If thermowell are ued during the tet and a large portion of the thermowell i expoed to the atmophere, the area around the expoed portion hould be inulated to preclude the ambient air from affecting the temperature reading. G. Check inertion depth of thermowell. H. Where preure tap involve tubing run, the tubing hould be checked for leak. I. The proper number of capable peronnel hould be on ite to enure that all the data can be recorded in a reaonable amount of time. 3.3 Pre-Tet Equipment Checkout Prior to running the field performance tet, the following hould be performed: Wah the ga turbine compreor thoroughly. Clean air inlet filter panel (if neceary). Verify fuel and ite load to aure continuou operation of the unit and full-load condition a required at the time of the tet. Perform a viual walk-through of the turbine compreor package to eliminate any ource of hot air ingetion or recirculation. Conult with ga control on tation operation. Check if ga cooling i available and if recirculation of ga i an option during field tet. Notify all partie of time frame for tet. 3.4 Pre-Tet Information The following information hould be obtained a a reult of the tet preparation and pre-tet meeting: Impeller diameter. Predicted performance curve for compreor (or exiting tet curve). Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 16

Flow meter information: Pipe ID, orifice bore or beta ratio (for orifice meter), K-factor (for turbine or vortex hedding meter), flow coefficient (for annubar or nozzle) caling frequency, configuration log (for ultraonic meter or to adjut turbine or ma flow meter). Engine performance data, uch a factory tet data and predicted performance. Manufacturer Engine Performance Map or their electronic repreentation. Piping geometry between compreor and tet intrumentation. 3.5 Tet Stability In order to obtain teady tate condition, the ga turbine and compreor hould be tarted prior to the initiation of the tet (compreor require at leat 30 minute of heat oak time, ga turbine require between 1 to hour of heat oak time). The field tet hould be performed when the ga turbine and compreor operating condition have reached teady tate and the operating condition hould tay contant during each tet point. Power fluctuation hould not occur during the performance teting. A it i very difficult to determine fuel ga compoition variation during the hort tet interval, it i important to enure that the fuel and proce ga compoition will remain unchanged for the duration of the teting period for each tet point. Multiple ga ample of the proce ga and fuel ga mut be taken for each tet point if the ga compoition ignificantly change (heating value change of more than 1.0%) in between tet point. Temperature meaurement will epecially be affected by any intability during the tet. Temperature probe reach equilibrium through relatively low heat tranfer and heat oaking, while the ytem operating condition vary at much fater rate. The heat toring capacity of the compreor and ytem piping will need adequate time to reach equilibrium after any operating condition have changed. It i, thu, critical to maintain extended table operating condition prior to beginning the tet in order to reach thermal equilibrium and meaure accurate ga temperature. Regardle of the aumption of teady tate tet operation, any variation in meaured parameter during the tet interval hould be accounted for in the uncertainty calculation. Note that an increae in preure ratio due to drift during the tet will caue an increae in the temperature a well, though the temperature change will lag behind the preure change. Refer to Section 5.0 on uncertainty for more dicuion of unteady condition and drifting condition during a tet. Thee added uncertaintie due to drift during the tet interval are in addition to non-ideal effect dicued in Section 5.. 3.5.1 Compreor Steady State The compreor hould be operated for at leat 30 minute prior to the tet or until table reading are reached. Steady tate i achieved if all of the compreor meaurement lited in Table 3 apply during a 10-minute interval. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 17

Table 3. Aement of Stability of Compreor During Pre-Tet Criteria 1 Tet Reading Suction Temperature Dicharge Temperature Suction Preure Dicharge Preure Compreor Speed Compreor Flow Maximum Allowable Variation During 10-min Interval + 1ºC (+ 1.5ºF) + 1ºC (+ 1.5ºF) + 1% of Average Value + 1% of Average Value + 10 rpm + 1.0% of Average Value Alternatively, the following performance condition hown in Table 4 hould be atified: Table 4. Aement of Stability of Compreor During Pre-Tet Criteria Tet Reading Efficiency Head Shaft Power Maximum Allowable Variation During 10-min Interval Fluctuation < + 0.5% of Average + 0.5% of Average Value + 1% of Average Value 3.5. Ga Turbine Steady State Before reading are taken for any individual tet point, ga turbine teady tate operating condition mut be achieved. The ga turbine mut be heat oaked according to manufacturer pecification. If manufacturer pecification are not available, ga turbine hould be heat oaked for at leat 1 hour for aeroderivative ga turbine and mall ga turbine (<10,000 hp), and hour for large ga turbine (>10,000 hp), or until table operation (per Table 5) have been reached. To verify tability of the ga turbine, the parameter given in Table 4 hould be checked. Three to ten data point of each parameter over a 10-minute period hould be recorded to verify tability. If the ga turbine ha reached equilibrium, each of the parameter in Table 5 will fall within the tability criteria provided. Table 5. Aement of Stability of Ga Turbine During Pre-Tet Tet Reading Turbine Inlet Temperature Or Ambient Temperature Ga Producer Speed Shaft Load Firing Temperature Power Turbine Speed Fuel Flow Maximum Allowable Variation During 10-min Interval + 1 ºC (+ 1.5 ºF) + 1% Average Speed + 1% Average Load + 5 ºC (+ 9 ºF) + 10 rpm + % Average Flow Generator Line Voltage + 1% Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 18

3.5.3 Unteady Operation If unteady operation cannot be avoided during the tet interval, meaurement may till be valid, but the fluctuation have to be accounted for in the uncertainty calculation of the reult. If fluctuation during the tet exceed quai-teady condition a given in Table 3, 4, and 5, the tet may need to be performed again. For meaurement cae where there i a imple drift in the average operating condition, the criteria lited above hould be employed to determine whether a data point i teady. If the drift in any of the intrument reading exceed the teady tate condition (a defined in Table 3, 4, and 5), it i difficult to determine any valid performance reult from thi meaured data becaue of the high degree of interdependence of all meaured parameter and the ytem a a whole. Namely, a the validity of the data depend on the rate of drift, heat torage capacity of the pipe and meaurement ytem, and the frequency repone of the tranducer, a total uncertainty cannot be determined. On the other hand, if the fluctuation in the data can be determined to be varying around a mean value, without the average drifting ignificantly, the reultant meaurement error i primarily due to a time lag of the temperature tranducer. Namely, while the preure and flow tranducer generally meaure at a high frequency and, thu, capture rapid operating change accurately, the temperature tranducer lag due to the requirement of complete heat oaking of the piping and meaurement ytem. Thu, if the fluctuation produce a mean performance value, the criteria for acceptance of unteady operation can be extended to allow up to twice (i.e., factor-of-two range) the fluctuation lited in Table 3, 4, and 5 for compreor and ga turbine teady tate teting. In thee cae, the fluctuation mut be accounted for in the uncertainty calculation. A thi can generally reult in very high total uncertaintie for efficiency and power, one hould carefully evaluate whether to accept thi tet data. Alo, once thi factor-of-two range i exceeded, the non-linear behavior of the ytem a a whole make it unrealitic to determine accurate performance reult from experimental data. 3.6 Safety Conideration Safety conideration hould remain a priority during the pre-tet phae, a well a the actual teting of the compreor and turbine. Abnormal operating condition hould be dicued with tation peronnel prior to running the tet. If poible, a chematic of the yard piping hould be given to all tet peronnel. Unit vibration equipment operation hould be verified. When cable are run to tet intrumentation, the cable hould be covered with mat or correctly taped down (if poible) to reduce trip hazard. Cable connection hould be ecured. Finally, the requirement of the field tet hould not be given priority over tation afety precaution in order to reduce meaurement uncertainty or meet tet chedule. 4. MEASUREMENT AND INSTRUMENTATION The ga turbine and centrifugal compreor hould be equipped to meaure the tet variable hown in Figure 1 and. For teting purpoe, a dedicated et of laboratory quality intrumentation hould be utilized. Thi dedicated et of tet intrumentation hould be maintained and frequently calibrated uing acceptable reference tandard. A valid calibration certificate for all meaurement intrumentation i recommended. An end-to-end calibration of the data acquiition ytem, wiring, and intrumentation i alo recommended prior to the field tet but may not alway be practical. If poible, all meaurement intrumentation hould be intalled inide the branch piping to the compreor recirculation flow loop uch that the meaured value repreent the true flow through the compreor. If the tet intrumentation i located outide the recycle loop for the compreor, the recycle valve mut be fully cloed during the tet for the reult to be valid. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 19

A piping configuration uing a cloed loop through the compreor or tation recycle line may alo be utilized for the performance teting of the compreor. In thi cae, a proce ga cooler on the dicharge of the compreor will generally be required to maintain the ga temperature table in the cloed piping loop. Alo, for thi tet cenario, the effect of ga lean out mut be conidered a the heavier component in the tet ga may liquefy and drop out due to equential compreion and cooling. Thu, prior to the performance tet, the compreor hould be run in the cloed loop configuration while monitoring the ga uing an online ga chromatograph until there i no ignificant change in the ga compoition. 4.1 Meaurement of Preure 4.1.1 Recommended Bet Practice Total (tagnation) preure mut alway be ued for performance calculation. However, it i often more convenient to meaure tatic preure (P tat ) and then convert tatic to total preure (P) uing: P = Ptat + 0.5ρU (4.1) In equation (4.1), the flow velocitie can be calculated uing the meaured flow rate and the pipe diameter (U=Q/A). Whenever feaible, it i recommended to ue four preure tap and four temperature tap at the preure and temperature location indicated in Figure 1 and, conitent with ASME PTC 10 recommendation. The accuracy of the tatic preure or temperature meaurement i dependent upon the elected location. Four preure and temperature enor aure that the average meaurement of preure or temperature will be accurate, even in a non-uniform flow field. Additional preure and temperature meaurement can be employed, if four enor are not ufficient. Two different approache are appropriate for locating the uction and dicharge preure and temperature tap. The firt approach i to place meaurement tap at location relatively far uptream and downtream from the compreor in the longet available traight pipe egment to aure a uniform flow field at the tranducer tap. Thee location may be relatively far away from the compreor, o the preure meaurement value mut be corrected uing empirical lo factor (i.e., head loe) for the traight pipe, elbow, tee, and reducer that lie in between the meaurement location and the compreor inlet/dicharge. The econd approach i recommended for field teting, if poible. The approach i to meaure the preure and temperature a cloe a poible to the compreor, uing multiple temperature and preuretap at uction and dicharge. Generally, the flow field near the compreor will be highly non-uniform and, thu, at leat four preure and temperature tap hould be ued on both uction and dicharge. Nonuniformity of the flow field affect the uncertainty of the meaurement data. If le than four tranmitter or tet tap (for preure or temperature) are available, the firt meaurement approach i recommended. Uing le than four preure or temperature enor will reult in an increae in the total uncertainty for preure or temperature, a dicued in Section 5.. 4.1. Intallation The intallation of the preure meaurement device, preure tap ize, and ymmetry i critical to the meaurement accuracy. ASME PTC 10 provide pecific guideline for correct intallation and location of preure probe. The preure tapping hould be inpected prior to intallation of the preure meaurement device. The tube and tatic tapping ued to make the dynamic preure meaurement hould have a contant length to diameter ratio and mut be greater than. The ratio between the preure tubing Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 0

and the pipe diameter hould be a mall a poible to prevent the preure meaurement from altering the flow pattern. In addition, the wall tap hould be exactly perpendicular and fluh to the urface. Burr or lag in the tap are not acceptable and will influence meaurement accuracy. 4.1.3 Calibration Prior to performing the field tet, the tranmitter or tranducer hould be calibrated, uch that the maximum device error i le than or equal to 0.1% of the actual value. The calibration procedure hould contain at leat three point. Recalibration of the preure tranmitter hould be performed frequently. The calibration proce will not eliminate all meaurement error, ince the calibration proce itelf i ubject to non-linearitie, hyterei, and reference condition error. 4.1.4 Accuracy Achieved in Practice The preciion uncertainty in preure meaurement will depend upon the uniformity of the flow field. If piping vibration or flow-induced pulation are high at the location of the tatic preure meaurement, the meaurement of preure will how a ignificantly higher random uncertainty. Non-uniformitie, location, intallation, and calibration error will affect the preure meaurement. The ignal from the tranmitter hould be tranformed into a digital ignal by mean of a portable data acquiition ytem (DAS). The data acquiition ytem hould have an intrumentation accuracy of better than 0.01 to 0.05% of reading. The main ource of preure meaurement error i incorrect intallation and location of preure probe. Table 6 provide typical value for ource of preure meaurement error encountered during field tet. All value are percent full cale. For cae of multiple tranmitter, it i aumed that the tranmitter are intalled at equal angular interval in the pipe and the flow field i uniform. Table 6 aume that the intallation meet the uptream and downtream requirement of ASME PTC 10. Intallation configuration, which do not meet ASME PTC 10, will have ignificantly higher location uncertaintie in preure meaurement. See Figure 5 for ASME PTC 10 recommended intallation. Table 6. Typical Uncertaintie in Preure Meaurement (hown a percent of full cale) Senor Type Location 1 Intallation Calibration Device Acquiition One Static Tranmitter 0.15 0.0 0.10 0.10 0.005 Two Static Tranmitter 0.10 0.0 0.10 0.10 0.005 Four Static Tranmitter 0.10 0.0 0.10 0.10 0.005 1 Error in location will largely be dependent on uniformity of flow field at meauring location and the number of preure meaurement device ued at a ingle location. Wall tatic error will caue high uncertainty if wall tap are not correct. Wall tap hould be exactly perpendicular to the urface and fluh (with no burr or lag). 4. Meaurement of Temperature 4..1 Recommended Bet Practice The approach to meaurement of temperature i imilar to preure, in that temperature may be meaured very cloe to the compreor to aure that the meaured temperature i repreentative of the compreor temperature. However, if the temperature meaurement i taken at thi location, four temperature enor hould be ued to identify any inconitent meaurement and aure that bad reading are dicarded. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 1

Temperature hould alway be meaured downtream of preure, if poible. The preure and temperature enor hould not be intalled in the ame line of ight. Figure 5. ASME PTC 10 Recommended Intallation Configuration for Preure and Temperature Meaurement Thermocouple, thermitor, and reitance temperature device (RTD) are typically ued to meaure temperature. RTD are recommended for meaurement of temperature in the flow tream over a broad temperature range. Thermocouple can be ued for high temperature meaurement, but below 00 F (93 C) the reolution will be reduced. Alo, thermocouple tend to drift more than RTD and, thu, require more frequent recalibration. At low temperature, thermitor are ueful but hould be carefully calibrated becaue of inherent nonlinearitie. 4.. Intallation Thee device hould be inerted into a thermowell, though RTD enor may be ued a direct inert device. Direct inert RTD will provide a fater repone time. The temperature enor hould be intrumented to a temperature tranmitter that i connected to the field tet data acquiition ytem. The meaurement location hould aure that the temperature enor will be relatively inenitive to radiation, convection, and conduction between the temperature enor and all external bodie. The inertion depth Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page

can produce a large error in the temperature meaurement, if the enor i placed too deep or too hallow in the flow tream (ee Table 7). The manufacturer afety guideline hould be conulted for inertion depth of RTD without thermowell and extra long thermowell to enure the pipe velocity meet acceptable afety level. Table 7. Recommended Depth of Thermowell Pipe Diameter (inche) Thermowell Depth (inche) 6.0 8.5-3.0 10 3.0-3.5 1 4.0 14 4.5-5.0 16 5.0-5.5 18 6.0 >18 7.5 minimum Note: Above 18-inch diameter, a minimum depth of 7.5 inche from the inner wall i enough to avoid pipe influence and breakage. The ASME PTC 10 tandard provide pecific guideline for proper intallation and location of temperature enor. Though the field tet contraint may make ideal meaurement location impoible, it i important to be aware of the required pecification to ae meaurement error and the propagation of additional meaurement uncertainty (ee Section 5. on Non-Ideal Intallation). 4..3 Calibration The temperature enor hall be calibrated, uch that the maximum meaurement uncertainty for each enor i <0.15 ºC. Tranmitter ued in acquiring data from the temperature enor hould be calibrated in tandem (i.e., the tranmitter ued to read the ignal from the RTD hould be calibrated with the RTD a a ingle meaurement chain). The calibration procedure hould involve at leat three point. The calibration proce can introduce error into the temperature meaurement, primarily through non-linear repone, intrument drift, cold junction, and reference temperature error. 4..4 Accuracy Achieved in Practice Table 8 provide typical uncertainty value for the five main ource of temperature meaurement error encountered during field tet. Uncertaintie in the temperature originate from the following five major ource of error: (i) location: incorrect poition of the thermal enor in the ga tream; (ii) intallation: wall conduction heat tranfer to and from the enor due to inadequate inulation; (iii) calibration: intrument drift, nonlinearitie, cold junction, and reference temperature error; (iv) device: inherent accuracy limitation of the enor device; and (v) acquiition: amplifier, tranmiion, noie, read, and analog-digital converion error. Location, intallation, and calibration error may be minimized eaily in production or laboratory tet facilitie. However, for field teting thi i more difficult becaue time and cot contraint can force the tet engineer to accept field tet arrangement with improperly located, intalled, and calibrated intrument. While it i often impoible to correct thee problem during the hort field tet duration, it i imperative to recognize them and account for them in the uncertainty analyi. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 3

Table 8 how that the location, intallation, and calibration error are the dominant factor, while the device and acquiition error are a maller contribution to the total temperature error. Alo note that field tet device and acquiition error are ignificantly larger than value quoted by intrument manufacturer (>0.005 percent full cale). Again, the circumtance and limitation encountered in the field tet may not alway allow for ideal handling of the enitive meaurement intrument. Table 8 aume that the intallation meet the uptream and downtream requirement of ASME PTC 10 for temperature enor intallation. Intallation configuration, which do not meet ASME PTC 10, will have ignificantly higher location uncertaintie in temperature meaurement. Table 8. Typical Uncertaintie in Temperature Meaurement (hown a percent of full cale) Senor Type Location 1 Intallation Calibration Device Acquiition Hg Thermometer 0.10 0.0 0.03 0.03 0.10 Thermitor 0.10 0.0 0.10 0.05 0.05 Thermocouple 0.10 0.0 0.10 0.10 0.05 RTD 0.10 0.0 0.05 0.05 0.05 Infrared Senor 0.40 0.0 0.10 0.5 0.05 1 Location error i baed on having four (4) equally paced enor in the pipe and aume uniform flow in the pipe. For a ingle enor intallation, the location uncertainty hould be multiplied by four (4). For two () enor, the location uncertainty hould be multiplied by two (). For highly non-uniform flow field thee value may be larger. 4..5 Temperature and Preure Meaurement Other Conideration To obtain the total temperature or preure uncertainty, the individual uncertaintie mut be added uing the root-quare um method. Typically, the tagnation and tatic value for preure and temperature are aumed to be the ame, and any difference between thee two value are aumed to not affect the performance calculation. Thi aumption i valid for inlet and outlet compreor Mach number le than 0.1 (Brun and Kurz, 003.) However, at higher compreor Mach number (>0.1), an additional uncertainty term hould be accounted for becaue of the difference between tagnation and tatic preure and temperature. At a compreor Mach number of 0.10, the preure error i approximately 0.6%, while the temperature error i 0.15%. At a compreor Mach number of 0.30, the preure error i 7.0% and the temperature error 1.6%. 4.3 Meaurement of Flow An accurate meaurement of the ga flow through a compreor i eential for proper determination of the performance and i neceary to identify degradation in the performance of a compreor. The mot common meter type intalled at ga compreor field ite i orifice meter. Other meter that are available at ome time are full bore turbine meter, ultraonic meter, flow nozzle, and a range of inertion type meter, uch a vortex hedding meter, inertion turbine meter, and multi-port pitot probe. Fuel ga flow rate are alo meaured with thee common meter, including orifice, turbine, inertion, and Corioli ma flow meter. The proper izing, intallation, maintenance, adjutment, and calibration are neceary for any of thee meter to achieve the deired level of preciion and repeatability in flow meaurement. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 4

4.3.1 Recommended Bet Practice Orifice, ultraonic, and turbine flow meter are typically employed to meaure pipeline flow at a high level of accuracy. However, proper intallation, maintenance, and calibration are critical to achieve a deired level of preciion and repeatability. All three meter type have uptream length requirement, which may be mitigated through the ue of a flow conditioner. When intalled correctly with a properly calibrated differential preure tranducer, an orifice flow meter may be ued to meaure flow over a 3:1 range with an accuracy of 1.0%. Turbine meter have a greater flow range than orifice meter. Turbine meter are very repeatable in both high and low flow ituation and can provide accuracie better than 1.0% dependent upon the quality of calibration. A calibrated ultraonic meter will provide flow meaurement accuracy better than 1.0%. 4.3. Intallation The uptream piping configuration at field compreor intallation are normally not ideal and reult in ditorted velocity profile at the meter. Non-ideal meter piping will reult in error in the flow meaurement unle omething i done to correct the metering configuration. The bet olution i the intallation of the flow conditioner either of the traditional tube bundle type with relatively long length of traight uptream piping per AGA Report No. 3 or the ue of the recently developed perforated plate type flow condition. Table 9 give the recommended ditance between variou uptream diturbance and the orifice flow meter baed on ISO 5167. The flow conditioner required by ISO 5167 i any of the variou plate type flow conditioner (intead of a 19-tube bundle). Table 9. ISO 5167 Recommended Intallation Length for Orifice Flow Meter Required uptream length of primary device (orifice meter) given in nominal pipe diameter Beta Ratio Single 90 bend or tee Two or more 90 bend in ame plane Two or more 90 bend in different plane Reducer D to D over a length of 1.5D to 3D Expander 0.5D to D over a length of D 0.0 10 (6) 14 (7) 34 (17) 5 16 (8) 0.30 10 (6) 16 (8) 34 (17) 5 16 (8) 0.40 14 (7) 18 (9) 36 (18) 5 16 (8) 0.50 14 (7) 0 (10) 40 (0) 6 (5) 18 (9) 0.60 18 (9) 6 (13) 48 (4) 9 (5) (11) 0.70 8 (14) 36 (18) 6 (31) 14 (7) 30 (15) Beta Ratio Full bore ball or gate valve fully open Abrupt ymmetrical reduction with diameter ratio >0.5 Thermometer pocket or well of diameter <0.03D Thermometer pocket or well of diameter between 0.03D and 0.13D Downtream ditance - Fitting 0.0 1 (6) 30 (15) 5 (3) 0 (10) 4 () 0.30 1 (6) 5 (.5) 0.40 1 (6) 6 (3) Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 5

0.50 1 (6) 6 (3) 0.60 14 (7) 7 (3.5) 0.70 0 (10) 7 (3.5) 1. Value without parenthei are zero additional uncertainty, while value in parenthei require an additional 0.5% uncertainty due to intallation effect. If an orifice flow meter i ued, it may be beneficial to ue a maller beta ratio plate for the performance tet purpoe (though thi will provide higher DP), becaue lower beta ratio are le uceptible to intallation configuration and will typically provide a more accurate flow meaurement. The meaurement calculation, intallation requirement and calibration of a turbine meter hould follow the pecification of AGA Report No. 7. The recommended intallation (AGA Report No. 7, Third Reviion) for a turbine meter require at leat ten pipe diameter of traight pipe uptream of the meter inlet, with a flow conditioner outlet located at five pipe diameter uptream of the meter inlet. Downtream, an additional five pipe diameter of traight pipe hould be provided. Pipe connection or protruion uptream of the meter (<10D) are not permitted. In the recommended intallation, the additional uncertainty due to location or intallation error i negligible. AGA Report No. 7 allow for optional intallation configuration, with a relatively higher meaurement uncertainty. The hort-coupled intallation configuration hown in Figure 6 may be ued when pace i limited. The cloe-coupled intallation configuration hown in Figure 7 may be ued where pace i everely limited. Figure 6. Short-Coupled Intallation for a Turbine Meter (AGA-7, Rev. 3) Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 6

Figure 7. Cloe-Coupled Intallation for a Turbine Meter (AGA-7, Rev. 3) Ultraonic meter hould be intalled with proper flow conditioning and uptream length a tated in AGA Report No. 9. Thi tandard enure that wirling or ditorted velocity profile will not occur at the meter. Either extremely long, 80 to 100 pipe diameter, traight length of uptream pipe, or flow conditioner are required to prevent ditorted velocity profile from reaching an ultraonic meter. If a flow conditioner i not available or uptream traight pipe i not ufficient, an additional bia uncertainty hould be added to the flow meaurement uncertainty term. Modern perforated plate flow conditioner of the proven type are preferred and allow horter traight uptream length than tube bundle flow conditioner. Straight uptream length of 0 to 30 pipe diameter are uually required with a tube bundle flow conditioner. Total uptream length with a proper perforated plate flow conditioner for an ultraonic flow meter can be a little a 10 to 15 pipe diameter. Meter run that are horter than the guideline provided here are ubject to ignificant intallation error. 4.3.3 Calibration The primary advantage of orifice meter are that they do not require calibration of the meter. The differential preure tranducer ued to meaure DP mut be calibrated, however. Orifice meter for compreor proce ga flow meaurement and for fuel ga metering hould be inpected prior to a performance tet to enure they are clean and in good condition. Turbine meter require calibration at near the operating condition of the meter. The characteritic nonlinearity of the turbine meter calibration curve can caue meaurement error of 1 to 3% at low flow, if the non-linearity i not accounted for in the calibration. Ultraonic meter mut be individually calibrated. Every ultraonic meter hould be calibrated in a ga flow, at preure condition imilar to the intended operating condition. A calibration factor or linearization routine may be ued to correct the afound meter to achieving an accuracy of at leat 1.0% over the meter range (typically 10:1). 4.3.4 Accuracy Achieved in Practice Pulation adverely affect mot type of meter and, therefore, mut be avoided during centrifugal compreor and ga turbine performance teting. However, a mot flow meaurement intrument provide a low frequency output repone, it i often difficult to determine pulation magnitude and frequencie. RMS output variation on the flow meter can be ued to etimate pulation amplitude, but flow turbulence alo contribute to RMS flow velocity and preure variation. AGA Report No. 3 define that when the preure differential or the velocity fluctuation acro the meaurement device exceed 10% RMS value, the flow meter reult cannot be conidered valid. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 7

In order to calculate flow accurately for an orifice meter, the temperature, preure, ga compoition and differential preure mut be meaured accurately. Properly ized orifice meter are uitable for teting centrifugal compreor over a normal operating rang from urge to tonewall. Orifice meter are highly uceptible to intallation-effect reulting from improperly conditioned flow, inufficient uptream length, uptream bend, elbow or valve, or extreme beta ratio (>0.65). If intalled correctly with a beta ratio le than 0.65, orifice meter will provide a flow meaurement accuracy of le than 1.5%. Turbine meter can be calibrated to obtain a meaurement uncertainty of le than 1.0%. If the ga preure or flow rate i outide the calibration curve, the meaurement will contain a bia error, which can be a large a 1.5 to.0% additional meaurement uncertainty. If a turbine meter i over-ranged by exceeding it maximum velocity, permanent damage to the rotor may caue the meaurement uncertainty of the meter to exceed.0%. The accuracy of an ultraonic meter decreae at flow velocitie of le than 5 to 7 feet per econd and at high flow velocitie, above 70 to 90 feet per econd. Therefore, ultraonic meter hould only be ued for compreor teting, if the flow range in the pipe i between 5 to 70 ft/ec. Ultraonic meter hould not be overized uch that low flow velocitie routinely occur, or underized, uch that high velocitie are experienced. The field accuracy of ultraonic meter i normally in the range of 0.5 to 1.0 % and i baed on the meter calibration and having a uitable piping configuration. Other differential preure device (annubar, v-cone, etc.) and venturi meter (onic nozzle) may alo be ued to meaure ga flow through the compreor. Thee meter type typically have a lower preure drop than an orifice meter, but the flow meaurement error i highly enitive to the meaurement of differential preure acro the device. Typical meter accuracy i 0.5 to 1.5% if the differential preure enor i calibrated and operating well within it range. Venturi meter and differential preure (DP) type meter are imilar to an orifice meter, in that large intallation error can occur (1 to 5%) if intalled incorrectly. Intallation guideline for venturi meter are provided in ISO 5167, Meaurement of Fluid Flow by Mean of Orifice Plate, Nozzle and Venturi Tube, and ASME MFC-3M-1989, Meaurement of Fluid Flow in Pipe Uing Orifice, Nozzle and Venturi Tube. All differential preure flow device mut meet a tet protocol tandard pecified in American Petroleum Intitute Manual of Petroleum Meaurement Standard (API MPMS) Chapter 5.7, Teting Protocol for Differential Preure Flow Meaurement Device. Specific intallation requirement for DP type meter hould be provided by the meter manufacturer and hould aure that the meter conform to API MPMS Chapter 5.7. 4.4 Meaurement of Ga Compoition 4.4.1 Recommended Bet Practice Both the ga turbine fuel ga and compreor proce ga compoition hould be evaluated at regular interval throughout the field tet, either through automatic ga chromatograph ampling or by taking regular ga ample. At a minimum, a ga ample hould be taken before and after the tet. Multiple ampling method are defined in GPA Standard 166 and the American Petroleum Intitute Manual of Petroleum Meaurement Standard (API MPMS) Chapter 14.1. Thee include both pot method and compoite ampling (on-line method). If an automatic ampling probe i ued (uch a a ga chromatograph probe regulator), the probe hould be properly ized to draw ample from the center one-third of the pipe, o that liquid that may appear in the flow cannot be eaily ingeted into the probe and ample line. Velocitie in the location where ample are taken hould not exceed 150 ft/ec in order to avoid poible probe vibration and failure. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 8

To properly determine the ga propertie from the ga ample, the ga compoition hould be evaluated up to C 6+. Namely, a a minimum, the ga ample hould be analyzed for all hydrogen, oxygen, water, ulfur compound, carbon dioxide, nitrogen, nitrou oxide, other inert gae, and all hydrocarbon gae or vapor between C 1 and C 6. If the hydrocarbon dewpoint of the ga mixture i within 0 to 11ºC of the temperature of the ampling equipment, or above the temperature of the ampling equipment (ambient temperature), additional precaution mut be taken. The hydrocarbon dewpoint will vary with different ga mixture and primarily be influenced by the preence of heavier hydrocarbon, above C 6. The bet practice in thi cae i to preheat the ample line and ampling container prior to taking the ga ample. If pre-heating i not practical, dead-end pot ampling method may be ued in combination with re-heating the ample above the mixture dew point during the analyi proce. Dead-end pot ampling method include the water or glycol diplacement method, the piton diplacement method, the evacuated cylinder method (evacuated, reduced preure, or helium pop), and the fill and empty method. Thee method work bet becaue the depleted ga i not convected out of the cylinder in the ampling proce. If condenate i formed on the wall of the ampling cylinder, re-heating the ample will caue the condenate to re-vaporize a part of the ampled ga mixture. 4.4. Intallation All ampling line and equipment that come in contact with the ample tream hould be made of tainle teel or other material that are inert, compatible with the ga and minimize adorption of heavy hydrocarbon from the ga tream. Polyethylene, Nylon, and Teflon will caue ample ditortion becaue of thee material preferential aborption of pecific hydrocarbon component. The probe and line hould be inulated to avoid condenation of the heavier hydrocarbon contituent or water vapor in the ample. The probe and ample line hould alo be arranged above the pipeline. A tated in API MPMS Chapter 14.1, the ampling bottle hould have a pigtail line connected to it outlet to aure that the proce ga i kept above the hydrocarbon dewpoint ee Figure 8 below. Prior to ampling the ga, the ga ampling equipment hould be cleaned, preferably by team cleaning or uing acetone or liquid propane. Filter in the ample line are required in mot cae. All fitting, tubing, and preure regulator hould be rated for the appropriate operating preure of the tation. Figure 8. Sampling Method with Pigtail a Recommended in API MPMS Chapter 14.1 Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 9

4.4.3 Calibration Ga chromatograph are almot excluively ued to determine the ga chemical compoition, in order to determine ga denity, compreibility, and energy content. A ga chromatograph hould not be regarded a an infallible device. A calibration ga tandard hould be ued to calibrate the ga chromatograph regularly. 4.4.4 Accuracy Achieved in Practice The ga compoition will almot alway differ from the ga compoition ued in the baeline or factory tet. Deviation will occur in the calculated performance value if only the pecific gravity of the new ga i ued, intead of the entire chemical ga compoition. (Note: ASME PTC 10 aume that for a Type 1 tet the ga i almot identical to the ga pecified at acceptance condition.) Error in the determination of the ga compoition will affect the denity, compreibility, and the energy content determination. Denity error will propagate in the flow meaurement when converting between ma and volume flow. Online ga chromatograph mut be calibrated regularly (at leat once per week) to enure accurate ga compoition with a calibration ga that i imilar in compoition to the proce ga being meaured. 4.5 Meaurement of Rotational Speed The peed of rotation hould be meaured uing magnetic peed pickup on the power turbine or the key phaor probe of the ga compreor. Either method i acceptable and can be ued with ufficient accuracy. The ignal from the magnetic peed pickup or key phaor hould be tranformed into a digital ignal uing the field package data acquiition ytem. 4.6 Meaurement of Torque Determination of torque with a torque meter i recommended to reduce tet uncertainty in the meaured haft power (ga turbine output power). Variou torque meauring ytem are available in the indutry. If the torque meter i ued, the total uncertainty in the ga turbine power calculation will be coniderably reduced to poibly le than 1.0%. The torque meter calibration mut be maintained during the entirety of the tet. Practice ha hown that harh tet environment and high peed can eaily affect torque meter calibration. Thu, calibration hould be verified before and after the tet. A torque meter can alo provide a good baeline for verifying the compreor performance determined from heat balance method. 4.7 Meaurement of Generator Power For electric generator ga turbine application, the generator output i meaured in order to determine the ga turbine haft power. If a gearbox i preent between ga turbine and generator, the power loe alo need to be conidered. The generator electrical power output can be meaured directly at the generator terminal. Typically, three current tranformer (CT) and two potential tranformer (PT) are ued to meaure the line voltage (E) and current (I). The power factor (PF) can be determined from the phae angle between the voltage and the current a hown in equation (4.). The generator output can be calculated by equation (4.3). PeI, active PF = (4.) P ei, apparent Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 30

P ei = 3 E I PF (4.3) For increaed accuracy, pecially calibrated current tranformer and potential tranformer can be ued. 5. TEST UNCERTAINTY Tet uncertainty mut be calculated to determine the accuracy or quality of the tet and the bound of any meaured quantity. There are two primary component to uncertainty of any phyical meaurement: random (preciion) uncertainty and bia (fixed) uncertainty. Tet uncertaintie need to be clearly ditinguihed from machine building tolerance. Building tolerance cover the inevitable manufacturing tolerance and the uncertaintie of the performance prediction. The actual machine that i intalled on the tet tand will differ in it actual performance from the predicted performance by the machine building tolerance. Building tolerance are entirely the reponibility of the manufacturer and mut be excluded in any uncertainty calculation. In addition, the tet uncertainty i not equivalent to the contractual tet tolerance. The contractually agreed upon tet tolerance might be influenced by conideration of how accurate a tet can be performed or by more commercial conideration, uch a the amount of rik the partie are willing to accept. An increaed tet uncertainty increae the rik of failing the tet if the turbomachinery i actually performing better than the acceptance level, but reduce the rik of failing if the turbomachinery i performing below the acceptance level. Becaue it i normal practice to ue a lower performance than predicted a an acceptance criterion, it i in the interet of the manufacturer, a well a the uer, to tet a accurately a poible. The following definition hould be applied to the dicuion of uncertainty: Preciion (Random) Error: The error due to random fluctuation of the meaured quantity. The true value of the meaurement hould lie within the catter of the data point, if no bia error exit. Thi error i reduced by taking more meaurement of the tet quantity. Bia (Fixed) Error: A ytematic deviation of an intrument output from a fixed input. Bia can be a complex functional form over the intrument operational range, but in mot cae, it i jut the conitent over- or under-reading of input data. It i often due to intallation effect or calibration error. Bia error mut be etimated in the uncertainty analyi. Note: In a field ite tet, the bia error and preciion error may not be ditinguihable. Thee two component of the uncertainty are often treated a a ingle combined uncertainty. Linearity: Compare the deviation of a ytem output to a traight-line aumption. Clearly, few phyical ytem behave linearly over a wide range and, thu, linearity mut alway be tated with an upper and lower limit. Hyterei: Refer to the ytem or intrument output dependency on directionality of the input. Hyterei ha nothing to do with an intrument accuracy degradation over time. In mot cae, it i defined a the maximum difference in intrument reading for a given input value when the value i approached firt with increaing, and then with decreaing, input ignal. Hyterei i often caued by energy aborption in the element of the meauring intrument or ytem. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 31

All of the above are factor that contribute to, but are fundamentally different than the definition of meaurement uncertainty. Uncertainty doe not refer to a ingle intrument accuracy, but evaluate the complete range of poible tet reult given a ingular tet condition. The field tet cannot be performed with all variable fixed. Conequently, the meaured performance calculation and tet reult mut alo be a range rather than a point and mut account for all poible input combination of all input variable. It i important to undertand that if the input range to the ytem are defined a tatitical bound, uch a 95% confidence interval, then the output from the uncertainty analyi will alo preent the ame 95% confidence interval tatitical bound. Similarly, if the input are abolute error of meaurement, then the uncertainty analyi will alo yield abolute error (i.e., whatever i the type of uncertainty range for the input variable will be the type of uncertainty range for the reult). Conitent application and definition of the input variable uncertainty range i, thu, critically important in any uncertainty analyi. Furthermore, prior to determining a tet uncertainty, it i important to know whether the meaured variable in the tet are independent or dependent, a thi determine the method of uncertainty calculation that mut be employed. For almot all real meaurement cenario, there i ome phyical dependency between the input variable and, thu, unle one i abolutely certain that all meaured and given ytem input are independent, it i afer to opt for the more conervative aumption of meaurement dependence. Thu, a the determination whether an experiment meaured variable are interdependent directly etablihe the uncertainty analyi method that mut be employed, a thorough phyical undertanding of the meaured ytem i imperative. The tet uncertainty calculation hould be performed uing one of the three method decribed in Appendix C. To evaluate the tet data and the ga turbine/compreor package itelf, the uncertainty of the tet mut be calculated correctly, and the required uncertainty limit mut be undertood prior to the tet. For example, data with an uncertainty of 3.0% cannot yield concluion requiring an accuracy of 1.0% and, thu, if 1% accuracy i required, the tet preparation, intrumentation, and planning mut reflect thi requirement. Alo, in comparing the field tet data to any other et of data of the ame machine (uch a hitorical data or the factory tet data), the uncertaintie in both tet mut be conidered in the comparion. The tet uncertainty tolerance are recommended in Table 10 for the primary meaurement parameter in the performance tet. Table 10. In-Practice Achievable Uncertainty for Meaured Tet Parameter Meaurement Preure Temperature Flow Torque Ga compoition (Denity, compreibility, ga contant, pecific heat, energy content) Achievable Uncertainty 0.3 -.0% Full Scale 0.3-4.0 ºC (0.5-7.5 ºF) 0.5 -.0% of value 0.5-1.5% of value 0. 3.0% of value For all parameter derived from an equation of tate (uch a compreibility, heating value, ientropic coefficient, denity, pecific heat, and ga contant), there i an added inherent uncertainty, ince the equation of tate i an empirical model. Unle direct experimental data for comparion i available for the ga compoition ued in the performance tet, it i difficult to quantify the added EOS model Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 3

uncertainty. However, a conitent application of the elected EOS between the factory tet, field tet, and prediction will minimize any potential performance analyi difference and, thu, reduce the contribution of the EOS model uncertainty to a negligible contribution. The effect of typical near ideal meaurement uncertaintie on the total compreor and ga turbine uncertainty i provided in Section 5.1. Non-ideal intallation effect on uncertainty are provided in Section 5. below. 5.1 Ideal Field Tet Condition For Reducing Uncertaintie In an ideal field intallation, the uncertainty in meaured power and efficiency for the centrifugal compreor and ga turbine i at a minimum. Departure from the ideal intallation will increae thee uncertaintie. Uncertaintie hould be calculated uing the method decribed in Appendix C and intrument uncertainty value lited in the preceding ection. Thi ection decribe an example of a near ideal field tet intallation and provide a typical baeline uncertainty in power and efficiency for thi cae. The effect of non-ideal meaurement condition on the total performance uncertaintie are dicued and compared in Section 5.. In the example, uncertainty calculation given in Section 5.1.1 and 5.1. and in the non-ideal intallation hown in Section 5., the perturbation method wa ued to determine the total performance uncertainty, a decribed in Appendix C. 5.1.1 Compreor Uncertainty Example The validity of a compreor performance field tet depend on the level of uncertainty of meaured efficiency and power. Power and efficiency uncertaintie hould be calculated from the individual meaurement uncertaintie (temperature, preure, flow rate, and ga propertie). An example uncertainty calculation for a centrifugal compreor tet i given in Table 11(a-b). The value of the meaured variable hown in Table 11(a-b) repreent a typical centrifugal compreor application in pipeline (low compreion ratio) ervice. Operating condition are alo hown on thee table. A repreentative ga compoition wa ued to compute the ga propertie, coniting of the following component: 90.0% methane 5.37% ethane 1.7% propane 0.74% iobutene 0.331% n-butane 0.055% iopentane 0.09% n-pentane 0.07% n-hexane 1.06% carbon dioxide 1.05% nitrogen The Benedict-Webb-Rubin (BWR) equation of tate model wa ued to compute the compreibility, pecific heat, and molecular weight. The meaurement uncertaintie calculated in Table 11(a-b) aume near-ideal tet condition, procedure, and efficiencie. Thee uncertaintie are baed on proper intallation, application, and acquiition of the tet intrumentation, a recommended previouly. The calculated property uncertaintie (Z, cp, k, R) are Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 33

baed on typical variation in a ampled ga compoition due to ample variation and uncertainty introduced by the ga ampling proce (Δ = +0.3% for methane and ethane, Δ = +0.1% for propane, Δ = -0.3% for carbon dioxide, Δ = -0.4% for nitrogen). The calculated property uncertaintie include the uncertainty due to ga chromatograph analyi for a calibrated ga chromatograph. Baed on all the input uncertaintie, the reulting uncertainty in compreor power i 1.43%. The reulting uncertainty in compreor efficiency i.39%. Thee value of meaurement uncertainty for the compreor are cloe to the minimum attainable tet uncertainty for thi cae. 5.1. Ga Turbine Uncertainty Example The level of uncertainty in meaured ga turbine efficiency and haft output power determine the validity of the field performance tet. The efficiency uncertainty of the ga turbine i typically calculated from the individual meaurement uncertaintie in fuel flow, fuel heating value, and ga turbine haft power output. The haft output power and it aociated uncertainty i uually determined from the driven equipment via torque coupling, compreor heat balance, or generator terminal power a dicued in the preceding ection. Table 1(a-b) provide an example of a repreentative ga turbine in a pipeline compreion application, which matche the typical centrifugal compreor example decribed in Table 11(a-b). The fuel flow i given a a ma flow, although thi would typically be meaured with a volumetric meter and converted to ma flow through denity (which add another uncertainty term). However, thee term can be combined ince the denity uncertainty term of the fuel i uually mall. The heating value uncertainty i baed on the uncertainty due to ampling variation and ga chromatograph analyi. The meaurement uncertaintie in fuel flow and heating value repreent ideal tet condition, procedure, and efficiencie. The meaured uncertainty in ga turbine haft power output i baed on the compreor power uncertainty calculated for the near-ideal cae in Table 11(a-b). Baed on the input uncertaintie, the reulting uncertainty in ga turbine efficiency i 1.77%, which repreent a minimum attainable tet uncertainty for thi example. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 34

Table 11a. Example of Total Uncertainty Calculation for Compreor in Near Ideal Cae SI Unit Cae 1: Ideal Cae Input Parameter Value Input Δ[%] 3 Δ Power Δη Meaured propertie: P [MPa] 1.10 0.3 19.47 0.006 T [K] 300 0.1 55.17 0.005 Pd [MPa] 1.55 0.3 19.5 0.006 Td [K] 340 0.1 48.80 0.005 Qa [m3/] 1 9.13 0.5 3.45 0.000 Calculated propertie baed on ga compoition at uction condition: Z 0.9763 0.05 3.5 0.000 cp [J/kgK] 177.14 0.3 19.47 0.000 k 1.31 0.08 0.00 0.003 R [J/kgK] 460.1 0.3 19.47 0.000 Performance Parameter Value Total ΔPower [%] Total Δη [%] Pactual [kw] 6490 1.35 1.81 Efficiency, η [%] 0.636 1 Qa i actual flow rate at uction condition, v=0 m/ in a 30" diameter pipe. Z, cp, k and R repreent a typical hydrocarbon tranmiion grade ga. 3 Typical value of uncertainty repreent ideal preure and temperature meaurement uing four enor on uction and dicharge, recommended flow meter intallation and ga property calculation made with conitent EOS model and accurate ga ample. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 35

Table 11b. Example of Total Uncertainty Calculation for Compreor in Near Ideal Cae Englih Unit Cae 1: Ideal Cae Input Parameter Value Input Δ[%] 3 Δ Power Δη Meaured propertie: P [pia] 159.54 0.3 6.11 0.006 T [R] 540 0.1 73.97 0.005 Pd [pia] 4.80 0.3 6.18 0.006 Td [R] 61 0.1 65.44 0.005 Qa [ft3/] 1 3.4 0.5 43.51 0.000 Calculated propertie baed on ga compoition at uction condition: Z 0.9763 0.05 4.35 0.000 cp [Btu/lbmR] 1.69 0.3 6.11 0.000 k 1.31 0.08 0.00 0.003 R [Btu/lbmR] 0.3563 0.3 6.11 0.000 Performance Parameter Value Total ΔPower [%] Total Δη [%] Pactual [hp] 8704 1.35 1.81 Efficiency, η [%] 0.636 1 Qa i actual flow rate at uction condition, v=65.6 ft/ in a 30" diameter pipe. Z, cp, k and R repreent a typical hydrocarbon tranmiion grade ga. 3 Typical value of uncertainty repreent ideal preure and temperature meaurement uing four enor on uction and dicharge, recommended flow meter intallation and ga property calculation made with conitent EOS model and accurate ga ample. Table 1a. Ideal Intallation for Ga Turbine Total Uncertainty Calculation SI Unit Cae 1: Ideal Cae Input Input Parameter Value Δ[%] 3 Δ Power-in Δ η Mf, Fuel Flow [kg/] 1 0.60 1 300 0.00 HV, Heating Value [kj/kg] 50000 0.3 90 0.001 Power-out [kw] 63 1.35 0 0.003 Performance Parameter Value Power-in [kw] 30000 Total ΔPower [%] Total Δη [%] Turbine Efficiency 0.07 1.04 1.71 1 Fuel flow i given a a ma flow for typical natural ga. Power out i delivered power of turbine = aborbed power for centrifugal compreor. 3 Input fuel flow i typical for volumetric meter with denity converion or orifice meter. Input heating value i typical due to ga ampling / ga chromatograph. Output power uncertainty baed on calculated power uncertainty of compreor for ideal cae. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 36

Table 1b. Ideal Intallation for Ga Turbine Total Uncertainty Calculation Englih Unit Cae 1: Ideal Cae Input Input Parameter Value Δ[%] 3 Δ Power-in Δ η Mf, Fuel Flow [lbm/] 1 1.3 1 40 0.00 HV, Heating Value [Btu/lbm] 1496 0.3 11 0.001 Power-out [hp] 8345 1.35 0 0.003 Performance Parameter Value Power-in [hp] 408 Total ΔPower [%] Total Δη [%] Turbine Efficiency 0.07 1.04 1.71 1 Fuel flow i given a a ma flow for typical natural ga. Power out i delivered power of turbine = aborbed power for centrifugal compreor. 3 Input fuel flow i typical for volumetric meter with denity converion or orifice meter. Input heating value i typical due to ga ampling / ga chromatograph. Output power uncertainty baed on calculated power uncertainty of compreor for ideal cae. 5. Effect of Non-Ideal Intallation on Uncertainty Deviation in the ideal tet condition or procedure (a recommended previouly) will increae the individual meaurement uncertaintie and reult in a higher total performance meaurement uncertainty for the compreor and ga turbine. Depending upon the effect of the non-ideal intallation on the meaurement, the reulting increae in uncertainty can range from a mall increae of 0.0% in ome cae to above 5.0%, in either efficiency or power. Some typical non-ideal effect are lited in Table 13 through 15. The reulting increae in total uncertainty i hown in thee table, baed upon the example tet cae decribed in Section 5.1. Table 13 illutrate the effect of non-ideal temperature and preure meaurement for the previouly decribed pipeline compreion example. The increae in uncertainty in the temperature or preure meaurement i primarily due to non-uniformitie in the compreor uptream or downtream flow field when le than four enor are ued. For a uniform flow field where the uptream and downtream traight pipe length meet the intallation requirement of ASME PTC 10, the increae in temperature or preure meaurement uncertainty i uually not a evere a hown in Table 13. However, conervative wort cae aumption hould be ued for uncertainty calculation. Other frequently encountered non-ideal effect in compreor teting are lited in Table 14. Table 15 provide ome example of non-ideal effect that could occur in the ga turbine performance tet for the ubject pipeline compreion example. The common departure from an ideal tet are principally due to field tet intallation with inufficient uptream length involving a ingle elbow or double elbow directly uptream of the flow meaurement point or temperature/preure enor. In the non-ideal cae where uptream diturbance affected the flow meaurement, an additional uncertainty wa aumed for the flow meter baed on publihed literature. Thee table give the increae in uncertainty for each meaured property and the additional compreor uncertainty, for the typical baeline cae preented in Table 11(a-b). Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 37

Table 13. Effect of Non-Ideal Temperature or Preure Meaurement Increae in Compreor Power Uncertainty (Additional uncertainty above baeline Δ = 1.35%) No. of RTD' / Preure Senor 4 3 1 Suction Temperature (T) 0 0.64 1.41. 1 Dicharge Temperature (Td) 0 0.5 1.17 1. 86 Suction Preure (P) 0 0.0 0.04 0. 07 Dicharge Preure (Pd) 0 0.0 0.04 0. 07 Increae in Compreor Efficiency Uncertainty (Additional uncertainty above baeline Δ = 1.81%) No. of RTD' / Preure Senor 4 3 1 Suction Temperature (T) 0 0.53 1. 1.95 Dicharge Temperature (Td) 0 0.53 1. 1.95 Suction Preure (P) 0 0.14 0.9 0. 46 Dicharge Preure (Pd) 0 0.14 0.9 0. 46 Table 14. Non-Ideal Intallation Effect on Compreor Uncertainty. Non-Ideal Intallation Single elbow 1-3 pipe diameter uptream of flow meaurement point (no flow conditioner) Double elbow in-plane, econd elbow 1-3 pipe diameter uptream of flow meaurement point (no flow conditioner) Double elbow out of plane, econd elbow 1-3 pipe diameter uptream of flow meaurement point (no flow conditioner) Partially cloed gate or ball valve within 1-3 pipe diameter uptream of flow meaurement point (no flow conditioner) Single elbow within 1-3 pipe diameter of temperature and preure enor Total ΔPower (%) Deviation from Baeline Δ Power Total Δη (%) Deviation from Baeline Δη 1.73 0.38 1.81 0 1.95 0.60 1.81 0.79 1.44 1.81 0 3.7.37 1.81 0.39 1.04.85 1.04 Double elbow in-plane, econd elbow within 1-3 pipe diameter of temperature and preure enor Double elbow out of plane, econd elbow within 1-3 pipe diameter of temperature and preure enor 3.19 1.84 3.66 1.85 4.84 3.49 5.37 3.56 RTD not fully inerted into flow tream.37 1.0.66 0.85 Ue of thermocouple intead of RTD 3.15 1.8 3.38 1.57 Error in ga ampling (no pigtail ued) with heavy hydrocarbon ga 1.38 0.03.01 0. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 38

Table 15. Non-Ideal Intallation Effect on Ga Turbine Uncertainty. Non-Ideal Intallation Single elbow 1-3 pipe diameter uptream of fuel ga flow meter (no flow conditioner) Double elbow in-plane, econd elbow 1-3 pipe diameter uptream of fuel ga flow meter (no flow conditioner) Double elbow out of plane, econd elbow 1-3 pipe diameter uptream of fuel ga flow meter (no flow conditioner) Partially cloed gate or ball valve within 1-3 pipe diameter uptream of fuel ga flow meter (no flow conditioner) Error in fuel ga ampling procedure or ga compoition analyi of 1.0%-3.0% in denity Total ΔPower-in (%) Deviation from Baeline ΔPowerin Total Δη (%) Deviation from Baeline Δη 1.4 0.4.0 0.3 1.7 0.7. 0.5.7 1.7 3.0 1.3 3.7.7 4.0. 1.5-3.4 0.4-.3.0-3.6 0.3-1.9 Error in Power-out of.0-5.0% 1.0 0.0 3.5-6.4 1.8-4.7 Other non-ideal effect typically een at a field ite include non-recommended ga ampling procedure, flow meter error, or temperature enor intallation error. Note that an error in the ga ample or ga compoition will affect the ga propertie uncertaintie ued in calculating compreor power (a hown in Table 11(a-b)) but may alo affect the flow meaurement uncertainty, if the denity i ued to convert ma flow to volumetric flow. A Table 13 through 15 illutrate, non-ideal intallation will affect the overall performance meaurement uncertainty ignificantly. 6. INTERPRETATION OF TEST DATA 6.1 Data Reduction and Checking Uncertaintie Averaging of temperature, preure, and flow from different tet point taken at different point in time hould be avoided a the non-linear effect will not be averaged correctly. Intead, an average of the reulting performance parameter (flow coefficient, head coefficient, efficiency, etc.) hould be calculated once the performance reult have been computed for each data point. Data reduction procedure hould be aimed at minimizing time and cot in the determination of performance. If the tet data from the field tet deviate more than the level of tet uncertainty, the ource of the deviation hould be explored further. Repeating the performance tet i not recommended by thi guideline unle the data i clearly un-uable. Data taken during a field tet hould be corrected to common datum condition. For the ga compreor, Mach number and volume/flow ratio difference can caue coniderable deviation in the overall performance of the compreor. The prediction procedure hould be repeated for actual condition. If the head veru flow curve ha hifted horizontally, the flow may have been meaured incorrectly or contain a bia error. If ome of the point on the curve match prediction and other do not, the ga compoition (or another influential parameter) may not have been table during the tet. A hift toward lower efficiency or head i often caued by worn compreor eal. For the ga turbine, eparate calculation of power can be ued to check the data. The power calculated uing the ga compreor power hould be checked againt the predicted power from the initial factory tet data. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 39

6. Generation of Performance Curve from Recorded Data Point Each data point recorded during the field tet hould be evaluated individually. The average of all data point at a particular condition hould be ued to compute the average head, flow, and efficiency. Two method may be applied to the data reduction procedure in order to determine the centrifugal compreor performance curve. The firt method ue linear interpolation between the individually meaured ientropic head data point and meaured efficiencie. Thee two interpolation provide a curve for the a-teted efficiency and ientropic head. The aborbed power i calculated baed on the a-teted ientropic head and efficiency curve. At the flow rate condition of interet, the predicted ientropic head, efficiency, and power may be determined baed on the field tet data point. The econd method relie on the non-dimenional head and flow coefficient. The tet point are plotted for the head coefficient veru flow coefficient map and the flow coefficient veru efficiency map. A data fit curve i determined (linear or polynomial). At the flow coefficient value of interet, the correponding point on the curve fit for efficiency and head coefficient i found. The peed needed to meet the head coefficient and flow coefficient value i obtained. The teted aborbed power hould be calculated according to the mechanical efficiency, the ma flow at the flow point of interet, the head at the flow point of interet, and the determined tet efficiency: P tet H i = ηmwi (6.1) ηtet 6.3 Standardized Uncertainty Limit ASME PTC 10 provide uncertaintie a a guideline for acceptable uncertainty limit in factory teting. However, thee uncertainty limit are generally not realitic in a field etting and hould, therefore, not be utilized. The uncertainty calculation method decribed in thi guideline hould be employed to calculate the actual field teting uncertainty, with the goal of minimizing thee uncertaintie whenever poible. 6.4 Uing Redundancy to Check Tet Meaurement and Uncertainty Redundant calculation hould be performed, if poible, to check tet meaurement. The ga turbine driver full load performance hould be known baed on factory teting. The compreor haft power meaurement during the field tet hould match thi value, if the engine can be run at full load output during the field tet. Similarly, the ga turbine fuel flow meaurement may be checked againt the heat rate. Ue of the indirect meaurement for ga turbine power input to the compreor may be ued to check the direct meaurement of haft power or generator power, whichever i ued in the field tet. The calculated value or factory tet (manufacturer upplied) value hould match the meaured value within the aociated uncertainty for both value. The uncertainty on any meaured value obtained in the field tet hould be calculated (or etimated a accurately a poible). Thi uncertainty will be a plu or minu value. It hould overlap with the uncertainty band (alo a plu or minu) on the calculated/factory tet value. Thi analyi will determine if the redundant meaurement i tatitically equal to the meaured value. Thi method of comparion hould alway be ued in order to practically determine if meaured value are correct. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 40

6.5 Effect of Fouling on Tet Reult The ga turbine hould be thoroughly cleaned prior to a field tet. Fouled compreor blade can caue deviation in predicted ga turbine power of more than 3%. Like any prime mover, a ga turbine i uceptible to the effect of wear and tear. The problem i in predicting the effect of degradation on the engine after many hour of operation. Power and efficiency (and related peed and firing temperature) are the evident indicator of fouling or degradation of the ga turbine. On driven equipment, uch a the centrifugal compreor, the increaed clearance in labyrinth eal, balance piton eal and hroud eal will caue the aborbed power to increae. On high-preure ratio machine with low flow, worn balance piton eal will caue a ignificant increae in power becaue of the increaed balance piton recirculation caued by the eal (Kurz and Brun, 001). 6.6 Analyi of Meaured Reult The true value of the compreor performance parameter (head, efficiency, and power) and the ga turbine performance lie within the meaured data point, auming the data ha been recorded correctly without a ignificant bia error. The meaured data point hould be viewed a a repreentation of the bracket urrounding the true value. If the meaured head and meaured flow data point are plotted on an x- and y-axi, an uncertainty band on each meaured head and meaured flow exit. An ellipe urround the meaured data point (ee Figure 9). The predicted performance tet point or manufacturer factory tet curve may lie within the uncertainty band produced from the field tet, though the exact value from the field tet do not exactly match the manufacturer uggeted curve. Thi example hown in Figure 9 how good performance of the compreor during the field tet. The compreor performance in the field tet i tatitically equal to the factory tet in thi example (Kurz and Brun, 005). Predicted Performance Tet Point Head Coefficient Tet point and repective uncertainty ellipe Flow Coefficient Figure 9. Example of Tet Uncertainty Range 7. OTHER FIELD TESTING CONSIDERATIONS The additional recommendation included in thi ection highlight the importance of undertanding influential tet parameter and provide conideration for teting under wet ga condition. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 41

7.1 Determination of Influential Tet Parameter The determination of influential tet parameter hould be ued to ae the meaurement parameter in order to improve the accuracy of the field tet. The uncertainty analyi can be ued to determine the influential tet parameter. The term in the total uncertainty equation can be compared at different operating condition. If the comparion reveal that a certain term become more ignificant to the overall uncertainty, then extra effort to improve thi meaurement will be worthwhile. 7. Field Teting of Compreor Under Wet Ga Condition Wet ga condition will negatively influence the accuracy of the tet, a well a the correct comparion of the tet data with data gathered with dry ga. Tet reult may ignificantly deviate from prediction, if the tet ga i not completely dry. Relative to a dry compreor, the field tet with wet ga condition will reult in a higher-preure ratio becaue of the increaed ga-volume fraction. The increaed preure ratio i a reult of heavier ga. A decreaed temperature ratio i to be expected a well becaue of the tranfer of energy from the ga to the liquid phae and the limited condenate phae tranition (Brenne et al., 005.) The ue of the polytropic head coefficient and the polytropic efficiency i recommended in dealing with wet ga condition. The pecific volume of ga-liquid mixture may be treated a a combined homogenou fluid or a two fluid model. Either approach i valid, though the phae tranition contribution i aumed to be negligible. For multi-tage compreor with a high-preure ratio, thi aumption may not be valid. Similarity variable for the compreor will need to be compenated by the correct two-phae term. The modified thermodynamic equation for the two-phae head and flow coefficient are given in Appendix D. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 4

8. REFERENCES ASME PTC 10, Compreor and Exhauter, American Society of Mechanical Engineer, New York, New York, 1997. ASME PTC 19.1, Meaurement Uncertaintie, American Society of Mechanical Engineer, New York, New York, 1985. ASME PTC, Ga Turbine Power Plant, American Society of Mechanical Engineer, New York, New York, 1997. Brenne, L., Bjorge, T., Gilarranz, J. L., Koch, J. M, and Miller, H. Performance Evaluation of a Centrifugal Compreor Operating Under Wet Ga Condition, Proceeding of the Thirty-Fourth Turbomachinery Sympoium, Houton, Texa, 005. Brown, R. N. Fan Law, the Ue and Limit in Predicting Centrifugal Compreor Off Deign Performance, Proceeding of the Twentieth Turbomachinery Sympoium, Turbomachinery Laboratory, Texa A&M Univerity, College Station, Texa, 1991. Brun, K. and Kurz, R. Meaurement Uncertaintie Encountered During Ga Turbine Driven Compreor Field Teting, Journal of Engineering for Ga Turbine and Power, Tranaction of the ASME, Vol. 13, pp. 6-69, January 001. Cooper, G. M. Hydraulic Shop Performance Teting of Centrifugal Compreor, Proceeding of the Thirty-Fourth Turbomachinery Sympoium, Houton, Texa, 005. Edmiter, W. C. and Lee, B. I. Applied Hydrocarbon Thermodynamic Volume 1, Second Edition, Gulf Publihing Company, Houton, Texa, 1984. Huntington, R. A., Evaluation of Polytropic Calculation Method for Turbomachinery Performance, ASME Journal of Engineering for Ga Turbine and Power. ISO 314, Ga Turbine Acceptance Tet, International Standard Organization, Second Edition, 1989. ISO 5389, Turbocompreor Performance Tet Code, International Standard Organization, Second Edition, 005. Kumar, S. K., Kurz, R., O Connell, J. P. Equation of State for Compreor Deign and Teting, ASME Paper No. 99-GT-1, 1999. Kurz, R. and Brun, K. Site Performance Tet Evaluation for Ga Turbine and Electric Motor Driven Compreor, Proceeding of the Thirty-Fourth Turbomachinery Sympoium, Houton, Texa, 005. Kurz, R. Turbomachinery Tet Data and What to Do With It, Ga Machinery Conference 00, Nahville, Tenneee. Kurz, R. and Brun, K. Degradation in Ga Turbine Sytem, Journal of Engineering for Ga Turbine and Power, Tranaction of the ASME, Vol. 13, pp. 70-77, January 001. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 43

Kurz, R., Brun, K., Legrand, D. D. Field Performance Teting of Ga Turbine Driven Compreor Set, Proceeding of the Twenty-Eighth Turbomachinery Sympoium, Texa A&M Univerity, College Station, Texa, 1999. McKeon, B. J. and Smit, A. J., Static Preure Correction in High Reynold Number Fully Developed Turbulent Pipe Flow, Meaurement Science and Technology, Intitute of Phyic Publihing, September 00. Moffat, R. J. Decribing the Uncertaintie in Experimental Reult, Experimental Thermal and Fluid Science, Vol. 1, pp. 3-17, 1988. Poling, B. E, Praunitz, J. M. and O Connell, J. P. The Propertie of Gae and Liquid, Fifth Edition, McGraw-Hill, 001. Riazi, M. R. Characterization and Propertie of Petroleum Fraction, ASTM, Wet Conhohocken, PA, USA, 005. Sandberg, M. R. Equation of State Influence on Compreor Performance Determination, Proceeding of the Thirty-Fourth Turbomachinery Sympoium, Houton, Texa, 005. Sapiro, L., Advantage and Limitation of Factory Aerodynamic Compreor Tet: Open Loop and Cloed Loop. Schubring, S. and Munoz, I. Field Performance Teting from an Operator Point of View, Ga Turbine Uer Sympoium 005, La Vega, Nevada, 005. Shaw, R., The Influence of Hole Dimenion on Static Preure Meaurement, Journal of Fluid Mechanic, 1960. Schultz, J. M. The Polytropic Analyi of Centrifugal Compreor, Journal of Engineering for Power, Tranaction of the ASME, pp. 69-85 and p., January 196. VDI 045, Acceptance and Performance Tet on Turbo Compreor and Diplacement Compreor, Verein Deutcher Ingenieure e.v., Dueldorf, Germany, 1993. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 44

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APPENDIX A METHODS OF CALCULATING GAS TURBINE POWER Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 46

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APPENDIX A If a field tet i conducted uing the ame tandard a for a factory tet, the field teting of the ga turbine will typically yield higher tet uncertaintie than the factory tet. The main reaon for thi lie in the methodology of meauring the input turbine power. In a factory, haft power i meaured by running the ga turbine againt a generator, a dynamometer, or a water brake. The power turbine applie torque directly to the generator, dynamometer, or water brake. The aborbed power i accurately meaured with a load cell or other method. In a field tet, haft power i determined in one or more of the following way: 1. Direct meaurement: Uing a torque meauring coupling between power turbine and driven equipment (high accuracy, mall uncertainty).. Direct meaurement: Uing the meaured output of the generator (high accuracy, mall uncertainty). 3. Indirect meaurement: Uing the calculated power of the driven compreor (ee below) (high uncertainty due to uncertainty in aerodynamic power of compreor). 4. Indirect meaurement: Verifying with a redundant meaurement, uch a a heat balance (high uncertainty due to meaurement of air flow). Field tet with a torque metering coupling (method 1) or a driven generator can achieve accuracie imilar to factory tet method. The generator electrical power output (method ) can be meaured directly at the generator terminal with the proper intrumentation. Thee two method are the mot accurate a they are direct meaurement. Uing the power input into the driven compreor to determine ga turbine power (method 3) i ubject to much higher meauring uncertaintie, becaue of the indirect method of meaurement. Calculation of ga turbine haft power uing method 3 require the aerodynamic power of the compreor, the mechanical efficiency, and any loe in the gearbox (if preent). The ga turbine power output i then determined from the following: Pg P = + P η m GB (A.1) Where: P g = aerodynamic or ga power delivered by the proce compreor η m = mechanical efficiency of the compreor, typically given by the manufacturer a 98 to 99% of the aborbed power of the compreor (P C ) P GB = loe in the gearbox The fourth method take advantage of the conervation of energy in a thermodynamic ytem, requiring the energy flowing into the ytem be balanced by the energy leaving the ytem: ( w1 + w f ) h + P + Er Em w + 1h1 + w f LNV η comb + w f h f = 7 (A.) The ma flow and enthalpy of the air at the ga turbine inlet (w 1 h 1 ), a well a the fuel flow and fuel enthalpy (w f h f ), lower heating value (LHV) of the fuel, and the enthalpy of the exhaut ga (h 7 ) can be meaured. The radiated heat energy (E r ) and the mechanical loe (E m ) leaving the ytem a heat tranferred to the lube oil can be etimated but will be mall. The combution efficiency (η comb ) can be Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 48

etimated a well and i typically about 99% or better. Therefore, the haft power of the turbine (P) can be calculated from the above equation. For thi field method, it i eential to meaure the airflow through the ga turbine, which uually i not poible in the field with ufficient accuracy for precie tet reult. However, the equation i ueful to verify one of the three other method becaue mot of the ga turbine characteritic, including airflow veru ga producer peed, are recorded during factory teting. Thu, it i poible to ubtitute parameter that cannot be meaured in the field with information gathered during a factory tet. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 49

APPENDIX B EQUATIONS OF STATE Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 50

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APPENDIX B The following explanation of the equation of tate model i taken from Equation of State for Ga Compreor Deign and Teting by Kumar, Kurz and O Connell, 003. While the operating condition for ga compreor are typically defined in term of preure, temperature, and ma or tandard flow, the relevant data that decribe the behavior of a compreor are the head (H), which i related to the work input, the volumetric flow (Q) and efficiency (η), which compare the real proce to an ientropic proce between the ame inlet tate and outlet preure. The head, or pecific enthalpy difference between two tate (e.g., inlet and dicharge ide of the compreor), i defined by: ( p T,{} y ) h( p, T { y} H = h, ) (B.1), 1 1 The enthalpy (h) i a function of preure, temperature, and ga compoition defined through a et of mole fraction (y}. The actual aborbed power (P ga ) involve the ma flow rate (W): P ga = WH (B.) The ma flow rate i obtained from the actual or volumetric flow rate (Q) and the ga denity (ρ): The denity i found from the temperature (T) and preure: W = ρq (B.3) (p) with the compreibility factor (Z). When Z differ from unity, the ga i not ideal and it value i a: ρ = p/zrt (B.4) function of T, p, and ga compoition. The reult of thee definition i that P ga i found from: p P ga = ρ QH = QH (B.5) ZRT In order to define the quality of the compreion proce, H i uually compared to the head for an ideal compreion proce, which i defined a compreion between the ame inlet T 1 and p 1 and outlet p, with the outlet temperature being fictitiou T : Δ ( p T,{} y ) ( p, T { y} ) 0 =, 1 1 = (B.6) Thi ientropic change of tate define an ientropic head, H i, uch that: H ( p, T,{} y ) h( p T { y} ) = h (B.7) 1, 1 The quality or efficiency of the compreion i defined by: Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 5

H η = (B.8) H Compreor characteritic, in term of head veru flow and efficiency veru flow, are found by comparing tet data, taken with tet gae uch a Nitrogen, with reult obtained from the thermodynamic calculation above. The characteritic can later be ued to calculate the performance of the compreor under arbitrary condition of preure, temperature, and ga compoition. A long a the ame EOS i ued for obtaining compreor performance prediction and data reduction, error are minimized. An EOS i a relation among variable of a fully pecified ytem: T, p, ρ and the N-1 component mole fraction y i (Alberty and Silbey, 1997). Thi i uually expreed in the form: Z = Z (ρ, T, {y}) (B.9) ince in a multiphae region, multiple value of ρ give the ame value of p. Thermodynamic give rigorou relation for enthalpy and entropy difference from derivative and integral of Z from any EOS and ideal ga pecific heat, C 0 p. A ga i aid to be in a pecified tate if it ha zero degree of freedom. The degree of freedom are the number of propertie that can be arbitrarily et before all other propertie become pecified. The formula for the degree of freedom of N nonreacting gae i: DF = N # phae + (B.10) In ga compreor deign calculation, only one phae exit and the ga compoition i uually pecified, o two more degree of freedom mut be choen. Generally, p and T are pecified and the number of phae i alway one. Then, all other thermodynamic propertie are fixed and calculated via an EOS. Since real ga behavior commonly play a role in ga compreor, knowledge of the relationhip between preure and temperature, on one hand, and enthalpie, entropie and denitie, on the other hand, i of great importance in compreor deign, their performance under arbitrary operating condition, and tet data reduction. Epecially during ga compreor performance tet, the election of a particular EOS can have an important effect on the apparent efficiency and aborbed ga power. Thermodynamic Approach In order to decide on the mot appropriate (EOS) to be ued for deigning and teting ga compreor for natural ga application, five frequently applied EOS were tudied: original Redlich-Kwong, Redlich- Kwong-Soave, Peng-Robinon (Reid et al., 1986), Lee-Keler-Ploecker (Ploecker et al., 1978) and Starling verion of the Benedict-Webb-Rubin model (Starling, 1973). The variation in entropy or enthalpy between two tate of a ga or mixture, each defined by a temperature and preure, i independent from the path choen from one tate to the other (Reid et al., 1986). A convenient path involving three tep of changing the real ga to an ideal ga at T 1, changing the ideal ga from T 1 to T and changing the ideal ga back to the real ga at T (Figure B-1). Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 53

T T1 Iotherm Preure Zero preure Enthalpy Figure B-1. Calculation Path for Equation of State h = dh = h ( h / p) dp + ( h / T ) = ( h / p) + ( h T ) h h1 = / h f ( p, T ) 1 p p1 T T T 0 0 ( h h ) + c dt ( p1 T1 T T1 p T1 p dt p h 0 DT h ) p T (B.11) The term in the parenthee of equation (B.11) are called departure function, real ga contribution, or reidual propertie, which relate the enthalpy at ome p and T to that at an ideal ga reference tate at T, H 0. Thee departure function can be calculated olely from the EOS. The ame approach can be ued for the entropy. The ideal ga law i baed on the aumption that the molecule of the ga do not interact with each other or that there i no attractive or repulive force between two molecule. The heat capacity of a ga i the amount of energy, which the ga need to aborb before it temperature increae one unit. For an ideal ga, the heat capacity C 0 p i a function only of T. An empirical equation for the ideal ga heat capacity can be tated a a polynomial, e.g., third order polynomial: 0 C p = A + BT + CT + DT 3 (B.1) A, B, C, and D are empirical parameter or contant baed on the type of ga being analyzed. Once an equation for C 0 p i found, the ideal ga enthalpy change, which i the change in total energy in the ga a it goe from tate one to tate two, can be found by: Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 54

Δ h 0 T = T1 C p dt (B.13) Even for an ideal ga, the entropy change depend upon the initial and final temperature and preure. The entropy change i expreed by: 0 T C p P Δ = S dt R ln (B.14) T1 T P1 When calculating the enthalpy or entropy of a given tate, an arbitrary reference tate mut be elected whoe enthalpy and entropy are et to zero. The enthalpy and entropy for a given tate i calculated relative to thi reference. Therefore, any abolute value of the enthalpy or entropy of a ga at a given tate ha no real meaning, given it dependence on the reference tate. However, when the enthalpy difference between two tate i calculated, the reference tate cancel out, o an enthalpy or entropy difference i an actual value that doe not depend on the reference tate. Functionality of Equation of State The departure function for enthalpy and entropy for each of the five EOS can be found in the literature (Reid et al., 1986; Peng and Robinon, 1976; Ploecker et al., 1978; and Starling, 1973). Herein, the RK, RKS, and PR EOS are referred to a cubic. In equation (B.15), Z repreent the compreibility factor of the ga, defined a: pv Z = (B.15) RT The quantitie X and Y are two other type of compreibility factor ued in compreor deign. The formula for each: Y X p Z = 1 (B.16) Z p T T Z = (B.17) Z T The calculation of the molecular weight and the heat capacity at given temperature of the ga mixture i completed by uing the following mixing rule: ~ MW = ~ C = p y y MW i i C Pi i (B.18) MW i and y are the molecular weight and mole fraction of each component in the mixture. The heat capacitie are divided by R to make them dimenionle, o when the linear function i found at a given temperature, the reult hould be multiplied by R in the deired unit to get the heat capacity in thoe unit. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 55

The linear function for ideal Cp 0 /R i calculated uing the Cp 0 /R value at 10 and 149 C (50 and 300 F). Thee two point are ued to find the lope of a traight line on a Cp 0 /R veru temperature plot. Thi lope i ued to olve for the y intercept of the following imple linear equation: 0 c p = CT B R + (B.19) Finally, the pecific gravity (SG) and the real ga parameter (RG) are calculated. SG i calculated relative to the molecular weight of air: ~ MW SG = (B.0) 8.964 The RG parameter i given by: 0.87kJ / kgk R G = (B.1) SG The Redlich-Kwong and Peng-Robinon model are cubic equation of tate. The LKP equation i like the BWRS, a modification of the original BWR EOS. The LKP EOS ha mixing rule that are very different from the cubic. The Starling verion (BWRS) of the original BWR EOS added three extra parameter for improving the temperature dependence of the eight parameter form. Thee parameter mut be found for each pure ga. There alo are mixing rule for the 11 parameter (Starling, 1973). For the cubic EOS, an analytical method can be ued to olve for the three root of ρ, thu, yielding Z. There are three root to any cubic equation; however, when Tr >1 only the larget real root ha any phyical ignificance. After Z i calculated, the X and Y compreibility factor, along with pecific heat, are calculated. For the LKP and BWRS model, Z i found by an iterative method. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 56

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APPENDIX C UNCERTAINTY ANALYSIS OF INDEPENDENT VARIABLE MEASUREMENTS Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 58

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APPENDIX C Prior to determining a tet uncertainty, it i important to know whether the meaured variable in the tet are independent or dependent a thi determine the method of uncertainty calculation that mut be employed. For almot all real meaurement cenario, there i ome phyical dependency between the input variable and, thu, unle one i abolutely certain that all meaured and given ytem input are independent, it i afer to opt for the more conervative aumption of meaurement dependence. If the meaured variable in an experiment are truly found to be independent, then the method to determine total uncertainty i imply an addition of all individual meaurement uncertaintie. Thi i mathematically expreed a: ΔF = n Δx1 + Δx + Δx3 +... Δx n = Δx i (C.1) i= 1 where ΔF i the total reult uncertainty and Δx are the individual meaurement uncertainty range. Thi i the abolute value method rather than quare root of the um of quare method, which i more commonly utilized (a hown in C.). The abolute value addition preent a true uperpoition of individual uncertaintie rather than a blended um. Thi method yield more conervative uncertainty reult than the quare-root-um method, but both approache are generally acceptable for uncertainty analye. Δ V = Δx + Δx + Δx3 + Δx (C.) 1... n Uncertainty Analyi for Independent Variable Meaurement If the meaured variable in an experiment are dependent, which i uually the cae, then the analyi become more complex. Specifically, the individual meaurement uncertaintie, Δx, are now functionally related and thi mut be accounted for in the analyi. There are three method that are commonly ued by modern engineer for thi type of uncertainty analyi: Partial Derivative Method Coefficient Method Perturbation Method All three method are baed on a functional tranfer from input to output variable but employ a different approach to the determination of the proper tranfer function. The Partial Derivative Method The mot traditional method for uncertainty calculation i baed on determining the tranfer function uing a partial derivative and adding the individual uncertainty tranformation. Namely, ΔF = ΔF( Δx ) + ΔF( Δx = Δx 1 F x 1 1 + Δx F x ) + ΔF( Δx + Δx 3 F x 3 ) +... ΔF( Δx ) 3 +... Δx n F x n n = n Δx F x i i= 1 i (C.3) Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 60

To undertand thi method, one mut analyze the principal term F Δ xi and derive ome baic x phyical undertanding. Figure C-1 how a graphical interpretation of the functional tranformation from range Δx to ΔF uing thi term. Effectively, the input range Δx i multiplied by the lope of the function F at the meaurement point x 1, x, x 3, etc., to determine the ΔF output range. Thi aume that the function F i linear over the interval Δx from the pecified meaurement point, which i a reaonable aumption for mall Δx and any linear functional form. However, few phyical law are linear over a wide range and, thu, thi method will be inaccurate for teeply loped function combined with large individual meaurement uncertaintie. Alo, thi method aume that the function F i in an algebraic form that can be readily differentiated. Thi i obviouly not alway the cae a many phyical governing equation include ordinary and partial differential term. i Figure C-1. Determination of Uncertainty uing Differential Method Coefficient Method F Clearly, the above partial differential can be determined numerically uing a imple forward x 1 difference approach. Thi i commonly called the coefficient method and i hown below. c i = F i x i = F( x ) F( x i Δx i i + Δx ) i (C.4) and ΔF = c1 Δx1 + c Δx + c3 Δx3 +... c Δx = c Δx (C.5) n n n i= 1 i i Both the partial derivative and coefficient method hould yield identical anwer when properly applied. Again, a long a Δx i mall and the lope of the function F i moderate, thi approach will yield Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 61

reaonably accurate uncertaintie. A light variation of thi approach center the numerical derivative around x, pecifically: c i F = x = F( x 0.5Δx) F( x + 0.5Δx) Δx (C.6) Thi modified method often provide an improved determination of the uncertainty for meaurement centered ditribution. Unfortunately, for convenience, the coefficient method i often miapplied by auming fixed coefficient for a tandard analyi. A number of well etablihed engineering code and pecification publih fixed number for uncertainty coefficient of tandard engineering analyi problem. Thi approach can only be valid if the actual phyical equation i trictly linear, which i eldom the cae. Alo, unle all unit of meaurement are identical to thoe of the publihed coefficient, largely incorrect uncertainty reult will be obtained. Perturbation Method The mot accurate analyi to determine total uncertainty of dependent variable meaurement ytem i the perturbation method, a it i baed on the actual function F and doe not require any linearity aumption. It i imply expreed a: ΔF = ΔF( Δx ) + ΔF( Δx = = F( x ) F( x n i= 1 1 F( x ) F( x i 1 1 + Δx ) + F( x i 1 + Δx ) i ) + ΔF( Δx 3 ) F( x ) +... ΔF( Δx ) + Δx n ) + F( x 3 ) F( x 3 + Δx 3 ) +... F( x n ) F( x n + Δx ) n (C.7) The term F x ) F( x + Δ ) i graphically reviewed in Figure C- and demontrate that the ΔF ( 1 1 x1 uncertainty obtained uing thi method i the actual tranformation of Δx. Figure C-. Determination of Uncertainty Uing Perturbation Method Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 6

The variation of parameter method i implemented by equentially perturbing the input value (temperature, preure, etc.) by their repective uncertaintie and recording the effect on the calculated output quantity (i.e., efficiency, power, etc.). Auming the uncertainty perturbation i fairly mall, any term in equation (C.8) can be determined in thi manner: f Δ u ) (C.8) ( u 1 + Δu 1 ) f ( 1 1 f u u1 The contribution of the variable u 1 toward the overall uncertainty can be determined by calculating f twice at the oberved value at u 1 and at the perturbed value of u 1 + Δu 1. For everal variable, the reult for each term hould be ummed uing the quare-root-um or abolute value of the individual term. The benefit of thi approach are that it doe not matter if the uncertainty i an abolute or relative number, the procedure can be implemented uing any preadheet program, and the value in the preadheet can be the reult of complex, iterative relationhip. Implementation of the Partial Derivative Method for Compreor The partial derivative method wa decribed in detail by Brun and Kurz [ASME Journal of Engineering for Ga Turbine and Power, 001]. The implementation for both compreor and ga turbine i briefly decribed herein: For the pecific heat uncertainty, Δc p i obtained: R ΔZ L MW Univeral R + ΔL L Univeral MW Z + ΔMW R Univeral L MW Z (C.9) The above equation (C.9) i valid if the phyical ga propertie, pecific heat ratio, compreibility factor, and molecular weight are directly determined from teting. A phyical property uncertainty, due to the effect of applying uncertaintie in T and p to the non-ideal ga tate equation ha to be included; i.e., ince there i a meaurement error in T and p, there will be an added error in determining c p from the ga equation. Thi uncertainty i mot conveniently obtained numerically by varying temperature and preure parametrically in the ga equation and, thu, determining the gradient dγ/dt, dγ/dp, dz/dt, and dz/dp indirectly. Recognizing that dγ/dt = dl/dt and dγ/dp = dl/dp, one can eaily determine correction for ΔZ and ΔL: ΔZ = ΔT γ T + Δp γ p (C.10) Δ Z Z Z = ΔT + Δp (C.11) T p The uncertainty in c p, i alo affected by the variation of the ga propertie during the duration of the tet. Thi effect i again mathematically difficult to decribe but can be eaily handled numerically uing a procedure imilar to the one hown above for the variation in T and p. It i beyond the cope of thi paper to lit all poible ga compoition variation; however, it i important to realize that they can trongly affect Z, L, and MW. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 63

The uncertainty of the compreor head i determined uing equation (C.11). Since the head uncertainty i not dependent on the abolute temperature, but rather on the temperature difference (T d T ), and ince the pecific heat (c p ) for the dicharge and uction are functionally related, the temperature difference (T d T ) hould be employed for the derivation rather than the abolute temperature value (T d, T ). ( ) ( ) ( ) ( ) p d p d d p T c T T c T T T c H Δ + Δ + Δ = Δ (C.1) The uncertainty for the ientropic (ideal) compreor outlet temperature i obtained uing equation (C.1). Ientropic Temperature 1 1 * Δ + Δ + Δ = Δ + L L d L L d d L d d p p LT p p p LT p p p T T (C.13) The uncertainty of the compreor efficiency i given in equation (C.15). The temperature difference hould be ued rather than the abolute temperature value for the derivation of the ientropic enthalpy given in equation (C.14). Ientropic Enthalpy ( ) ( ) ( ) ( ) * * * * d pt pt d d p c T c T T T c h Δ + Δ + Δ = Δ (C.14) Ientropic Efficiency * * * Δ + Δ = Δ H h H H h η (C.15) Ma Flow Δ + Δ = Δ Univeral Univeral ZT R Q p MW ZT R Q MW p W Δ + Δ + Univeral Univeral T Z R Q MW p Z ZT R MW p Q Δ + Univeral ZT R Q MW p T (C.16) Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 64

Power ΔP = W ΔH η M H + ΔW ηm + Δη M H W η M (C.17) The flow rate uncertainty, ΔQ, depend trongly on the device type employed for the meaurement. A detailed dicuion of flow meaurement uncertainty i provided in ASME PTC 19.1 [3] and i, thu, not further dicued herein. By evaluating equation (C.14) through (C.17), etimate of the total meaurement uncertaintie for the compreor efficiency, head, and required driver power can be obtained. However, one ource of meaurement uncertainty that i often overlooked i the uncertainty due to a finite ample ize. The above uncertainty tatitic are valid only for mean parameter with an aumed Gauian normal ditribution. Thi i a good aumption for meaurement where ample ize are larger than 30. But for field tet, it i ometime difficult to maintain a teady tate ytem operating condition for a time period adequate to collect 30 or more ample. Implementation of the Partial Derivative Method for Ga Turbine To complete the above field tet meaurement uncertainty evaluation, one alo need to look at the complete turbocompreor train (ga turbine and compreor efficiency) performance. The ga turbine haft output power ha to equal the compreor required power (P GT = P). Thu, the following two equation can be ued to define the ga turbine thermal efficiency, η TH, and the total package efficiency, η p : Thermal Efficiency Package Efficiency η P (C.18) TH = W q fuel η p = η * η η (C.19) M TH Here W fuel i the fuel flow into the engine and q i the fuel heating value. The fuel flow i typically meaured uing an orifice plate in a metering run and the heating value i determined from the chemical compoition of the fuel (often the centrifugal compreor dicharge ga i ued a the fuel ga). Baed on the above equation, the correponding ga turbine uncertainty, Δη TH, and package uncertainty, Δη P, are given by: Thermal Efficiency Δ 1 p P η + TH = Δ P Δ W + Δ fuel q (C.0) w q w q W q fuel fuel fuel Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 65

Package Efficiency ( Δη * η η ) + ( Δη η * η ) + ( Δη η η *) Δ η = (C.1) p M TH M To complete the above equation (C.0) and (C.1), the only additional information needed i the fuel flow uncertainty and the fuel heating value uncertainty. Since the fuel flow i meaured in the ame way a the flow through the ga compreor, uncertainty value in Table C-1 can be ued. Alo, ince the heating value i obtained directly from ga compoition, the ame percent uncertainty a wa obtained for the pecific heat equation (C.9) can be ued, namely: TH TH M Δq Δc = q c p p (C.) By introducing the uncertainty experience value from thoe uggeted in thi guideline, the meaurement uncertainty for a field tet can be predicted prior to the tet. Conequently, the above method allow the ga turbine/compreor manufacturer and the end-uer to determine reaonable tet uncertaintie, a well a neceary requirement for the tet intrumentation prior to the tet. Thi method can alo be employed to reolve oberved variation of field tet performance reult from theoretically predicted and/or factory tet reult. The different equation of tate model will provide different value of head, ientropic head, and compreibility for the compreor baed on the difference in calculated enthalpy and compreibility. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 66

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APPENDIX D SIMILARITY CALCULATIONS FOR WET GAS CONDITIONS Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 68

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APPENDIX D The following equation hould be ued to calculate the head and flow coefficient when wet ga condition exit in the proce ga through the centrifugal compreor. Additional information on performance evaluation in wet ga condition i provided in Performance Evaluation of a Centrifugal Compreor Under Wet Ga Condition by Brenne et al., 005. Polytropic Exponent Two Phae P ln P1 n TP = (D.1) vtp 1 ln vtp Ma Flow Rate Two Phae, Polytropic Proce ntp W P TP = ( P vtp P1 vtp1 ) (D.) n 1 TP where the two-phae pecific volume i defined a: v TP 1 = GVF ρ + (1 GVF ) ρ g l (D.3) and the Ga Volume Fraction (GVF) i calculated a: Qdotg GVF = (D.4) Qdot + Qdot g l Alternatively, the Ma Flow Rate for the Two Phae mixture may be calculated a: n 1 n R P n o WP TP x1 Z1 T1 1 + (1 x1 ) vl1 ( P P1 ) n 1 MW gl P = (D.5) 1 where x, the fluid quality, i defined a: mdotg x1 = (D.6) mdot + mdot g l Head Coefficient Two Phae, Polytropic Proce v WP TP ϕ (D.7) U g1 P TP = GVF1 vtp 1 Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 70

Flow Coefficient Two Phae = Qdot TOT 1 φ TP (D.8) N 3 GVF1 π D 60 Efficiency Two Phae, Polytropic Proce WP TP P TP = Pc η (D.9) where P c i the pecific compreor haft power defined a the power conumed by the compreor per unit ma of wet ga. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 71

APPENDIX E EQUATION OF STATE MODEL COMPARISON OF PREDICTED PERFORMANCE DATA Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 7

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APPENDIX E The following comparion of the equation of tate model relie on reult preented in Enthalpy Determination Method for Compreor Performance Calculation by David Ranom, Rainer Kurz, and Klau Brun. Approach for EOS Model Comparion For thi comparion, a matrix of three ga compoition and two preure ratio are conidered. Enthalpy value are calculated uing variou EOS model and ued to calculate compreion power and ientropic efficiency. The three ga compoition (Table E-1) are intended to repreent a variety of typical compreion product including natural ga, high hydrogen, and high diluent compoition. (Note that ga mixture 1 i the ame compoition ued in the uncertainty analyi in Section 5.0.) The two preure ratio included in thi comparion (PR = 1.3 and.) are conitent with typical two- and ix-tage machine repectively, although neither value repreent any pecific application. In all cae, inlet condition of 1000 pia and 80 F are aumed. For each analyi configuration (ga mix and preure ratio), both the ientropic and actual ga horepower are determined, followed then by the ientropic efficiency. Ga power i a function of ma flow (aumed to be meaured) and the change in enthalpy of the working fluid. Table E-1. Ga Mixture Ued in EOS Model Comparion Component Mix 1 Mix Mix 3 Methane 90.00 80.00 7.65 Ethane 5.37 5.37 1.06 Propane 1.70 1.70 0.0 Io-Butane 0.7 0.7 0.00 N-Butane 0.33 0.33 0.00 Io-Pentane 0.06 0.06 0.00 N-Pentane 0.09 0.09 0.00 Hexane 0.07 0.07 0.00 Carbon Dioxide 1.06 6.06 0.85 Nitrogen 1.05 6.05 3.85 Hydrogen 0.00 0.00 86.34 Hydrogen Suflide 0.00 0.00 0.05 Total 100.00 100.00 100.00 Table E-. Aumed Meaured Condition; PR = 1.3 Parameter Mix 1 Mix Mix 3 P 1 (pia) 1000 1000 1000 T 1 ( F) 80 80 80 P (pia) 195 195 195 T ( F) 119 117 17 Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 74

Table E-3. Aumed Meaured Condition; PR =. Parameter Mix 1 Mix Mix 3 P 1 (pia) 1000 1000 1000 T 1 ( F) 80 80 80 P (pia) 00 00 00 T ( F) 01 199 35 Four EOS model are included in thi comparion: Redlich-Kwong-Soave (Soave, 197), Peng-Robinon (1976), Lee-Keler-Ploecker (Ploeker et al., 1978), and Benedict-Webb-Rubin-Starling (Starling, 1973). Uing the appropriate EOS, three enthalpy value are determined a follow: Determine the inlet enthalpy (h1) and entropy (1) a a function of the inlet condition (P1, T1); determine the ientropic dicharge enthalpy (h) a a function of ientropic dicharge condition (P, 1); and determine the actual dicharge enthalpy (h) a a function of the actual dicharge condition (P, T). A graphic repreentation of thi proce i provided below on a generic T- diagram (Figure E-1). Figure E-1. Compreion T-S Diagram Once thee value are determined, it i a very imple calculation to determine the ientropic and actual ga horepower value (equation E.1 and E.). P Actual = m& ( h h1) (E.1) P i = m& ( h h1) (E.) Ientropic efficiency i calculated uing equation (.14). Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 75

Enthalpy Determination Reult The reult for ga horepower and ientropic efficiency for each of the EOS model are hown in Table E-4 and E-5. For the ake of comparion, the ma flow for Mix 3 (high hydrogen ga) i adjuted to provide a imilar horepower a the natural ga compoition. Note that reult are not hown for BWRS for the High H ga compoition (Mix 3) ince BWRS doe not contain hydrogen data. Thee reult demontrate the relative agreement between the four EOS method applied in thi tudy. At the lower preure ratio, for the firt two ga mixture, the tandard deviation i about 30 Hp, or 1.% of the average value. In the cae of the high hydrogen ga (Mix 3), the tandard deviation i approximately 140 HP, or 1.7% of the average value at the ame preure ratio. For the higher preure ratio, the deviation in the firt two mixture between the EOS model i approximately the ame a the lower preure ratio. The deviation increae to 1.8% at the higher preure ratio for the high hydrogen ga (Mix 3). It hould alo be noted that the Peng-Robinon model conitently predict lightly lower horepower for all three ga mixture, while the SRK model typically predict higher horepower within the deviation tated above. The ientropic efficiencie calculated uing the variou EOS model how relatively cloe agreement a well. However, the tandard deviation among the four method ued in thi tudy i a high a %, which can be ignificant when evaluating compreor performance againt the promied performance, uually pecified within 1%. In the extreme cae, the ientropic efficiency between one particular EOS model and another can be a high a 3.8%. Thee reult undercore the importance of applying the ame EOS model throughout the performance analyi. Table E-4. Horepower and Efficiency Calculation for EOS Model at Preure Ratio of 1.3 Mix1 Mix Mix3 EOS Model Hp-Act Eff-i Hp-Act Eff-i Hp-Act Eff-i LKP 530 68.% 49 63.6% 8400 87.9% BWRS 5 64.6% 6 64.7% SRK 58 65.6% 61 66.% 8368 88.% PR 460 65.0% 00 65.6% 813 88.% Stdev 33.30 1.606% 9.07 1.11% 100.18 0.08% Avg 510 0.659 43 0.650 837 0.881 Stdev - %avg 1.33%.44% 1.30% 1.7% 1.0% 0.4% Table E-5. Horepower and Efficiency Calculation for EOS Model at Preure Ratio of. Mix1 Mix Mix3 EOS Model Hp-Act Eff-i Hp-Act Eff-i Hp-Act Eff-i LKP 8840 61.3% 7879 60.3% 8169 87.3% BWRS 8843 60.9% 79 61.% SRK 8940 61.7% 7986 6.3% 8046 87.7% PR 8695 60.8% 7767 61.5% 746 87.8% Stdev 101.07 0.376% 9.13 0.831% 377.77 0.43% Avg 8830 0.61 7889 0.613 789 0.876 Stdev - %avg 1.14% 0.61% 1.17% 1.36% 1.35% 0.8% Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 76

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APPENDIX F APPLICATION OF COMPRESSOR EQUATIONS FOR SIDE STREAM ANALYSIS Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 78

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APPENDIX F The following equation hould be ued to calculate the power and ientropic efficiency of a centrifugal compreor when a ide tream i ued in the compreion proce (a hown in Figure F-1). 3 Comp. Outlet: Combined Stream 1 Compreor Inlet: Main Stream Compreor Inlet: Side Stream Figure F-1. Diagram of Compreor Stage Point with Side Stream Compreor Power (with ide tream) P C = m3 h3 m1 h1 m h = ( m1 + m) h3 m1 h1 m h (F.1) Ientropic Efficiency (with ide tream) If power from driver (P out ) i available: PC η * = (F.) P out Alternatively, the ientropic efficiency may be calculated by comparing the ideal and actual power: P * * ideal m1 ( h3 h1 ) + m ( h3 h ) η * = = (F.3) Pactual m1 ( h3 h1 ) + m ( h3 h ) Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 80