VALVE SIZING REFERENCE GUIDE

Transcription

1 VALVE SIZING REFERENCE GUIDE //data/public/pdf/valve-sizing-maual.doc 1 of 43 10/10/2008

2 TABLE OF CONTENTS Introduction... 4 Valve Flow Terminology... 4 The Sizing Process... 5 Operating Conditions... 5 Fluid Properties... 5 Rangeability... 5 C v and Flow Sizing Formulas... 6 C V Formulas for Liquid Flow C V Formulas for Vapor Flow C V Formulas for Two Phase Flow Flow Velocity Formulas... 7 Flow Velocity for Liquid Flow Flow Velocity for Vapor Flow Nomenclature... 8 Conversion to Cg and Cs... 9 Seat Actuator Sizing P Tables Actuator Air Volume Application Guide for Cavitation, Flashing and Compressible Flow Services Liquid Flow Cavitation Cavitation Definition Cavitation Countermeasures Application of Norriseal 2700A Trims in Cavitation Service Cavitation Avoidance Cavitation Tolerant Cavitation Containment Cavitation Prevention Application Summary The Cavitation Phenomena Fluid and Profiles Choked Flow and Incipient Cavitation Cavitation Damage Flashing Flashing Definition Flashing Countermeasures Body Material Trim Selection Application of Norriseal 2700A Valves in Flashing Service Body Material Trim Selection The Flashing Phenomena Liquid Flow Velocity - Body Material Compressible Flow Noise Compressible Flow Noise Discussion Compressible Flow Noise Countermeasures Application of Norriseal 2700A Trims in Compressible Flow Applications Standard Trims DB I and DB II Multiple Orifice Trims Compressible Flow Velocity Limits //data/public/pdf/valve-sizing-maual.doc 2 of 43 10/10/2008

3 TABLES Two Stage Trims and Backpressure Orifices The Compressible Flow Noise Phenomena Table 1-Trim Rangeability... 6 Table 2-Cg & Cs Conversion Factors... 9 Table 3-Fluid Properties Table 4-F L Factors Table 5-Flanged Body Inlet and Outlet Diameters Table 6-Allowable Seat Classes Table 7-Allowable P Ratings 2700A/E Cage Control Trim, Teflon Packing 9 Actuator Table 8-Allowable P Ratings 2700A/E Cage Control Trim, Teflon Packing 12 Actuator Table 9-Allowable P Ratings 2700A/E Cage Control Trim, Teflon Packing 16 Actuator Table 10-Allowable P Ratings 2700A/E Cage Control Trim, Teflon Packing 18 Actuator Table 11-Allowable P Ratings 2700A/E Cage Control Trim, Grafoil Packing 9 Actuator Table 12-Allowable P Ratings 2700A/E Cage Control Trim, Grafoil Packing 12 Actuator Table 13-Allowable P Ratings 2700A/E Cage Control Trim, Grafoil Packing 16 Actuator Table 14-Allowable P Ratings 2700A/E Cage Control Trim, Grafoil Packing 18 Actuator Table 15-Allowable P Ratings 2700A/E Plug Control Trim, 12, 16 & 18 Actuators Table 16-Allowable P Ratings for Unbalanced Trim, No.9 Actuator Table 17-Allowable P Ratings for Unbalanced Trim, No.12 Actuator Table 18Allowable P Ratings for Unbalanced Trim, No.16 Actuator Table 19-Actuator Air Chamber Volume & Required Added Air to Actuate Table 20-Liquid Flow Velocity Limits Table 21-Flow Coefficients, C V, for 2200/2220 Unbalanced Modified Percent. Plug Control Table 22-Flow Coefficients, C V, for 2275A Unbalanced Modified Percentage Plug Control Table 23-Flow Coefficients, C V, for 2400/2420 Unbalanced Modified Percent. Plug Control Table 24-Flow Coefficients, C V, for 2700A/E Balanced Quick Opening Cage Control Table 25-Flow Coefficients, C V, for 2700A/E Balanced Linear Cage Control Table 26-Flow Coefficients, C V, for 2700A/E Balanced Equal Percentage Cage Control Table 27-Flow Coefficients, C V, for 2700A/E Balanced DB I Cage Control Table 28-Flow Coefficients, C V, for 2700A/E Balanced DB II Control Table 29-Flow Coefficients, C V, for 2700A/E Balanced CAV II Cage Control Table 30-Flow Coefficients, C V, for 2700A/E Balanced Modified Percentage Plug Control Table 31-Flow Coefficients, C V, for 2700A/E Balanced Quick Opening Plug Control Table 32-Flow Coefficients, C V, for 2700A/E Unbalanced Modified Percent Plug Control FIGURES Graph 1- Drop Profile Graph 2-Liquid Flow Relationship with Drop Graph 3-CAV II Flow Noise Attenuation Graph 4- Profiles, Single Stage and Three stage Trims Graph 5-DB I & DB II Flow Noise Attenuation //data/public/pdf/valve-sizing-maual.doc 3 of 43 10/10/2008

4 INTRODUCTION A Control Valve performs a special task, controlling the flow of fluids so a process can be controlled. In addition to controlling the flow, a control valve may be used to shut off flow. A control valve may be defined as a valve with a powered actuator that responds to an external signal. The signal usually comes from a controller. The controller and valve together form a basic control loop. The control valve is seldom full open or closed but in an intermediate position controlling the flow of fluid through the valve. In this dynamic service condition, the valve must withstand the erosive effects of the flowing fluid while maintaining an accurate position to maintain the process variable. A Control Valve will perform these tasks satisfactorily if it is sized correctly for the flowing and shut-off conditions. The valve sizing process determines the required C V, the required F L, Flow Velocities, Flow Noise and the appropriate Actuator VALVE FLOW TERMINOLOGY C V : The Flow Coefficient, C V, is a dimensionless value that relates to a valve s flow capacity. Its most basic form is As the F L value becomes smaller the vena contracta pressure becomes increasingly lower than the valve s outlet pressure and the valve is more likely to cavitate. A valve s Rated F L varies with the valve and trim style, it may vary from.99 for a special multiple stage trim to.60 for a ball valve. Rated F L : The Rated F L is the actual F L value for a particular valve and trim style. Required F L : The Required F L is the F L value calculated for a particular service condition. It indicates the required F L needed to avoid choked flow. If the Rated F L is less than the Required F L, the liquid flow will be choked with cavitation. variable such as fluid pressure, fluid level, Q flow rate or temperature C V where P Q=Flow rate and P=pressure drop across the valve. See pages 5 and 6 for the equations for liquid, gas, steam and twophase flow. The C V value increases if the flow rate increases or if the P decreases. A sizing application will have a Required C V while a valve will have a Rated C V. The valve s rated C V must equal or exceed the required C V. F L : The F L, Liquid Recovery Coefficient, is a dimensionless constant used to calculate the pressure drop when the valve s liquid flow is choked. Increasing the pressure drop when the flow is choked will not increase the flow rate. The F L is the square root of the ratio of valve pressure drop to the pressure drop from the inlet pressure to the pressure of the vena contracta. See page 5 for the F L equation. The F L factor is an indication of the valve s vena contracta pressure relative to the outlet pressure. See Graph 1. If the F L were 1.0, the vena contracta pressure would be the same as the valve s outlet pressure and there would be no pressure recovery. Vena Contracta: The vena contracta is where the jet of flowing fluid is the smallest immediately downstream of the trim's throttle point. At the vena contracta, the fluid's velocity is the highest and the fluid's pressure is the lowest. Vapor : A fluid's vapor pressure is the pressure where the fluid will change from a liquid to a vapor. The liquid will change to a vapor below the vapor pressure and a vapor will change to a liquid above the vapor pressure. The vapor pressure increases as the temperature increases. //data/public/pdf/valve-sizing-maual.doc 4 of 43 10/10/2008

5 Choked Flow: Liquid flow will become choked when the trim's vena contracta is filled with vapor from cavitation or flashing. Vapor flow also will become choked when the flow velocity at the vena contracta reaches sonic. A choked flow rate is limited, a further decrease of the outlet pressure does not increase flow. Choked flow is also called critical flow. Cavitation: Cavitation is a two stage liquid flow phenomena. The first stage is the formation of vapor bubbles in the liquid as the fluid passes through the trim and the pressure is reduced below the fluid's vapor pressure. The second stage is the collapse of the vapor bubbles back to a liquid as the fluid passes the vena contracta and the pressure recovers and increases above the vapor pressure. The collapsing bubbles are very destructive when they contact metal parts and the bubble collapse may produce high noise levels. Flashing: Flashing is similar to cavitation except the vapor bubbles do not collapse, as the downstream pressure remains less than the vapor pressure. The flow will remain a mixture of vapor and liquid. Laminar Flow: Most fluid flow is turbulent. However, when the liquid flow velocity is very slow or the fluid is very viscous or both, the flow may become laminar. When the flow becomes laminar, the required C V is larger than for turbulent flow with similar conditions. The ISA sizing formulas adjust the C V when laminar flow exists. THE SIZING PROCESS The first sizing step is to determine the required C V value for the application. Next determine if there are unusual conditions that may affect valve selection such as cavitation, flashing, high flow velocities or high flow noise. The valve sizing process will determine the proper valve size, valve trim size, valve trim style and actuator size. Norriseal s Valve Sizing Program will accurately calculate the C V, flow velocity and flow noise. The program will also show messages when unusual conditions occur such as cavitation, flashing, high velocity or high noise. The results from Norriseal s Valve Sizing Program are only one element of the valve selection process. Knowledge and judgment are also required. This manual will give the user some of the sizing basics. The liquid, gas and steam C V calculation methods, in this manual, are in accordance with ISA and the gas and steam flow noise calculations are in accordance with ISA These two ISA Standards are in agreement with IEC-534. These standards have worldwide acceptance as the state of the art in C V and Flow Noise determination. OPERATING CONDITIONS The most important part of Valve Sizing is obtaining the correct flowing conditions. If they are incorrect or incomplete, the sizing process will be faulty. There are two common problems. First is having very conservative conditions that overstate the C V and provide a valve less than ½ open at maximum required flow. The second is stating only the maximum flow condition that has minimum pressure drops and not stating the minimum flow conditions with high pressure drops that often induce cavitation or have very high rangeability requirements. Fluid Properties Table 3 lists many fluid properties needed for valve sizing. These fluid properties are in Norriseal s Valve Sizing Program s database and do not need manual entry. Rangeability: Rangeability is the ratio of maximum to minimum controllable C V. This is also sometimes called C V Ratio or Turndown. The maximum flow for Norriseal valves is at maximum travel. The minimum controllable C V is where the Flow //data/public/pdf/valve-sizing-maual.doc 5 of 43 10/10/2008

6 Characteristic (C V vs. Travel) initially deviates or where the valve trim cannot maintain a consistent flow rate. The Trim s rangeability is not always the useable range as seat erosion may be a governing factor. A valve with a significant pressure drop at low flow rates should not be used to throttle near the seat for extended periods of time. The rangeability values, listed in Table 1, apply to the rated C V, not the required C V. For example, an application may require a maximum C V of 170. A 4 Equal Percentage Trim may be selected that has a maximum CV of 195. Using the rangeability value for this trim, the minimum C V is 195/100=19.5, not 170/100=17. Valve applications subject to pressures from nature, such as gas and oil production, are usually sized for full flow at about 80% open as the pressure may be unknown when the valve is sized and the pressure may vary with time. Those valve applications with fairly consistent inlet pressures, such as process control and power applications are usually sized at full travel. The valve specifier usually includes a fair margin of safety in the stated sizing conditions. If the valve supplier includes additional safety, such as full flow at 80% open, the valve may be at full flow at less than ½ travel giving poor performance. Table 1 - TRIM RANGEABILITY Valve Trim Rang ability Equal Percent - Balanced Cage Control 100:1 Linear - Balanced Cage Control 100:1 Quick Opening - Balanced Cage Control 30:1 DB I - Balanced Cage Control 100:1 DB II & CAV II - Balanced Cage Control 100:1 Modified Percent - Balanced Plug Control 50:1 Modified Percent - Unbalanced Plug Control 25:1 V Control Ball 300:1 C V AND FLOW SIZING FORMULAS The following formulas are for information and for understanding the sizing process. Norriseal s Valve Sizing Program is recommended for the calculation process. Flow noise equations are not listed below as they are highly complex and should only be made on our verified computer program. Formulas are shown both for calculation the C V when the flow rate is known and for calculating the flow when the C V is known. C V Formulas for Liquid Flow Required F F F L P1 P2 P P F 1 V F P P If the Rated F L is larger than the Required F L : Q Gf P P C V or Q C V FP FR F F P P G P R 1 2 When the Rated F L is smaller than the Required F L, choked flow exists in the vena contracta limiting the flow. If the Rated F L is smaller than the Required F L : Q G f CV F F Rated P F P or Q C V P P L L F F ( Rated) 1 V C F P F 2 P for choked flow FL P1 FFP V psi P for incipient cavitation K P P psi (See discussion in Choked Flow and Incipient Cavitation section) 1 G F f V P V C 1 V 1 2 f //data/public/pdf/valve-sizing-maual.doc 6 of 43 10/10/2008

7 C V Formulas for Vapor Flow P1 P2 x Limit x x T P1 k x FK Y FK xt If the flow rate is in volumetric units, SCFH, then C or Q V If the flow rate is in mass flow units, Lb./Hr., W C V 63.3 F P Y x P1 1 then or W C Q F 63.3 C V F P Y x P To convert SCFH to Lb./Hr.: W= Q G g = Lb./Hr. Specific Gravity of a Vapor Molecular Weight of the Vapor Molecular Weight of Air C V Formulas for Two Phase Flow Drop for liquid phase = 2 P F P F P V P F P Y P f L 1 1 P Y 1 G F g G T x g 1 V Z x T Z 1 FLOW VELOCITY FORMULAS Flow Velocity for Liquid Flow Liquid Flow Velocity through the Valve: Q VV 2 Ft./ Sec. D b Liquid Flow Velocity through the Pipe: Q VP 2 Ft./ Sec. D Flow Velocity for Vapor Flow P Downstream Specific Volume for a Gas T Z 3 Vapor: V2 Ft. / Lb. M P 2 Downstream Specific Volume for Steam: V 2 Refer to Keenan & Keyes Steam Tables Vapor Flow Velocity through the Valve: 3.06WV 0.234QG 2 g VV Ft./ Min. 2 2 DV DV Vapor Flow Velocity through the Pipe: 3.06WV 0.234QG 2 g VP Ft./ Min. 2 2 DP DP Sonic Velocity of a Vapor Fluid: V 4650 P2 V2 Ft./ Min. SONIC Vapor FlowVelocity, VV orv Mach Number: V SONIC P Drop for vapor phase = P F x P g K T 1 f f = weight fraction of total flow as liquid f g = weight fraction of total flow as vapor C V W f f f g FP PF 1 P 1 f g g Y 2 //data/public/pdf/valve-sizing-maual.doc 7 of 43 10/10/2008

8 Nomenclature C V = Valve Flow Coefficient. D B = Inside Diameter of Valve Body Outlet = Inches. See Table 5. D P = Inside Diameter of Outlet Pipe = Inches. F F = Liquid Critical Ratio Factor: = Ratio of specific Heats Factor. F k F L = Liquid Recovery Factor. F L Required = The F L factor to avoid Choked Flow. F L Rated = The F L factor rated for individual Trim Styles. See Table 4. F P = Piping Geometry Factor, If the valve size and pipe size are equal us 1.0, if not refer to ISA section 4.3. F R = Reynolds Number Factor, Normally = 1.0 but varies with very slow fluid velocities or very viscous fluids. Refer to ISA section 4.4. G f = Specific Gravity of a Liquid relative to water at 60 F. G g = Specific Gravity of a Vapor relative to air at 60 F 14.7 PSIA. k = Ratio of specific Heats. See Table 3. K C = Cavitation Index. See Table 4. M = Molecular Weight. See Table 3. P 1 = Valve Inlet (psia). P 2 = Valve Outlet (psia). P C = Fluid s Critical (psia). See Table 3. P V = Fluid s Vapor (psia). Q = Volumetric Flow Rate: Liquids (GPM) Vapor (SCFH) T = Fluid Temperature in Degrees Rankine. R = F V 2 = Specific Volume of vapor, either gas or steam = Ft. 3 / Lb. W = Mass Flow Rate = Lb./Hr. x = Drop Ratio. x T = Maximum Drop Ratio, varies with Trim Style. See Table 4. Y = Fluid Expansion Factor for vapor flow. Z = Compressibility Factor for vapor flow. Usually 1.0. Refer ISA Handbook of Control Valves, 2nd Edition, pages = Specific Weight = Lb./Ft. 3 Subscripts: 1 = Inlet conditions 2 = Outlet conditions v = Valve p = Pipe f = Liquid g = Vapor b = Body //data/public/pdf/valve-sizing-maual.doc 8 of 43 10/10/2008

9 Flow velocity of a vapor, gas or steam, physically cannot exceed sonic velocity or Mach 1.0. Vapor flow is physically limited at sonic velocity and becomes choked. The choked sonic limitation may apply either at the valve trim or at the valve body s outlet. When the flow rate increases with the velocity at the valve s outlet at sonic, the valve s outlet pressure will rise increasing the fluid density and allowing a higher flow rate still limited at sonic velocity. When a sizing program shows a Valve MACH Number exceeding 1, the inputted outlet pressure is incorrect. Increase P 2 until the MACH number equal 1.0. This determines the valve s outlet pressure that develops to increase the fluid density sufficiently for the fluid to flow out of the valve at sonic velocity. The specifier may write a lower pressure that may occur further downstream after the piping system causes additional pressure drops. The ISA noise prediction formulas for vapor flow loses accuracy at Mach numbers larger than.33. Conversion to C g and C s Not all valve suppliers use the ISA sizing coefficient and may use a C g or C s value instead. The ISA C V coefficient can be converted to C g or C s using these equations. C C conversion factor C C C g s V V C V V conversion factor 20 C conversion factor C 20 s conversion factor g Table 2 - Cg Conversion Factors Valve General DB I DB II N/A N/A 30 //data/public/pdf/valve-sizing-maual.doc 9 of 43 10/10/2008

10 Name of Fluid Table 3 - FLUID PROPERTIES Fluid Form Liquid Gas Molecular Weight Critical Critical Temperature Ratio of specific Heats k M Pc psia Tc (F) Acetylene G Air G Ammonia L G Argon G Benzene L G Butane G Butanol L Butene-1 G Butylene Oxide L 63.6 Butadiene L Butene L n-butane G Isobutane G n-butanol L Isobutylene L Carbon Dioxide L G Carbon Monoxide L G Carbon Tetrachloride L Chlorine L G Chlorobenzene L Chloroform L Chloroprene L Cyclobutane L Cyclohexane L Cyclopentane L Cyclopropane L Crude Oil L Ethane L G Ethanol L Ethylbenzene L Ethyl Chloride G Ethyl Oxide L Ethylene L G Ethylene Glycol L Triethylene Glycol L Freon 11 L G Freon 12 L G Freon 22 L G Helium G Heptane G Hydrazine L Hydrogen L G Hydrogen Bromide L Hydrogen Chloride L G Hydrogen Floride L Hydrogen Iodide L Hydrogen Sulphide G //data/public/pdf/valve-sizing-maual.doc 10 of 43 10/10/2008

11 Name of Fluid Fluid Form Liquid Gas Molecular Weight Critical Critical Temperature Ratio of specific Heats k M Pc psia Tc (F) Isoprene L Methane L G Methanol L Methyl Chloride L G Methylchloride L O-Methylene Chloride L Napthalene L Natural Gas G Neon G Nitric Oxide L G Nitrogen L G Nitrogen Dioxide L Nitrous Oxide L G n-nonane G n-octane G Oxygen L G Pentane G Phenol L Propane L G n-propanol L Propene G Propylene L Propyl Oxide L Sea Water/Brine L Sulfuric Acid L Sulfur Dioxide L G Sulfur Trioxide L Tolulene L Water L G M-Xylene L O-xylene L P-xylene L Table 4 - F L, K C & X T Factors Valve Trim Style Rated K C X T CAV II Cage Control DB I Cage Control.75 DB II Cage Control.75 Plug Control (Flow Up) Ported Cage Control (Flow Up) Ported Cage Control (Flow Down) Butterfly Valve V Control Ball Valve = No value for vapor flow = No value for liquid flow F L //data/public/pdf/valve-sizing-maual.doc 11 of 43 10/10/2008

12 SEAT LEAKAGE Table 5 - Flanged Body Inlet and Outlet Diameters Nominal ANSI Class Body " 1.06" 1.06" 1.00" 1.00" 1.00" " 1.63" 1.63" 1.63" 1.63" 1.50" " 2.00" 2.00" 2.00" 2.00" 1.75" " 3.00" 3.00" 3.00" 2.69" 2.69" " 4.00" 4.00" 4.00" 3.69" 3.44" " 6.00" 6.00" 5.75" 5.75" 5.50" " 8.00" 8.00" 7.62" 7.25" 7.00" The Fluids Control Institute (FCI) Standard ANSI/FCI 70.2 establishes a Valve s allowable seat Rate. The standard recognizes five degrees of seat tightness. Table 6 - ALLOWABLE SEAT LEAKAGE CLASSES Class Maximum Seat Test Test Relative Seat Fluid Tightness Class II 0.5% of rated C V Water 45 to 60 PSI 1.0 Class IIA (Norriseal) 0.2% of rated C V Water 45 to 60 PSI 2.5 Class III 0.1% of rated C V Water 45 to 60 PSI 5.0 Class IV 0.01% of rated C V Water 45 to 60 PSI 50 Class V ml /min/inch Max Operating Water of trim size/ P(PSI) P 300,000 Class VI About 0.9 ml/min Air 50 PSI 600,000 rate varies by valve size, Refer to the Standard ANSI/FCI Norriseal offers Class IIA (Norriseal), Class IV, Class V & Class IV The Relative Seat Tightness is at a 50 P. For example, a Class IV leakage rate is 1/50 as much as Class II Class VI is for resilient seated valves; the other classes are for metallic seats. ACTUATOR SIZING The actuator sizing process matches our condition. The flowing conditions also actuator s force output with our valve trim s require an adequate match between the required stem forces. The result is the actuator and trim forces but the shut off maximum obtainable pressure drop at the condition is dominant and determines the different seat leakage classes. The allowable. process considers the valve s shut off 2 2 UA UnbalancedArea BalancedTrim Cage ID Seat ID = In UA UnbalancedArea UnbalancedTrim Seat ID = In 2 4 CL Seat Contact Load Seat ID Load Factor = Lb./In. of circumference Load Factors vary with seat leakage class //data/public/pdf/valve-sizing-maual.doc 12 of 43 10/10/2008

13 PF = Packing Friction (Teflon Packing)= 25 Lb. PF = Packing Friction (Grafoil Packing)= (Stem Dia.) (P 1 ) (Packing Height) (.15) PF for Grafoil Packing friction should never be less than 25 Lb. 2 2 RF Plug Seal Ring Friction Cage ID 2 Cage ID Seal Groove P Direct Actuator Output = (Effective Diaph. Area) (Actuator Press.- Final Spring ) Reverse Actuator Output = (Effective Diaph. Area) (Initial Final Spring ) The Initial Spring is the actuator pressure when the valve stem begins to move. The Final Spring is the actuator pressure when the valve stem reaches full travel. Allowable P Allowable P P Tables Actuator Output PF RF CL UA Actuator Output PF CL UA For Balanced Trim Flow to Close For Unbalanced Trim Flow to Open The following eleven tables contain calculated P pressures, in psi, using the above formulas. The first four tables are for No. 9, 12, 16, & 18 actuators and valves with balanced trim and Teflon packing, the second four are with Grafoil packing.. The four Grafoil packing tables show lower allowable due to the significantly higher friction with Grafoil packing. The last three are for unbalanced trims with No. 9, 12 & 16 actuators. The difference in the allowable P pressures for the Seat Classes requires different seat contact forces. A lower leakage rate, except for Class VI, is obtained by increasing the net seat contact force. Classes IV & VI (resilient seat) share the same contact forces and allowable pressures even though their leakage rates are quite different. The allowable pressure drop cannot exceed the Body s ANSI pressure rating. The table s first column for direct acting actuators is the air supply pressure to the actuator. A 3-15 psi actuator spring is assumed. If a 6-30 psi spring is used in a direct actuator, add 15 to the pressure in the first column. The table s first column for reverse acting actuators is the initial pressure corresponding to the amount of compression in the actuator s spring when the valve is closed. The Initial air pressure is actuator diaphragm pressure when the valve begins to open. The final air pressure is determined by adding 12 psi to the initial air pressure of a 3-15 psi spring and by adding 24 psi to the initial air pressure of a 6-30 psi. //data/public/pdf/valve-sizing-maual.doc 13 of 43 10/10/2008

14 Table 7 ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM TEFLON PACKING, FLOW DOWN, No. 9 Direct Actuator, 3 to 15 psi Spring Air Supply Trim Class II IV & VI 18 V 20 II IV & VI V 22 II IV & VI V 24 II IV & VI V 27 II 1, IV & VI V 30 II 1,400 1,223 1,147 1, IV & VI 1, V II 1,726 1,524 1,438 1, IV & VI 1,474 1,183 1, V II 1,944 1,724 1,633 1,490 1, IV & VI 1,691 1,383 1, V 554 Usually direct acting actuators use a 3-15 psi spring. With an 18 psi air supply pressure, there is a 3 psi (18-15=3) net closure force on the trim, or for a 27 psi supply the net closure force is 12 psi. If a 6-30 psi spring is used in a direct acting actuator, add 15 to pressure in the air supply column. ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM TEFLON PACKING, FLOW DOWN, No. 9 Reverse Actuator Initial Air * Class Trim II IV & VI 3 V 6 II IV & VI V 9 II IV & VI V 12 II 1, IV & VI V The Initial air pressure is actuator diaphragm pressure when the valve begins to open. For example, a 3-15 has an initial pressure of 3 psi. The spring may have additional compression to provide the 6, 9 and 12 psi initial pressures. //data/public/pdf/valve-sizing-maual.doc 14 of 43 10/10/2008

15 Table 8 ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM TEFLON PACKING, FLOW DOWN, No.12 Direct Actuator, 3 to 15 psi Spring Air Supply Class Trim 1" 1.5" 2" 3" 4" 18 II IV & VI V 20 II IV & VI V 22 II 1,291 1,123 1, IV & VI 1, V - 24 II 1,726 1,524 1,438 1, IV & VI 1,474 1,183 1, V II 2,379 2,124 2,021 1,863 1, IV & VI 2,126 1,784 1,622 1, V II 3,032 2,725 2,604 2,422 1, IV & VI 2,779 2,384 2,205 1,911 1, V 1, II 3,685 3,325 3,187 2,981 2, IV & VI 3,432 2,984 2,788 2,470 1, V 2,295 1, II 4,120 3,725 3,575 3,354 2, IV & VI 3,867 3,385 3,177 2,843 2, V 2,730 1,852 1, Usually direct acting actuators use a 3-15 psi spring. With an 18 psi air supply pressure, there is a 3 psi (18-15=3) net closure force on the trim, or for a 27 psi supply the net closure force is 12 psi. If a 6-30 psi spring is used in a direct acting actuator, add 15 to pressure in the air supply column. ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM TEFLON PACKING, FLOW DOWN, No. 12 Reverse Actuator Initial Air Trim * Class 1" 1.5" 2" 3" 4" 3 II IV & VI V 6 II 1, IV & VI V 9 II 1,726 1,524 1,438 1, IV & VI 1,474 1,183 1, V II 2,379 2,124 2,021 1,863 1, IV & VI 2,126 1,784 1,622 1, V The Initial air pressure is actuator diaphragm pressure when the valve begins to open. For example, a 3-15 has an initial pressure of 3 psi. The spring may have additional compression to provide the 6, 9 & 12 psi initial pressures. //data/public/pdf/valve-sizing-maual.doc 15 of 43 10/10/2008

16 Table 9 ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM TEFLON PACKING, FLOW DOWN, No.16 Direct Actuator, 3 to 15 psi Spring Air Supply Trim Class 1" 1.5" 2" 3" 4" 18 II IV & VI V 20 II 1,633 1,438 1,355 1, IV & VI 1,380 1, V II 2,379 2,124 2,021 1,863 1, IV & VI 2,126 1,784 1,622 1, V II 3,125 2,810 2,687 2,502 1, IV & VI 2,873 2,470 2,288 1,991 1, V 1, II 4,244 3,840 3,686 3,461 2, IV & VI 3,992 3,499 3,288 2,950 2, V 2,854 1,966 1, II 5,364 4,869 4,686 4,420 3, IV & VI 5,111 4,529 4,287 3,908 2, V 3,973 2,996 2,492 1, II 6,483 5,899 5,685 5,378 4, IV & VI 6,230 5,558 5,286 4,867 3, V 5,093 4,025 3,491 2,568 1, II 7,229 6,585 6,351 6,017 4, IV & VI 6,976 6,244 5,952 5,506 4, V 5,839 4,711 4,157 3,207 1,777 Usually direct acting actuators use a 3-15 psi spring. With an 18 psi air supply pressure, there is a 3 psi (18-15=3) net closure force on the trim, or for a 27 psi supply the net closure force is 12 psi. If a 6-30 psi spring is used in a direct acting actuator, add 15 to pressure in the air supply column. ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM TEFLON PACKING, FLOW DOWN, No.16 Reverse Actuator Initial Air Trim Class 1" 1.5" 2" 3" 4" 3 II IV & VI V 6 II 2,006 1,781 1,688 1,543 1,174 6 IV & VI 1,753 1,440 1,289 1, V II 3,125 2,810 2,687 2,502 1,955 9 IV & VI 2,873 2,470 2,288 1,991 1,401 9 V 1, II 4,244 3,840 3,686 3,461 2, IV & VI 3,992 3,499 3,288 2,950 2, V 2,854 1,966 1, The Initial air pressure is actuator diaphragm pressure when the valve begins to open. For example, a 3-15 has an initial pressure of 3 psi. The spring may have additional compression to provide the 6, 9 & 12 psi initial pressures. //data/public/pdf/valve-sizing-maual.doc 16 of 43 10/10/2008

17 Table 10 ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM TEFLON PACKING, FLOW DOWN, No.18 Direct Actuator, 3 to 15 psi Spring Air Supply Trim Class 1" 1.5" 2" 3" 4" II 1,447 1,266 1,189 1, IV & VI 1, V II 2,566 2,296 2,188 2,023 1, IV & VI 2,313 1,955 1,789 1,512 1, V 1, II 3,685 3,325 3,187 2,981 2,345 1, IV & VI 3,432 2,984 2,788 2,470 1, V 2, II 4,804 4,354 4,186 3,940 3,126 1,611 1, IV & VI 4,551 4,014 3,787 3,429 2,572 1, V 3,414 2,481 1,992 1, II 6,483 5,899 5,685 5,378 4,297 2,250 1, IV & VI 6,230 5,558 5,286 4,867 3,743 1,791 1, V 5,093 4,025 3,491 2,568 1, II 8,161 7,443 7,183 6,816 5,468 2,889 2, IV & VI 7,909 7,102 6,785 6,305 4,914 2,430 1, V 6,771 5,569 4,990 4,006 2, II 9,840 8,987 8,682 8,255 6,639 3,528 2, IV & VI 9,587 8,646 8,283 7,744 6,085 3,069 2, V 8,450 7,113 6,489 5,444 3,592 1, II ,016 9,681 9,213 7,419 3,954 2, IV & VI ,675 9,283 8,702 6,866 3,495 2, V 9,569 8,143 7,488 6,403 4,373 1, Usually direct acting actuators use a 3-15 psi spring. With an 18 psi air supply pressure, there is a 3 psi (18-15=3) net closure force on the trim, or for a 27 psi supply the net closure force is 12 psi. If a 6-30 psi spring is used in a direct acting actuator, add 15 to pressure in the air supply column. ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM TEFLON PACKING, FLOW DOWN, No.18 Reverse Actuator Initial Air Trim Class 1" 1.5" 2" 3" 4" II 1,447 1,266 1,189 1, IV & VI 1, V 56 6 II 3,125 2,810 2,687 2,502 1, IV & VI 2,873 2,470 2,288 1,991 1, V 1, II 4,804 4,354 4,186 3,940 3,126 1,611 1,147 9 IV & VI 4,551 4,014 3,787 3,429 2,572 1, V 3,414 2,481 1,992 1, II 6,483 5,899 5,685 5,378 4,297 2,250 1, IV & VI 6,230 5,558 5,286 4,867 3,743 1,791 1, V 5,093 4,025 3,491 2,568 1,250 The Initial air pressure is actuator diaphragm pressure when the valve begins to open. For example, a 3-15 has an initial pressure of 3 psi. The spring may have additional compression to provide the 6, 9 & 12 psi initial pressures. //data/public/pdf/valve-sizing-maual.doc 17 of 43 10/10/2008

18 Table 11 ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM GRAFOIL PACKING, FLOW DOWN, No.9 Direct Actuator, 3 to 15 psi Spring Air Supply Class Trim 1" 1.5" 2" 3" 4" 18 II IV & VI 18 V 20 II IV & VI V 22 II IV & VI V 24 II IV & VI V 27 II IV & VI V 30 II 1, IV & VI V II 1,301 1,187 1,133 1, IV & VI 1, V II 1,455 1,333 1,277 1, IV & VI 1, V 470 Usually direct acting actuators use a 3-15 psi spring. With an 18 psi air supply pressure, there is a 3 psi (18-15=3) net closure force on the trim, or for a 27 psi supply the net closure force is 12 psi. If a 6-30 psi spring is used in a direct acting actuator, add 15 to pressure in the air supply column. ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM TEFLON PACKING, FLOW DOWN, No.9 Reverse Actuator Initial Air Trim Class 1" 1.5" 2" 3" 4" 3 II IV & VI 3 V 6 II IV & VI V 9 II IV & VI V 12 II IV & VI V The Initial air pressure is actuator diaphragm pressure when the valve begins to open. For example, a 3-15 has an initial pressure of 3 psi. The spring may have additional compression to provide the 6, 9 & 12 psi initial pressures. //data/public/pdf/valve-sizing-maual.doc 18 of 43 10/10/2008

19 Table 12 ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM GRAFOIL PACKING, FLOW DOWN, No.12 Direct Actuator, 3 to 15 psi Spring Air Supply Trim Class 1" 1.5" 2" 3" 4" 18 II IV & VI V 20 II IV & VI V 22 II IV & VI V 24 II 1,301 1,187 1,133 1, IV & VI 1, V II 1,763 1,626 1,565 1,464 1, IV & VI 1,584 1,377 1,270 1, V II 2,226 2,066 1,996 1,884 1, IV & VI 2,047 1,816 1,701 1,500 1, V 1, II 2,689 2,505 2,427 2,304 1, IV & VI 2,510 2,256 2,132 1,920 1, V 1,704 1, II 2,997 2,798 2,714 2,583 2, IV & VI 2,818 2,549 2,419 2,200 1, V 2,012 1,427 1, Usually direct acting actuators use a 3-15 psi spring. With an 18 psi air supply pressure, there is a 3 psi (18-15=3) net closure force on the trim, or for a 27 psi supply the net closure force is 12 psi. If a 6-30 psi spring is used in a direct acting actuator, add 15 to pressure in the air supply column. ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM GRAFOIL PACKING, FLOW DOWN, No.12 Reverse Actuator Initial Air Trim Class 1" 1.5" 2" 3" 4" 3 II IV & VI V 6 II IV & VI V 9 II 1,301 1,187 1,133 1, IV & VI 1, V II 1,763 1,626 1,565 1,464 1, IV & VI 1,584 1,377 1,270 1, V The Initial air pressure is actuator diaphragm pressure when the valve begins to open. For example, a 3-15 has an initial pressure of 3 psi. The spring may have additional compression to provide the 6, 9 & 12 psi initial pressures. //data/public/pdf/valve-sizing-maual.doc 19 of 43 10/10/2008

20 Table 13 ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM GRAFOIL PACKING, FLOW DOWN, No.16 Direct Actuator, 3 to 15 psi Spring Air Supply Trim Class 1" 1.5" 2" 3" 4" 18 II IV & VI V 20 II 1, IV & VI 1, V II 1,763 1,626 1,565 1,464 1, IV & VI 1,584 1,377 1,270 1, V II 2,292 2,129 2,057 1,944 1, IV & VI 2,113 1,879 1,762 1,560 1, V 1, II 3,085 2,882 2,797 2,663 2, IV & VI 2,906 2,633 2,502 2,280 1, V 2,100 1,511 1, II 3,878 3,635 3,536 3,383 2, IV & VI 3,699 3,386 3,241 2,999 2, V 2,893 2,264 1,913 1, II 4,671 4,389 4,275 4,102 3, IV & VI 4,492 4,140 3,980 3,719 3, V 3,686 3,018 2,652 1,993 1, II 5,200 4,891 4,768 4,582 3, IV & VI 5,021 4,642 4,473 4,198 3, V 4,215 3,520 3,145 2,473 1,465 Usually direct acting actuators use a 3-15 psi spring. With an 18 psi air supply pressure, there is a 3 psi (18-15=3) net closure force on the trim, or for a 27 psi supply the net closure force is 12 psi. If a 6-30 psi spring is used in a direct acting actuator, add 15 to pressure in the air supply column. ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM GRAFOIL PACKING, FLOW DOWN, No.16 Reverse Actuator Initial Air Trim Class 1" 1.5" 2" 3" 4" 3 II IV & VI V 6 II 1,499 1,375 1,318 1, IV & VI 1,320 1,126 1, V II 2,292 2,129 2,057 1,944 1,611 9 IV & VI 2,113 1,879 1,762 1,560 1,170 9 V 1, II 3,085 2,882 2,797 2,663 2, IV & VI 2,906 2,633 2,502 2,280 1, V 2,100 1,511 1, The Initial air pressure is actuator diaphragm pressure when the valve begins to open. For example, a 3-15 has an initial pressure of 3 psi. The spring may have additional compression to provide the 6, 9 & 12 psi initial pressures. //data/public/pdf/valve-sizing-maual.doc 20 of 43 10/10/2008

21 Table 14 ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM GRAFOIL PACKING, FLOW DOWN, No.18 Direct Actuator, 3 to 15 psi Spring Air Supply Trim Class 1" 1.5" 2" 3" 4" II 1, IV & VI V II 1,896 1,752 1,688 1,584 1, IV & VI 1,717 1,502 1,393 1, V II 2,689 2,505 2,427 2,304 1,922 1, IV & VI 2,510 2,256 2,132 1,920 1, V 1,704 1, II 3,482 3,259 3,166 3,023 2,544 1,391 1, IV & VI 3,303 3,009 2,871 2,639 2,103 1, V 2,497 1,887 1, II 4,671 4,389 4,275 4,102 3,477 1,930 1, IV & VI 4,492 4,140 3,980 3,719 3,036 1,542 1, V 3,686 3,018 2,652 1,993 1, II 5,861 5,519 5,384 5,181 4,410 2,470 1, IV & VI 5,681 5,270 5,089 4,798 3,969 2,082 1, V 4,876 4,148 3,761 3,072 1, II 7,050 6,649 6,492 6,260 5,343 3,010 2, IV & VI 6,871 6,400 6,197 5,877 4,902 2,622 1, V 6,065 5,278 4,870 4,151 2, II 7,843 7,403 7,232 6,980 5,965 3,369 2, IV & VI 7,664 7,153 6,937 6,596 5,524 2,982 2, V 6,858 6,031 5,609 4,871 3,538 1, Usually direct acting actuators use a 3-15 psi spring. With an 18 psi air supply pressure, there is a 3 psi (18-15=3) net closure force on the trim, or for a 27 psi supply the net closure force is 12 psi. If a 6-30 psi spring is used in a direct acting actuator, add 15 to pressure in the air supply column. ALLOWABLE PRESSURE DROP RATINGS FOR 2700A CAGE CONTROL TRIM GRAFOIL PACKING, FLOW DOWN, No.18 Reverse Actuator Initial Air Trim Class 1" 1.5" 2" 3" 4" II 1, IV & VI V 56 6 II 2,292 2,129 2,057 1,944 1, IV & VI 2,113 1,879 1,762 1,560 1, V 1, II 3,482 3,259 3,166 3,023 2,544 1,391 1,015 9 IV & VI 3,303 3,009 2,871 2,639 2,103 1, V 2,497 1,887 1, II 4,671 4,389 4,275 4,102 3,477 1,930 1, IV & VI 4,492 4,140 3,980 3,719 3,036 1,542 1, V 3,686 3,018 2,652 1,993 1,050 The Initial air pressure is actuator diaphragm pressure when the valve begins to open. For example, a 3-15 has an initial pressure of 3 psi. The spring may have additional compression to provide the 6, 9 & 12 psi initial pressures. //data/public/pdf/valve-sizing-maual.doc 21 of 43 10/10/2008

22 Air Supply Table 15 ALLOWABLE PRESSURE DROP RATINGS FOR 2700A PLUG CONTROL TRIM, TEFLON PACKING FLOW UP, Direct Actuators, 3 to 15 psi Spring Trim Class No 12 Direct Actuator No 16 Direct Actuator No 18 Direct Actuator 1.5" 2" 3" 4" 1.5" 2" 3" 4" 1.5" 2" 3" 4" 6 8" 18 II IV II IV II IV II IV II IV II IV II IV II IV Usually direct acting actuators use a 3-15 psi spring. With an 18 psi air supply pressure, there is a 3 psi (18-15=3) net closure force on the trim, or for a 27 psi supply the net closure force is 12 psi. If a 6-30 psi spring is used in a direct acting actuator, add 15 to pressure in the air supply column. Initial * Air ALLOWABLE PRESSURE DROP RATINGS FOR 2700A PLUG CONTROL TRIM, TEFLON PACKING FLOW UP, Reverse Actuators Trim Class No 12 Direct Actuator No 16 Direct Actuator No 18 Direct Actuator 1.5" 2" 3" 4" 1.5" 2" 3" 4" 1.5" 2" 3" 4" 6 8" II IV II IV II IV II IV The Initial air pressure is actuator diaphragm pressure when the valve begins to open. For example, a 3-15 has an initial pressure of 3 psi. The spring may have additional compression to provide the 6, 9 & 12 psi initial pressures. //data/public/pdf/valve-sizing-maual.doc 22 of 43 10/10/2008

23 Air Supply Table 16 ALLOWABLE PRESS. DROP RATINGS FOR UNBALANCED TRIM TEFLON PACKING, FLOW UP, No.9 Direct Actuator, 3 to 15 psi Spring Class Trim ".250".375" II 6,199 2,684 1, IV & VI 5,560 2,257 1, V 2, II > ,220 2,896 1, IV & VI > ,792 2,576 1, V > ,872 1, II > ,754 4,322 1,885 1, IV & VI > ,328 4,002 1, V > ,408 2, II >10000 > ,748 2,519 1, IV & VI > ,863 5,428 2,306 1, V > ,943 3,988 1, II >10000 > ,887 3,470 1, IV & VI >10000 > ,567 3,256 1, V >10000 > ,127 2,296 1, II >10000 >10000 > ,420 2,466 1, IV & VI >10000 > ,706 4,207 2, V >10000 > ,266 3,247 1, II >10000 >10000 > ,371 3,001 1, IV & VI >10000 >10000 > ,158 2,841 1, V >10000 >10000 > ,198 2, II >10000 >10000 > ,005 3,358 1, IV & VI >10000 >10000 > ,792 3,198 1, V >10000 >10000 > ,832 2, Usually direct acting actuators use a 3-15 psi spring. With an 18 psi air supply pressure, there is a 3 psi (18-15=3) net closure force on the trim, or for a 27 psi supply the net closure force is 12 psi. If a 6-30 psi spring is used in a direct acting actuator, add 15 to pressure in the air supply column. Initial Air ALLOWABLE PRESS. DROP RATINGS FOR UNBALANCED TRIM TEFLON PACKING, FLOW UP, No.9 Reverse Actuator Class Trim ".250".375" II 6,199 2,684 1, IV & VI 5,560 2,257 1, V 2, II > ,487 3,609 1, IV & VI > ,060 3,289 1, V > , II >10000 > ,748 2,519 1, IV & VI > ,863 5,428 2,306 1, V > ,943 3,988 1, II >10000 > ,887 3,470 1, IV & VI >10000 > ,567 3,256 1, V >10000 > ,127 2,296 1, The Initial air pressure is actuator diaphragm pressure when the valve begins to open. For example, a 3-15 has an initial pressure of 3 psi. The spring may have additional compression to provide the 6, 9 & 12 psi initial pressures. //data/public/pdf/valve-sizing-maual.doc 23 of 43 10/10/2008

24 Air Supply Table 17 ALLOWABLE PRESS. DROP RATINGS FOR UNBALANCED TRIM TEFLON PACKING, FLOW UP, No.12 Direct Actuator, 3 to 15 psi Spring Class Trim.187".250".375" II 6,487 3, IV & VI 6,060 3, V 4,140 1, II > ,461 2,836 1, IV & VI > ,141 2,626 1, V 9,210 4,701 1, II > ,313 4,104 2, IV & VI > ,993 3,890 2, V > ,553 2,930 1, II >10000 > ,371 3,001 1, IV & VI >10000 > ,158 2,841 1, V >10000 > ,198 2, II >10000 > ,272 4,071 1, IV & VI >10000 > ,059 3,911 1, V >10000 > ,099 3,191 1, II >10000 > ,174 5,140 2,267 1, IV & VI >10000 > ,961 4,980 2,160 1, V >10000 > ,001 4,260 1, II >10000 >10000 > ,210 2,742 1, IV & VI >10000 >10000 > ,050 2,635 1, V >10000 > ,902 5,330 2,155 1, II >10000 >10000 > ,923 3,059 1, IV & VI >10000 >10000 > ,763 2,952 1, V >10000 >10000 > ,043 2,472 1,271 Usually direct acting actuators use a 3-15 psi spring. With an 18 psi air supply pressure, there is a 3 psi (18-15=3) net closure force on the trim, or for a 27 psi supply the net closure force is 12 psi. If a 6-30 psi spring is used in a direct acting actuator, add 15 to pressure in the air supply column. Initial Air ALLOWABLE PRESS. DROP RATINGS FOR UNBALANCED TRIM TEFLON PACKING, FLOW UP, No.12 Reverse Actuator Class Trim.187".250".375" II 6,487 3,609 1, IV & VI 6,060 3,289 1, V 4,140 1, II > ,887 3,470 1, IV & VI > ,567 3,256 1, V > ,127 2,296 1, II >10000 > ,371 3,001 1, IV & VI >10000 > ,158 2,841 1, V >10000 > ,198 2, II >10000 > ,272 4,071 1, IV & VI >10000 > ,059 3,911 1, V >10000 > ,099 3,191 1, The Initial air pressure is actuator diaphragm pressure when the valve begins to open. For example, a 3-15 has an initial pressure of 3 psi. The spring may have additional compression to provide the 6, 9 & 12 psi initial pressures. //data/public/pdf/valve-sizing-maual.doc 24 of 43 10/10/2008

25 Air Supply Table 18 ALLOWABLE PRESS. DROP RATINGS FOR UNBALANCED TRIM TEFLON PACKING, FLOW UP, No.16 Direct Actuator, 3 to 15 psi Spring Class Trim.250".375" II 6,665 2, IV & VI 6,345 2, V 4,905 1, II > ,099 2,848 1, IV & VI > ,886 2,688 1, V 9,794 3,926 1, II > ,272 4,071 1, IV & VI > ,059 3,911 1, V > ,099 3,191 1, II > ,445 5,293 2,335 1, IV & VI > ,232 5,133 2,228 1, V > ,272 4,413 1, II >10000 > ,127 3,150 1, IV & VI >10000 > ,967 3,043 1, V >10000 > ,247 2,563 1, II >10000 > ,960 3,964 2, IV & VI >10000 > ,800 3,858 2, V >10000 > ,080 3,378 1, II >10000 >10000 > ,779 2, IV & VI >10000 >10000 > ,673 2, V >10000 > ,913 4,193 2, II >10000 >10000 > ,323 2, IV & VI >10000 >10000 > ,216 2, V >10000 >10000 > ,736 2,544 Usually direct acting actuators use a 3-15 psi spring. With an 18 psi air supply pressure, there is a 3 psi (18-15=3) net closure force on the trim, or for a 27 psi supply the net closure force is 12 psi. If a 6-30 psi spring is used in a direct acting actuator, add 15 to pressure in the air supply column. Initial Air ALLOWABLE PRESS. DROP RATINGS FOR UNBALANCED TRIM TEFLON PACKING, FLOW UP, No.16 Reverse Actuator Class Trim.250".375" II 6,665 2,926 1, IV & VI 6,345 2,713 1, V 4,905 1, II > ,186 3,460 1, IV & VI > ,973 3,300 1, V > ,013 2, II > ,445 5,293 2,335 1,303 9 IV & VI > ,232 5,133 2,228 1,223 9 V > ,272 4,413 1, II >10000 > ,127 3,150 1, IV & VI >10000 > ,967 3,043 1, V >10000 > ,247 2,563 1,682 The Initial air pressure is actuator diaphragm pressure when the valve begins to open. For example, a 3-15 has an initial pressure of 3 psi. The spring may have additional compression to provide the 6, 9 & 12 psi initial pressures. //data/public/pdf/valve-sizing-maual.doc 25 of 43 10/10/2008