Fundamentals Metering, Proving and Accuracy

Fundamentals Metering, Proving and Accuracy Transportation PR0A020I Issue/Rev. 0.0 (7/07) - Slide 1

Circa 1990 Custody Transfer Metering Technologies PD Meters For Heavy Products Turbine Meters For Light Products PR0A020I Issue/Rev. 0.0 (7/07) - Slide 2

Today s Metering Technologies Meters PD Conventional Turbine Meters Helical Turbine Meters Coriolis Mass Flow and Density Meters Ultrasonic Meters PR0A020I Issue/Rev. 0.0 (7/07) - Slide 3

Accurate Measurement Requires the Right Meter Choice for the Application PR0A020I Issue/Rev. 0.0 (7/07) - Slide 4

Applications Crude oil transportation Ship and barge loading and unloading Refined product transportation Terminal loading Marketing Fuel oil delivery Aviation fuels PR0A020I Issue/Rev. 0.0 (7/07) - Slide 5

API MPMS Chapter 5, Section 1 General Considerations for Measurement by Meters PR0A020I Issue/Rev. 0.0 (7/07) - Slide 6

What is API s Opinion on: The Advantages of Metering Design of Meter Installations Meter Performance Meter Proving PR0A020I Issue/Rev. 0.0 (7/07) - Slide 7

The Advantages of Metering Increases the availability of tanks. Isolation for the sole purpose of measurement is unnecessary Provides instantaneous values calculation, indication and display of flow rate and volume Can deliver a measure volume taken from several sources at the same time Into a single receiver, or from a single source into several receivers. Accuracy can be readily checked Standard references Dynamic volumes correction Simplified temperature measurement and online product sampling API 5.1.1 Introduction PR0A020I Issue/Rev. 0.0 (7/07) - Slide 8

Design of Meter Installations The installation should provide for proving each meter and should be capable of duplicating normal operating conditions at the time of proving. API 5.1.4 Consideration for the Design of Meter Installations PR0A020I Issue/Rev. 0.0 (7/07) - Slide 9

Meter Performance For custody transfer applications, meters with the highest inherent accuracy should be used and should be proven on site. API 5.1.8 Meter Performance PR0A020I Issue/Rev. 0.0 (7/07) - Slide 10

Meter Proving The optimum frequency of proving depends on so many operating conditions that it is unwise to establish a fixed time or throughput interval for all conditions API 5.1.9.4.2 Meter Proving PR0A020I Issue/Rev. 0.0 (7/07) - Slide 11

Meter Proving Proving should be frequent (e.g., every tender or every day) when a meter is initially installed After frequent proving has shown that the meter factors for any given liquid are being reproduced within narrow limits, the frequency of proving can be reduced if the factors are under control and the overall repeatability of measurement is satisfactory to the parties involved API 5.1.9.4.3 Meter Proving PR0A020I Issue/Rev. 0.0 (7/07) - Slide 12

Basic Custody Transfer Requirements Accuracy of Measured Volume must be Traceable to a standard recognized by International Bureau of Legal Metrology (BIML) Validated at operating conditions PR0A020I Issue/Rev. 0.0 (7/07) - Slide 13

Provers and Proving PR0A020I Issue/Rev. 0.0 (7/07) - Slide 14

What is a Liquid Flow Prover? Per API 4.1 An open or closed vessel of known volume utilized as a volumetric reference standard for the calibration of meters in liquid petroleum service. PR0A020I Issue/Rev. 0.0 (7/07) - Slide 15

Purpose of Proving To eliminate bias, its calibrated volume is traceable to an internationally recognized measurement standard PR0A020I Issue/Rev. 0.0 (7/07) - Slide 16

Definition of Terms From API Chapter 4 Calibration: The procedure to determine the volume of a prover Proving: The procedure to determine a meter factor Meter Factor: The ratio obtained by dividing the actual volume passed by the indicated volume registered Actual MF = Indicated PR0A020I Issue/Rev. 0.0 (7/07) - Slide 17

Definition of Terms From API Chapter 4 (cont d) Prover pass: In a displacement prover, one movement of the displacer between detectors Prover round: In a bidirectional prover, the trip forward and reverse passes PR0A020I Issue/Rev. 0.0 (7/07) - Slide 18

Meter Factor Meter Factor = Prover Volume Meter s Indicated Volume Factors influencing the meter s meter factor Flow rate Temperature Pressure Viscosity Wear Contamination PR0A020I Issue/Rev. 0.0 (7/07) - Slide 19

Open Tank Prover and Master Meter Prover Master Meter Prover Open Tank Prover PR0A020I Issue/Rev. 0.0 (7/07) - Slide 20

Small Volume Prover PR0A020I Issue/Rev. 0.0 (7/07) - Slide 21

Pipe Provers PR0A020I Issue/Rev. 0.0 (7/07) - Slide 22

Prover Volume Pre-run 10,000 pulses Distance Between Detectors PR0A020I Issue/Rev. 0.0 (7/07) - Slide 23

Calibration Waterdraw System PR0A020I Issue/Rev. 0.0 (7/07) - Slide 24

Bidirectional Prover PR0A020I Issue/Rev. 0.0 (7/07) - Slide 25

Condition Statement Proving conditions should match the operating conditions Flow rate Temperature Proving Pressure Conditions Liquid characteristics API gravity Viscosity Operating Conditions PR0A020I Issue/Rev. 0.0 (7/07) - Slide 26

Proving Direct Proving Best Accuracy Transfer Proving Reduced Accuracy with added uncertainty of master meter Master Meter Offsite Proven Significantly Reduced Accurate with added systemic error caused by installation and operating conditions PR0A020I Issue/Rev. 0.0 (7/07) - Slide 27

Product Characteristics PR0A020I Issue/Rev. 0.0 (7/07) - Slide 28

Product Characteristics Petroleum product characteristics can be classified into two general categories: Crude oil Refined products PR0A020I Issue/Rev. 0.0 (7/07) - Slide 29

Crude Oil Assays A Crude Oil Assay provides important information on the product s properties which is used to determine a meter s performance PR0A020I Issue/Rev. 0.0 (7/07) - Slide 30

Crude Oil Characteristics to Determine Meter Performance: 1. API gravity 2. Viscosity 3. Temperature 4. Cloud point 5. Vapor pressure 6. Sediment and water 7. Gases 8. Chemical contaminants PR0A020I Issue/Rev. 0.0 (7/07) - Slide 31

API Gravity API gravity is a measure of the weight density of crude oil at a specific temperature compared to water at a standard temperature, 60ºF The relationship between specific gravity (S.G.) and API gravity is: S.G. at 60ºF = 141.5 / (131.5 + API) PR0A020I Issue/Rev. 0.0 (7/07) - Slide 32

PR0A020I Issue/Rev. 0.0 (7/07) - Slide 33

Viscosity Viscosity expresses the readiness of a fluid to flow when it is acted on by a force. The absolute viscosity of a liquid is its resistance to internal deformation or shear stress The unit for absolute viscosity or dynamic viscosity in the metric system is a Poise (P) PR0A020I Issue/Rev. 0.0 (7/07) - Slide 34

Viscosity Units Commonly Used in the Petroleum Industry Dynamic viscosity (Symbolically, μ) has units of Poise (P) which equal 100 centipoises (cp) Kinematic viscosity (Symbolically, ν) has units of Stokes (St) which equal 100 centistokes (cst), where: ν (cst) = μ (cp) / S.G. (Specific Gravity) Saybolt Universal Second (SUS or SSU) Can be converted to cst using a conversion table PR0A020I Issue/Rev. 0.0 (7/07) - Slide 35

Temperature Effect on Petroleum Products The relationship of temperature and viscosity: The viscosity of a petroleum product decreases as the temperature increases but not proportionally The more viscous the product the greater the effect of temperature on the products viscosity PR0A020I Issue/Rev. 0.0 (7/07) - Slide 36

Cloud-Point The temperature at which wax crystals begin to form as it is cooled If a meter is operated below the cloud-point, wax can form on the measuring element and can significantly decrease an inference meter s ability to measure accurately PR0A020I Issue/Rev. 0.0 (7/07) - Slide 38

Sediment and Water (S&W) API defines S&W as: A material, coexisting with and yet foreign to a petroleum liquid, may include free water and sediment (FW&S) and emulsified or suspended water and sediment (SW&S) Pipeline Quality Oil Normally less than 1% S&W A requirement of pipeline operators Crude oil at the production level may be a problem Consider the fluid characteristics carefully before deciding on the type of meter to use. S&W greater than 1% can cause ultrasonic signals to deflect, lowering the number of velocity samples being processed which can affect the meter accuracy PR0A020I Issue/Rev. 0.0 (7/07) - Slide 39

Gases Slugs of gas can seriously damage mechanical meters like PD and turbine meters Entrained gas may not damage a meter but it: Does affect the measurement accuracy PD and Turbine Meters Interrupts the output signal Coriolis Mass and Ultrasonic PR0A020I Issue/Rev. 0.0 (7/07) - Slide 40

Gases In ultrasonic meters even a small number of gas bubbles can cause attenuation of the ultrasonic signal The degree of attenu-ation depends on a number of factors such as pressure, bubble size, amount of free gas, signal frequency, etc. PR0A020I Issue/Rev. 0.0 (7/07) - Slide 41

Chemical Contaminants Normally pipeline quality oil is not a problem. Crude oils at the production level can have a variety of chemicals and it is important to check the compatibility of the meters materials of construction with the crude oil assay. PR0A020I Issue/Rev. 0.0 (7/07) - Slide 42

Crude Oil Assay Website This website is operated on behalf of the UK Energy Institute HMC-4 Oil Transportation Measurement Committees to provide rapid access to crude oil measurement and property data. http://www.melvcon.co.uk/crude_oil_data/crude_oil_data.html PR0A020I Issue/Rev. 0.0 (7/07) - Slide 43

Crude Oil Assay Website PR0A020I Issue/Rev. 0.0 (7/07) - Slide 44

Refined Products PR0A020I Issue/Rev. 0.0 (7/07) - Slide 45

Topics of Discussion Viscosity/viscosity index (lubricating quality)/ driving torque Vapor pressure PR0A020I Issue/Rev. 0.0 (7/07) - Slide 46

Viscosity Viscosity Index abbreviated VI or lubricating quality is an arbitrary scale (0 400) used to show the magnitude of change in kinematic viscosity with temperature for refined products Fluid Driving Torque is defined as the turning force that is applied to a rotary mechanism to cause it to rotate. The amount of rotary torque is a function of fluid density (mass per unit volume). The lower the density, the lower the effective driving torque of the fluid on the rotor PR0A020I Issue/Rev. 0.0 (7/07) - Slide 47

Flow Fundamentals PR0A020I Issue/Rev. 0.0 (7/07) - Slide 51

Topics of Discussion Newtonian fluids Reynolds number Flow profile Swirl and cross flow Flow conditioning PR0A020I Issue/Rev. 0.0 (7/07) - Slide 52

Newtonian Fluid A Newtonian fluid is defined as a fluid which, when acted upon by an applied shearing stress, has a velocity gradient that is solely proportional to the applied stress Shear Stress (T) Newtonian Fluid Non-Newtonian Fluid Petroleum products and most mixtures of particles in petroleum products are Newtonian fluids Shear Rate dv ( dx ) PR0A020I Issue/Rev. 0.0 (7/07) - Slide 53

Reynolds Number d pipe ID v velocity R e = dνρ/μ ρ density μ viscosity A dimensionless parameter expressing the ratio between the inertia (driving) and viscous (retarding) forces. Useful formulas: Re = 2214 x BPH / (D x ν) or Re = 351 x m 3 /hr / (D x ν) Where the flow rate is in BPH barrels/hour (or m 3 /hr); D is the diameter of the meter in inches; and, ν is the kinematic viscosity of the fluid. PR0A020I Issue/Rev. 0.0 (7/07) - Slide 54

Flow Profile vs. Reynolds Number Laminar < Re = 2,000; Turbulent > Re = 4,000 to 6,000 PR0A020I Issue/Rev. 0.0 (7/07) - Slide 55

Flow Profile vs Performance Laminar Flow (Re < 2,000) Higher Viscosities Velocity Max. V Turbulent or Plug Flow (Re > 6,000) Low Viscosities Max. V Average V Average V Average Velocity 3/4 Maximum Velocity Average Velocity Maximum Velocity K-Factor Reynolds Number (Re No.) PR0A020I Issue/Rev. 0.0 (7/07) - Slide 56

Petroleum Products vs Reynolds No. Heavy Crude Medium Crude Light Crude Refined Products K-Factor Heating Oil Diesel Gasoline LPG 2,000 50,000 1,000,000 Reynolds Number (Re No.) PR0A020I Issue/Rev. 0.0 (7/07) - Slide 57

Fluid Flow and Velocity Profile REDUCERS EXPANDERS Secondary flow Secondary flow Elbow Valve High-flow entering pipe Two or more elbows Two elbows, same plane, with valve PR0A020I Issue/Rev. 0.0 (7/07) - Slide 58

Fluid Flow and Swirl PR0A020I Issue/Rev. 0.0 (7/07) - Slide 59

Flow Conditioning PR0A020I Issue/Rev. 0.0 (7/07) - Slide 60

Why Flow Conditioning? Improper flow pattern upstream of a turbine meter showing fluid swirl Flow in two directions This condition is caused by: Elbows Valves Reducers Strainers PR0A020I Issue/Rev. 0.0 (7/07) - Slide 61

Flow Profile Proper flow profile can be distorted by obstructions This unwanted condition may also be caused by: Partially open ball valves Eccentric reducers, elbows PR0A020I Issue/Rev. 0.0 (7/07) - Slide 62

Conventional Straightening Section API Recommended Flow Conditioning 10 Pipe Diameters 5 Pipe Diameters Straightening Vanes Upstream Pipe Section Meter Downstream Pipe Section PR0A020I Issue/Rev. 0.0 (7/07) - Slide 63

Fin Type High Performance Flow Conditioner FLOW 10 Pipe Diameters PR0A020I Issue/Rev. 0.0 (7/07) - Slide 64

Flow Conditioners High Performance Flow Conditioner with Fins Conventional Flow Conditioner with Tube Bundle PR0A020I Issue/Rev. 0.0 (7/07) - Slide 65

Mathematical Model Testing of Flow Conditioners Objective Evaluate Flow Conditioners for their ability to remove swirl and to condition distorted flow profiles Procedure Using a Computational Fluid Dynamics (CFM) model to determine the efficiencies of the flow conditions of different designs over a wide Reynolds Number range PR0A020I Issue/Rev. 0.0 (7/07) - Slide 66

Mathematical Model Testing - Conventional Flow Conditioners V Cross Sectional Velocity Profile at 7 Diameters Downstream PR0A020I Issue/Rev. 0.0 (7/07) - Slide 67

Mathematical Model Testing - High Performance Flow Conditioner V Cross Sectional Velocity Profile at 7 Diameters Downstream PR0A020I Issue/Rev. 0.0 (7/07) - Slide 68

Conclusion Flow Conditioning Conventional Flow Conditions (CFC s) are effective at reducing swirl and are adequate for many applications High Performance Flow Conditioners (HPFC s) reduce swirl and flow profile distortion over a wider range of operating conditions Fin type HPFC have a lower pressure drop than most flow conditioners PR0A020I Issue/Rev. 0.0 (7/07) - Slide 69

Accuracy PR0A020I Issue/Rev. 0.0 (7/07) - Slide 70

Accuracy The closeness in the agreement between the result of a measurement and the true value of the measurement. The quantitative expression of accuracy is in terms of uncertainty. Good accuracy implies small random and systematic errors. PR0A020I Issue/Rev. 0.0 (7/07) - Slide 71

The Cost of Inaccuracy Application 12" Pipeline Throughput of 100,000 BPD Cost Per Barrel - $90 Value of each 0.1% of bias: $9,000/Day $3,285,000/Year PR0A020I Issue/Rev. 0.0 (7/07) - Slide 72

Types of Errors Spurious errors Errors that result from obvious failures that can be identified and documented. Remedy: Good procedures Random errors Errors that cause a variation in output reading even when the input parameter has not changed. Remedy: Track Repeatability and Define an Uncertainty Tolerance PR0A020I Issue/Rev. 0.0 (7/07) - Slide 73

Types of Errors Systemic error A bias that may vary over the range but is constant in time, and could, in principle, be corrected out of the reading Remedy: In-situ proving of the meter PR0A020I Issue/Rev. 0.0 (7/07) - Slide 74

Uncertainty Statement: An estimate characterizing the range of values within which the true measured value of a quantity lies and how frequently the reading does lie within this range - Confidence Level. Custody Measurement starts with verification or proving a meter to a repeatability of 0.05% with 5 runs. Statistically this is an uncertainty of: +/- 0.027% at 95% confidence level. PR0A020I Issue/Rev. 0.0 (7/07) - Slide 75

Uncertainty Statement: PR0A020I Issue/Rev. 0.0 (7/07) - Slide 76

Accurate Measurement ± 0.1% repeatable 20 out of 20 100% confidence level Zero bias 20 0 0 0 0 Center of Target PR0A020I Issue/Rev. 0.0 (7/07) - Slide 77

Custody Measurement ± 0.1% repeatable 19 out of 20 95% confidence level Zero bias 19 0 1/2 1/2 0 Center of Target PR0A020I Issue/Rev. 0.0 (7/07) - Slide 78

Repeatable but Biased ± 0.1% repeatable 19 out of 20 95% confidence level 0.4% bias 19 Bias 0 1/2 1/2 0 Center of Target PR0A020I Issue/Rev. 0.0 (7/07) - Slide 79

Poor Repeatability ± 0.3% repeatable 19 out of 20 95% confidence level Zero bias 8 1/2 1 4 1/2 4 1/2 1 1/2 Center of Target PR0A020I Issue/Rev. 0.0 (7/07) - Slide 80

Basic Measurement - Summary ± 0.1% repeatable 20 out of 20 100% confidence level Zero bias ± 0.1% repeatable 19 out of 20 95% confidence level Zero bias ± 0.1% repeatable 19 out of 20 95% confidence level 0.4% bias ± 0.3% repeatable 19 out of 20 95% confidence level Zero bias PR0A020I Issue/Rev. 0.0 (7/07) - Slide 81

Conclusion The key criteria for accurate measurement Understand the fundamentals for the Custody Transfer Applications Proper Application to Minimize Systematic Errors In-situ Proving that is Traceable to a Measurement Standard PR0A020I Issue/Rev. 0.0 (7/07) - Slide 82