API Review. Copyright 2007, FMC Technologies Measurement Solutions, Inc. PR0A028I Issue/Rev. 0.0 (7/07) - Slide 1

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1 API Review PR0A028I Issue/Rev. 0.0 (7/07) - Slide 1

2 API MPMS Chapter 5, Section 1 General Considerations for Measurement by Meters PR0A028I Issue/Rev. 0.0 (7/07) - Slide 2

3 Introduction The advantages of metering: Increases the availability of tanks Leads to display of instantaneous flow rate and volume Delivers a volume taken from several sources at the same time into one receptor Delivers a volume taken from a single source into multiple receptors Can be checked against standards Simplified Temperature averaging & sampling PR0A028I Issue/Rev. 0.0 (7/07) - Slide 3

4 API Design Considerations Typical schematic diagram of single Inferential flow meter installation The installation should provide for proving each meter and should be capable of duplicating normal operating conditions at the time of proving Note: All sections of line that may be blocked between valves shall have provisions for pressure relief (preferably not installed between the meter and prover). 1 Block Valve* 2 Differential Pressure Device* 3 Strainer and/or Air Eliminator* 4 Flow Conditioning Element 5 Inferential Flow Meter 6 Straight Pipe 7 Pressure Measurement Device 8 Temperature Measurement Device 9 Temperature Test Well 10 Positive Shutoff Double Block and Bleed Valve 11 Control Valve* 12 Check Valve* 13 Densitometer* 14 Detector Switch 15 Prover *If Required PR0A028I Issue/Rev. 0.0 (7/07) - Slide 4

5 Meter Performance For custody transfer applications, meters with the highest inherent accuracy should be used and should be proven on site PR0A028I Issue/Rev. 0.0 (7/07) - Slide 5

6 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 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 PR0A028I Issue/Rev. 0.0 (7/07) - Slide 6

7 API MPMS Chapter 5, Section 8 Measurement of Liquid Hydrocarbons by Ultrasonic Flow Meters Using Transit Time Technology PR0A028I Issue/Rev. 0.0 (7/07) - Slide 7

8 8.1 Introduction This document describes methods for the installation and operation of ultrasonic flow meters (UFM s) when they are used to measure liquid hydrocarbons Ultrasonic meters are inferential meters that derive the liquid flow rate by measuring the transit times of high-frequency sound pulses PR0A028I Issue/Rev. 0.0 (7/07) - Slide 8

9 8.3 Field of Application The field of application of this standard is the dynamic measurement of liquid hydrocarbons While this document is specifically written for custody transfer measurement, other acceptable applications may include: Allocation measurement Check meter measurement Leak detection measurement PR0A028I Issue/Rev. 0.0 (7/07) - Slide 9

10 8.6 Design Considerations Typical schematic diagram of single ultrasonic flow meter installation Note: All sections of line that may be blocked between valves shall have provisions for pressure relief (preferably not installed between the meter and prover). 1 Block Valve* 2 Differential Pressure Device* 3 Strainer and/or Air Eliminator* 4 Flow Conditioning Element 5 Ultrasonic Flow Meter 6 Straight Pipe 7 Pressure Measurement Device 8 Temperature Measurement Device 9 Temperature Test Well 10 Positive Shutoff Double Block and Bleed Valve 11 Control Valve* 12 Check Valve* 13 Densitometer* 14 Detector Switch 15 Prover *If Required PR0A028I Issue/Rev. 0.0 (7/07) - Slide 10

11 8.9.1 Flow Conditioning Flow conditioning elements intended to reduce swirl or velocity profile distortion may be required The design shall ensure appropriate flow conditioning upstream and downstream (same requirements as turbine meters) unless the meter manufacturer s recommendations or flow research support different lengths PR0A028I Issue/Rev. 0.0 (7/07) - Slide 11

12 8.10 Meter Performance Meter factor shall be determined by proving the meter at stable operating conditions i.e., essentially constant: flow rate, density, viscosity, temperature and pressure Chapter Operation of Proving Systems PR0A028I Issue/Rev. 0.0 (7/07) - Slide 12

13 8.10 Proving (cont d) Questions often arise concerning the differences between proving or calibrating a meter in a laboratory (bench) versus in-situ (field) These two proving locations can produce different results and cannot necessarily be interchanged without introducing measurement error PR0A028I Issue/Rev. 0.0 (7/07) - Slide 13

14 In-situ Proving In-situ proving is normally preferred because it verifies the meter's accuracy under actual operating conditions Operating conditions can affect a meter's accuracy and repeatability In-situ proving at stable operating conditions compensates for variations in performance caused by flow rate, viscosity, density, temperature, pressure, as well as flow conditions, piping configurations and contaminants PR0A028I Issue/Rev. 0.0 (7/07) - Slide 14

15 Conclusion From API Field Tests 1 The batch volumes measured by the UFM s agree very well with the batch volumes measured with the referee meters the conclusion to be drawn is that the test meters and referee meters compare well so long as current meter factors obtained at operating conditions are used for each meter This simply reinforces the long held axiom that a custody transfer meter needs to be proved at conditions that are close to the conditions at which the meter will be used to measure custody transfer quantities 1. Ultrasonic Flow Meter Performance Evaluation of Field Test Data, Wesley G. Poynter, Ph.D., August 12, 2001 PR0A028I Issue/Rev. 0.0 (7/07) - Slide 15

16 Laboratory Proving Laboratory proving is normally not preferred because laboratory conditions may not duplicate the operating conditions While there are more measurement uncertainties associated with laboratory proving, under certain conditions, it may provide the best alternative PR0A028I Issue/Rev. 0.0 (7/07) - Slide 16

17 11 Proving Accuracy and Repeatability Proving accuracy can be affected by the delayed manufactured flow pulses from a UFM These delayed manufactured flow pulses can lead to a bias error in the calculated meter factor depending upon the magnitude of the flow rate change that occurs during the proving run and the duration of the prove run PR0A028I Issue/Rev. 0.0 (7/07) - Slide 17

18 12.5 Zeroing the Meter Zeroing an UFM is a procedure that involves checking the output while the meter is blocked-in Under these conditions, and if the output of the meter does not indicate zero flow, then the manufacturer s (re-) zeroing procedure shall be followed Whenever the meter is re-zeroed, it shall be re-proved PR0A028I Issue/Rev. 0.0 (7/07) - Slide 18

19 14 Diagnostics Certain parameters can be monitored based on the specific application. The parameters below are typical of those that may be accessed via a serial data interface or other means Comparing lab determined diagnostic parameters to the same parameters when installed in the field may help identify field installation effects or other parameter changes PR0A028I Issue/Rev. 0.0 (7/07) - Slide 19

20 Appendix B Verification and Validation of Meter Performance The turbulent flow field in a pipe is complex and contains numerous turbulent eddies and non-axial velocity components Turbine meters and other mechanical flow measurement devices integrate this field through mechanical convergence and are not particularly influenced by minor changes in flow stability PR0A028I Issue/Rev. 0.0 (7/07) - Slide 20

21 Meter Verification (cont d) Ultrasonic flow meters take snapshots of the fluid velocity along one or more sample paths Real time integration of the flow field, including both axial and non-axial components, results in a less well-behaved output and inherently more scatter. However, this scatter, because it is random, will be evenly distributed around the mean meter factor PR0A028I Issue/Rev. 0.0 (7/07) - Slide 21

22 Meter Factor Uncertainty UFM performance verification can be ascertained by conventional means and to a level consistent with API MPMS, Ch. 4.8, Table A-1 which is: ±0.027% uncertainty at 95% confidence level PR0A028I Issue/Rev. 0.0 (7/07) - Slide 22

23 What Does This Mean? Based on field data LUFM s may require a larger prover volume to achieve this same level of meter factor uncertainty More than 5 proving runs may be required to verify the meter s performance PR0A028I Issue/Rev. 0.0 (7/07) - Slide 23

24 PR0A028I Issue/Rev. 0.0 (7/07) - Slide 24

25 PR0A028I Issue/Rev. 0.0 (7/07) - Slide 25

26 Appendix C Manufactured Flow Pulses and Their Impact on the Proving Process Because the UFM uses an electronic sampling methodology to determine flow rate, the manufactured pulse train obtained from a UFM at any instant in time will represent flow (or volume throughput) that has already occurred (i.e., the manufactured flow pulses lag the measured flow). PR0A028I Issue/Rev. 0.0 (7/07) - Slide 26

27 Increased Sampling In order to optimize the flow measurement, and accommodate unique installation effects, some UFM's can be configured to process a larger number of measurement samples. Increasing the number of measurement samples increases the time delay between the flow or volume represented by the manufactured flow pulses PR0A028I Issue/Rev. 0.0 (7/07) - Slide 27

28 Time Delay in Proving In normal operation, delay between flow pulses and the actual measured flow has little impact on measurement accuracy if the correct meter factor has been used However, during the proving process, delayed flow pulses may cause poor run to run repeatability and/or introduce a bias error in the calculated meter factor PR0A028I Issue/Rev. 0.0 (7/07) - Slide 28

29 - Performance Data Flowrate vs K-Factor Ultra6 10B - Groups Proving 30K Test System K-Factor (P/BBL) No FC: 11.2:1 Turndown Linearity = +/ % HPFC: 10.4:1 Turndown Linearity = +/ % Flowrate (BPH) 10B NO FC 10B HPFC PR0A028I Issue/Rev. 0.0 (7/07) - Slide 29

30 - Performance Data Flowrate vs Repeatability Ultra6 10B - Groups Proving 30K Test System Groups Repeatability (%) Flowrate (BPH) Repeatability Criterion 10B NO FC Repeatability Data 10B HPFC Repeatability Data PR0A028I Issue/Rev. 0.0 (7/07) - Slide 30

31 - Performance Data Flowrate vs. K-Factor LUFM 8B - Ellerbek Testing July Linearity: (11:1 Turndown) With HPFC: +/ % No FC: +/ % K-Factor (P/BBL) Flowrate (BPH) 8B with HPFC 8B with NO FC PR0A028I Issue/Rev. 0.0 (7/07) - Slide 31

32 - Performance Data Flowrate vs. Repeatability LUFM 8B - Ellerbek Testing July Total Repeatability (%) Flowrate (BPH) 8B w HPFC 8B Acceptance Criteria (HPFC) 8B w NO FC 8B Acceptance Criteria (NO FC) PR0A028I Issue/Rev. 0.0 (7/07) - Slide 32

33 Recommendations To minimize any meter factor bias error, and/or to obtain the best possible span of repeatability results, it is important to ensure that: The flow rate remains constant just before the first detector and throughout each prove run. The time delay between the manufactured pulses and the actual measured flow is minimized in accordance with the manufacturer s recommendations. PR0A028I Issue/Rev. 0.0 (7/07) - Slide 33