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Developments in the Self-Diagnostic Capabilities of Orifice Plate Meters by

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Developments in the Self-Diagnostic Capabilities of Orifice Plate Meters by

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    1. Developments in the Self-Diagnostic Capabilities of Orifice Plate Meters by Mark Skelton, BP Exploration Operating Co. Simon Barrons, ConocoPhillips UK Jennifer Ayre, Swinton Technology Richard Steven, DP Diagnostics

    2. BP CATS Metering Team have a Vision

    3. Less Expensive Auditing

    4. The Vision

    5. So Here is the Story...

    7. Since then, nothing changed…

    8. … until now! 2008 & 2009: DP Diagnostics described diagnostic methods for DP meters 2010: Swinton Technology developed “Prognosis” with DP Diagnostics BP CATS have given Prognosis an extensive field trial & CoP TGT have given Prognosis an initial field trial This paper discusses the results of these field trials

    9. A Brief Review of the Diagnostic Methods

    10. The Diagnostic Methods & Presentation The 3 “meters” are compared to each other (x-axis) The 3 DP ratios are compared to ISO baselines (y-axis) This gives 3 points on a diagnostic graph

    11. The diagnostic software can be applied via the meter’s flow computer Applying the Diagnostic Solution

    12. The Trials

    15. BP CATS, May 2010 Pipe ID 13.738” d=8.195” (0.596 beta)

    16. BP CATS Field Trial Examples Baseline (correct operation) Incorrectly entered inlet diameter Incorrectly entered orifice diameter Saturated DP transmitter Incorrectly calibrated DP transmitter Reversed plate Worn orifice edge

    17. Baseline Results at BP CATS First baseline test results were inside the NDB (as required) The theoretical correction factor was applied due to downstream tap >6D & thermowell upstream of this tap

    18. Keypad Diameter Orifice Errors (d= 8.195”) d=8.100” -2.6% flowrate error d=8.295” +2.9% flowrate error

    19. Keypad Diameter Inlet Errors (D = 13.738”) ID=13.938” (sch 100) -0.5% flowrate error ID=13.562” (sch 120) +0.4% flowrate error

    20. Saturated DP Transmitter (DPt=17.5kPa) DP transmitter stack: Low range transmitter, 0–15kPa, saturated If used it induces a -6.2% flowrate error Pattern indicates a DP problem & that it’s a traditional DP problem Also:

    21. DP Transmitter Calibration Issues (Correct Calibration: 4mA-0kPa & 20mA-62kPa) 20mA – 60kPa -1.6% flowrate error 20mA – 64kPa +1.6% flowrate error

    22. Reversed Orifice Plate A reversed plate in stream 5 produced a -15% error. Streams 2,3 & 5 were on line However all meters stated the same flowrates!? Meter 5’s flow resistance is reduced, & flow favours stream 5 by +15%, so error cancels this! Similar equilibrium existed for all other stream combinations tried It is not possible to monitor orifice meter performance in parallel runs by inter-comparing the parallel meters

    23. Reversed Orifice Plate (cont.) Stream 5’s reversed plate diagnostic result All meters read the same however.., Prognosis indicated the error

    24. Worn Orifice Edge Stream 5’s plate was deliberately worn, inducing a -2% error Streams 1,2 & 5 on line Again all meters showed same flow Prognosis alone indicated the error

    25. ConcoPhillips TGT CoP operates TGT in Lincolnshire, UK The terminal is co-owned by BP & CoP It receives gas from multiple operators Initial field trials of Prognosis were carried out on a corner tap 36”, 0.5997 beta ratio orifice meter at TGT The natural gas flow was averaging (approx) 400 tonnes /hr

    26. Baseline Results at CoP TGT A slight bias in the diagnostic baseline was found due to the downstream tapping configuration A small zeroing factor was therefore applied

    27. Keypad Diameter Inlet Errors (D =850.335mm) ID=870.335mm -0.65% flowrate error ID=830.335mm +0.75% flowrate error

    28. Summary Swinton Technology have developed the DP Diagnostics orifice meter diagnostics concept into a practical industrial product (‘Prognosis”) Field tests at BP CATS & CoP TGT were successful and are ongoing Prognosis is designed to warn of orifice meter system malfunctions, hence reducing costly exposure Most orifice meter errors could be seen at = 1% error

    29. Less Frequent Meter Inspections

    30. Observed Benefits BP and CoP regard Prognosis as a means of assurance that a meter does not have a problem Custody transfer orifice meters are currently regularly inspected with routine maintenance. A system showing that the meter is OK, saves on needless maintenance Besides the cost saving this also reduces the quantity of gas released to the environment & personnel exposure to the dangers of the high pressure system

    31. Realisation

    33. Operator views continued

    34. Thank You QUESTIONS?

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