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1. Developments in the Self-Diagnostic Capabilities of Orifice Plate Metersby Mark Skelton, BP Exploration Operating Co.
Simon Barrons, ConocoPhillips UK
Jennifer Ayre, Swinton Technology
Richard Steven, DP Diagnostics
2. BP CATS Metering Teamhave 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?