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Orifice Plate Diagnostics and Prognosis
Presented by
Jennifer Ayre, Swinton Technologyon behalf of
Mark Skelton, BP Exploration Operating Co.
Slide 1
Oil and Gas Focus Group MeetingWeds 11th May 2011, Norwich
BP CATS Metering Teamhave a Vision
Slide 2
Less Expensive Auditing
Less Calibration
Less Frequent Inspections
Slide 3
4
The Vision
Preventative Maintenance, Accuracy Assurance, Mismeasurement Alerts
So Here is the Story...
Slide 5
1st Orifice Plate Inspection
5167 years B.C
Slide 6
Since then, nothing changed…
Slide 7
… 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 presentation discusses the results of these field trials
Slide 8
A Brief Review of the Diagnostic Methods• 3 DP’s give 3 DP pairs ,each pair
provides a DP ratio and 2 mass flows.
Ideally 6D downstream
Slide 9
The Diagnostic Methods & Presentation ● 1 DP pair gives 1 DP ratio and 2 mass flows
● The difference between the DP ratio and an ISO calculated value is divided by a comparable uncertainty (y-axis)
● The difference between the 2 mass flows is divided by an assigned uncertainty (x-axis)
● The DP pair y and x coordinates form one point in the diagnostics box .The other 2 DP pairs provide 2 more points in diagnostics box
(-1,1) (1,1)
(1,-1)(-1,-1)
Slide 10
• The diagnostic software can be applied via the meter’s flow computer
Field Data
Flow Computer
Metering Supervisory PC
+ Diagnostics Software
Additional I/O
Metering Supervisory PC
Applying the Diagnostic Solution
Diagnostics PC
• The diagnostic software can be applied via the meter’s flow computer OR via a separate I/O device to a dedicated PC
• DCS,• Historians• Maint
Scheduling• Email etc
Slide 11
The Trials
Testing at CEESI Colorado
Testing at CEESI Iowa
BP CATS Field Trial
CoP TGT Field Trial
Slide 12
Slide 13
• BP operates CATS in Teesside, UK
• The terminal receives gas from multiple operators including BP & ConocoPhillips
• BP CATS has metering stations with multiple large orifice meters in parallel
•
• Field trials of Prognosis were carried out on one flange tapped 16”, 0.596 beta ratio orifice meter in a BP CATS metering station
• The stations natural gas flow was averaging (approx) 525 tonnes /hr
BP CATS
Slide 14
BP CATS, May 2010
• Pipe ID 13.738”
d=8.195” (0.596 beta)
Slide 15
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 edgeSlide 16
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
Slide 17
18
Keypad Diameter Orifice Errors (d= 8.195”)
d=8.100” -2.6% flowrate error
d=8.295” +2.9% flowrate error
Slide 18
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
Slide 19
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: kPakPa 2.112.67.15 Slide 20
21
DP Transmitter Calibration Issues (Correct Calibration: 4mA-0kPa & 20mA-62kPa)• 20mA – 60kPa -1.6% flowrate error
• 20mA – 64kPa +1.6% flowrate error
Slide 21
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
Slide 22
Reversed Orifice Plate (cont.)• Stream 5’s reversed
plate diagnostic result
• All meters read the same however..,
• Prognosis indicated the error
Slide 23
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
Slide 24
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
Slide 25
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
Slide 26
27
Keypad Diameter Inlet Errors (D =850.335mm)
ID=870.335mm-0.65% flowrate error
ID=830.335mm+0.75% flowrate error
Slide 27
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
Slide 28
Reduced Carbon Footprint (orifice)
Assurance of Compliance and Accuracy
Less visits to remote operations
Less Frequent Meter Inspections
Reduced safety risks Proof of meter
performance over time
Observed Benefits
Realisation
Slide 31
The Future.....Wow look at this!!
Centralised Remote Diagnostics at a
Glance !!!
Slide 32
DECC Statement
"DECC actively supports the use of two or three different DP measurements and associated software for diagnostic purposes on DP meters as introduced by Dr Richard Steven in [1] and [2]
as it has the potential to detect measurement errors as they arise, and to therefore greatly reduce the required frequency of
maintenance activities associated with DP-based measurement systems. Operators of relevant systems are encouraged to
approach DECC with a view to adopting condition-based monitoring strategies featuring this method.”
[1] 2008 NSFMW paper: Diagnostic Methodologies for Generic Differential Pressure Flow Meters
[2] 2009 NSFMW paper: Significantly Improved Capabilities of DP Meter Diagnostic Methodologies
Thank You
QUESTIONS?
Slide 34