Transcript Developments in the Self-Diagnostic Capabilities of

Oil and Gas Focus Group Meeting
Weds 11th May 2011, Norwich
Orifice Plate Diagnostics and
Prognosis
Presented by
Jennifer Ayre, Swinton Technology
on behalf of
Mark Skelton, BP Exploration Operating Co.
Slide 1
BP CATS Metering Team
have a Vision
Slide 2
Less Frequent
Inspections
Less Calibration
Less Expensive Auditing
Slide 3
The Vision
Preventative Maintenance, Accuracy
4
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.
Slide 9
Ideally 6D
downstream
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)
Slide 10
(1,1)
(1,-1)
Applying the Diagnostic Solution
• The diagnostic software can be applied via the
meter’s flow computer OR via a separate I/O
device to a dedicated PC
Metering
Supervisory
PC
+ Diagnostics
Software
Field Data
Flow Computer
•DCS,
•Historians
•Maint Scheduling
•Email etc
Diagnostics PC
Additional I/O
Slide 11
The Trials
Testing at
CEESI Iowa
CoP TGT Field Trial
BP CATS Field Trial
Testing at CEESI
Colorado
Slide 12
Slide
13
BP CATS
• 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
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 edge
Slide 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
Keypad Diameter Orifice Errors (d= 8.195”)
d=8.100”
-2.6% flowrate error
d=8.295”
+2.9% flowrate error
Slide 18
18
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
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: 15.7kPa 
6.2  11.2kPa
Slide 20
DP Transmitter Calibration Issues
(Correct Calibration: 4mA-0kPa & 20mA-62kPa)
• 20mA – 60kPa
• 20mA – 64kPa
-1.6% flowrate error
+1.6% flowrate error
Slide 21
21
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 22
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
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
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
Keypad Diameter Inlet Errors (D =850.335mm)
ID=870.335mm
-0.65% flowrate error
ID=830.335mm
+0.75% flowrate error
Slide 27
27
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
28
Observed Benefits
Assurance of
Compliance
and Accuracy
Less Frequent
Meter Inspections
Less visits to
remote operations
Reduced Carbon
Footprint (orifice)
Reduced safety
risks
Proof of meter
performance over
time
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