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Measuring Circumferential Metal Loss
Rates in Subsea Pipelines
Presented by
Dan Clarke
1
Dan Clarke
7 December 2012
Contents
Introduction to Corrosion Monitoring
RPCM™ Technology Overview
2
Measurement Performance
Case Studies
Inspection
Data
Introduction to Corrosion MonitoringIntegrity Management
3
Mitigation
Monitoring Data Analysis
Integrity Monitoring forms an essential part of any Integrity
Management Strategy
Introduction to Corrosion MonitoringCorrosion Modelling
4
?
S R
ProtectedExposed
x S
RPCM™ Technology OverviewElectrical Resistance Measurement Principle
5
Cumulative Corrosion (x0 – x) = f(VS / VR)
Corrosion rate = -dx / dt
VS VR
I
bl
xx0 S
RPCM™ Technology OverviewSubsea Corrosion Probe
6
Basic implementation of high resolution ER measurement.
• Full circumference corrosion and temperature measurement (8 sectors)
• CEION® technology sub-micron measurement
• Welded or flanged into pipe
• Designed for life of field (>25 years)
RPCM™ Technology OverviewKey Attributes
S1S2
S3
S8
S7
S6S5
S4
7
• Designed for life of field (>25 years)
• No diameter transition / ‘piggable’
• Typical applications: flowline spools, export pipelines, onshore
• ‘Online’ device (Modbus, Canbus)
• 18-30VDC continuous, <10W
• Qualified for subsea HTHP applications
• 15kpsi, 350F, 3000m water depth
S5
HPHT(High pressure High Temperature)
PUP PieceCustomer supplied Material
Recoverable Electronics Drop Protection Frame
RPCM™ Technology OverviewComponents
8
Inner spoolForged Reducers
PUP PieceCustomer supplied Material
RPCM™ Technology OverviewRing Pair Sensor Operation
CRA flange
Pipe rings
9
• Ceramic coated rings machined from free-issue pipe (usually carbon steel) are
retained between 2 CRA flanges.
• Sample rings inner surfaces are left uncoated.
• Ceramic provides isolation and corrosion resistance.
• Wires attached on outside of sensor rings are fed out to a non-retrievable pod via
primary and secondary HTHP penetrators.
S RS R S R
Electrical Contact
Sample Reference
IIN,0
I1,IN
12
3
6
7
8
12
3
46
7
8 Sector Metal Loss (nm)
Ref Temp (degC)
1
2
3
Ring Pair Data
I1,OUT
RPCM™ Technology OverviewMeasurement Operation
10
45
6 45
6
• Sample and Reference Rings are in series with one another and a controlled current source.
• Each Ring Pair operates independently from other Ring Pairs (allows redundancy).
• For each measurement cycle, current is injected in Mode 0 (4sec), then switched to Mode 1 (4 sec).
• Total measurement cycle is approximately 10 seconds.• Real time calculation of Metal Loss per sector
3
4
5
6
7
8
Average
IOUT,0
RPCM™ Technology OverviewRing Pair Configurations
Ring Pair Type Corrosion Type
General “Uniform”, TOL, Mesa, Pitting
Welded Preferential Weld
11
• Corrosion mechanisms measured
by changing geometry and ring
material
• 2-4 RPs is the ‘standard’
configuration but more possible.
• Typical Config: 4 RPs, 2 General, 2
Welded
CRA (e.g. Duplex) Pitting
Pre-Pitted Pitting / Crevice
High Sensitivity All
Redundant All
Measurement PerformanceThe Importance of Resolution
Corrosion Rate Time to Detection
1 micron resolution
100 microns resolution
0.1 mm / yr <4 days 1 yr
0.5 mm / yr <18 hours 73 days
12
• Resolution is defined as the smallest change that can be
detected
• High resolution enables changes in corrosion rate to be
identified quickly.
• An amount of metal equivalent to the resolution is lost before
the operator has a chance to respond.
0.5 mm / yr <18 hours 73 days
1.0 mm / yr <9 hours 37 days
Measurement PerformanceThe Importance of Resolution
1.5
2.0
2.5
3.0
3.5
Re
solu
tio
n (
mic
ron
s)RPCM Metal Loss Resolution vs Pipe Diameter
1.5
2.0
2.5
3.0
3.5
Re
solu
tio
n (
mic
ron
s)RPCM Metal Loss Resolution vs Pipe Diameter
Filter Time Constant ~ 3 hours
13
0.0
0.5
1.0
0 5 10 15 20 25 30 35 40
Re
solu
tio
n (
mic
ron
s)
Pipe Diameter
300 bar 600 bar
0.0
0.5
1.0
0 5 10 15 20 25 30 35 40
Re
solu
tio
n (
mic
ron
s)
Pipe Diameter
300 bar 600 bar
• Low pass 1st order filter with TC ~ 3 hours
• Resolution determined by magnitude of resistance
• Relatively insensitive for large pipe diameters
(inches)
400
500
600
700
800
Met
al L
oss
(M
icro
ns)
Sector 1Sector 2Sector 3
RPCM Sector Data
12
3
45
6
7
8
Measurement PerformanceTop-of-Line Corrosion Case Study
3
14
• Stratified flow / high temp
• Dissolved CO2 / H2S
• Cold spots are vulnerable
• Organic acids (acetic, HCl)
• BOL protected by inhibitor
0
100
200
300
0 100 200 300 400
Days
Met
al L
oss
(M
icro
ns)
Sector 4
Sector 5Sector 6Sector 7
5
Case StudyCoP Judy Jade North Sea 2001
15
2 x 16” Spool flanged into SSV
Case StudyCoP Judy Jade North Sea 2001
16
Performance of subsea spool after 5 years continuous
operation
• RPCMs have extensive field history
• Widely accepted technology for
subsea pipeline corrosion monitoring
• Full circumferential view
• Versatile configuration – allows
monitoring of: PWC, other alloys,
Conclusions
17
monitoring of: PWC, other alloys,
pitting etc
• Flexible platform for other
measurements
– PT
– Conductivity (EIS)
– Single Phase Flow
• Resolution circa 1 micron (near real-
time)
Thank you for your attention!
18