Measuring Circumferential Metal Loss Rates in Subsea Pipelines Presented by Dan Clarke 7 December 2012 1
Contents Introduction to Corrosion Monitoring RPCM Technology Overview Measurement Performance Case Studies 2
Introduction to Corrosion Monitoring Integrity Management Inspection Monitoring Data Analysis Mitigation 3 Integrity Monitoring forms an essential part of any Integrity Management Strategy
Introduction to Corrosion Monitoring Corrosion Modelling? 4
RPCM Technology Overview Electrical Resistance Measurement Principle Exposed Protected S R x 0 x S b l V S V R Cumulative Corrosion (x 0 x) = f(v S / V R ) Corrosion rate = -dx/ dt I 5
RPCM Technology Overview Subsea Corrosion Probe Basic implementation of high resolution ER measurement. 6
RPCM Technology Overview Key Attributes 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) 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 7 S1 S2 S8 S3 S7 S6 S4 S5
RPCM Technology Overview Components Recoverable Electronics Drop Protection Frame PUP Piece HPHT Customer supplied Material (High pressure High Temperature) PUP Piece Customer supplied Material Inner spool 8 Forged Reducers
RPCM Technology Overview Ring Pair Sensor Operation Pipe rings CRA flange 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 9 primary and secondary HTHP penetrators.
I 1,IN 10 RPCM Technology Overview Measurement Operation 7 8 I IN,0 1 Sample 2 3 Reference 6 4 6 4 5 5 7 Ring Pair Data 1 8 2 Sector Metal Loss 3 (nm) I OUT,0 I 1,OUT 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 1 2 3 4 5 6 7 8 Average Ref Temp (degc)
RPCM Technology Overview Ring Pair Configurations Ring Pair Type Corrosion Type General Welded Uniform, TOL, Mesa, Pitting Preferential Weld CRA (e.g. Duplex) Pre-Pitted High Sensitivity Redundant Pitting Pitting / Crevice All All Corrosion mechanisms measured by changing geometry and ring material 2-4 RPsis the standard configuration but more possible. Typical Config: 4 RPs, 2 General, 2 Welded 11
Measurement Performance The Importance of Resolution Corrosion Rate 1 micron resolution Time to Detection 0.1 mm / yr <4 days 1 yr 100 microns resolution 0.5 mm / yr <18 hours 73 days 1.0 mm / yr <9 hours 37 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.
Measurement Performance The Importance of Resolution Resolu ution (microns) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 RPCM Metal Loss Resolution vs Pipe Diameter Filter Time Constant ~ 3 hours 0 5 10 15 20 25 30 35 40 Pipe Diameter (inches) 300 bar 600 bar 13 Low pass 1 st order filter with TC ~ 3 hours Resolution determined by magnitude of resistance Relatively insensitive for large pipe diameters
Measurement Performance Top-of-Line Corrosion Case Study 2 1 8 3 800 700 RPCM Sector Data 3 7 600 4 5 6 Metal Loss (Microns) 500 400 300 200 Sector 1 Sector 2 Sector 3 Sector 4 Sector 5 Sector 6 Sector 7 Stratifiedflow / high temp Dissolved CO2 / H2S Cold spots are vulnerable Organic acids (acetic, HCl) BOL protected by inhibitor 100 0 0 100 200 300 400 Days 14
Case Study CoPJudy Jade North Sea 2001 15 2 x 16 Spool flanged into SSV
Case Study CoPJudy Jade North Sea 2001 16 Performance of subsea spool after 5 years continuous operation
Conclusions RPCMs have extensive field history Widely accepted technology for subsea pipeline corrosion monitoring Full circumferential view Versatile configuration allows monitoring of: PWC, other alloys, pitting etc Flexible platform for other measurements PT Conductivity (EIS) Single Phase Flow Resolution circa 1 micron (near real17 time)
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