shallow internal corrosion sensor technology for heavy pipe wall inspection rosen technology &...

Shallow Internal Corrosion Sensor Technology for Heavy Pipe Wall Inspection

ROSEN Technology & Research Center GermanyDr. Olaf Stawicki18-Nov-2009

Contents

• Motivation• Measurement Principle• Mechatronic Principle• Inspection Tool Design• Combining SIC with MFL• Test Results• On-Site Example• Summary

Copyright © ROSEN Group 2009 - Copy prepared for PPSA SIC Sensor Technology | O. Stawicki | 18-Nov-2009

Motivation


Risks for Pipeline Integrity and Operation

Pipeline Integrity

Assessment

ManufacturingSteel Production

Welding (SAW, ERW)…

OperationalCorrosion

Erosion, FatigueGround Movement

Mechanical Damage…

ConstructionGirth Weld FaultsPoor Pipe Support

…

Coating and CPPoor Surface Preparation

Inadequate Material Storage…

Motivation

Corrosion plays a crucial role in pipeline integrity… it is a time-dependent deterioration process

Heavy Wall Pipelines for Offshore Applications• Specified maximum corrosion growth rate• Controlled wall thickness reduction during the lifespan

Monitoring Internal Corrosion is inevitable for reliable and save operation!


Motivation

Top of Line Corrosion (TLC) or Dewing Corrosion… starts as Shallow Internal Corrosion (SIC)

Origin of TLC• Unprocessed wet gas is transported

from an offshore well

• Heat exchange between pipeline and

cold surrounding (such as sea water)

• Low pH water droplet condensation on the upper

half of the pipeline

• Dissolution of aggressive gases in droplets support corrosion


Motivation


Droplet Condensation

of Vapor Phase

TExt « TGas Vapor

H2O, CO2, H2S

Organic Acid (HAc)

Stratified Water Flow

Water Drain

TGas

TExt

Droplet Size Distribution ~ r -2/3 localized, small-scale corrosion

Motivation


TLC Controlling Parameters• Partial Pressure of CO2

• Partial Pressure of H2S

• Water Condensation Rate

• Gas Pressure, Velocity, Temperature

• Organic Acid (HAc) Concentration

TLC can reveal high growth rates, up to several mm/year

(Singer et al., 2009)

Motivation


Measurement Principle


Alternating current triggers Primary Magnetic Field

Magnetic flux change causes Eddy Currents in conductive material, e.g., pipe wall

Eddy Currents generate Secondary Magnetic Field

Secondary Field modifies Primary Field via mutual inductance

Eddy Currents imply change of coil impedance



Lift-Off

“In Air”

“Over Material” “Over Metal Loss”

Eddy Currents Eddy Current Distortion

Coil Impedance: Z = R + j ωL

R Ohmic Resistance

ω Frequency of driving current

L Inductance of Coil

• In Air

ωL

R

• Material

• Metal LossLift-Off



Penetration Depth determined by Skin EffectSkin Depth δ ~ 1/(ω μσ)1/2

Eddy Current Density decreases with depth.

Mechatronic Principle


SIC Sensor = Contour Following Touchless Proximity Sensor

(Compensated Deflection)

Radius Measurement =

δ Proximity Sensor (Lift-Off)+

β Electronic Angle Sensor

SIC sensor schematic view

coun

ts

Lift-Off

Inspection Tool Design


RoCorr·MFL/SIC 24" Combo Tool

SICMFL

Two plane sensor system 100% coverage

Available tool sizes 6" – 56"


Combining SIC with MFL

14

SIC Regime

MFL Regime

Inner Pipe Wall Surface

Outer Pipe Wall Surface

Compensation for Lift-off

Sensitive Pitting Discrimination

Wall Thickness

Detection & Sizing of External Defects

Depth Measurement of Metal Loss FeaturesMFL relative

SIC absolute

MFL

Combining SIC with MFL


Depth Sizing Accuracies

MFL ± 2 mm

SIC ± 0.5 mm

SIC feature sizing customizes MFL sizing model

Defect Diameter [mm]

De

fec

t D

ep

th [

mm

]

SIC Probe

DetectionRegime

Sample pipe with WT = 20 mm

Test Results


SIC Scan of Steel Plate with Spherical Pits

Lift-Off 3 mm

Resolution 2 x 2 mm

EDM-made pits

De

pth

[m

m]

x-direction [mm]

y-d

ire

cti

on

[m

m]


Test Results

Surface Diameters

P35.x

P25.x

P30.x

P15.x

P20.x

Depth t

35

Aspect Ratio

Aspect Ratio D/t ≥ 3

Test Results


SIC Scan of Steel Plate with TLC

De

pth

[m

m]

x-direction [mm]

y-d

ire

cti

on

[m

m]

Test Results


SIC Scan of Steel Plate with TLC

Real Depth [mm]

SIC

Dep

th [

mm

]


Test Results

Dent Simulation

16" Pump Test Line

Spiral Weld

Flange

Dent

Internal Defects

Test Results


SIC

MFL

16" Test Joint, WT = 12.6 mm

Test Results


TLC in 16" Test Pipeline

AUT CDP SIC

On-Site Example - World Longest Subsea Run


Requirements - 42" /44" Langeled Pipeline

Inspection Range 1200 km

Gas Speed 8 m/s

Active Speed Control set at 3 m/s

WT Range 3 – 38 mm

Maximum Pressure 220 bar



CDP 624 MFL Channels

RoGeo·Xt 330 Geometry Channels

SIC 864 Channels


Run Results• Traveling time 127.3 hrs• Tool velocity 1.5 – 3.0 m/s• Almost full pipeline length recorded• 3.82 km2 of pipe wall inspected ( = 521 football fields)• 11,7 measurement points per cm2

• 450 billion measurement points• 374 GB data recorded

… but data evaluation is still in process



Summary

• Based on Eddy Current Technology, SIC Sensors have been developed for metal loss inspection on inner pipe wall

• Compared to other measurement technologies:• SIC: Absolute depth of metal loss features • MFL: Relative depth based on wall thickness

• SIC tools have less friction compared to tools with magnet yokes

• SIC Inspection is contactless, i.e. no direct coupling to the pipe wall

• SIC sensor metal loss depth sizingTypically between 1 mm and 10 mm depth

Thank you for joining this presentation.

shallow internal corrosion sensor technology for heavy pipe wall inspection rosen technology &...

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