Section 3 - Lessons Learnt From Historical Equipment Failure

Fitness-for-Service (FFS) Assessment based on API RP579 Section 3 - Lessons learnt from Historical Equipment Failures

Copyright 2005, TWI Ltd

Copyright © 2005, TWI Ltd World Centre for Materials Joining TechnologyWorld Centre for Materials Joining Technology

Lesson learnt from Historical Equipment Failures


Session Agenda

• Fatigue and fracture case studies• Other failure mechanism case studies• Statistic on Oil and Gas failure rates




Failure Case Studies


Kings Bridge




Fawley Storage Tank


MV Kurdistan Tanker




Origin of failure in Kurdistan Tanker


Alexander L. Kielland Platform




Fatigue cracking in brace D6 of Alexander L. Kielland Platform


Cockenzie Boiler Drum




Union Oil Amine Absorber Tower


Summary of fatigue and fracture case studies

Union Oil

Cockenzie

Keilland

Kurdistan

Fawley

Kings Bridge

John Thompson

Subcritical growth

FabricationServiceTestResidualSecondary member

Main structure

Temp. significant

Low toughness

DefectRepairWeldStressInitiation siteCase




Corrosion failure• A section of a 30 inch

oil transit pipe line burst in an oilfield

• 10,000 to 15,000 barrels of oil leaked over a large area of a gathering station

• A subsequent fire and explosion occurred

• Source of leak a 830mm long split in the 6 o’clock position


Corrosion failure

View of resulting damage from explosion and fireView of resulting damage from explosion and fire




Corrosion failure

Burst pipe sample set to Burst pipe sample set to TWITWI


Corrosion failure

• TWI asked to determine the cause of failure in 30 inch pipe• Investigation approach:– Initial examination and photography– Measurement of wall thickness in damaged

region (AUT)– Sectioning of region close to split– Chemical analysis, hardness testing,

fractographic examination, Metallographic examination, mechanical testing– Engineering assessment




Corrosion failure

Nominal thickness 9.8 mmMinimum measured thickness 3.2 mmRupture tear

AUT thickness mapping TAUT thickness mapping T--scan modescan mode


Corrosion failure

• Metallurgical investigation determined corrosion result of coal tar paint break down • Resulting exposed area too great for

cathodic protection system• Failure initiation at several sites which

propagated to coalesce to a unstable single split




Corrosion failure

• Questions which remained were:– Was the pipe originally code compliant– Was the flaw fit-for-service

• A code and a fitness-for-service assessment were conducted• The code evaluation showed that the

pipeline was compliant with ASME B31.4 and not compliant with ASME B31.3


Corrosion failure

• Burst pressure was evaluated using BS7910 appendix G and B31.G• Material properties taken from from the

failed pipe e.g. yield stress• BS 7910 procedure based on UTS properties• B31.G procedure based on yield properties




Corrosion failure

Failu

re p

ress

ure

(ps

i)

100

200

300

400

500

600

700

AssessmentThickness (mm)

3.2 3.7

BS 7910B31.G

Minimum measured thickness

Averaged measured thickness

•• Flaw could have failed Flaw could have failed within operating bandwithin operating band

•• High probability pipe High probability pipe failed due to pressure failed due to pressure rise within operating rise within operating rangerange


Factors affecting structural integrity

MATERIALPROPERTIES

FLAWS,GEOMETRY STRESSES

Session 2/22




Lessons to be learnt from industrial failures

• Welds, including repairs and attachments• Flaws• Sub-critical crack growth• Fracture toughness• Temperature• Residual stresses• Environment• Inspection

Documents

Section 3 - Lessons Learnt From Historical Equipment Failure