Mohammad ShamimBP Sharjah Ltd

CUI Risk Reduction by Non-Intrusive Inspection

Outline

• Introduction• CUI Mechanism• BP Sharjah CUI Risk• NII Techniques for CUI• Risk Based Mitigation Methodology• Results: 2007-8 Inspection• Conclusion

IntroductionCorrosion of metals covered by hot or cold insulation due to various factors

More CUI Examples

CUI Mechanism

• Carbon and low alloy steels operating in a process temperature range of 10 to 350°F (-12 to 175°C)

• Austenitic stainless steels operating in a process temperature range of 140 to 400°F (60 to 205°C).

WaterIngress

Waterabsorption

of insulation

Absenceof adequate

coating

Out ofsight, out of

mind

Difficult /expensive to inspect

FactorsRelated to

CUI

SCC ofStainless

steel Non-uniform corrosion

rates

CUI Mechanism• Corrosion Under Insulation caused by:

• Ingress of water thu insulation• Water vapours condensation

• Corrosion promoted by:• Trapping of water • Elevated temperatures• Temperature gradient• Temperature cycling• Absence or poor condition of coating• Poor/broken insulation/cladding

CUI Severity FactorsKey issues regarding Corrosion and barriers to CUI are as follows:

• Metal type – Carbon steel corrodes readily when wet.

• Coating – Presence, type and age.

• Insulation – Type and water absorbency.

• Jacketing – Condition and sealing.

• Water – Amount of water present.

FIELD WELLS

GAS

PrimaryCond.

ProducedWater

DehydrationSweetening

MOL SIEVES

Liquids Recovery

LPG TRAINS

LPGSeparation

Propane

Butane

Condensate

Sales Gas

Stabiliser

Degassers Settling Tank Evap Basin

‘HC’s

PRODUCTS

INLETSEPARATORS

3,500 BPD of Liquid Propane Product.3,000 BPD of Liquid Butane Product

3 x 3,000 BBL C3 Storage Spheres[+50 DegC/ 250 psig].

2 x 3,000 BBL C4 Storage Spheres[+50 DegC/ 70 psig].

1 x 377,000 BBL C3 Refrigerated, atm.storage tank [-44 DegC/ atmos].1 x 305,000 BBL C4 Refrigerated, atm.storage tank [-6 DegC/ atmos].

BP SHARJAHGAS PRODUCTION FACILITIES

CUI at BP Sharjah• CUI due to cold insulation in LPG plant• Plant situated near coast and over 25 years old• Limited Inspection in the past

• Limited insulation rehabilitation• Material, coating and insulation• Current insulation condition

BP Sharjah CUI Risk• CUI identified as a major

threat to the integrity of BP Sharjah Assets.– Day time dew point is

between 48-88˚F (9-31˚C).– Insulation is generally old– Very little inspection,

rehabilitation in the past 25 years

– Small bore, temp cycling etc are common

– A CUI Leak in 2007

•10% of all leaks are CUI

• 92% on piping system, 6% on vessels

•20% of these result in production loss; between 1-10 days

•80% of CUI failure on piping

•Pipes < 4 inch dia are most vulnerable

•CUI is highly unpredictable

Risk Reduction Challenges

• Insulation Removal not practical• No single technique suitable for all situations• Most of the available technology only offers

“screening”• Slow speed of radiography• Access and piping congestion• Pipe supports/branching• P & IDs and Inspection Iso• Technology limitations

Risk Reduction Plan

• Fast Track Program– Criticality surveys/analysis– Removal of insulation where not required– Visual Inspection of selected critical

locations– Radiography of Critical locations– Repair/Rehabilitation

• Further risk reduction

Risk Based Strategy

• Defines rules to determine CUI Threat• Defines rules to determine inspection

scheduling• Defines appropriate CUI detection

techniques• Defines rules to determine inspection

anomalies• Defines Rules for Remedial Actions

RBI: Maximum Inspection Intervals

Corrosion Rate Estimation Corrosion Rate Vs Temprature

0

10

20

30

40

50

0 20 40 60 80 100 120 140 160

Temprature, Deg C

Mils

/ Ye

ar

CUI Inspection Scope• Fast Track Program• Further Risk reduction

– High, Medium, Low Risk Features

– Small Bores/Cyclic Lines– Profile radiography/Visual

Inspection– UT Inspection of Damaged

locations– Other NII techniques

Evaluation/Trial

Profile Radiography

RADIOGRAPHS OF 3/4” CORRODED BRANCH CONNECTION ON 18”-4-P-095-AL-CI

RADIOGRAPHS FOR P 4502B-DISCHARGE PIPE DRAIN12”-4-P-020-AL-CI

RADIOGRAPHS OF LINE # 03”-4-P-087-A-CI RADIOGRAPHS OF LINE # 10’’-4-P060-A-CI (PT4246)

CUI Inspection & Repair

Profile Radiography Results

• Reasonably accurate and fast for small bore piping

• Calculated Corrosion rates Vs radiograph indications

• Find Rate: 30% (2007), 15% (2008)• Save Rate: 10% (2007), 3.5% (2008)• Coatings not found at CVI locations

Conclusions• CUI Detection is a challenge; It is

highly unpredictable• Radiography as a technique• Limitations of Technology

– Localized corrosion Vs overall metal loss• RBI approach to risk reduction• Prevention is better than cure

– Avoid insulation if possible– Design: Coating, cladding, workmanship

etc.

END