cui risk reduction by non-intrusive inspection by mohammed shamim, bp sharjah
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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
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