Corrosion Under Insulation

Corrosion Under Insulation A practical prevention guide as per API 570

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Moisture Sources W Water Leaks L k

Mist Spray from

Condensation

Cooling Towers

CUI

Deluge systems

Rains

Leaking Process fluids

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Common Forms

Localized Corrosion of Carbon Steel

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Chloride Stress Corrosion of Austenitic Stainless Steels

Susceptible Piping Systems

A Areas exposedd to

Mist of Cooling Towers

St Steam Vents V t

D l Systems Deluge S t

P Process SSpills ill

A id VVapors Acid

Carbon Steel Systems insulated for Human pprotection operating p g between -4 deg C – 120 deg C

Carbon Steel Systems operating above 240 deg d C with ith iintermittent t itt t service i

SSystems t where h operating ti temperatures t t cause frequent condensation and re-evaporation of atmospheric moisture

AAustenitic t iti SS systems t with ith operating ti Temperature between 65 deg C to 204 deg C (Chloride Stress Corrosion)

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Susceptible Piping Systems

Deadlegs and attachments protruding from insulation

Vibration systems with damaged Insulation and jacketing

Steam tracing systems with tracing leaks

S Systems withh ddeterioratedd coating andd wrapping

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Susceptible Common Locations

Penetrations/breaches in jacket

Damaged/missing jacketing

Hardened, separated, or missing caulking

Piping low points in systems that have insulation breach

Jacket seams on top of horizontal piping or improperly lapped/sealed jacket

Carbon or low-alloy steel components in high-alloy systems

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Susceptible Common Locations

Termination in insulation at flanges and other piping components

Termination of insulation in a vertical pipe

Bulges or staining of insulation or jacketing system (bulges may indicate corrosion products)

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Special Considerations

Insulation damage at higher elevations May cause CUI at lower elevations

Insulation removal, RT may be required

Expand inspection as necessary

Systems may be excluded: 1. 2 2.

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Remaining life > 10 years Ad Adequately l protectedd externally ll

Piping Service Classes

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Recommended Inspection Interval

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CUI Inspection Targets

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THANKS ‐ thePetroStreet team

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