Brittle Fracture | Materials And Corrosion Control
Damage Mechanism |
Brittle Fracture |
Damage Description |
Sudden rapid fracture under stress (residual or applied) where the material exhibits little or no evidence of ductility or plastic deformation. |
Affected Materials |
· Carbon steels and low alloy steels are of prime concern, particularly older steels.
· 400 Series Stainless Steels are also susceptible. |
Control Methodology |
· Brittle fracture is best prevented by using materials specifically designed for low temperature operation.
· Control the operating conditions (pressure, temperature), minimizing pressure at ambient temperatures during startup and shutdown, and periodic inspection at high stress locations. · Establish the minimum pressurization temperature (MPT) from reactor manufacturers or derive from Charpy tests conducted with samples removed from the vessel. |
Monitoring Techniques |
· Inspection is not normally used to mitigate brittle fracture.
· Inspect to verify that reactors are crack-free, since defects promote brittle fracture. |
Inspection Frequency |
Every T&I to check for cracks by visual and conventional Non-Destructive Testing |
KPIs |
· MPT deviations · Number of cracks found and repaired · Number of cracks found and left in-situ · Number of toughness tests carried out from removed samples · Number of toughness tests showing reduced toughness properties |
Reference Resources (Standards/GIs/BPs) |
· API RP 571 (DM #31)
· API RP 579, Fitness-for-Service |
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