In-situ PWHT proven safe

In-situ PWHT proven safe

allowing safe vessel repair.

Client: Petroleum refinery

Tough Problem: A depropaniser vessel required in-situ Post Weld Heat Treatment (PWHT) 15 metres above its base following some repairs. Given the significant drop in mechanical properties that occur at PWHT temperature (650°C), the risk of vessel collapse due to weight and wind loads was extremely high.

Practical Solution: SVT calculated thermal stresses due to temperature gradient at the location where the circumferential heating band was installed. Finite Element Analysis (FEA) was performed to calculate the stresses due to weight and wind loads at the location of interest.

Calculating accurate material properties at PWHT temperature was crucial in determining the allowable stress limits, particularly considering lack of published data. 
The bottom line: SVT determined that PWHT could be performed safely. PWHT was carried out successfully saving client millions in downtime due to the quick turnaround by SVT.