PWHT vs PHT

[Trig_Shah]

I am new to Vessel Industry and would like to know the differance between PHT and PWHT. I have a vessel that has PHT stamped on it and I wanted to know does it mean the entire vessel is Post Weld Heat Treated or just the portions of the vessel (like Nozzle...) is Heat Treated.

 

[chaulklate]

Partial Heat Treatment - only part of the vessel has been stress relieved.

 

[Trig_Shah]

Thank You.