api 650 tank PWHT

[eegyman5000]

why does not api 650 define heating and cooling rates for PWHT,should i use ASME VIII DIV.1 UCS 56 to define it
also it requires PWHT for clean out door and nozzle openings what about shell?
and it states that nozzle of a a certain dia. in a certain shell thickness is to be prefabricated and the prefabricated assembly is to HAVE PWHT what does that mean?

 

[JoeTank]

eegyman5000,
We do not know why API-650 does not specify heating or cooling rates. Perhaps it is not critical to them? You should inquire directly to API.
PWHT is required for certain shell openings, but not the shell. API-650 does not require shell PWHT, but please notice that the plate thicknesses of tanks are limited to 1.75" max. And, many shell materials are limited to a lesser thickness.
"Prefabricated" means that the opening is to be sub-assembled into a shell plate (or a shortened shell plate) and PWHTd as an assemble BEFORE installation unto the tank. Openings may not be subjected to PWHT after installation.

Joe Tank