Hi Everybody?

1) When we say that vessel is subjected to hydrogen service?
2) What are the mandatory requirements of code (like PWHT, RT,
Impact testing, etc.) need to be satisfied?
3) Where (any standard) I will get the data related to hydrogen service /
requirement?

Please help me on above points.

Prashant

Hydrogen embrittlement: is a low ductility resulting from a presence of absorbed hydrogen in the steel.
Hydrogen attack: can occur when steel is exposed to environment containing dissociated hydrogen at high temperature and pressure.

Operating limits for carbon and low alloy steels are represented graphically in the form of curves for various steels as a function of temp. and hydrogen partial pressure. Curves were initially established in the 1940's by G.A. Nelson and are now maintained and updated by the API and are published in API 941.

NACE MR0175 / ISO 15156 - Materials for use in H2S-containing Environments in Oil and Gas Production.

Since H2S is a lethal substance, you shall follow the instructions of ASME VIII Div. 1 / UW-2 Service Restrictions for PWHT, NDE, permitted weld types, etc.