It is depending on Design Construction code / Client specification
Normally ASME SEC I , piping, equipment does not call for Hardness test .
As a practice , random hardness checks are carried out to ensure effective PWHT.
Maximum Hardness reading shall not exceed 275 - 280 BHN .
Hardness checking procedure shall outline Testing Method, type of equipment, Operator
API 938 , does specify Hardness of 250 BHN maximum .
Regards
Vishwas - IWE
International Welding Engineer