I've been trying to find a standard reference (ASME,AWS) that requires a UT inspection 24 hrs after welding carried out on process piplelines. I just cannot remember which standard it was mentioned in? I would appreciate your help in this regard.
The only place I've ever seen that stipulated is in an API spec, and it was for examination after a weld overlay repair.
Typically customers make this request for low alloy materials which are sensitive to delayed hydrogen cracking, such as P91. And it is not 24 hrs after welding, it is 24 hrs after the weld has cooled to ambient temperature.