Hello,
ASME B31.3 is not having any references clause for HOT welding procedure qualifications.
Yes, the fitting design shall be designed inline to B31.3 for process piping and the field welding of the fitting on the live system shall be done as per API 1104 .
Note : In case of fitting fabrication, let say in barred tee the weld joint between flange and sleeve , the shop welding can be carried out inline to ASME section IX.
Regards,
Sudhakar K CEng MWeldI,IWE.
Welding & Metallurgical Engineer,
Email: sudhak...@gmail.com.