help me where and which code mention about minimum distance between two longitudinal weld of pipe.follow ASME  section VIII or B31.1 , I'm can't finding this.

Thanks so much

What are the standard requirements on the proximity of welds?

Frequently Asked Questions
Weld proximity is covered by a number of international standards. Extracts from these standards are shown below and summarised in the following table:
Standard   Applies to   Minimum distance between weld toes   Notes
BS 2633:1987  Ferritic steel pipework  4t  t= nominal thickness of the pipe
See below for notes on attachment welds.
BS 4515:2009  C-Mn pipelines  4t  t= pipe thickness
BS 2971:1991  Carbon steel pipework  Agreed by parties  -
PD 5500:2012  Pressure vessels  4e or 100mm whichever is greater  e= design thickness
Refers to staggering of longitudinal welds
ASME B&PV  Boilers and pressure vessels  Not specified  -