What is the minimum distance to be maintained between two welds in a pipe?

Ans.:

The rule of thumb is that the minimum distance between adjacent butt welds is 1 x D. If not, it is never closer than 1-1/2″. This is supposedly to prevent the overlap of HAZ s. Minimum spacing of circumferential welds between centerlines shall not be less than 4 times the pipe wall thickness or 25 mm whichever is greater.