What is the minimum distance to be maintained between two welds in a pipe?
The thumb rule is that the minimum distance between adjacent butt welds is 1D. If not, it is never closer than 1-1/2 inch. This is supposedly to prevent the overlap of HAZs. Minimum spacing of circumferential welds between centerlines shall not be less than 4 times the pipe wall thickness or 25 mm whichever is greater.
For this reason many company standards advice the minimum spool length of pipe which is usally 100mm in genral but may differ.But in cases where required the minimum distance for adjacent welds can be considered