Used for small bore lines, usually 2 inch and under, socket welds are easy to align and need no bevel. The pipe is pulled back about 1/16 inch from the bottom of the socket before welding so that weld shrinkage and thermal growth do not crack the joint. The trapped crevice inside makes them a poor choice for corrosive or highly cyclic service.
Mark the pipe, bottom it out, pull it back a sixteenth and tack it, I don't want any cracked socket welds this time.
Inspectors look for that 1/16 inch gap; some sites require a gap ring or a radiograph to prove it.
Also heard as
- SW
- socket weld end
Related terms
Butt weld
An end connection where a beveled valve or fitting end is welded straight to beveled pipe with full penetration.
NPT
National Pipe Taper: the tapered pipe thread used for threaded valves and fittings in North America.
Nipple
A short length of pipe, threaded or plain on its ends, used to connect two fittings or a valve to a fitting.