Gap-A-Lets + Socket Welds

Why the gap between the pipe end and the internal shoulder of the fitting before welding?
The function of the gap is to permit thermal expansion of the pipe. Without the gap, the heat of welding can cause the pipe to expand at a faster rate than the fitting. If the pipe bottoms against the socket fitting, the thermal growth of the pipe strains the weld, possibly producing cracks in the root.
Failures have also been observed in socket welds subjected to thermal and mechanical cycling during service. The mechanism is similar to failure during welding. Rapid temperature changes cause the pipe to expand against the bottom of the fitting, straining and cracking the weld. Construction and Military codes such as ANSI, ASME, NAVSEA-250-1500-1, MIL-STD-278 and MIL STD-22 permit socket welds to be used, provided a minimum 1/16" (1.6 mm) is established between the pipe end and socket prior to welding.

  • Proper socket weld fit-up in one-tenth the time.
  • Accurate 1/16" min. gap without time-consuming measuring, scribing and pull-out.
  • Eliminate cracked welds resulting from improperly gapped joints.
  • Meets military and commercial construction code standards.
  • Patented-United States, Germany, United Kingdom, Japan and Canada.
  • Sizes from 1/4" NPS to 5" NPS in stock for immediate shipment.
  • Instrumentation tubing sizes 3/8" to 2".
  • Boiler tubing sizes as required.
Standard   Ring Free Ring  
GAP-A-LET   Outside Radial Ring
Ring Fitting Diameter Wall Thickness
1/4 NPQ .555 .600 .070 .025
3/8 NPQ .690 .730 .070 .025
1/2 NPQ .855 .880 .070 .025
3/4 NPQ 1.065 1.110 .070 .025
1 NPQ 1.330 1.385 .105 .030
1 1/4 NPQ 1.675 1.780 .105 .030
1 1/2 NPQ 1.915 2.020 .105 .030
2 NPQ 2.406 2.580 .105 .030
2 1/2 NPQ 2.905 3.010 .105 .030
3 NPQ 3.500 3.885 .105 .030
3 1/2 NPQ 4.000 4.150 .105 .030
4 NPQ 4.500 5.110 .103 .040
5 NPQ 5.563 5.880 .103 .040