Lapjoint or Stub End Flange Requirement

lap joints and stub end flanges are generally preffered for non critical lines

Lap Joint or stub-end flanges are used where flange bolt hole alignment is difficult and flange joints are at critical locations. Further Stainless steel flanges are very costly where as in Stub end combination only stub end is of SS but lap flange is of Carbon Steel. In modern Ammonia plants this type of flanges are in use at pressure 34 kg/cm2 and temperature up to 400°C or so.