Slip on Flanges

Continue to be preferred to welding neck flanges by may users due to their initially lower cost, the reduced accuracy required in cutting pipe to length and the somewhat greater ease of assembly alignment;however their final installed cost is probably not much, if any , less than that of welding neck flanges. Their calculated strength under internal pressure is of the order of two-thirds that of welding neck flanges, while their life under fatigue is about one-third. For these reasons slip on flanges are limited to size 1/2 to 2 1/2 in the 1500lb standard, are not shown in the 2500lb standard and the ASME Boiler Construction Code limits their use to the 4size.