The design of fittings

PROOF TESTING

 
The design of fittings may be established by mathematical analyses contained in nationally recognized pressure vessel or piping codes or, at the manufacturer's option, by design proof testing in accordance with applicable section herein. The design of fittings that cannot be qualified by such analyses shall be established by design proof testing.
5.2 Proof of Fitting Manufacturing Process
The validity of each tee and elbow manufacturing process must be periodically re-established by pressure proof testing. Each manufacturer shall perform a hydrostatic pressure proof test on the largest representative tee and elbow of each manufacturing process. As an example: A manufacturer intends to supply elbows in sizes 3 NPS to 12 NPS: and those 3 NPS to 6 NPS are seamless and those 8 NPS to 12 NPS are welded formed pieces. That vendor must test one 6 NPS and one 12 NPS elbow. This qualification will allow the vendor to fabricate a 6 NPS elbow but will not allow the vendor to make a seamless 8 NPS elbow without further tests. Retesting will be required for a change in manufacturing process, a change in corporate ownership, a change in factory location, a lapse of 5 years or a change in basic materials or a change in alloys sufficient to require a different heat treatment for annealing. Tests shall be conducted and certified by an independent laboratory and the results kept on file by the fitting manufacturer. Straight pieces of pipe shall be welded on to the other end of each fitting and these pieces shall be capped. The pipe pieces shall be no shorter than twice the pipe outside diameter. The pipe shall have the same rating as the fitting. Hydrostatic pressure shall be applied until the fitting ruptures. The test pressure prior to rupture shall be at least equal to the minimum manufacturing proof pressure defined as follows: