1.Q1. A pressure piping system design requires that two or more fittings be welded to one another in the piping. For example, an NPS ½ Thredolet® is to be welded to an NPS 8 ASME B16.9 butt-welding tee opposite the branch to act as a drain. Must the piping fabricator register the combination of fittings as a modified fitting?
1.R1. The welding of two or more fittings together, such as in the example given, is considered to be part of piping fabrication rather than modification of a fitting. Registration of the design consisting of the two or more fittings welded together is not required. Note, however, that the piping design engineer must have determined that the pressure-temperature rating of the combined fittings is still adequate for the rating of the line in which the combination fitting is installed. Combining fittings can significantly weaken one of the fittings because of the hole cut in it.
1.Q2. For the situation described in Q1, must the piping fabricator have modification of fittings in its registered quality management system?
1.R2. The piping fabricator need not have modification of fittings in its registered quality management system in order to be able to combine fittings in accordance with the engineered design when fabricating a pressure piping system.
1.Q3. Do two butt weld fitting pipe tees which have been split on the horizontal axis, with the two parted branch sections welded together with a full penetration weld to form a cross, require CRN registration for this modification?
1.R3 Yes. The original Canadian Registration Number (CRN) assigned to each tee would no longer cover the design of the altered fitting. It is understood that the original manufacturer’s markings and warranty of the tee would no longer be applicable to these fittings once fabricated into a cross.