These Technical Questions and Responses have been collected by ABSA Design Survey and have value to
prospective submitters for clarification on processes, general policies, and some specific scenarios for design submissions. The following Technical
Questions and Responses are related to fitting registration requirements.
1. Questions regarding modified fittings
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.
4. Questions regarding nozzles attached to a B16.5 blind
4.Q1. If a nozzle is welded to an ASME B16.5 blind flange, does the blind flange retain its B16.5 pressure-temperature rating? The nozzle is attached at the centre of the blind flange and the attachment weld is a full penetration weld through the nozzle neck plus an appropriately sized fillet weld. For the purposes of this question, it is assumed that the nozzle neck and any flange at the other end of the nozzle are of equal or higher rating compared to the blind flange.
4.R1. If the attached nozzle’s fully corroded inside diameter is smaller than the outside diameter of the smallest size (NPS) of reducing outlet requiring a hubbed flange listed in column 2, 4, or 6 of Table 6 of ASME B16.5-2003, a standard blind flange may be used at its B16.5 pressure-temperature rating. Larger diameter nozzles would require the use of a hubbed blind flange (refer to the Notes to Table 6 for details of the required hub size) to allow the full ASME rating of the blind flange. Otherwise, the maximum allowable working pressure of the blind flange with the central hole must be calculated in accordance with the applicable code of construction and for the required maximum temperature.
Note that this is a variation of the B16.5 Table 6 requirements to cover the situation where the nozzle is set onto the blind flange.
5. Question regarding bleed rings or spacers
5.Q1. A bleed ring or spacer is manufactured from plate or a forging. This ring will be gasketed between two flanges. A bleed ring would be thick enough to allow a small tapped hole, to which a valve may be attached so that some of the contents of the piping may be bled off. Does this bleed ring or spacer require a CRN?
5.R1. No. Such bleed rings or spacers would be comparable to very thick, solid metal gaskets and gaskets are not registered as fittings although they are pressure components. A valve attached to a bleed ring would have to be a registered fitting. Note that some end users may require such components to be registered as fittings before they may be installed in that user’s facility.
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Updated Jan 31, 2012