ASME B16.3:2016 pdf free download – Malleable Iron Threaded Fittings
4.1 Nominal Pipe Size
As applied in this Standard, the use of the phrase“nominal pipe size” or the designation NPS followedby a dimensionless number is for the purpose of identi-fying the end connection of fittings.The number is notnecessarily the same as the fitting inside diameter.4.2 Reducing Fittings
For reducing tees, crosses, and Y-branches (laterals),the size of the largest run opening shall be given first,followed by the size of the opening at the opposite endof the run. Where the fitting is a tee or Y-branch (lateral),the size of the outlet is given last. Where the fitting is a cross, the largest side-outlet opening is the thirddimension given, followed by the opposite opening.Thestraight-line sketches of Fig. 1 illustrate how the reduc-ing fittings are read.
7.1 General
The tolerances in Tables 2 and 1-2 are for center-to-enddimensions of the fittings.Center-to-end dimensions inmillimeters are given for both straight and reducingfittings in Tables 3 through 18(Tables I-3 through i-18are in u.s. Customary units).The sketches of fittingsshown in this Standard are representative and for thepurpose of illustration.
7.2 Reducing Fittings
7.2.1 The dimensions of reducing fittings shownin Tables 4,5,8,12,13, and 15 (Tables I-4,I-5,I-8,1-12,I-13, and I-15) are for use only when making patternsfor the specific reducing fitting in question and do notapply when a larger size pattern is reduced (i.e.,”bushed) to make the reduction or reductions in thefitting. Reducing pipe fitting patterns shall be designedto produce wall thicknesses, detail, and dimensions asrequired for the sizes involved.
7.2.2The transition in wall thickness from oneend size to another shall be in a manner that minimizes
the addition of stress caused by sudden chanaes in direc-tion or wall thickness.
7.2.3 Proof of design shall be verified by a hydro-static pressure test made at ambient temperature inwhich pressure is applied for a continuous period of noless than 1 min and at a constant minimum pressure ofno less than 5 times the pressure rating of the largestsize of end connection in the reducing fitting.Testing isconsidered successful only when no evidence of crack-ing, fracturing, or leakage is exhibited after holding forat least the minimum time at or above the requiredpressure.
7.3 Tolerances
lt is recognized that some variations are absolutelyunavoidable in the making of patterns and castings.Thefollowing tolerances shall apply.
(a) Metal Thickness Tolerances. Metal thickness at nopoint in the castings shall be less than 90% of the valuegiven in the tables.
(b)Center-to-End Tolerances. Permitted tolerances onthe center-to-end dimensions of the fittings are shownin Tables 2 and 1-2.Tolerances for end-to-end dimensionsand lengths of couplings and reducers shall be twicethose given.The largest opening in a reducing fittinggoverns the tolerances to be applied to all openings.These tolerances do not apply to return bends and caps.