ASME B16.4 pdf download Gray Iron Threaded Fittings Classes 125 and 250
4.1 Nominal Pipe Size As applied in this Standard, the use of the phrase “nominal pipe size” or the designation NPS followed by a dimensionless number is for the purpose of identi- fying the end connection of fittings. The number is not necessarily the same as the fitting inside diameter.
4.2 Reducing Fittings For reducing tees and crosses, the size of the largest run opening shall be given first, followed by the size of the opening at the opposite end of the run. Where the fitting is a tee, the size of the outlet is given last. Where the fitting is a cross, the largest side-outlet opening is the third dimension given, followed by the opposite opening. The straight-line sketches of Fig. 1 illustrate how the reducing fittings are read.
(a) Each Class 125 fitting shall be marked for identifi- cation with the manufacturer’s name or trademark.
(b) Each Class 250 fitting shall be marked for identifi- cation with
(1) the manufacturer’s name or trademark
(2) the numerals “250”
6 MATERIAL Castings shall be produced to meet the requirements of ASTM A126, Class A, B, or C. The manufacturer shall be prepared to certify that the product has been so produced and that the chemical and physical properties thereof, as proved by test specimens, are equal to these requirements.
7 DIMENSIONS AND TOLERANCES
(a) Center-to-end dimensions in millimeters are given for standard straight and reducing fittings in Tables 2 through 6 (Tables I-2 through I-6 are in U.S. Customary units). The sketches of fittings shown in the Standard are representative and for the purpose of illustration.
(b) The dimensions in Tables 2 through 6 (Tables I-2 through I-6) of reducing fittings are for use only when making patterns for the specific reducing fitting in ques- tion and do not apply when a larger size pattern is bushed to make the reducing fitting wanted.
(c) The following tolerances shall be permitted:
(1) Metal Thickness Tolerances. Metal thickness at no point in the castings shall be less than 90% of the value given in Tables 2 through 6 (Tables I-2 through I-6).
(2) Center-to-End Tolerances. Permitted tolerances onthecenter-to-end dimensionsofthe fittings are shown inTables 7and I-7. Tolerances for end-to-end dimensions and lengths of couplings and reducers shall be twice those given. The largest opening in a reducing fitting governs the tolerances to be applied to all openings. These tolerances do not apply to return bends and caps.
(a) All fittings shall be threaded according to ANSI/ASME B1.20.1, and the variations in threading shall be limited to one turn large or one turn small from the gaging notch on the plug when using working gages.
(b) The reference point for gaging internal fittings threads depends upon the chamfer diameter. When the internal chamfer diameter exceeds the major diameter of the internal thread, the reference point is the last thread scratch on the chamfer cone. When the internal chamfer diameter does not exceed the major diameter of the internal thread, the reference point is the end of the fitting (see Fig. 2).
(c) For the purpose of easier entrance in making a joint and for protection of the thread, all threads shall be countersunk a distance of not less than one-half the pitch of the thread at an angle of approximately 45 deg with the axis of the thread. Countersinking shall be con- centric with the threads.
(d) The length of the threads specified in all tables shall be measured to include the countersink.
(e) The maximum allowable variation in the align- ment of threads of all openings of threaded fittings shall be 5.0 mm/m (0.06 in./ft) (0.5% slope).
(a) The addition of ribs or lugs is permitted on threaded fittings. Where ribs are used, it is recom- mended that their thickness be the same as specified for metal thickness of the fitting.
(b) Right-hand couplings shall have not more than two ribs.
(c) Right- and left-hand couplings shall have four or more ribs unless the left-hand openingis clearlymarked, in which case the use of ribs is optional with the manufacturer.
10 PLUGS, BUSHINGS, AND LOCKNUTS For dimensions of plugs, bushings, and locknuts to be used in connection with Classes 125 and 250 gray iron threaded fittings, see ASME B16.14. 11 FACE BEVEL A bevel not exceeding 5 deg is permitted on the faces of fitting openings. Center-to-end, end-to-end, and