ASME B16.4:2006 pdf download Gray lron Threaded Fittings Classes 125 and 250
3 SIZE
3.1 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.
3.2 Reducing Fittings
For reducing tees and crosses, the size of the largestrun opening shall be given first, followed by the size ofthe opening at the opposite end of the run. Where thefitting is a tee, the size of the outlet is given last. Wherethe fitting is a cross, the largest side-outlet opening isthe third dimension given, followed by the oppositeopening. The straight-line sketches of Fig. 1 illustratehow the reducing fittings are read.
4 MARKING
(a) Each Class 125 fitting shall be marked for identification with the manufacturer’s name or trademark.(b) Each Class 250 fitting shall be marked for identification with
(1) the manufacturer’s name or trademark(2) the numerals “250″
5 MATERIAL
Castings shall be produced to meet the requirementsof ASTM A 126,Class A B, or C. The manufacturershall be prepared to certify that the product has been soproduced and that the chemical and physical properties thereof, as proved by test specimens, are equal to theserequirements
6 DIMENSIONS AND TOLERANCES
(a) Center-to-end dimensions in millimeters are givenfor standard straight and reducing fittings in Tables 2through 6 (Tables I-2 through I-6 are in U.S. Customaryunits). The sketches of fittings shown in the Standardare representative and for the purpose of illustration.(b) The dimensions in Tables 2 through 6 (Tables I-2through I-6) of reducing fittings are for use only whenmaking patterns for the specific reducing fitting in ques-tion and do not apply when a larger size pattern isbushed to make the reducing fitting wanted.(c) The following tolerances shall be permitted:(1) Metal Thickness Tolerances. Metal thickness at nopoint in the castings shall be less than 90% of the valuegiven in Tables 2 through 6 (Tables I-2 through I-6).(2) Center-fo-End Tolerances. Permitted toleranceson the center-to-end dimensions of the fittings are shownin Tables 7 and I-7. 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.
7 THREADING
(a) All fittings shall be threaded according to ASMEB1.20.1, and the variations in threading shall be limited to one turn large or one turn small from the gagingnotch on the plug when using working gages.
(b) The reference point for gaging internal fittingsthreads depends upon the chamfer diameter. When theinternal chamfer diameter exceeds the major diameterof the internal thread, the reference point is the lastthread scratch on the chamfer cone. When the internalchamfer diameter does not exceed the major diameterof the internal thread, the reference point is the end ofthe fitting (see Fig. 2).
(c) For the purpose of easier entrance in making ajoint and for protection of the thread, all threads shallbe countersunk a distance of not less than one-half thepitch of the thread at an angle of approximately 45 degwith the axis of the thread. Countersinking shall be concentric with the threads.
(d) The length of the threads specified in all tablesshall be measured to include the countersink.(e) The maximum allowable variation in the align-ment of threads of all openings of threaded fittings shallbe 5.0 mm/m(0.06 in./ft)(0.5% slope).
RIBS8
(a) The addition of ribs or lugs is permitted onthreaded fittings.Where ribs are used, it is recommended that their thickness shall be the same as specified for metal thickness of the fitting.
(b) Right-hand couplings shall have not more thantwo ribs.
(c) Right- and left-hand couplings shall have four ormore ribs unless the left-hand opening is clearly markedin which case the use of ribs is optional with the manufacturer.