ASME B16.42 pdf download Ductile Iron Pipe Flanges and Flanged Fittings Classes 150 and 300
3.2 Ratings of Flanged Joints Ratings in this Standard apply to flanged joints that conform to the limitations on bolting in para. 6.2 and on gaskets in para. 7.8, and which are made up in accor- dance with good practice for alignment and assembly. See also para. 3.4. Use of the ratings for flanged joints not conforming to these limitations is the sole responsibility of the user. A flanged joint is composed of separate and indepen- dent, although interrelated, components: the flanges, the gasket, and the bolting, which are assembled by another influence, the assembler. Proper controls must be exer- cised in the selection and application for all these elements to attain a joint that has acceptable leak tightness. Special techniques, such as controlled bolt tightening, are described in ASME PCC-1. If the two flanges in a flanged joint do not have the same pressure–temperature ratings, the rating of the joint at any temperature is the lower of the two flange ratings at that temperature.
3.3 Rating Temperature Temperatures shown for corresponding pressure rat- ing shall be the material temperature of the pressure- retaining structure. It may be assumed that the material temperature is the same as the fluid temperature. Use of a pressure rating at a material temperature other than that of the contained fluid is the responsibility of the user and subject to the requirements of any applicable code or regulation.
3.4 Temperature Considerations Application of the ratings in this Standard to flanged joints at both high and low temperatures shall take into consideration the risk of leakage due to forces and moments developed in the connected piping or equip- ment. The provisions in paras.
3.4.1 and 3.4.2 are intended to minimize these risks.
3.4.1 Flange Attachment. Threaded flanges are not recommended for service above 260°C (500°F) if severe thermal gradients or thermal cycling is involved.
3.4.2 High-Temperature Service. When used above 205°C (400°F), Class 150 flanged joints may develop leak- age unless care is taken to avoid imposing severe exter- nal loads and/or severe thermal gradients.
3.5 Variances From Ratings Except as provided herein, ratings are the maximum allowable working pressure for the corresponding temperature.
3.5.1 Safety or Relief Valve Operation. Under condi- tions of safety valve, relief valve, or rupture disk opera- tion, the pressure on a flange or flanged fitting may exceed the rated pressure at the pressure-relieving tem- perature by no more than 10%. Such conditions are nec- essarily of short duration. Overpressure greater than the aforementioned under pressure-relieving conditions is the responsibility of the user, subject to the requirements of the applicable code or regulation.
3.5.2 Other Variances. Operating variations (tran- sients) that subject a flange or flanged fitting to pressure in excess of the rated pressure at the corresponding temperature are the responsibility of the user, subject to the requirements of the applicable code or regulation.
3.5.3 System Hydrostatic Test. Flanged joints and flanged fittings may be subjected to system hydrostatic tests at a pressure not to exceed the hydrostatic shell test pressure specified in para. 9.3. Testing at any higher pressure is the responsibility of the user.
4.1 Nominal 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 identifying the end connection of piping, flanges, or flanged fittings. The number is not necessarily the same as the inside diame- ter of the flange or flanged fitting. The diameter of a bolt is its nominal size. Use of nominal indicates that the stated size or dimension is only for designation, not measurement.
4.2 Reducing Fitting Sizes Reducing fittings shall be designated by the size of the openings in their proper sequence as indicated in the sketches. See Fig. 1.
4.3 Reducing Flange Sizes Reducing flanges shall be designated by the two nominal pipe sizes. See examples in Note (4) of Table 2. 5 MARKING Except as modified herein, flanges and flanged fittings shall be marked as required in MSS SP-25.
(a) Name. The manufacturer’s name or trademark shall be applied. (b) Material. The word “DUCTILE” or “DI” where space does not permit “DUCTILE.”
(c) Rating Class. Numerals shall be applied giving the pressure rating class for which the product is designed.
(d) Designation. The designation “B16” shall be applied, preferably located adjacent to the Class designa- tion, to indicate conformance to this Standard.