ASME B16.42:2021 pdf download

ASME B16.42:2021 pdf download DUCTILE IRON PIPE FLANGES AND FLANGED FITTINGS Classes 150 and 300
3 PRESSURE–TEMPERATURE RATINGS 3.1 ð21Þ General Cast ductile iron pipe flanges and flanged fittings covered by this Standard shall be designated Class 150 or Class 300. Except as provided in para. 3.5, ratings are maximum allowable workingpressures, expressed as gage pressure, at the service temperature from −29°C (−20°F) minimum to 343°C (650°F) maximum for ASTM A395 or 260°C (500°F) maximum for ASTM A536 Grade 65-45-12 (see Tables 3.1-1 and 3.1-1C). These minimum and maximum temperatures may be further limited by refer- encing regulations, codes, or specifications. For inter- mediate temperatures, linear interpolation is permitted. The method used for establishing pressure– temperature ratings is shown in Nonmandatory Appendix B.
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 accordance with good practice foralignmentand 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 independent, although interrelated, components: the flanges, the gasket, and the bolting, which are assembled by another influence, the assembler. Proper controls must be exercised 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. Ifthe two flanges in a flanged jointdo nothave 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 rating shall be the material temperature of the pres- sure-retainingstructure. Itmaybeassumedthatthemate- rial temperature is the same as the fluid temperature. Use ofa pressure rating at a material temperature other than that ofthe contained fluid is the responsibility ofthe user and subjectto the requirements ofany 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. Theprovisions inparas.
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 leakage unless care is taken to avoid imposing severe external 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- tionsofsafetyvalve,reliefvalve,orrupturediskoperation, the pressure on a flange or flanged fitting may exceed the rated pressure at the pressure-relieving temperature by no more than 10%. Such conditions are necessarily of short duration. Overpressure greater than the aforemen- tioned under pressure-relieving conditions is the respon- sibility of the user, subject to the requirements of the applicable code or regulation.
3.5.2 Other Variances. Operating variations (transi- ents) 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 SIZE
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 foridentifyingthe end connec- tion of piping, flanges, or flanged fittings. The number is not necessarily the same as the inside diameter 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 measure- ment.
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 Figure 4.2-1).