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ASME B31.3-2016 large rapid temperature changes or from unequal tem- of this Code may be used to extend the pressure— perature distribution as may result from a high heat flux temperature ratings of a component beyond the ratings through a comparatively thick pipe or stratified two- contained in the listed standard. phase flow causing bowing of the line. 302.2.2 Listed Components Not Having Specific (16) 301.7.3 Loads Due to Differences in Expansion Ratings Characteristics. These loads result from differences in (a) Some of the standards for fittings in Table 326.1 thermal expansion where materials with different ther- (e.g., ASME B16.9 and B16.11) state that pressure— mal expansion coefficients are combined,as in bimetal- temperature ratings are based on straight seamless pipe. lic, lined,jacketed, or metallic—nonmetallic piping. Such fittings shall be rated as calculated for straight seamless pipe with the same allowable stresses as the 301.8 Effects of Support, Anchor, and Terminal fitting and the nominal thickness corresponding to the Movements wall thickness or class designation of the fitting,less all The effects of movements of piping supports,anchors, applicable allowances (e.g.,thread depth and corrosion and connected equipment shall be taken into account allowance), and considering the manufacturing under- in the design of piping. These movements may result tolerances of the fittings and the pipe. from the flexibility and/or thermal expansion of equip- (b) For components with straight or spiral (helical ment, supports, or anchors; and from settlement, tidal seam)longitudinal welded joints,the pressure rating as movements, or wind sway. determined for seamless pipe shall be multiplied by the weld joint strength reduction factor, W, as defined in 301.9 Reduced Ductility Effects para. 302.3.5(e). The harmful effects of reduced ductility shall be taken (c) Other listed components not addressed in into account in the design of piping.The effects may,for para. 302.2.1 or 302.2.2(a) shall have their pressure— example,result from welding,heat treatment,forming, temperature ratings established in accordance with the bending, or low operating temperatures,including the rules in para. 304. chilling effect of sudden loss of pressure on highly vola- 302.2.3 Unlisted Components. Components not tile fluids. Low ambient temperatures expected during listed in Table 326.1 may be used within the following operation shall be considered. limitations: 301.10 Cyclic Effects (a) The designer shall be satisfied that composition, mechanical properties, method of manufacture, and Fatigue due to pressure cycling,thermal cycling,and design are suitable for the intended service. other cyclic loadings shall be considered in the design (b) Pressure—temperature ratings shall be established of piping. See Appendix F, para. F301.10. in accordance with the rules in para. 304. 301.11 Air Condensation Effects 302.2.4 Allowances for Pressure and Temperature At operating temperatures below —191°C (-312°F) in Variations. Occasional variations of pressure and/or ambient air,condensation and oxygen enrichment occur. temperature may occur in a piping system. Such varia- These shall be considered in selecting materials,includ- tions shall be considered in selecting design pressure ing insulation,and adequate shielding and/or disposal (para. 301.2) and design temperature (para. 301.3). The shall be provided. most severe coincident pressure and temperature shall determine the design conditions unless all of the follow- ing criteria are met: 302 DESIGN CRITERIA (a) The piping system shall have no pressure- 302.1 General containing components of gray iron or other nonductile metal. Paragraph 302 states pressure—temperature ratings, (b) Circumferential pressure stresses (based on mini- stress criteria,design allowances,and minimum design mum pipe wall thickness, less allowances) shall not values together with permissible variations of these fac- exceed the yield strength at temperature(see para.302.3 tors as applied to the design of piping. of this Code and Sy data in BPV Code,Section II,Part D, 302.2 Pressure—Temperature Design Criteria Table Y-1). (c) Combined longitudinal stresses shall not exceed 302.2.1 Listed Components Having Established the limits established in para. 302.3.6. Ratings. Except as limited elsewhere in the Code, (d) The total number of pressure—temperature varia- pressure—temperature ratings contained in standards for tions above the design conditions shall not exceed 1000 piping components listed in Table 326.1 are acceptable during the life of the piping system. for design pressures and temperatures in accordance (e) In no case shall the increased pressure exceed the with this Code. When the owner approves, provisions test pressure used under para.345 for the piping system.