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ASME B31.3-2016
<br /> (f) Occasional variations above design conditions (a) Tension. Basic allowable stresses, S,in tension for
<br /> shall remain within one of the following limits for pres- metals listed in Tables A-1 and A-IM, and design
<br /> sure design. stresses,S,for bolting materials listed in Tables A-2 and
<br /> (1) Subject to the owner's approval,it is permissible A-2M were determined in accordance with para.302.3.2.
<br /> to exceed the pressure rating or the allowable stress In equations elsewhere in the Code where the product
<br /> for pressure design at the temperature of the increased SE appears, the value S is multiplied by one of the
<br /> condition by not more than following quality factors:
<br /> (-a) 33% for no more than 10 h at any one time (1) casting quality factor E, as defined in
<br /> and no more than 100 h/y, or para. 302.3.3 and tabulated for various material specifi-
<br /> (-b) 20% for no more than 50 h at any one time cations in Table A-IA,and for various levels of supple-
<br /> and no more than 500 h/y mentary examination in Table 302.3.3C, or
<br /> The effects of such variations shall be determined by (2) longitudinal weld joint factor Ej as defined in
<br /> the designer to be safe over the service life of the piping 302.3.4 and tabulated for various material specifications
<br /> system by methods acceptable to the owner. (See and classes in Table A-113,and for various types of joints
<br /> Appendix V.) and supplementary examinations in Table 302.3.4
<br /> (2) When the variation is self-limiting (e.g., due to The stress values in Tables A-1,A-IM,A-2,and A-2M
<br /> a pressure-relieving event),and lasts no more than 50 h are grouped by materials and product forms, and are
<br /> at any one time and not more than 500 h/y,it is permissi- for stated temperatures up to the limit provided in para.
<br /> ble to exceed the pressure rating or the allowable stress 323.2.1(a). Straight-line interpolation between tempera-
<br /> for pressure design at the temperature of the increased tures is permissible. The temperature intended is the
<br /> condition by not more than 20% design temperature (see para. 301.3).
<br /> (g) The combined effects of the sustained and cyclic (b) Shear and Bearing. Allowable stresses in shear shall
<br /> variations on the serviceability of all components in the be 0.80 times the basic allowable stress in tension tabu-
<br /> system shall have been evaluated. lated in Appendix A. Allowable stress in bearing shall
<br /> (h) Temperature variations below the minimum tem- be 1.60 times that value.
<br /> perature shown in Appendix A are not permitted unless (c) Compression. Allowable stresses in compression
<br /> the requirements of para. 323.2.2 are met for the lowest shall be no greater than the basic allowable stresses in
<br /> temperature during the variation. tension as tabulated in Appendix A.Consideration shall
<br /> (i) The application of pressures exceeding pressure— be given to structural stability.
<br /> temperature ratings of valves may under certain condi- 302.3.2 Bases for Design Stresses The bases for (16)
<br /> tions cause loss of seat tightness or difficulty of opera- establishing design stress values for bolting materials
<br /> tion. The differential pressure on the valve closure and allowable stress values for other metallic materials
<br /> element should not exceed the maximum differential in this Code are as follows:
<br /> pressure rating established by the valve manufacturer. (a) Bolting Materials. Design stress values at tempera-
<br /> Such applications are the owner's responsibility. ture for bolting materials shall not exceed the lowest of
<br /> the following:
<br /> 302.2.5 Ratings at Junction of Different Services. (1) except as provided in (3) below, the lower of
<br /> When two services that operate at different pressure—
<br /> one-fourth of specified minimum tensile strength at
<br /> temperature conditions are connected, the valve segre- room temperature(ST)and one-fourth of tensile strength
<br /> gating the two services shall be rated for the more severe at temperature
<br /> service condition.Where multiple valves are used (e.g., (2) except as provided in (3) below, the lower of
<br /> in a double block and bleed arrangement), all of the two-thirds of specified minimum yield strength at room
<br /> valves shall be rated for the more severe service condi-
<br /> tion. If the valve(s) will operate at a different tempera- temperature
<br /> ture due to remoteness from a header or piece of
<br /> equipment, the valve(s) (and any mating flanges) may 1 If a component is made of castings joined by longitudinal welds,
<br /> be selected on the basis of the different temperature.For both a casting and a weld joint quality factor shall be applied.The
<br /> piping on either side of the valve,however,each system equivalent quality factor E is the product of E,,Table A-IA, and
<br /> shall be designed for the conditions of the service to Ep Table A-113.
<br /> These bases are the same as those for BPV Code, Section III,
<br /> which it is connected. Class 1 materials,given in Section II,Part D.Stress values in 1331.3,
<br /> Appendix A,at temperatures below the creep range generally are
<br /> 302.3 Allowable Stresses and Other Stress Limits the same as those listed in Section II, Part D, Tables 2A and 213,
<br /> and in Table 3 for bolting,corresponding to those bases.They have
<br /> (16) 302.3.1 General. The allowable stresses defined in been adjusted as necessary to exclude casting quality factors and
<br /> paras. 302.3.1(a), (b), and (c) shall be used in design longitudinal weld joint quality factors. Stress values at tempera-
<br /> tures in the creep range generally are the same as those in Section II,
<br /> calculations unless modified by other provisions of this Part D, Tables 1A and 113, corresponding to the bases for
<br /> Code. Section VIII,Division 1.
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