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ASME B31.3-2016
<br /> When the computed stress range varies,whether from otherwise considers effects such as stress redistribution
<br /> thermal expansion or other conditions, SE is defined as across the weld.
<br /> the greatest computed displacement stress range. The (2) With the owner's approval,extensive successful
<br /> value of N in such cases can be calculated by eq. (1d) experience may be used to justify the factor W above
<br /> that shown in Table 302.3.5. Successful experience must
<br /> N = NE+Y—(ri5Ni) for i = 1,2, ...,n (1d) include same or like material,weld metal composition,
<br /> and welding process under equivalent, or more severe,
<br /> where sustained operating conditions.
<br /> NE = number of cycles of maximum computed dis-
<br /> placement stress range, SE 302.3.6 Limits of Calculated Stresses Due to (16)
<br /> Ni = number of cycles associated with displacement Occasional Loads
<br /> stress range, Si (a) Operation. The sum of the longitudinal stresses,
<br /> ri = Si/SE SE,due to sustained loads,such as pressure and weight,
<br /> Si = any computed displacement stress range and of the stresses produced by occasional loads, such
<br /> smaller than SE as wind or earthquake, may be as much as 1.33 times
<br /> the basic allowable stress given in Appendix A. Wind
<br /> (e) Weld Joint Strength Reduction Factor,W. At elevated and earthquake forces need not be considered as acting
<br /> temperatures,the long-term strength of weld joints may concurrently. When detailed analysis is performed, the
<br /> be lower than the long-term strength of the base mate- stresses shall be computed and combined using
<br /> rial. For longitudinal or spiral (helical seam) welded eqs. (23a) through (23d) with the applicable loads for
<br /> piping components,the product of the allowable stress the condition being evaluated.
<br /> and the applicable weld quality factor, SE, shall be For Elevated Temperature Fluid Service(see definition
<br /> multiplied by the weld joint strength reduction factor, in para. 300.2),as an alternative to the use of 1.33 times
<br /> W, when determining the required wall thickness for the basic allowable stress provided in Appendix A, the
<br /> internal pressure in accordance with para. 304. The allowable stress for occasional loads of short duration,
<br /> designer is responsible for the application of weld joint such as surge, extreme wind, or earthquake, may be
<br /> strength reduction factors to welds other than longitudi- taken as the strength reduction factor times 90% of the
<br /> nal and spiral (helical seam) (e.g.,circumferential). The
<br /> weld joint strength reduction factor, W, is equal to 1.0 yield strength at temperature for materials other than
<br /> when evaluating occasional loads such as wind and those with nonductile behavior.This yield strength shall
<br /> earthquake, or when evaluating permissible variations be as listed in the BPV Code,Section II,Part D,Table Y-1,
<br /> in accordance with para. 302.2.4. The pressure rating or determined in accordance with para. 302.3.2(f). The
<br /> strength reduction factor represents the reduction in
<br /> or allowable stress for the occasional load or variation
<br /> condition is not required to be reduced by the weld joint yield strength with long-term exposure of the material
<br /> strength reduction factor. It is also not required when to elevated temperatures and, in the absence of more
<br /> calculating the allowable stress range for displacement applicable data,shall be taken as 1.0 for austenitic stain-
<br /> stresses, SA,in para. 302.3.5(d). The weld joint strength less steel and 0.8 for other materials.
<br /> reduction factor only applies at weld locations.The weld For castings, the basic allowable stress shall be
<br /> joint strength reduction factor is the ratio of the nominal multiplied by the casting quality factor, Ec. Where the
<br /> stress to cause failure of the weld joint to that of the allowable stress value exceeds two-thirds of yield
<br /> base material for the same duration.Except as provided strength at temperature,the allowable stress value must
<br /> in (f)below,the weld joint strength reduction factor, W, be reduced as specified in para. 302.3.2(e).
<br /> shall be in accordance with Table 302.3.5. (b) Test. Stresses due to test conditions are not subject
<br /> (f) Unlisted Weld Strength Reduction Factors. A weld to the limitations in para. 302.3. It is not necessary to
<br /> strength reduction factor other than that listed in consider other occasional loads,such as wind and earth-
<br /> Table 302.3.5 may be used in accordance with one of the quake, as occurring concurrently with test loads.
<br /> following criteria:
<br /> (1) Creep test data may be used to determine the 302.4 Allowances
<br /> weld joint strength reduction factor, W. However, the In determining the minimum required thickness of
<br /> use of creep test data to increase the factor W above that a piping component, allowances shall be included for
<br /> shown in Table 302.3.5 is not permitted for the CrMo corrosion, erosion, and thread depth or groove depth.
<br /> and Creep Strength Enhanced Ferritic (CSEF) steels See definition for c in para. 304.1.1(b).
<br /> materials, as defined in Table 302.3.5. Creep testing of
<br /> weld joints to determine weld joint strength reduction 302.5 Mechanical Strength
<br /> factors,when permitted,should be full thickness cross-
<br /> weld specimens with test durations of at least 1000 h. (a) Designs shall be checked for adequacy of mechani-
<br /> Full thickness tests shall be used unless the designer cal strength under applicable loadings.When necessary,
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