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ASME B31.3-2016
<br /> (1) Sy/1.5 in Division 3 shall be replaced by S from stress intensity shall be determined in accordance with
<br /> Table K-1, and Articles KD-2 and KD-3.The allowable amplitude of the
<br /> (2) the Division 3 stress intensity limits due to sus- equivalent alternating stress shall be determined from
<br /> tained loads may be increased by the same factor applied the applicable design fatigue curve in Article KD-3.
<br /> in para.K302.3.6(a)when wind or earthquake loads are (2) If it can be shown that the piping component
<br /> included. However, this limit shall not exceed 90% of will fail in a leak-before-burst mode, the number of
<br /> Syt listed in the BPV Code,Section II,Part D,Table Y-1. design cycles (design fatigue life) may be calculated in
<br /> (d) for(a),(b),and(c)above,interpolations supported accordance with either Article KD-3 or Article KD-4. If
<br /> by analysis are permitted between sizes, wall thick- a leak-before-burst mode of failure cannot be shown,the
<br /> nesses,and pressure classes,as well as analogies among fracture mechanics evaluation outlined in Article KD-4
<br /> related materials with supporting material property shall be used to determine the number of design cycles
<br /> data. Extrapolation is not permitted. of the component.
<br /> K304.7.3 Components With Nonmetallic Parts. (c) Additional Considerations. The designer is cau-
<br /> Except for gaskets and packing, nonmetallic parts are tioned that the considerations listed in para.K302.1 may
<br /> not permitted.
<br /> reduce the fatigue life of the component below the value
<br /> predicted by para. (a) or (b) above.
<br /> K304.7.4 Bellows Type Expansion Joints. Bellows K304.8.3 Pressure Stress Evaluation for Fatigue
<br /> type expansion joints are not permitted. Analysis
<br /> K304.8 Fatigue Analyses (a) For fatigue analysis of straight pipe,eq. (37) may
<br /> be used to calculate the stress intensity9 at the inside
<br /> (16) K304.8.1 General. A fatigue analysis shall be per- surface due only to internal pressure.
<br /> formed on each piping system, including all compo-
<br /> nents6 and joints therein, and considering the stresses S _ PD' (37)
<br /> resulting from attachments, to determine its suitability 2(T-c)[D - (T-c)]
<br /> for the cyclic operating conditions?specified in the engi-
<br /> neering design.Except as permitted in(a)and(b)below, (b) For fatigue analysis of curved pipe, eq. (37) may
<br /> or in paras. K304.8.4 and K304.8.5,this analysis shall be be used,with the dimensions of the straight pipe from
<br /> which it was formed, to calculate the maximum stress
<br /> in accordance with the BPV Code, Section VIII,
<br /> Division 2 or Division 3.8 The cyclic conditions shall intensity at the inside surface due only to internal pres-
<br /> includepressure variations as well as thermal variations sure,provided that the centerline bend radius is not less
<br /> than ten times the nominal outside diameter of the pipe,
<br /> or displacement stresses. The requirements of
<br /> para. K304.8 are in addition to the requirements fora and that the tolerance and strain limits of para. K332
<br /> flexibility analysis stated in para. K319. No formal are met. Bends of smaller radius shall be qualified as
<br /> fatigue analysis is required in systems that required by para. K304.7.2.
<br /> (a) are duplicates of successfully operating installa- (c) If the value of S calculated by eq. (37) exceeds
<br /> tions or replacements without significant change of sys- three times the allowable stress from Table K-1 at the
<br /> terns with a satisfactory service record or average temperature during the loading cycle,an inelas-
<br /> (b) can readily be judged adequate by comparison tic analysis is required.
<br /> with previously analyzed systems K304.8.4 Fatigue Evaluation by Test. With the own-
<br /> K304.8.2 Amplitude of Alternating Stress er's approval, the design fatigue life of a component
<br /> (a) Fatigue Analysis Based Upon Section VIII,Division 2. may be established by destructive testing in accordance
<br /> The value of the alternating stress amplitude for compar- with para. K304.7.2 in lieu of the above analysis
<br /> requirements.
<br /> ison with design fatigue curves shall be determined in
<br /> accordance with Part 5. The allowable amplitude of K304.8.5 Extended Fatigue Life. The design fatigue
<br /> alternating stress shall be determined from the applica- life of piping components may be extended beyond that
<br /> ble design fatigue curve in Part 3,para. 3.15. determined by Section VIII,Division 2,Part 3,para.3.15
<br /> (b) Fatigue Analysis Based Upon Section VIII,Division 3 and Part 5; or Division 3, Article KD-3; as applicable,
<br /> (1) The values of the alternating stress intensity,the by the use of one of the following methods, provided
<br /> associated mean stress, and the equivalent alternating that the component is qualified in accordance with
<br /> para. K304.7.2:
<br /> (a) surface treatments, such as improved surface
<br /> b Bore imperfections may reduce fatigue life. finish
<br /> 7 If the range of temperature change varies,equivalent full tem-
<br /> perature cycles N may be computed using eq.(1d)in para.302.3.5. (b) prestressing methods, such as autofrettage, shot
<br /> 8 Fatigue analysis in accordance with Section VIII,Division 2 or peening, or shrink fit
<br /> Division 3, requires that stress concentration factors be used in
<br /> computing the cyclic stresses. 9 The term stress intensity is defined in Section VIII,Division 3.
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