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STRESS ANALYSIS OF PIPING SYSTEMS B.139

2. Stresses due to occasional loads. The sum of the longitudinal stresses due topressure, weight, and other sustained loads and of the stresses produced byoccasional loads such as earthquake or wind shall not exceed 1.33Sh. Earthquakeand wind loads need not be considered as acting simultaneously.

3. Stress range due to expansion loads. The displacement stress range SE shall notexceed SA:

where SE =Sb = resultant bending stress, psi

= [(iiMi )2 +(ioMo)2]1/2 / Z

TABLE B4.4c SIFs for Class 3000 Half-Couplings (Branch Pipe Schedule 80) (Run Pipe Size:NPS 1½ to 8 (DN 40 to 200))

1 in = 25.4 mm

(B4.28)

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STRESS ANALYSIS OF PIPING SYSTEMS



GENERIC DESIGN CONSIDERATIONSB.140

Mi = in-plane bending moment, in · lb Mo = out-of-plane bending moment, in · lb ii = in-plane stress intensification factor obtained from Fig. B4.5a (see also

figure note 10) io = out-of-plane stress intensification factor obtained from Fig. B4.5a (seealso figure note 10)

St = torsional stress, psi = Mt /(2Z) Mt = torsional moment, in · lb

TABLE B4.4d SIFs for Class 3000 Half-Couplings (Branch Pipe Schedule 80) (Run Pipe Size:NPS 10 to 24 (DN 250 to 600))

1 in = 25.4 mm







SA = allowable displacement stress range= f (1.25Sc + 0.25Sh)= f [1.25(Sc + Sh) - SL] when Sh > SL

Sc = basic allowable stress at minimum metal temperature, psi

f = stress range reduction factor per Table B4.2

ASME B31.4 Liquid Transportation Systems for Hydrocarbons, Liquid PetroleumGas, Anhydrous Ammonia, and Alcohols Piping Code.10 The scope of ASME B31.4,Liquid Transportation Systems for Hydrocarbons, Liquid Petroleum Gas, AnhydrousAmmonia, and Alcohols, governs piping transporting liquids such as crude oil,

TABLE B4.4e SIFs for Class 6000 Half-Couplings (Branch Pipe Schedule 160) (Run Pipe Size:1½ to 8 in (DN 40 to 200))

1 in = 25.4 mm






GENERIC DESIGN CONSIDERATIONSB.142

condensate, natural gasoline, natural gas liquids, liquefied petroleum gas, liquidalcohol, liquid anhydrous ammonia, and liquid petroleum products between producers’lease facilities, tank farms, natural gas processing plants, refineries, stations, ammoniaplants, terminals, and delivery and receiving points. Excluded from B31.4 are auxiliary

piping such as water, air, steam, lubricating oil, gas, and fuel; piping with an internalgauge pressure at or below 15 psi (103.5 kPa) regardless of temperature; piping withan internal gauge pressure above 15 psi (103.5 kPa) and a temperature below -20°F(-29°C) or above 250°F (121°C); and piping for petroleum refinery, gas transmissionand distribution, ammonia refrigeration, and so on, that is covered by other ASMEB31 sections.

TABLE B4.4f SIFs for Class 6000 Half-Couplings (Branch Pipe Schedule 160) (Run Pipe Size:10 to 24 in (DN 250 to 600))

1 in = 25.4 mm







The limits of calculated stresses are as follows:

1. Stresses due to sustained loads. The sum of the longitudinal stresses due to pressure,weight, and other sustained external loads shall not exceed 0.75SA, where SA =

0.72Sy (specified minimum yield strength).2. Stresses due to occasional loads. The sum of the longitudinal stresses produced

by pressure, live and dead loads, and those produced by occasional loads, such aswind or earthquake, shall not exceed 0.8Sy.

3. Stresses due to expansion loads

a. Restrained lines. The net longitudinal compressive stress due to the combinedeffects of temperature rise and fluid pressure shall be computed from the equation.

(B4.29)

where SL = longitudinal compressive stress, psi SH = hoop stress due to fluid pressure, psi T 1 = temperature at time of installation, °F T 2 = maximum or minimum operating temperature, °F E = modulus of elasticity, psi

α = linear coefficient of thermal expansion, in/(in · °F)v = Poisson’s ratio = 0.30 for steel

Then the equivalent tensile stress is calculated as

(B4.30)

where Seqiv = the equivalent tensile stress, psi. Beam bending stresses shall beincluded in the longitudinal stress for those portions of the restrained linewhich are supported aboveground.

b. Unrestrained lines. Stresses due to expansion for those portions of the pipingwithout substantial axial restraint shall be combined in accordance with thefollowing equation:

(B4.31)

whereSE = stress due to expansion, psi Sb = [(iiMi)2 +(ioMo

2) ]1/2 /Z= equivalent bending stress, psi

St = Mt / (2Z) = torsional stress, psi Mi = in-plane bending moment, in · lb Mo = out-of-plane bending moment, in · lb Mt = torsional moment, in · lb

ii = in-plane stress intensification factor obtained from Fig. B4.5a

io = out-of-plane stress intensification factor obtained from Fig. B4.5a Z = section modulus of pipe, in3

ASME B31.5 Refrigeration Piping Code.11 The scope of this code covers refrigerantand secondary coolant piping for temperatures as low as -320°F (196°C). Excludedfrom this code are piping designed for external or internal gauge pressure not exceeding


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