 Wall Thickness Calculation of Shells and Tubes Under External Pressure As per para. 304.1.3 Straight Pipe Under External Pressure by ASME B31.3 Section VIII Div 1 - UG 28(c)(1) - Thickness of Shells and Tubes under External Pressure Cylinders having Do/t values ≥ 10 (Enter values in yellow cells for calculations) STEP 1 Enter the indicated input data Calculated Values Minimum required thickness,  t = mm L/Do = Length between any two sections stiffened,  L = m Do/t = Outside diameter,  Do = mm STEPS 2 TO 5 Enter the indicated input data Material = A53 Gr. A A53 Gr. B A106 Gr. A A106 Gr. B A106 Gr. C A268 TP410 A268 TP430 A333 Gr. 3 A333 Gr. 6 A335 P1 A335 P5 A335 P9 A335 P11 A335 P12 A335 P21 A335 P22 A312 TP304 A312 TP304L A312 TP304H A312 TP316 A312 TP316L A312 TP316H A312 TP309 A312 TP310 A312 TP310H A312 TP317 A312 TP317L A312 TP321 >3/8 thk. (C <0.04%) A312 TP321 >3/8 thk. (C ≥0.04%) A312 TP321 ≤3/8 thk. (C <0.04%) A312 TP321 ≤3/8 thk. (C ≥0.04%) A312 TP321H >3/8 thk. A312 TP321H ≤3/8 thk. A312 TP347 (C <0.04%) A312 TP347 (C ≥0.04%) A312 TP347H A376 TP304 A376 TP304H A376 TP316 A376 TP316H A376 TP321 >3/8 thk. (C <0.04%) A376 TP321 >3/8 thk. (C ≥0.04%) A376 TP321 ≤3/8 thk. (C <0.04%) A376 TP321 ≤3/8 thk. (C ≥0.04%) A376 TP321H >3/8 thk. A376 TP321H ≤3/8 thk. A376 TP347 (C <0.04%) A376 TP347 (C ≥0.04%) A376 TP347H Design Temp. = °C With L/Do and Do/t get Factor A = From ASME Sec. II D Fig. G External Pressure Chart No. = From ASME Sec. II D Figs. CS, HA, HT For values of A falling to the left of the material/ With Factor A get Factor B = temperature line, the factor B is not determined. Go to Step 7. STEP 6 Input data Calculated Value Factor B = Do/t = Using the factor B, calculate the value of the maximum allowable Pa = 4B external working pressure Pa 3(Do/t) Pa = bar STEP 7 Input data Calculated Value Factor A = Do/t = Pa = 2AE Modulus of elasticity,  E = x 10ᶟ Mpa 3(Do/t) Pa = bar For values of A falling to the left of the applicable material/temperature line. STEP 8 Compare the calculated value of Pa obtained in Step 6 or Step 7 with P External design pressure, P = bar Pa = bar Pa ≥ P If Pa is smaller than P, select a larger value for t and repeat the design procedure until a value of Pa is obtained that is equal to or greater than P. Wall Thickness Calculation of Shells and Tubes Under External Pressure As per para. 304.1.3 Straight Pipe Under External Pressure by ASME B31.3 Section VIII Div 1 - UG 28(c)(1) - Thickness of Shells and Tubes under External Pressure Cylinders having Do/t values ≥ 10 (Enter values in yellow cells for calculations) STEP 1 Enter the indicated input data Calculated Values Minimum required thickness,  t = in. L/Do = Length between any two sections stiffened,  L = ft. Do/t = Outside diameter,  Do = in. STEPS 2 TO 5 Enter the indicated input data Material = A53 Gr. A A53 Gr. B A106 Gr. A A106 Gr. B A106 Gr. C A268 TP410 A268 TP430 A333 Gr. 3 A333 Gr. 6 A335 P1 A335 P5 A335 P9 A335 P11 A335 P12 A335 P21 A335 P22 A312 TP304 A312 TP304L A312 TP304H A312 TP316 A312 TP316L A312 TP316H A312 TP309 A312 TP310 A312 TP310H A312 TP317 A312 TP317L A312 TP321 >3/8 thk. (C <0.04%) A312 TP321 >3/8 thk. (C ≥0.04%) A312 TP321 ≤3/8 thk. (C <0.04%) A312 TP321 ≤3/8 thk. (C ≥0.04%) A312 TP321H >3/8 thk. A312 TP321H ≤3/8 thk. A312 TP347 (C <0.04%) A312 TP347 (C ≥0.04%) A312 TP347H A376 TP304 A376 TP304H A376 TP316 A376 TP316H A376 TP321 >3/8 thk. (C <0.04%) A376 TP321 >3/8 thk. (C ≥0.04%) A376 TP321 ≤3/8 thk. (C <0.04%) A376 TP321 ≤3/8 thk. (C ≥0.04%) A376 TP321H >3/8 thk. A376 TP321H ≤3/8 thk. A376 TP347 (C <0.04%) A376 TP347 (C ≥0.04%) A376 TP347H Design Temp. = °F With L/Do and Do/t get Factor A = From Subpart 3 ASME Sec. II D Fig. G External Pressure Chart No. = From Subpart 3 ASME Sec. II D Figs. CS, HA, HT For values of A falling to the left of the material/ With Factor A get Factor B = temperature line, the factor B is not determined. Go to Step 7. STEP 6 Input data Calculated Value Factor B = Do/t = Using the factor B, calculate the value of the maximum allowable Pa = 4B external working pressure Pa 3(Do/t) Pa = psi STEP 7 Input data Calculated Value Factor A = Do/t = Pa = 2AE Modulus of elasticity,  E = × 10⁶ psi 3(Do/t) Pa = psi For values of A falling to the left of the applicable material/temperature line. STEP 8 Compare the calculated value of Pa obtained in Step 6 or Step 7 with P External design pressure, P = psi Pa = psi Pa ≥ P If Pa is smaller than P, select a larger value for t and repeat the design procedure until a value of Pa is obtained that is equal to or greater than P.