Wall Thickness Calculation - ASME B31.8 2007 (Template)

ATTACHMENT - X Document No. X Wall Thickness Calculation of 36in Gas Pipeline (Location Class-3, D.F.=0.5, Corr. Allow.=1.5mm) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

DESIGN INPUT

F

ASME B31.8 36 in 1.5 mm 3 0.5

Steel Coefficient of Expansion, Modulus of Elasticity

α E

0.0000117 2.07E+05

Pressure and Temperature Data Design Pressure Design Temperature (Underground) Installation (backfill) Temp

P Td Ti

63.5 65 13

16 17 18 19 20 21 22 23

Weld joint factor Temperature Derating Factor

E T

1 1

24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Next higher API wall thickness D/t Check ( Should be < 96)

46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68

D A

914

mm

o

per deg C Mpa

6.50E-06 in/in/ C 3.05E+07 Psi

bar g C C

921.0 149.0 55.4

o o

psi g F F

o o

A. WALL THICKNESS Grade SMYS of Line Pipe Wall Thickness Calculated tmin = P x D / (2x Sx Fx E x T) + A

X60 60200 15.5

psi mm

415 MPa 0.610 inch

15.9 58

mm

0.626 inch

B. EQUIVALENT STRESS CHECK FOR CORRODED PIPE CONDITION Wall thickness (t) Hoop Stress = Sh = PD/2t

14.4 201.6

mm MPa

B.1 Restrained Pipe (Underground) Thermal Stress = ST = a (Ti - Td) E Longitudinal Stress due to pressure = SP = 0.3 Sh

-125.9 60.5

MPa MPa

-65.5 OK

MPa

267.1 241.1 267.1

MPa MPa MPa

Longitudinal Stress, SL SL = SP + ST + SB + SX

S tmin t

≤

0.9 x SMYS = 374 MPa

Without considering SB (Bending stress) and SX (Axial stress due to external loading): SL = SP + ST Longitudinal Stress check : hence SL ≤ 0.9 x SMYS Equivalent Stress, SE SE1 = | Sh - SL | SE2 = [ Sh2 + SL2 - Sh SL ]1/2 SE = Max (SE1, SE2) Equivalent Stress check :

≤

0.9 x SMYS = 374 MPa SE ≤ 0.9 x SMYS

SE1 SE2 SE hence

OK

B.2 Unrestrained Pipe (Aboveground) Longitudinal Stress due to pressure = SP = 0.5 Sh

100.8

MPa

Longitudinal Stress, SL SL = SP +SB + SX ≤ 0.75 x SMYS = 312 MPa Without considering SB (Bending stress) and SX (Axial stress due to external loading): SL = SP SL ≤ 0.75 x SMYS Longitudinal Stress check : hence

100.8 OK

MPa

C. MINIMUM BENDING RADIUS Minimum bending radius for underground section is calculated from maximum margin of bending stress, based on Max (SE1, SE2) = 0.9 x SMYS. Hence, bending stress SB = -106.5 MPa R (Minimum Bend Radius) = E D / (2 |Sb|) 889 m D. CHECK ON THINNING DUE TO COLD BENDS: BEND RADIUS = 40 D

G

41 42 43 44 45

Design Code Pipeline Size / Nominal O.D Corrosion Allowance Location Class Design Factor

Inner bend radius divided by diameter, (n) As per PD 8010-1:2004, % of Wall thinning = 50 / (n+1) Pipe thk. before bending = cal thk/(1-thinning %) Available thickness for bending (= Selected thk) Adequacy Check (Pipe thk before bending < Available thk)

39.5 1.23 15.7 15.9 OK

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% mm mm