ANALYSIS OF EXTERNAL LOADS ON BURIED PIPE
(Based on ALA - Guidlines for the design of Buried steel pipe) Project : 13404Pipeline : 6" Jet fuel pipeline
1.) EARTH LOAD 1
Total dry unit weight, r = 120 LB/FT^3 18.86 kN/m3
Height of backfill above pipe, C = 59.06 INCH 1.50 m
unit weight of water , rw = 62.4 LB/FT^3 9.81 kN/m3
height of water above pipe, hw = 59.06 INCH 1.50 m
Water buoyancy factor, Rw = (1-0.33(hw/C) = 0.67 Earth Load,Pv = rw.hw+Rw.r.C = 4.88 PSI 2.) LIVE LOAD
Concentrated load at the surface
above pipe, Ps = 18000 lb offset distance from pipe to line of
application of surface load d = 0 inch Impact factor, F' = 1.15
Pressure Transmitted to pipe, Pp = F'*3Ps/(2*π*C2[1+(d/C)2]2.5)
= 2.83 PSI
3.) OVALITY
FLOODED NON-FLOODED
3.) OVALITY
Pipe Outside Diameter, D = 6.625 INCH Deflection lag factor, D1(~1.0 -1.5) = 1.5 Bedding constant, K (~0.1) = 0.1 Modulus of sol reaction, E` = 500 PSI thickness of pipe, t = 0.280 INCH Youngs modulus of pipe, E = 29000000 PSI thicknes of liner, tL = 0 INCH modulus of elasticity of liner, EL = 0 PSI
thicknes of coating , tc = 0.1063 INCH modulus of elasticity of coating, Ec= 113000 PSI
Pressure on pipe due to load, P = 7.71 PSI Equi. pipe wall stiffness, (EI)eq = 53016.52
Ovality , dy/D = (D1.K.P)/((EI)eq/R^3 + 0.061 E') 0.001 INCH
Ovality percentage = 0.15% Check Ovality <3% OK
Generally in steel pipelines, buckling typically occurs when the ovality reached 20%, however as per API RP-1102 recommends to limit cross section ovality to 3%
4.) RING BUCKLING PRESSURE
FS= factor of safety
Factor of safety, FS 2.5 2.5 for C/D=>2
Empirical coeff of elastic support, B'= 1/(1+4e^(-0.065C/D)) 3 for (C/D)<2 0.309
Critical Ring buckling Pressure Qrb= (1/FS)*sqrt(32.Rw.B'.E'.(ET)eq/D^3)) 310.64 PSI
Notes:-1.) The surface loads are assumed to be acting as a point load 2.) The analysis is carried out for empty condition of pipe
PROJECT: 13404
PIPELINE: 6" Jet Fuel Pipeline
Initial Design information Pipe and operational characteristics:Outside Diameter, D (inches) 6 = 168.3 mm
Design/Oper. Pressure, p (bar g) 19.6 Barg = 284.3 1.960 Mpa
Line Pipe Steel Grade API 5L Gr. B
Specified min. yield strength, SMYS (psi) 35000 psi 240 MPa
Design Factor, F 0.72
Allowable Design Factor, Fa 0.72
Longitudinal joint Factor, E 1
Temperature derating Factor T 1
Design Wall Thickness, t (mm) 7.11 mm
Corrossion Allownace, c (mm) 0 mm
Corroded Wall Thickness, tw (mm) 7.11 mm
Installation Temp Deg C 13 C
Maximum operating Temp Deg C 65 C
Installation and Site Characteristics
Depth H (Meters) 1.5 m 4.92 feet
Bored diameter, Bd 168.3 mm
Soil Type Loose Sand & Gravel
Modulus of soil reaction, E' (ksi) 0.5 ksi = 3.4 MPa
Resilient modulus, Er (ksi) 5 ksi = 34 MPa
Unit Weight of soil, Lamda , lbs/in³ 0.070 lbs/in³ = 1926 Kg/m³
Type of Longitudinal Weld SMLS
Design Wheel Load from axle, Ps/t (kips) 17.8125 = 79.23 KN
Pavement type (Flexible / No Pavement / Rigid) Rigid
Ap (Area of Tire Contact)sq.m = 0.053 m²
Critical Axle Configuration Single
Other Steel Properties
Young's modulus, Es 30000000 psi 206842.772 MPa
Poisson's ratio, Vs 0.3
Coefficient of Thermal Expansion mm/mm/deg C 0.0000117 Check Allowable Barlow Stress
Equation 8a, (Shi=p.D/2.tw) less than or equal to FxExTxSMYS
p = 1.96 MPa D= 168.3 mm tw= 7.11 mm F= 0.72 E= 1 SMYS= 240 MPa T= 1 Shi (Barlow) 23.197 < or = 172.80 MPa
Barlow Criteria fulfilled (Shi less than F.E.T.SMYS) OK
Circumferential Stress Due to Earth Load
tw/D 0.0422
E' 3.4
From Figure 3 of API RP1102, KHe 800
Dia of earth surrounding the pipeline Bd 168.3 mm
H/Bd 8.91
From Figure 4 of API RP1102, Factor Be = 1.300
Bd /D = 1.00
From Figure 5 of API RP1102 Factor Ee = 0.820
Unit Weight of Soil Lamda 1926 kg/m³
SHe from Equation 1 of API RP1102, (SHe=KHe.Be.Ee.Lamda .D) 2.71 MPa 2711 KPa
Track Crossing Calculation-Uncased (as per API 1102)
Impact Factor Fi and Applied Design Surface Pressure, w
Fi from Figure 7 & Sect 4.7.2.2.2 1.50
Ap (Area of Tire Contact)sq.m = 0.05295796 m²
w = Pt/Ap lbs/in2 1496.09 KPa
Cyclic Circumferential Delta SHh
From Fig 14 of API RP1102, for tw/D and Er values KHh = 8.00
From Fig 15 of API RP1102, GHh = 1.30
From Table 2 of API RP1102, R = 1.10
From Table 2 of API RP1102, L = 1.00
From Equation 5 of API RP1102, Delta SHh = KHh.GHh.R.L.Fi.w 25.67 MPa 25673 KPa Cyclic Longitudinal Delta SLh
From Fig 16 of API RP1102, for tw/D and Er values KLh = 9.00
From Fig 17 of API RP1102, GLh = 1.550
From Eqn 6 of API RP1102, Delta SLh =KLh.GLh.R.L.Fi.w 34.44 MPa 34436 KPa Circumferential Stress Due to Internal Pressure
From Eqn 7 of API RP1102, SHi =p(D-tw)/2.tw 22.22 MPa 22217 KPa
Principle Stresses S1, S2, & S3
From Eqn 9 of API RP1102, Circumferential S1 =SHe+Delta SHh+Shi 50.60 MPa S1-S2 134.53 MPa
From Eqn 10 of API RP1102, Longitudinal S2 = -83.93 MPa S2-S3 -81.97 MPa From Eqn 11 of API RP1102, Radial S3 = -p = -MAOP -1.96 MPa S3-S1 -52.56 MPa
From Equation 12, Page 2, Seff = 117.43 MPa
Check Allowable Effective Stress
Total effective stress in pipeline, Seff not to exceed SMYSxFa
SMYS x Fa 172.80 MPa
OK 67.96%
Check Fatigue
F =
0.72
From Table 3 of API RP 1102 SFG = 12000 psi = 82.74 MPa
Delta SLh = 34.44 MPa
SFG x F = 59.57 MPa
Longitudinal welds F = 0.72
From Table 3 of API RP 1102 SFL = 21000 psi = 144.79 MPa
Delta SHh shall be less than or equal to SFL x F
Delta SHh = 25.67 MPa
SFL x F = 104.25 MPa
IF Seff is Equal or Less Than (SMYS x F) then Crossing is
Girth Welds Delta SLh < = SFG x F Girth Welds OK for Fatigue
Longitudinal welds Delta SHh < = SFL X F Longitudinal Welds OK for Fatigue
ANALYSIS OF EXTERNAL LOADS ON BURIED PIPE
(Based on ALA - Guidlines for the design of Buried steel pipe) Project : 13404Pipeline : 3" Jet fuel pipeline
1.) EARTH LOAD 1
Total dry unit weight, r = 120 LB/FT^3 18.86 kN/m3
Height of backfill above pipe, C = 59.06 INCH 1.50 m
unit weight of water , rw = 62.4 LB/FT^3 9.81 kN/m3
height of water above pipe, hw = 59.06 INCH 1.50 m
Water buoyancy factor, Rw = (1-0.33(hw/C) = 0.67 Earth Load,Pv = rw.hw+Rw.r.C = 4.88 PSI 2.) LIVE LOAD
Concentrated load at the surface
above pipe, Ps = 18000 lb offset distance from pipe to line of
application of surface load d = 0 inch Impact factor, F' = 1.15
Pressure Transmitted to pipe, Pp = F'*3Ps/(2*π*C2[1+(d/C)2]2.5)
= 2.83 PSI
3.) OVALITY
FLOODED NON-FLOODED
3.) OVALITY
Pipe Outside Diameter, D = 3.5 INCH Deflection lag factor, D1(~1.0 -1.5) = 1.5 Bedding constant, K (~0.1) = 0.1 Modulus of sol reaction, E` = 500 PSI thickness of pipe, t = 0.216 INCH Youngs modulus of pipe, E = 29000000 PSI thicknes of liner, tL = 0 INCH modulus of elasticity of liner, EL = 0 PSI
thicknes of coating , tc = 0.984 INCH modulus of elasticity of coating, Ec= 113000 PSI
Pressure on pipe due to load, P = 7.71 PSI Equi. pipe wall stiffness, (EI)eq = 33380.52
Ovality , dy/D = (D1.K.P)/((EI)eq/R^3 + 0.061 E') 0.001 INCH
Ovality percentage = 0.12% Check Ovality <3% OK
Generally in steel pipelines, buckling typically occurs when the ovality reached 20%, however as per API RP-1102 recommends to limit cross section ovality to 3%
4.) RING BUCKLING PRESSURE
FS= factor of safety
Factor of safety, FS 2.5 2.5 for C/D=>2
Empirical coeff of elastic support, B'= 1/(1+4e^(-0.065C/D)) 3 for (C/D)<2 0.428
Critical Ring buckling Pressure Qrb= (1/FS)*sqrt(32.Rw.B'.E'.(ET)eq/D^3)) 756.12 PSI
Notes:-1.) The surface loads are assumed to be acting as a point load 2.) The analysis is carried out for empty condition of pipe
PROJECT: 13404
PIPELINE: 3" Jet Fuel Pipeline
Initial Design information
Pipe and operational characteristics:
Outside Diameter, D (inches) 3 = 88.9 mm
Design/Oper. Pressure, p (bar g) 19.6 Barg = 284.3 1.960 Mpa
Line Pipe Steel Grade API 5L Gr. B
Specified min. yield strength, SMYS (psi) 35000 psi 240 MPa
Design Factor, F 0.72
Allowable Design Factor, Fa 0.72
Longitudinal joint Factor, E 1
Temperature derating Factor T 1
Design Wall Thickness, t (mm) 5.49 mm
Corrossion Allownace, c (mm) 0 mm
Corroded Wall Thickness, tw (mm) 5.49 mm
Installation Temp Deg C 13 C
Maximum operating Temp Deg C 65 C
Installation and Site Characteristics
Depth H (Meters) 1.5 m 4.92 feet
Bored diameter, Bd 88.9 mm
Soil Type Loose Sand & Gravel
Modulus of soil reaction, E' (ksi) 0.5 ksi = 3.4 MPa
Resilient modulus, Er (ksi) 5 ksi = 34 MPa
Unit Weight of soil, Lamda , lbs/in³ 0.070 lbs/in³ = 1926 Kg/m³
Type of Longitudinal Weld SMLS
Design Wheel Load from axle, Ps/t (kips) 17.8125 = 79.23 KN
Pavement type (Flexible / No Pavement / Rigid) Rigid
Ap (Area of Tire Contact)sq.m = 0.053 m²
Critical Axle Configuration Single
Other Steel Properties
Young's modulus, Es 30000000 psi 206843 MPa
Poisson's ratio, Vs 0.3
Coefficient of Thermal Expansion mm/mm/deg C 0.0000117
Check Allowable Barlow Stress
Equation 8a, (Shi=p.D/2.tw) less than or equal to FxExTxSMYS
p = 1.96 MPa D= 88.9 mm tw= 5.49 mm F= 0.72 E= 1 SMYS= 240 MPa T= 1 Shi (Barlow) 15.869 < or = 172.80 MPa
Barlow Criteria fulfilled (Shi less than F.E.T.SMYS) OK
Circumferential Stress Due to Earth Load
tw/D 0.0618
E' 3.4
From Figure 3 of API RP1102, KHe 400
Dia of earth surrounding the pipeline Bd 88.9 mm
H/Bd 16.87
From Figure 4 of API RP1102, Factor Be = 1.350
Bd /D = 1.00
From Figure 5 of API RP1102 Factor Ee = 0.820
Unit Weight of Soil Lamda 1926 kg/m³
SHe from Equation 1 of API RP1102, (SHe=KHe.Be.Ee.Lamda .D) 0.74 MPa 744 KPa
Track Crossing Calculation-Uncased (as per API 1102)
Impact Factor Fi and Applied Design Surface Pressure, w
Fi from Figure 7 & Sect 4.7.2.2.2 1.50
Ap (Area of Tire Contact)sq.m = 0.05295796 m²
w = Pt/Ap lbs/in2 1496.09 KPa
Cyclic Circumferential Delta SHh
From Fig 14 of API RP1102, for tw/D and Er values KHh = 4.25
From Fig 15 of API RP1102, GHh = 1.45
From Table 2 of API RP1102, R = 1.10
From Table 2 of API RP1102, L = 1.00
From Equation 5 of API RP1102, Delta SHh = KHh.GHh.R.L.Fi.w 15.21 MPa 15212 KPa
Cyclic Longitudinal Delta SLh
From Fig 16 of API RP1102, for tw/D and Er values KLh = 7.50
From Fig 17 of API RP1102, GLh = 2.100
From Eqn 6 of API RP1102, Delta SLh =KLh.GLh.R.L.Fi.w 38.88 MPa 38880 KPa
Circumferential Stress Due to Internal Pressure
From Eqn 7 of API RP1102, SHi =p(D-tw)/2.tw 14.89 MPa 14889 KPa
Principle Stresses S1, S2, & S3
From Eqn 9 of API RP1102, Circumferential S1 =SHe+Delta SHh+Shi 30.85 MPa S1-S2 113.12 MPa
From Eqn 10 of API RP1102, Longitudinal S2 = -82.27 MPa S2-S3 -80.31 MPa
From Eqn 11 of API RP1102, Radial S3 = -p = -MAOP -1.96 MPa S3-S1 -32.81 MPa
From Equation 12, Page 2, Seff = 100.80 MPa
Check Allowable Effective Stress
Total effective stress in pipeline, Seff not to exceed SMYSxFa
SMYS x Fa 172.80 MPa
OK 58.33%
Check Fatigue
F =
0.72
From Table 3 of API RP 1102 SFG = 12000 psi = 82.74 MPa
Delta SLh = 38.88 MPa
SFG x F = 59.57 MPa
Longitudinal welds F = 0.72
From Table 3 of API RP 1102 SFL = 21000 psi = 144.79 MPa Delta SHh shall be less than or equal to SFL x F
Delta SHh = 15.21 MPa
SFL x F = 104.25 MPa
IF Seff is Equal or Less Than (SMYS x F) then Crossing is
Girth Welds Delta SLh < = SFG x F Girth Welds OK for Fatigue
