1. pipeline design-installation

SUBSEA PIPELINE DESIGN CRITERIAINSTALLATION CONDITION

CHAPTER IPREFACE

This file provides detail calculation for designing subsea pipeline that includes:

Wall thickness selection;On-bottom stability analysis; andFree-span analysis

Detail calculation here only provides for installation condition, while calculation on other condition has been provided in other file.

CHAPTER IIDESIGN BASIS

2.1 Pipeline Design Parameter.

Corrosion coating thickness tcorr 4mm:=

Outer diameter Ds 24in 609.6 mm=:=

2.2 Material Properties

Steel density s 490pcf:=

Corrosion coating density corr 80pcf:=

Concrete coat density cc 190pcf:=

Modulus elasticity E 3.002 107psi:=

Coefficient of thermal expansion 11.7 106

K1

:=

Structural damping 0.125:=

Poisson ratio 0.3:=

Pipeline material API5L_Gr_X 52:=

SMYS 290MPa API5L_Gr_X 42=if

317MPa API5L_Gr_X 46=if






:= SMYS 3.59 108

Pa=

SMTS 414MPa API5L_Gr_X 42=if







:= SMTS 4.55 108

Pa=

Manufacturing process Seamless = 1

UO; TRB; ERW = 2

UOE = 0.85

PF 1:=

2.4 Environmental Parameter

Pipeline condition Installation = 1

Hydrotest = 2

Operation = 3

PC 1:=

Highest astronomical tide HAT 0.53m:=

Lowest astronomical tide LAT 0.61m:=

Water depth dmax 22.708m HAT+:= dmax 23.238 m=

dmin 14.935m HAT+:= dmin 15.465 m=

Kinematic viscosity of seawater v 1.076 105

ft2

sec1

:=

Seawater density sw 64pcf:=

Gravity g 9.807 m s2

=

Current at 90% water depth Ur 0.45m s1

PC 1= PC 2=if

0.48m s1

PC 3=if

:= Ur 0.45m

s=

Significant wave height Hs 1.8m PC 1= PC 2=if

3.6m PC 3=if

:= Hs 1.8 m=

Significant Wave period Ts 6.3s PC 1= PC 2=if

8.3s PC 3=if

:= Ts 6.3 s=

2.5 Pipeline Operational Data

Content density cont 0kg m3

PC 1=if

1025kg m3

PC 2=if

57.522pcf PC 3=if

:=

Design pressure Po 0psi PC 1=if

1350psi PC 3=if

1.5 1350 psi PC 2=if

:=

Design temperature Td 140F:=

Seabed temperature Tsw 23 C:=

Corrosion allowance Ca 2.54mm:=

External pressure Pe.max sw g dmax:= Pe.max 2.336 105

Pa=

Pe.min sw g dmin:= Pe.min 1.555 105

Pa=

Axial pressure Fa 0N:=

Bending stress M 72% SMYS:= M 258.48 MPa=

2.6 Soil Parameter

Soil type 1 = sand

2 = clay

soil 2:=

Medium density of sand sand 1860kg m3

:=

Medium density of clay clay 326.309kg m3

:=

Medium density of soil soil sand soil 1=if

clay soil 2=if

:= soil 326.309kg

m3

=

Undrained shear stress Su 2kPa:=

2.8 Design Factor

Internal pressure factor design

ASME B31.8 F 0.72:=

API RP 1111 fd 0.72:=

Weld joint factor

ASME B31.8 Ee 1:=

API RP 1111 fe 1:=

Temperature derating factor

ASME B31.8 T 1:=

API RP 1111 ft 1:=

Collapse factor

ASME B31.8

f0 0.7:=API RP 1111

Propagation buckling design factor

ASME B31.8

fp 0.8:=API RP 1111

Local buckling factor

DNV 1981

xp 0.72:=Longitudinal stress usage factor

Hoop stress usage factor yp 0.92:=

Material resistance factor m 1.15:=

Incidental factor inc 1.05:=

CHAPTER IIIWALL THICKNESS SELECTION

3.1 Internal Pressure Contaiment Criteria

On the installation conditions, the pipe was empty,

so that the internal pressure contaiment criteria for installation conditions will not be calculated.

Internal pressure Pi Po:= Pi 0 Pa=

3.2 External Pressure Collapse

Initial steel wall thicknesstint.epc 6mm:=

External pressurePe.max 2.336 10

5 Pa=

Elastic stress Pel 2 E

tint.epc

Ds

3

1 2

:= Pel 4.337 10

5 Pa=

Yield stress Py 2 SMYStint.epc

Ds

:= Py 7.067 106

Pa=

Collapse stress Pc

Pel Py

Pel2

Py2

+

:= Pc 4.329 105

Pa=

External pressure collapse

criteria

ExternalPressureCollapse_API_criteria "accepted" Pe.max Pi f0 Pcif

"not accepted" otherwise

:=

ExternalPressureCollapse_API_criteria "accepted"=

Safety factor SFipc

f0 Pc

Pe.max Pi:= SFipc 1.297=

3.3 Local Buckling Criteria

Initial steel wall thickness tint.lb 7mm:=

Cross sectional area A Ds tint.lb( ) tint.lb:= A 0.013 m2=

Longitudinal stress (axial) x.N

Fa

A:= x.N 0=

Longitudinal stress (bending) x.M 0.72 SMYS:= x.M 2.585 108

Pa=

Longitudinal stress x x.N x.M+:= x 2.585 108

Pa=

Critical longitudinal stress (axial) xcr.N SMYSDs

tint.lb

20if

SMYS 1 0.001

Ds

tint.lb

20

20

Ds

tint.lb

< 100if

:=

ycr 2.793 107

Pa=

value lb 1300

Ds

tint.lb

y

ycr

+:= lb 2.255=

LocalBuckling_Criteria "accepted"

x

xcr

lby

ycr

+ 1if

"not accepted"

x

xcr

lby

ycr

+ 1>if

:=Local buckling criteria

LocalBuckling_Criteria "accepted"=

Safety factor SFlb

1

x

xcr

lby

ycr

+

:= SFlb 1.124=

3.4 Propagation Buckling Criteria

Initial steel wall thickness tint.pb 9mm:=

External pressure Pe.max 2.336 105

Pa=

Buckle propagation pressure Ppb 24 SMYStint.pb

Ds

2.4

:= Ppb 3.478 105

Pa=

Propagation buckling criteria PropagationBuckling_API_Criteria "not accepted" Pe.max Pi fp Ppbif

"accepted" otherwise

:=

PropagationBuckling_API_Criteria "accepted"=

Safety factor SFpb

fp Ppb

Pe.max Pi:= SFpb 1.191=

3.5 Selected Wall Thickness

This following t.int.ins is selected wall thickness from installation condition.

The final selected wall thickness is obtain from comparing this initial wall thickness eith other initial wall thicness

from hydrotest and operation condition.

tint.ins max tint.epc tint.lb, tint.pb, ( ):=

tint.ins 9 mm=

tint.hyd 17mm:= (Obtained from hydrotest condition calculation)

tint.op 18.54mm:= (Obtained from operation condition calculation)

tcalc max tint.ins tint.hyd, tint.op, ( ):= tcalc 0.73 in=Selected wall thickness from calculation

Selected wall thickness Pipe OD 6.625" WT 0.75" ts 0.75in:=

CHAPTER IVON BOTTOM STABILITY ANALYSIS

4.1 Vertical Stability

4.1.1 Pipe Weight Calculation

Initial concrete coating thickness tint.cc 25mm:=

Internal diameter ID Ds 2 ts Ca( ) := ID 576.58 mm=Corrosion coating diameter Dcorr Ds 2 tcorr+:= Dcorr 617.6 mm=

Total outer diameter Dtot Ds 2 tcorr+ 2 tint.cc+:= Dtot 667.6 mm=

Steel pipe mass / length mst

4Ds

2ID

2

s:= mst 241.454

kg

m=

Corrosion coating mass / length mcorr

4Dcorr

2Ds

2

corr:= mcorr 9.881

kg

m=

Concrete coat mass / length mcc

4Dtot

2Dcorr

2

cc:= mcc 153.605

kg

m=

Content mass / length mcont

4ID

2 cont:= mcont 0

kg

m=

Added mass;

Dicplaced water; Buoyancy / length

B

4Dtot

2sw:= B 358.859

kg

m=

Total pipe mass / length mtot mst mcorr+ mcc+ mcont+ B:=

mtot 46.081kg

m=

Total pipe weight / length Wtot mtot g:= Wtot 451.905N

m=

4.1.2 Vertical Stability Calculation

Vertical stability VS

mtot B+( )B

:= VS 1.128=

Vertical_Stability "accepted" VS 1.1>if

"not accepted; enlarge concrete coating thickness" VS 1.1if

:=

Vertical_Stability "accepted"=

4.2 Lateral Stability

4.2.1 Hydrodynamics Parameter Calculation

4.2.1.1 Wave-Induced Particle Velocity

Spectral peak period Tp 1.05 Ts:= Tp 6.615 s=

Periode

referensi

Tn

dmin

g:= Tn 1.256 s=

Peakedness

parameter

Tp

Hs

:= 4.931s

m0.5

=

5 3.6sec

m

if

1 5sec

m

if

3.3 otherwise

:= 3.3=

Figure 4.1 Significant water velocity, Us* (DNV RP E305)

Water particle velocity

(Wave induced)

Tn

Tp

0.19=

Us

0.22 Hs

Tn

:= Us 0.315m

s=

4.2.1.2 Zero-Up Crossing Period

Figure 4.2 Zero-up crossing period, Tu (DNV RP E305)

Zero-up crossing period Tu 1 Tp:= Tu 6.615 s=

4.2.1.3 Average Velocity on Pipeline

Velocity on 90% depth Ur 0.45m

s=

The amount of current passing through the pipe is affected by the type of seabed soil in which the pipe is laid.

In terms of the soil is clay soil, the soil roughness is negligible, so in this case UD = Ur

UD Ur:= UD 0.45m

s=

4.2.1.4 Hydrodynamics coefficient

Reynold's number Re

UD Us+( )v

Dtot:= Re 5.111 105

=

Wave - current velocity ratio M

UD

Us

:= M 1.427=

Drag coefficient CD 1.2 Re 5 104

4.2.2 Seabed Soil Factor

Figure 4.4 Recommended friction factors for clay (DNV RP E305)

ratio

Dtot Su

mtot g:= ratio 2.955=

Soil friction

factor

2.3:=

4.2.3 Hydrodynamics Force

Wave particle acceleration As 2 Us

Tu

:= As 0.3m

s2

=

Lift force fL. ( )1

2

sw

g Dtot CL Us cos ( ) UD+( )2:=

Drag force fD. ( )1

2

sw

g Dtot CD Us cos ( ) UD+( )2:=

Inertia force fI. ( ) Dtot

2

4

sw

g CM As sin ( ):=

4.2.4 Lateral Stability Calculation

4.2.4.1 Calibration Factor

Figure 4.3 Calibration factor, Fw, as function of K and M (DNV RP E305)

K

Us Tu

Dtot

:= K 3.125=Keulegan-Carpenter number

Calibration factor Fw 1:=

4.2.4.2 Lateral Stability Check

i 0 180..:=phase angle range

i i deg:=

Required submerged weight ms. ( )fD. ( ) fI. ( )+( ) fL. ( )+

Fw:=

mreq. ( ) max ms. ( )( ):=

mreq. ( ) 22kg

m=

SFw

mtot

mreq. ( ):= SFw 2.095=

LS "accepted" SFw 1if

"not accepted, enlarge concrete coating thickness" SFw 1

CHAPTER VFREE-SPAN ANALYSIS

5.1 Static Analysis

Static span length Lfr.st 130m:=

Total pipe weight / length Wtot 451.905N

m=

Drag force FD max fD. ( )( ) g:= FD 140.312N

m=

Inertia force FI max fI. ( )( ) g:= FI 161.23N

m=

Support type 1 = pinned - pinned

2 = fixed - pinned

3 = fixed - fixed

support 1:=

End condition constant Cfr.st 8 support 1=if

10 support 2=if

12 support 3=if

:= Cfr.st 8=

Distributed pipe weight Wd Wtot2

FD2

FI2

+

2

+:= Wd 499.9N

m=

Area moment of inertia I

64Ds

4ID

4

:= I 1.354 10

3 m

4=

Section modulus ZI

Ds

2

:= Z 4.441 103

m3

=

Longitudinal stress l

Wd Lfr.st2

Cfr.st Z:= l 2.378 10

8 Pa=

Hoop stress y 1.017 107

Pa=

Equivalent stress e l2

y2

+:= e 2.38 108

Pa=

Allowable stress allow 0.72 SMYS( ) PC 1=if

0.9 SMYS( ) PC 2= PC 3=if

:=

allow 2.585 108

Pa=

Static span criteria static_span_criteria "Static span length accepted" e allow

5.2 Dynamic Analysis

5.2.1 Critical Span Length

5.2.1.1 Stability Parameter

Effective mass meff mst mcorr+ mcc+ mcont+ B+:=

meff 763.799kg

m=

Stability parameter Ks

2 meff

sw Dtot2

:= Ks 0.418=

5.2.1.2 Reduced Velocity

Figure 5.1 Reduced velocity for cross-flow oscillations based on the reynolds number.

Figure 5.2 Reduced velocity for inline oscillations based on the stability parameter

Reynold's number Re 5.111 105

=

Reduced velocity for cross-flow

oscillation

Vr.cf 5.9:=

Reduced velocity for inline oscillation Vr.in 1.4:=

5.2.1.3 Critical Span Length

End condition constant Cfr.dy 2

support 1=if

15.5 support 2=if

22 support 3=if

:= Cfr.dy 9.87=

Critical span length for cross-flow

motion

Lfr.dy.cf

Cfr.dy Vr.cf Dtot

2 Us Ur+( )E I

meff

:= Lfr.dy.cf 69.973 m=

Critical span length for inline motion Lfr.dy.in

Cfr.dy Vr.in Dtot

2 Us Ur+( )E I

meff

:= Lfr.dy.in 34.085 m=

Critical span selected for dynamic

analysis criteria

Lfr.dy min Lfr.dy.cf Lfr.dy.in, ( ):= Lfr.dy 34.085 m=

5.2.2 Dynamic Stress

5.2.2.1 Vortex Shedding Frequency

Figure 5.3 Strouhal's number for circular cylinder as function of Reynold's number

Reynold's number Re 5.111 105

=

Strouhal's number St 0.2:=

Vortex shedding frequency fv

St Us Ur+( )Dtot

:= fv 0.2291

s=

5.2.2.2 Pipeline Natural Frequency

Pipeline natural frequency fn

Cfr.dy

2

E I

meff Lfr.dy4

0.5

:= fn 0.8191

s=

Pipe frequency criteria pipe_frequency_check "pipeline critical span accepted" fv 0.7fnif

"redesign pipe" otherwise

:=

pipe_frequency_check "pipeline critical span accepted"=

DEFINITION

pcflb

ft3

:=

year 31536000sec:=

C K:=

1. pipeline design-installation

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