Wallthickness Design Report

GAMBA EXPORT LOADING LINE (SHELL GABON) Wall thickness Report Issued Date 17/12/13

PROJECT NUMBER: 13027 DOCUMENT NUMBER :

Z.202.1

REVISION CONTROL SHEET REV.NO

SECTION NO.

SUMMARY OF CHANGES

B

Table 4.1

WT changed

B

Table 4.2

WT changed

B B

Table 5.2 Table 6.2

Design parameters confirmed WT changed

Sht. No.

Rev. No.

2 of 25

B



Z.202.1

Sht. No.

Rev. No.

3 of 25

B

TABLE OF CONTENTS 1.0

INTRODUCTION .............................................................................. 4 General ......................................................................................... 4 Scope of work ............................................................................... 4

2.0

UNITS, ABBREVIATIONS & NOMENCLATURES .......................... 6 System of Units ............................................................................. 6 Abbreviations ................................................................................ 6 Nomenclature ................................................................................ 6

3.0

REFERENCE DOCUMENTS ........................................................... 9 Company Engineering Standards .................................................. 9 International Codes, Standards and Guidelines ............................. 9 Project Reference Documents ....................................................... 9

4.0

SUMMARY, RESULTS, CONCLUSIONS & RECOMMENDATIONS10 Summary & Results ..................................................................... 10 Conclusions & Recommendations ............................................... 10

5.0

DESIGN DATA .............................................................................. 12 Fluid category .............................................................................. 12 Design Pressure & Temperature ................................................. 12 Line Pipe Design Data ................................................................. 13 Corrosion Allowance ................................................................... 13 Design Factors ............................................................................ 13 Dimensional Tolerances .............................................................. 14 Water depth & Ground Elevation along the route......................... 14 Tidal and Wave data ................................................................... 15

6.0

DESIGN METHODOLOGY ............................................................ 16 General ....................................................................................... 16 Required Wall thickness .............................................................. 16 Pressure Containment ................................................................. 17 Hydrostatic Collapse due to External Pressure ............................ 17 Propagation Buckling................................................................... 18 Design Loads .............................................................................. 18 Results ........................................................................................ 19

APPENDIX A – WALL THICKNESS CALCULATIONS .................................. 20



Z.202.1

Sht. No.

Rev. No.

4 of 25

B

1.0 INTRODUCTION General Shell Gabon is operating and producing oils from numerous fields located in the western part of Gabon. Crude is treated and exported from the Gamba Terminal to tankers through a 30 inch dual offshore export line connected to a SBM via a PLEM and 2 x 16 inch floating hose strings (risers).

The total length of the existing export line is about 10.7km from the export pump in Gamba terminal to a PLEM (1.3km located onshore and 9.4km located offshore).

Figure 1-1: Project Location

Shell Gabon intends to replace the existing export pipeline. Zeetech B.V. has been awarded by Shell to perform a concept replacement study for dual pipelines and Front End Engineering Design (FEED) for the selected concept. Scope of work The wall thickness of the both offshore and onshore 22 inch Gamba Export dual pipelines with material grade API 5L X-65 are calculated based on the following failure modes have been considered in this analysis. 

Internal Pressure containment as per ASME B31.8 & ISO 13623



Propagating buckle pressure & Collapse as per API RP 1111



Sht. No.

Rev. No.

5 of 25

B

Z.202.1

The required wall thickness has been calculated by taking into account of the corrosion allowance and fabrication tolerances. The selected wall thicknesses are determined in accordance to API SPEC 5L standard wall thickness.



Z.202.1

Sht. No.

Rev. No.

6 of 25

B

2.0 UNITS, ABBREVIATIONS & NOMENCLATURES System of Units In accordance with Shell DEP 00.00.20.10. (Ref. [1]), the International System (SI) of units is adopted as the main system of units unless noted otherwise. Abbreviations API

American Petroleum Institute

ASME

American Society of Mechanical Engineers

DEP

Design Engineering Practice

FEED

Front End Engineering Design

HAT

Highest Astronomical Tide

ISO

International Standard

LAT

Lowest Astronomical Tide

MAOP

Maximum Allowable operating Pressure

MSL

Mean Sea Water Level

OD

Outside diameter

PLEM

Pipeline End Manifold

RP

Recommended practice

SBM

Single Buoy Mooring

SI

International System of Units

SMYS

Specified minimum yield strength

SPEC

Specification

TBC

To be Confirmed

WD

Water Depth

Nomenclature

Ap

Area of Pipe

D

Outside Diameter

DFoff

Design factor offshore pipeline

DFon

Design factor onshore pipeline



Z.202.1

dmax

Design water depth for collapse & buckling criteria

dmin

Design water depth for Hoop stress criteria

E

Young’s modulus

fo

Collapse factor

fp

Propagating buckling factor

Hmax

Wave Height

HWL

Highest water level

oC

Temperature in degrees Celsius

Pb

Specified minimum bursting pressure

Pc

Collapse pressure

Pe

Elastic collapse pressure

Pe_max Pe_min

External Hydrostatic pressure for Collapse & Buckling External Hydrostatic pressure for hoop stress

PiH

Maximum Operating Pressure

Pp

Critical buckling pressure

Py

Yield pressure at collapse

Ta

Axial tension in pipe

tCA

Corrosion allowance thickness

Teff

Effective tension in pipe

tf

Fabrication tolerance thickness( 8% of tprovide)

tmin

Minimum pipeline wall thickness

tminI

Minimum pipeline wall thickness based on D/t ratio

tminp

Minimum thickness including Corrosion allowance

tprovide

Final thickness of pipeline

treq

Required thickness

Ty

Yield tension in pipe

U

Minimum ultimate tensile strength

UCcom

Combined load check

WDmax

Maximum water depth

WDmin

Minimum water depth

ϑ

Poissons ratio

Sht. No.

Rev. No.

7 of 25

B



Z.202.1

ρsea

Seawater density

σa

Axial stress in pipe wall

σhd

Circumferential hoop stress due to Fluid pressure

Sht. No.

Rev. No.

8 of 25

B



Z.202.1

Sht. No.

Rev. No.

9 of 25

B

3.0 REFERENCE DOCUMENTS The following company standards, codes and standards have been utilized in the wall thickness calibration. Company Engineering Standards [1]

Shell DEP 00.00.20.10, the Use of SI Quantities and Units, 2005.

[2]

Shell DEP 31.40.00.10, Pipeline Engineering (amendments/ supplement to ISO 13623), 2010.

[3]

Shell DEP 34.00.01.30, Minimum Requirements for Structural Design and Engineering, 1998.

[4]

Shell DEP 34.28.00.31, Steel Structures, 1996.

International Codes, Standards and Guidelines [5]

ISO 13623, Petroleum and Natural Gas Industries, Pipeline Transportation Systems, 2009.

[6]

DNV OS F101, Submarine Pipeline Systems, 2010.

[7]

API RP 1111, Design, Construction, Operation and Maintenance of Offshore Hydrocarbon Pipelines– Limit state Design, 2009.

[8]

ASME B31.8, Gas Transmission and Distribution Piping Systems, 2007.

[9]

API Specification 5L, Specification for Line Pipe, 44th Edition, 2007.

Project Reference Documents The following related project documents are referenced. [10] Design Basis Doc. No:13027-ER-001 [11] Concept Evaluation - Gamba Export Loading Line, Doc.No: Z.100.1. [12] Gabon Metocean Geophysical and Environmental data collection, Doc. No: GSL-08207-GPH-003.


PROJECT NUMBER: 13027

Sht. No.

Rev. No.

DOCUMENT NUMBER :

10 of 25

B

Z.202.1

4.0 SUMMARY, RESULTS, CONCLUSIONS & RECOMMENDATIONS Summary & Results This section presents the summary of results in accordance with the calculations performed in Appendices A of this report.

The analyses have been performed considering the following pipe outer diameters, material grade and manufacturing process: 

22 inch (559 mm) Outer Diameter Pipe, API Spec 5L - X65 Material Grade (Seamless).

Analyses have been performed to confirm the required wall thicknesses for the above mentioned pipe parameters for the following assessment criterion: 

Pressure Containment(bursting)



Hydrostatic System Collapse



Buckle Propagation

Design methodology of the above-mentioned analyses has been presented in Section 6.0 of this report. Based on the calculations performed, the results have been summarized in the following table. Table 4.1: Summary of wall thickness Results Pipe Material tCA Governing tf OD(mm) Grade (mm) Load Case (mm) 559 559

X65 X65

0.0 3.0

Hydrotest Internal Pressure

8% 8%

Minimum Required WT(mm) 5.74 8.74

Selected WT(mm) 10.0 10.0

Conclusions & Recommendations The proposed wall thickness for dual pipelines is based on API 5L Specification Standard wall thickness and meets all requirements of the wall thickness checks.



Sht. No.

Rev. No.

DOCUMENT NUMBER :

11 of 25

B

Z.202.1

It is recommended that a single wall thickness fulfilling all wall thickness checks be proposed for both offshore and onshore sections. The results are tabulated in the following table. Table 4.2: Recommended wall thickness from PLEM to landfall Pipe

Material

OD(mm)

Grade

558.8

X65

WT(mm)

D/t

10.0

58.84

Note: 

No buckle arrestors are required based on the cases analyzed for buckle propagation in the calculations.



The Diameter to the wall thickness (D/t) ratio for the recommended wall thickness is in accordance with reference [2].



Sht. No.

Rev. No.

DOCUMENT NUMBER :

12 of 25

B

Z.202.1

5.0 DESIGN DATA Unless otherwise stated, all design data considered in the wall thickness calculations for the proposed offshore pipeline, presented in the following subsections, have been obtained from the Specification –Design Basis (Ref. [10]). Fluid category Fluids transported by the pipeline system are to be categorized according to their hazard potential with respect to public safety (Reference.2, Table 1).

Fluid Category A B

C

D E

Table 5.1: Categorization of Fluids Description Typical non-flammable water-based fluids. Flammable and/or toxic fluids that are liquids at ambient temperature and at atmospheric pressure conditions. Typical examples are oil and petroleum products. Methanol is an example of a flammable and toxic fluid. Non-flammable fluids that are non-toxic gases at ambient temperature and atmospheric pressure conditions. Typical examples are nitrogen, carbon dioxide, argon and air. Non-toxic, single-phase natural gas. Flammable and/or toxic fluids that are gases at ambient temperature and atmospheric pressure conditions and are conveyed as gases and/or liquids. Typical examples are hydrogen, natural gas (not otherwise covered in category D), ethane, ethylene, liquefied petroleum gas (such as propane and butane), natural gas liquids, ammonia and chlorine.

As the product to be transported through the pipelines oil, the product belongs to Category B. Design Pressure & Temperature The operating/ design pressure and temperatures have been extracted from design basis (Ref. [10]) and presented in the following table. Table 5.2: Design Pressure & Temperature Parameter Unit Value Design Pressure Design Temperature

barg o C

60 60



Sht. No.

Rev. No.

DOCUMENT NUMBER :

13 of 25

B

Z.202.1

Line Pipe Design Data The line Pipe material properties extracted from the Design Basis (Ref. [10]).and are tabulated in the following table. Table 5.3: Line Pipe material Properties Parameter Dual pipelines OD Material Grade Specified Minimum Yield Stress Young’s Modulus Density Poisson’s ratio

Unit

Value

mm

559(22”)

-

API 5L X65

Psi/MPa

65000/448

MPa

207 x 103

kg/m3

7850

ϑ

0.3

Corrosion Allowance The corrosion allowance 3.0mm shall be considered as specified by Company. Design Factors Design factors considered for the wall thickness analysis as tabulated below table. Table 5.4: Design Factors Description

Hoop

offshore

onshore

General

0.77

-

Landfall

0.67

-

-

0.77

-

0.67

stress General route

design factor

Value

Crossings

Temperature derating factor

1.0

Collapse design factor, fo

0.70

Propagating buckling design factor, f p

0.8



Sht. No.

Rev. No.

DOCUMENT NUMBER :

14 of 25

B

Z.202.1

Dimensional Tolerances Dimensional tolerances for the dual pipelines are as follows, in accordance API Spec 5L for Line Pipe (Ref. [9]): - Wall thickness: -8%, +19.5% - Out of roundness: no greater than 0.75 Water depth & Ground Elevation along the route The maximum water depth along the offshore pipeline are taken from the Design basis (Ref. [10]).

Figure.5-1: Seabed profile along the Existing Pipeline route.

Figure.5-2: Ground Elevation along the Existing Pipeline route



Sht. No.

Rev. No.

DOCUMENT NUMBER :

15 of 25

B

Z.202.1 Table 5.5: Water Depth

Description

KP (from – To)

Min.Water Depth (m)

Max.Water Depth (m)

Offshore dual Pipelines

0.000-10.700

0.0

24.0

Tidal and Wave data Tidal and wave data considered in the design are taken from the Gabon LNG Metocean Geophysical and Environmental data (Ref. [12]) and those values are tabulated as below: Table 5.6: Tidal & Wave data Description Unit Highest Astronomical Tide(HAT) Mean Sea Level ( MSL) Max.Wave Height, Hmax (Assumed)

m m m

Height 1.99 1.01 7.0



Sht. No.

Rev. No.

DOCUMENT NUMBER :

16 of 25

B

Z.202.1

6.0 DESIGN METHODOLOGY General This section presents the design methodology for the wall thickness checks for the proposed dual pipelines. Pipeline wall thickness shall be calculated in accordance with API RP 1111, ISO 13623 & ASME B31.8 (Ref. [7], Ref. [5] & Ref. [8]) to ensure that the pipelines are strong enough to withstand both the Operating and Hydrotest conditions. Wall thickness design shall also consider collapse and buckle propagation due to external Hydrostatic pressure.

Figure.6-1: Dual Pipelines concept layout. Required Wall thickness The required wall thickness shall considerer corrosion allowance and fabrication tolerance as follow: 𝑡𝑟𝑒𝑞 = 𝑡𝑚𝑖𝑛 + 𝑡𝐶𝐴 + 𝑡𝑓

(Eq.6.2.1)

The final selected wall thickness refers to API Spec. 5L and shall be not less than 𝑡𝑟𝑒𝑞 .



Sht. No.

Rev. No.

DOCUMENT NUMBER :

17 of 25

B

Z.202.1

Pressure Containment The hoop stress formula in API RP 1111 is used to determine minimum required wall thickness for the dual pipelines. The analyses are performed for the Hydrotest and Operating conditions.

In this analysis, the minimum required wall thickness is calculated based on the net internal design pressure, design factor, fabrication tolerance, corrosion allowance, pipe outside diameter and the SMYS of the line pipe.

The minimum required wall thickness for a given net internal design pressure is determined using the following formula: 𝜎ℎ𝑑 =

(𝑃𝑖𝐻 −𝑃𝑒_𝑚𝑖𝑛 )(𝐷−𝑡𝑚𝑖𝑛 ) 2𝑡𝑚𝑖𝑛 𝐷𝐹𝑜𝑓𝑓

(Eq.6.3.1)

Hydrostatic Collapse due to External Pressure The pipeline shall be designed to resist collapse due to external pressure in accordance with API RP 1111(Ref. [7]).

Hydrostatic Collapse shall be checked for operation condition considering a corroded, non-pressurized pipe for a depressurization case.

According to section 4.3.2.1 of API RP 1111, the collapse pressure of the pipe must exceed the net external pressure everywhere along the pipeline as follows:

Collapse Pressure, 𝑃𝑐 =

𝑃𝑦 𝑃𝑒

(Eq.6.4.1)

√(𝑃𝑦 2 +𝑃𝑒 2

Yield Pressure at Collapse, 𝑡𝑚𝑖𝑛 ) 𝐷

𝑃𝑦 = 2 𝑆𝑀𝑌𝑆 (

(Eq.6.4.2)



Sht. No.

Rev. No.

DOCUMENT NUMBER :

18 of 25

B

Z.202.1

Elastic Collapse Pressure, 𝑃𝑒 =

𝑡 2 𝐸 ( 𝑚𝑖𝑛 ) 𝐷

(Eq.6.4.3)

(1−𝜗2 )

Permissible Criteria Check, 𝑃𝑒_𝑚𝑎𝑥 − 𝑃𝑖𝐻 ≤ 𝑓𝑜 𝑃𝑐

(Eq.6.4.4)

Propagation Buckling The propagation buckling pressure shall be determined in accordance with API RP 1111 (Ref. [7]). Any requirements such as increased line pipe wall thickness or using buckle arrestors shall be assessed in this section.

The use of buckle arrestors regularly spaced along the pipeline length potentially subject to propagation buckling will be preferred to an increase of the pipeline wall thickness.

The propagation buckling assessment has been performed for the pipeline lying on the seabed after installation, empty and without any internal pressure.

Critical Propagation Buckling Pressure, 𝑡𝑚𝑖𝑛 2.4 ) 𝐷

𝑃𝑝 = 24 𝑆𝑀𝑌𝑆 (

(Eq.6.5.1)

Permissible Criteria Check, 𝑃𝑒_𝑚𝑎𝑥 − 𝑃𝑖𝐻 ≤ 𝑓𝑝 𝑃𝑝

(Eq.6.5.2)

Design Loads The load combinations to be considered in the wall thickness analysis for the operating & Hydrotest conditions are summarized below:



Sht. No.

Rev. No.

DOCUMENT NUMBER :

19 of 25

B

Z.202.1

Table 6.1: Design loads for Wall thickness analysis Design Load

Design Condition Pressure Containment

Collapse Buckling Propagation Buckling

Operating

Hydrotest

Operating

Operating

design

hydrotest

de-pressurized

de-pressurized

Pressure

pressure

pressure

Corrosion

100% tCA

un-corroded

100% tCA removed

un-corroded

allowance

removed

Fabrication

tf removed

tf removed

tf removed

tf removed

min.WD

min.WD

max.WD

max.WD

Internal

tolerance Water Depth

Note: 1. Water depths are in accordance with Section 5.7

Results Based on Mathcad sheets are attached in Appendix A, results of wall thickness calculation for the 22 inch dual pipelines is presented in the following Tables. The wall thickness has been selected in accordance with the wall thickness presented in API 5L specification. No buckle arrestors are required. The analyses performed herein satisfy the requirements for wall thickness checks for the pre-project engineering stage.

Table 6.2: Wall thickness Results Pipe

Material

OD(mm)

Grade

tCA

Governing

(mm) Load Case

tf

Minimum

Selected

(mm) Required

WT(mm)

WT(mm) 559

X65

0.0

hydrotest

8%

5.74

10.0

559

X65

3.0

Internal pressure

8%

8.74

10.0



Sht. No.

Rev. No.

DOCUMENT NUMBER :

20 of 25

B

Z.202.1

APPENDIX A – Wall Thickness Calculations



Sht. No.

Rev. No.

DOCUMENT NUMBER :

21 of 25

B

Z.202.1



Sht. No.

Rev. No.

DOCUMENT NUMBER :

22 of 25

B

Z.202.1



Sht. No.

Rev. No.

DOCUMENT NUMBER :

23 of 25

B

Z.202.1



Sht. No.

Rev. No.

DOCUMENT NUMBER :

24 of 25

B

Z.202.1



Sht. No.

Rev. No.

DOCUMENT NUMBER :

25 of 25

B

Z.202.1

Wallthickness Design Report

Recommend Documents