api 1117 (1996) movementin-servpipelines

A P I R P U L L L 7 96 W 0732290 0 5 5 8 3 5 0 6 6 0 m

Movement of ln-Service Pipelines

API RECOMMENDED PRACTICE 1 11 7 SECOND EDITION, AUGUST 1996

day 5 Environmental Partnership

American Petroleum Institute

COPYRIGHT American Petroleum InstituteLicensed by Information Handling ServicesCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services

API RP*LLL7 96 m 0732290 055835L 5 T 7

One of the most significant long-term trends affecting the future vitality of the petroleum industry is the public's concerns about the environment. Recognizing this trend, API member companies have developed a positive, forward looking strategy called STEP: Strategies for Today's Environmental Partnership. This program aims to address public concerns by improving industry's environmental, health and safety performance; docu- menting performance improvements; and communicating them to the public. The founda- tion of STEP is the API Environmental Mission and Guiding Environmental Principles. API standards, by promoting the use of sound engineering and operational practices, are an important means of implementing API's STEP program.

API ENVIRONMENTAL MISSION AND GUIDING ENVIRONMENTAL PRINCIPLES

The members of the American Petroleum Institute are dedicated to continuous efforts to improve the compatibility of our operations with the environment while economically developing energy resources and supplying high quality products and services to consum- ers. The members recognize the importance of efficiently meeting society's needs and our responsibility to work with the public, the government, and others to develop and to use natural resources in an environmentally sound manner while protecting the health and safety of our employees and the public. To meet these responsibilities, API members pledge to manage our businesses according to these principles:

o To recognize and to respond to community concerns about our raw materials, products and operations.

o To operate our plants and facilities, and to handle our raw materials and products in a manner that protects the environment, and the safety and health of our employees and the public.

o To make safety, health and environmental considerations a priority in our planning, and our development of new products and processes.

o To advise promptly appropriate officials, employees, customers and the public of information on significant industry-related safety, health and environmental hazards, and to recommend protective measures.

o To counsel customers, transporters and others in the safe use, transportation and disposal of our raw materials, products and waste materials.

o To economically develop and produce natural resources and to conserve those resources by using energy efficiently.

o To extend knowledge by conducting or supporting research on the safety, health and environmental effects of our raw materials, products, processes and waste materials.

o To commit to reduce overall emissions and waste generation.

o To work with others to resolve problems created by handling and disposal of hazardous substances from our operations.

o To participate with government and others in creating responsible laws, regulations and standards to safeguard the community, workplace and environment.

o To promote these principles and practices by sharing experiences and offering assistance to others who produce, handle, use, transport or dispose of similar raw materials, petroleum products and wastes.


A P I RP*LLL7 96 m 0732290 0558352 433

Movement of In-Service Pipelines

Manufacturing, Distribution and Marketing Department API RECOMMENDED PRACTICE SECOND EDITION, AUGUST 1996

American Petroleum Institute


A P I RP*LLL7 9 6 U732290 0558353 37T m

SPECIAL NOTES

API publications necessarily address problems of a general nature. With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed.

API is not undertaking to meet the duties of employers, manufacturers, or suppliers to warn and properly train and equip their employees, and others exposed, concerning health and safety risks and precautions, nor undertaking their obligations under local, state, or federal laws.

Information concerning safety and health risks and proper precautions with respect to particular materials and conditions should be obtained from the employer, the manufacturer or supplier of that material, or the material safety data sheet.

Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither should anything contained in the publication be construed as insuring anyone against liability for infringement of letters patent.

Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least every five years. Sometimes a one-time extension of up to two years will be added to this review cycle. This publication will no longer be in effect five years after its publication date as an operative API standard or, where an extension has been granted, upon republica- tion. Status of the publication can be ascertained from the API Authoring Department [telephone (202) 682-8000]. A catalog of API publications and materials is published annually and updated quarterly by N I , 1220 L Street, N.W., Washington, D.C. 20005.

This document was produced under API standardization procedures that ensure appropriate notification and participation in the developmental process and is designated as an API standard. Questions concerning the interpretation of the content of this standard or comments and questions concerning the procedures under which this standard was developed should be directed in writing to the director of the Authoring Department (shown on the title page of this document), American Petroleum Institute, 1220 L Street, N.W., Wash- ington, D.C. 20005. Requests for permission to reproduce or translate all or any part of the material published herein should also be addressed to the director.

API publications may be used by anyone desiring to do so. Every effort has been made by the Institute to assure the accuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any federal, state, or municipal regulation with which this publication may conflict.

API standards are published to facilitate the broad availability of proven, sound engineering and operating practices. These standards are not intended to obviate the need for applying sound engineering judgment regarding when and where these standards should be utilized. The formulation and publication of API standards is not intended in any way to inhibit anyone h m using any other practices.

Any manufacturer marking equipment or materials in conformance with the marking requirements of an API standard is solely responsible for complying with all the applicable requirements of that standard. API does not represent, warrant, or guarantee that such products do in fact conform to the applicable A P I standard.

All rights reserved. No part of this work may be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or other-

wise, without prior written permission from the publishel: Contact the Publisher; API Publishing Services, 1220 L Street, N. W , Washington, DC 20005.

Copyright 8 1996 American Petroleum Institute


API RP*llL7 96 m 0732290 055835Y 206 m

FOREWORD

The few pipeline failures that have followed movement operations demonstrate the need for an industry recommended practice on movement of pipelines. A movement operation increases the longitudinal stress in the segment of the pipeline being moved. In most cases this additional stress has caused no significant problems. In 1978, however, a propane pipeline failed after being moved while in service. Although the movement may not have contributed to the failure, the incident demonstrated the need for uniform guidelines to ensure that the movement of an in-service pipeline is done with reasonable safety. Conse- quently, the American Society of Mechanical Engineers, the American Petroleum Insti- tute, and the Office of Pipeline Safety Regulation of the U.S. Department of Transporta- tion jointly sponsored a study to establish guidelines for safely moving pipelines without taking them out of service. After the release of the “Guidelines for Lowering Pipelines While in Service” by authors at the Battelle Columbus Laboratories, the American Petro- leum Institute solicited qualified engineers responsible for the design, construction, and operation of petroleum pipelines to review the Battelle work and other available work and to prepare an industry recommended practice on the safe lowering andfor raising of in-service pipelines.

The purpose of this recommended practice is to address the criteria, methods, values, and recommendations that should be considered in the design and execution of practical and safe pipeline-movement operations. However, it is impossible to foresee all possible pipeline-movement situations or circumstances. This recommended practice is to be used as a guide for moving pipelines while they remain in service. It is not a rigid standard.

This recommended practice is not intended to be an endorsement of moving pipelines as a method for addressing the safety of an existing pipeline at a new road crossing, rail- road crossing, foreign utility crossing, or any other crossing. It is merely intended to pro- vide guidance to pipeline operators and contractors who choose the alternative of moving.

This recommended practice has been revised to reflect that the methodology used in moving pipelines can be used for other pipeline movement operations.

API publications may be used by anyone desiring to do so. Every effort has been made by the Institute to assure the accuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any federal, state, or municipal regulation with which this publication may conflict.

Suggested revisions are invited and should be submitted to the director of the Manufac- turing, Distribution and Marketing Department, American Petroleum Institute, 1220 L Street, N.W., Washington, D.C. 20005.

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CONTENTS

Page

SECTION 1"GENERAL ............................................ .i 1.1 Sc0 pe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.3 Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.4 Safety Considerations ................................................. 1 1.5 Conformance to MI'S Environmental Mission

and Guiding Principles ................................................ 1 1.6 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.7.1 Referenced Standards, Codes, and Manuals .............................. 2 1.7.2 Other References ................................................... 2 1.8 Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

SECTION 2-DESIGN ................................................ 3 2.1 Design Considerations ................................................ 3 2 . 1 . 1 General ............................................................ 3 2.1.2 Total Longitudinal Stress ............................................. 3 2.1.3 Longitudinal Tensile Stress due to Internal Pressure ....................... 3 2.1.4 Longitudinal Tensile Stress due to Temperature Change .................... 3 2.1.5 Longitudinal Flexural Stress due to Existing Elastic Curvature . . . . . . . . . . . . . . . 3 2.1.6 Existing Longitudinal Stress .......................................... 3 2.1.7 Longitudinal Stress due to Bending ..................................... 4 2.1.8 Longitudinal Stress due to Elongation ................................... 4 2.1.9 Dynamic Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2 . 1 . 10 Previous Movements ............................................... 4

2.2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2.2 Total Longitudinal Stress Limit ........................................ 4 2.2.3 Available Longitudinal Bending Stress .................................. 4

2.2.5 Trench (or Displacement) Profile ...................................... 4 2.3 SupportSpacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.4 A Sample Problem and Its Solution ...................................... 6

2.2 Design Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.2.4 Trench Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

SECTION 3-PROCEDURE CONSIDERATIONS ..................... 8

3.2 Safety Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.2.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2.2 Internal Operating Pressure ............................................ 8

3.2.4 Other Underground Facilities ......................................... 8

3.2.6 Attached Appurtenances ............................................. 8

3.3 Terrain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.4 Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.5 Other Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.6 Trenching Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.7 supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.2.3 Pipeline Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.2.5 Girth Weld Inspection ............................................... 8

3.2.7 Excavation Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

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3.7.1 Control of Unitended Movement ...................................... 9 3.7.2 Point Loading ..................................................... 9 3.7.3 Soil Bearing Capacities .............................................. 9 3.7.4 Pipeline-Supporting Methods ......................................... 9 3.7.5 Pipeline-Movement Methods ......................................... 9

SECTION &INSPECTION ......................................... 13 4.1 General ........................................................... 13 4.2 Girth Welds ....................................................... 13 4.3 Inspection for External Corrosion ....................................... 13 4.4 Inspection for Mechanical Damage ..................................... 13 4.5 Externalcoating .................................................... 13 4.5.1 Inspection ....................................................... 13 4.5.2 Repair Method .................................................... 13

SECTION 5-CLEANUP ............................................ 13 5.1 General ........................................................... 13 5.2 Backfilling ........................................................ 13 5.3 Surface Restoration ................................................. 13

SECTION &DOCUMENTATION AND RECORDS . . . . . . . . . . . . . . . . . 14 6.1 General ........................................................... 14 6.2 Alignment Sheets ................................................... 14 6.3 Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

APPENDIX A-NOMENCLATURE ....................................... 15 APPENDIX B-DERIVATION OF THE EQUATION

FOR LONGITUDINAL STRESS DUE TO BENDING AND OF THE EQUATION FOR TRENCH LENGTH ............ 17

APPENDIX C-DERIVATION OF TRENCH PROFILE EQUATION . . . . . . . . . . . . . 19 APPENDIX D-DERIVATION OF EQUATION

FOR LONGITUDINAL STRESS DUE TO ELONGATION . . . . . . . . 21

FOR MAXIMUM FREE SPAN BETWEEN PIPE SUPPORTS ..... 23 APPENDIX E-DERIVATION OF EQUATION

APPENDIX F- EQUATIONS ............................................ 25

Figures I-Application of the Minimum Trench Length (L) ........................... 5 2-Preferred Trench Profile of the General Lowering .......................... 5 3-Preferred Trench Profile of a Sample Lowering ............................ 7 &Pig Pen Method of Pipeline Support ..................................... 9 5-Air Bag Method of Pipeline Support ................................... 10 &Earth Pillar Method of Pipeline Support ................................. 10 7-Sling Method of Pipeline Support ...................................... 11 8-Pipeline-Movement Method Using Two Side Booms ...................... 11 9-Pipeline-Movement Method Using One Side Boom and One Backhoe ......... 12

10-Pipeline-Movement Method in which Pipe is Slid into Ditch . . . . . . . . . . . . . . . . 12 D-1-Arc Length (A) of a Circular Curve .................................... 21 D-2-The Four Circular-Curve Segments in the Preferred Trench Profile

of the General Lowering ............................................. 21

Table I-Some Verticle Deflections (Ax) in the Preferred Trench Profile

of a Sample Lowering ....................................... ......... 7

vi


Movement of In-Service Pipelines

SECTION 1-GENERAL

1.1 Scope This recommended practice covers the design, execution,

inspection, and safety of a pipeline-lowering or other movement operation conducted while the pipeline is in service. (The terms lowering and movement can be used interchangeably.) This recommended practice presents general guidelines for conducting a pipeline-movement operation without taking the pipeline out of service. It also presents equations for estimating the induced stresses. To promote the safety of the movement operation, it describes stress limits and procedures. Additionally, it outlines recommendations to protect the pipeline against damage. The practicality and safety of trench types, support systems, and lowering or other methods are considered. Inspection procedures and limitations are presented.

The calculations in this recommended practice are based on methods developed from elastic free deflection theory to determine induced stresses and deflection profiles. Other calculation methods such as finite element analysis may be used instead. See the publications listed in 1.7.

Methods for handling field bends, valves, fittings, or other attachments to a pipeline and methods for moving a pipeline with attached appurtenances are beyond the scope of this recommended practice.

1.2 Applications This recommended practice applies to onshore steel pipe-

lines. Moving in-service pipelines can be a safe, cost-effective

means of relocating a pipeline without loss of service. The recommendations presented in this document should be applicable to any lowering or other movement of existing pipelines that is undertaken either to accommodate new roads, railroads, foreign utilities, ditches, or creeks or to accommodate any condition for which moving the pipeline is the chosen alternative.

1.3 Exceptions The recommendations in this document should not be

applied retroactively to pipelines that were moved prior to the effective date of this recommended practice. Also, these recommendations should not be applied to movement due to mining or natural subsidence. The movement of pipelines with attached appurtenances is beyond the scope of this recommended practice.

The following pipelines were not considered in developing the methods, criteria, values, and recommendations presented in this document: a. Offshore pipelines. b. Pipelines with valves, flanges, fittings, concrete coatings, or attached appurtenances in the section to be lowered. c. Pipelines joined by oxyacetylene welds, mechanical joints, or girth welds of known poor quality (unless welds are reinforced by full encirclement sleeves or other acceptable means).

1.4 Safety Considerations CAUTION: The recommendations in this document pro-

mote safety under conditions normally encountered in the pipeline industry. Requirements for abnormal or unusual conditions are not specified, and some details of engineering and construction are not provided. All movements of in-service pipelines should comply with applicable safety standards.

1.5 Conformance to APl’s Environmental Mission and Guiding Principles

This recommended practice has been reviewed to determine if it conforms to M I ’ S Environmental Mission and Guiding Principles.’ It was determined that because this recommended practice directly addresses safety and environmental issues, it does conform to API’s Environmental Mission and Guiding Principles. The following guiding principles were found to be especially relevant to this recommended practice:

To recognize and to respond to community concerns about our raw materials, products and operations. To operate our plants and facilities and handle our raw materials and products in a manner that protects the environment, and the safety and health of our employees and the public. To make safety, health and environmental considerations a priority in our planning, and our development of new products and processes. To counsel customers, transporters and others in the safe use, transportation, and disposal of our raw materials, products and waste materials.

‘ Charter and Bylaws of the American Petroleum Imtitute, American Petroleum Institute, Washington, D.C., ~ p r i i 3, 1991.

1


2

To participate with government and others in creating responsible laws, regulations and standards to safeguard the community, workplace and environment. To promote these principles and practices by sharing experiences and offering assistance to others who produce, handle, use, transport or dispose of similar raw materials, petroleum products and wastes.

1.6 Definitions 1.6.1 Some of the terms used in this recommended practice are defined in 1.6.2 through 1.6.9.

1.6.2 A pipe bend is a permanent inelastic deflection of a pipe.

1.6.3 Existing longitudinal stress is the longitudinal stress in the pipe before its movement, excluding residual stress in girth welds and in bends.

1.6.4 The free deflection method calculates bending stress in the pipe using elastic structural design methods.

1.6.5 An in-service pipeline is a pipeline containing a hazardous fluid and is operating at normal flow condition.

1.6.6 Lowering and moving are used interchangeably to describe the controlled displacement of a pipeline segment without cutting the pipeline.

1.6.7 Minimum trench length is the ,minimum longitudinal distance required to move a portion of a pipeline a cer- tain distance without exceeding its longitudinal stress limits.

1.6.8 Pipeline slack is the condition of a pipeline with neither longitudinal stress nor compressive longitudinal stress.

1.6.9 Total longitudinal stress is the longitudinal stress in a portion of a pipeline during or after its movement.

1.7 References 1.7.1 REFERENCED STANDARDS, CODES, AND

MANUALS

AIX2

A P I M01 6 Manual of Steel Construction

Std 1104 Welding of Pipelines and Related Facili-

RP 1107 Pipeline Maintenance Welding Practices ties

* American Institute of Steel Construction, h . . One East Wacker Drive, Suite 3100, Chicago, lllinois 60601-2001.

ASME3 B3 1.4 Liquid Transportation Systems for Hydro-

carbons, Liquid Petroleum Gas, Anhy- drous Ammonia, and Alcohols

B31.8 Gas Transmission and Distribution Pip- ing Systems

OSHA4 29 Code of Federal Regulations Part 1926

(Subpart P) RSPAs

49 Code of Federal Regulations Part 192 49 Code of Federal Regulations Part 195

1.7.2 OTHER REFERENCES

J. W. Cardinal and P. A. Cox, “Guidelines Studied for Lowering Pipe in Service,” Oil & Gas Journal, November 5, 1984, PP. 93-98.

Marshall D. Cromwell, “How to Lower an Existing Pipe Line That Is Still in Service,” Pipe Line Industry, July 1986, pp. 47-49.

J. F. Kiefner, and T. A. Wall, N.D. Ghadiali, K. Prabhat, and E.C. Rodabaugh, “Guidelines for Lowering Pipelines While in Service,” Report No. DCYl”RSPA-DMT-30/84/8, API, the American Society of Mechanical Engineers, and the U.S. Department of Transportation, February 25, 1985 (a Battelle Columbus Laboratories report sponsored by the American Society of Mechanical Engineers, jointly funded by the U.S. Department of Transportation, the American Society of Mechanical Engineers, and N I ) available from the National Technical Information Service, Springfield, Virginia 22161.

J. F. Kiefner and T. A. Wall, “Joint Research Project Develops Guidelines for Lowering In-Service Pipelines,” Pipe- line & Gus Journal. November 1985, pp. 45-47; February 1986, pp. 34-35; and March 1986, pp. 30,3344.36, and 38.

M. J. Rosenfeld, “Pipeline In-Service Relocation Engi- neering Manual,” December 31, 1994, AGA Catalog No. L51717.

P. B. Summers and D. J. Nyman, “Pipeline Stress Analy- sis for Lowering Operations,” 1985 Pressure Vessels and Piping Conference and Exhibition, New Orleans, Lousiana, June 23-27, 1985.

American Society of Mechanical Engineem, 345 East 47th Strett, New

Occupational Safety and Health Administration. U.S. Departmtnt of York, New York 10017

Labor. The Code of Federd Regulatiom is available h m the U.S. Govern- ment printing Office, Washington, D.C. 20402.

Research and Special Programs Administration, U.S. Dcpartmcnt of Transportation. The Code of Federal Regulatwm is available h m the U.S. Government printing Office, Washington, D.C. 20402.


MOVEMENT OF IN-SERVICE PIPELINES 3

P. B. Summers and D. J. Nyman, "Pipesag-A Micro- 1.8 Conventions computer Program to Assess the Effects of Large Ground- In this document, each equation term is defined in Appen- Deformations on Buried Pipelines," 1985 Pressure Vessels dix A and beneath the first equation that it. ~ l ~ ~ , nega- and Piping Conference and Exhibition, New Orleans, Loui- tive values for stress indicate compressive stress and siana, June 23-27, 1985. positive values indicate tensile stress.

In-Service Lines," Pipeline Digest, May 1987, pp. 9-10. R. N. Tennille, "Minimizing Stresses: A Goal In Lowering

SECTION 2"DESIGN

2.1 Design Considerations 2.1.1 GENERAL

2.1.4 LONGITUDINAL TENSILE STRESS DUE TO TEMPERATURE CHANGE

This subsection describes design methods for estimating The longitudinal tensile stress in the pipe due to a change the longitudinal stress in a pipe due to the pressure, temper- in its temperature may be estimated with the ature, bending, elongation, and initial conditions that would equation: be involved in any particular pipeline-movement operation S, = Ea (T, - T,) (2) covered by this recommended practice. It also considers mechanical influences and various loadings. Where:

2.1.2 TOTAL LONGITUDINAL STRESS The total longitudinal stress in the pipe can be estimated

with the following equation:

S, = S, + S, + S, Where:

S, = total longitudinal stress in the pipe, in psi. S, = existing longitudinal stress in the pipe, in psi. S, = longitudinal stress in the pipe due to bending

caused by the movement operation, in psi. S, = longitudinal stress in the pipe due to its elonga-

tion caused by the movement operation, in psi.

2.1.3 LONGITUDINALTENSILE STRESS DUE TO INTERNAL PRESSURE

The longitudinal tensile stress in the pipe due to internal pressure may be estimated with the following equation:

PDP s p = -

2t

Where:

S, = longitudinal tensile stress in the pipe due to inter-

P = maximum internal operating pressure of the pipe,

D = outside diameter of the pipe, in inches. p = Poisson's Ratio for steel, 0.3. t = nominal wall thickness of the pipe, in inches.

nal pressure, in psi.

in psi.

S, = longitudinal tensile stress in the pipe due to a change in its temperature, in psi.

E = modulus of elasticity of steel, 29 x10 psi. a = linear coefficient of thermal expansion of steel,

T, = temperature of the pipe at the time of the installa-

T, = operating temperature of the pipe at the time of

If the pipe's temperature at installation time is not known,

6.5 x10 inches per inch per "F.

tion, in "F.

the movement, in "F.

it should be reasonably estimated.

2.1.5 LONGITUDINAL FLEXURAL STRESS DUE TO EXISTING ELASTIC CURVATURE

When a pipeline is laid to conform elastically to a given trench profile, the pipeline will experience induced flexural stress in amounts proportional to its curvature. In hilly terrain, where slopes are unstable, or where soils are subject to frost heave or liquefaction, the pipeline is likely to experience stress of unpredictable and varying magnitude. This stress ( S c , defined in 2.1.6) can range from near-yield- strength levels in tension to near-buckling levels in com- pression. This existing stress should be considered prior to a movement operation.

2.1.6 EXISTING LONGITUDINAL STRESS The existing longitudinal stress in a pipeline will nor-

mally be in the range of -10,OOO psi to +20,000 psi. In flat or gently rolling terrain where soils are not subject to frost heave or liquefaction, the pipeline will experience only the longitudinal tensile stress due to internal pressure and temperature as discussed in 2.1.3 and 2.1.4 and the flexural stress


4

to the extent that it is elastically curved as discussed in 2.1 S .

mated with the following equation: The existing longitudinal stress in the pipe may be esti-

s E = s p + S , + s , (3)

Where:

Sc = longitudinal stress in the pipe due to existing elastic curvature, in psi.

2.1.7 LONGITUDINAL STRESS DUE TO BENDING The longitudinal stress in the pipe due to bending may be

estimated with the following equation:

Where:

WT =

L, =

S =

net uniformly distributed load required to achieve the desired mid-span vertical deflection of the pipe (A) [not the full weight of the pipe and fluid (see Appendix B)], in pounds per inch. minimum trench length required to reach the mid-span vertical deflection of the pipe (A), in inches. elastic section modulus of the pipe, in inches3.

2.1.8 LONGITUDINAL STRESS DUE TO ELONGATION

The longitudinal stress in the pipe due to elongation caused by the movement operation may be estimated with the following equation:

2 S, = 2.67E(g)

Where:

A = mid-span deflection of the pipe, in feet. L = minimum trench length required to reach the

mid-span deflection of the pipe (A), in feet.

The effects of this stress may be offset by an elastic compressive stress existing in the pipeline prior to the moving because of slack.

2.1.9 DYNAMIC EFFECTS Dynamic effects due to impact, vibration, earthquake,

subsidence or other potential dynamic load beyond the control of the pipeline operator should be considered in the design of movement operations. Dynamic loads from recon- ditioning, rehabilitation, and any other dynamic or temporary loading under the pipeline operator’s control should be considered in the design of the operation.

2.1.1 O PREVIOUS MOVEMENTS

The effects of previous movements should be considered in the design of movement operations.

2.2 Design Criteria 2.2.1 GENERAL

This subsection defines methodology and outlines criteria and minimum values that may be used in the design of pipeline-movement operations.

2.2.2 TOTAL LONGITUDINAL STRESS LIMIT

A total longitudinal stress limit should be established for the movement operation. This stress level is the specified minimum yield strength of the line pipe to be moved (SMYS) modified by a design factor (F,) determined by the pipeline operator. The design factor takes into account the condition and operating history of the pipeline and any applicable codes and regulations. Normally, it is most influ- enced by the condition of the girth welds.

2.2.3 AVAILABLE LONGITUDINAL BENDING STRESS

The longitudinal stress available for bending may be estimated with the following equation:

S, = F, SMYS - S, - S, (6)

Where:

S, = longitudinal stress available for bending, in psi. F, = design factor. SMYS = specified minimum yield strength of the pipe,

in psi.

2.2.4 TRENCH LENGTH

The minimum trench length required to achieve a particular mid-span deflection of the pipe without exceeding the longitudinal stress limit can be determined with the following equation, based on elastic free deflection theory, which treats the pipe as a single-span beam that is fixed at both ends and that has a uniformly distributed load (see Figure 1):

(7) 3.87 X lo7 DA+ 7.74 X lo7

L = FD SM YS - S E

2.2.5 TRENCH (OR DISPLACEMENT) PROFILE

A profile for the moved portion of the pipeline should be designed to minimize induced bending stress concentrations (see Figure 2). Therefore, to obtain acceptable longitudinal stress distribution due to bending, the deflection at any point


A P I RP*LL37 9 6 m 0732270 0 5 5 8 3 6 3 4 4 6 m


u2 u2

Pipeline lowered to pass a short obstruction

"

@ i a

4 b I' I - u2 Obstruction length u2

Required transition length at each end of an extended obstruction

Figure 1 -Application of the Minimum Trench Length (L)

L h

LI2 * LI2 " r - *

x3

x2 b I

Station

0+0° 7 Profile of

x, I Station existing *

I A

A

v L Station

LI2

Figure 2-Preferred Trench Profile of the General Lowering


6 API RECOMMENDED PRACTICE 11 17

along the trench profile can be determined with the following equation:

A, = 16x2A(L-x)’ L4

Where:

A, = vertical deflection of the pipe at distance x, in feet. x = distance along the length of the trench from the

starting point of the pipe deflection, in feet.

2.3 Support Spacing Based on a four-span, uniformly loaded beam, the maxi-

mum free span between supports can be determined with the following equation:

i 0.0286SA (D4-&)

D’ - 0.8724d2D Ls = (9)

Where:

LS = maximum free span between pipe supports, in feet. d = inside diameter of the pipe, in inches.

2.4 A Sample Problem and Its Solution The following is a step-by-step solution of a sample prob-

lem using the guidelines in this recommended practice for determining the minimum trench length required for the desired deflection of the pipe, the preferred trench profile, and the maximum free span between supports.

The following information is known:

a. Pipeline size is 12.75 inches O.D. by 0.250 inch W.T. - therefore, D = 12.75 inches, t = 0.250 inch, and d = 12.25 inches.

b. Pipe material is API 5L Grade X42 - therefore,

c. Desired vertical deflection of the pipe A = 5 feet. d. Maximum operating pressure P = IO00 psi. e. Installation temperature of pipe T, = 100°F. f. Operating temperature T2 = 30°F. g. The pipeline is under favorable conditions and has a

favorable operating history-therefore, design factor F, = 0.90.

Step I : With Equation 1, determine the longitudinal stress in the pipe due to internal pressure:

SMYS = 42,000 psi.

Step 2: With Equation 2, determine the longitudinal stress in the pipe due to temperature:

S, E a (T, - TZ)

= (29 x 106)(6.5 x lo-‘)( 100 - 30)

= 13,195 psi (tension)

Step 3: With Equation 3, determine the existing longitudinal stress in the pipe, assuming that the longitudinal stress due to existing elastic curvature is equal to zero:

SE = s p + S T + Sc

= 7650 + 13,195 + O

= 20,845 psi

Step 4: With Equation 7, determine the minimum trench length required to reach the desired vertical deflection of the pipe and remain within the longitudinal stress limits:

1f3.87 x lo7) DA + (7.74 x 107)A2 L = 1 1

F0 SMSY - SE

- - 3.87(107)(12.75)(5) + 7.74(107)(5’)

- y 0.9(42,000)-(20,845)

= 510feet

The minimum trench length required to achieve the desired vertical deflection of 5 feet and remain within the longitudinal stress limits is 510 feet.

Step 5: With Equation 8, determine the preferred trench profile:

Ax = 16x2A( L - x)* L4

- - 8Ox2(510-x)* 6.765 x 10”

Table 1 illustrates the results of using this equation to calcu- late the vertical deflection in the preferred trench profile at intervals of 25 feet. Figure 3 illustrates the minimum trench length and the preferred trench profile.

- - 1OOO( 12.75)(0.3) 2(0.250)

= 7650psi


A P I RP*LLL7 76 m 0732290 0 5 5 8 3 6 3 217 m


Step 6: With Equations 5 ,6 , and 9, determine the maximum allowable support spacing:

Table 1-Some Vertical Deflections (Ax) in the Preferred Trench Profile of a Sample Movement

2

S, = 2.67.(e)

= 2.67(29 X lo6)[ &J = 7442 psi

S,, = F, SMYS- SE-S,7

= 0.9(42,000) - 20,845 - 7442

= 9513psi

I

0.0286SA(Dd - d4)

D3 - 0.8724d’D L, = 1 -i 0.0286(9513)(( 12.75)4- ( 12.2514)

( 12.75)3 - 0.8724( 12.25)’( 12.75) -

= 51.3 feet

Conclusion: The minimum trench length required to achieve the desired 5-foot vertical deflection of the pipe is 5 10 feet. The pipeline must be supported every 5 1.3 feet.

Station x Deflection Ax Comment

0+00 0+25 0+50 0 + 7 5 1 +o0 1 + 2 5 1 +so 1 + 7 5 2 + 0 0 2 + 2 5 2 + 5 0 2 + 5 5 2 + 7 5 3 + 0 0 3 + 25 3 + 50 3 + 7 5 4 + 0 0 4 + 2 5 4 + 50 4 + 7 5 5 + 0 0 5 + I O

0.0 Beginning of movement 0.2 0.7 1.3 2.0 2.7 3.5 4.1 4.6 4.9 5 .O Midpoint of movement 5.0 4.9 4.7 4.3 3.7 3.0 2.3 1 .5 0.9 0.3 0.0 Minimum length for movement 0.0

Note: The deflection Ax is measured in feet. The first part of station x is measured in hundreds of feet, and the second part is measured in feet.

L = 510 feet

Station 2 + 55

G o + O0 1 +o0 2 + O0 I 3 + O0

Profile of existing

5+ 10 I

5 + O0

Begin lowering T

A = 5 feet

3.5

4.6 ” 4.7 3.U

lowered pipeline

Figure &Preferred Trench Profile of a Sample Lowering


8

SECTION 3-PROCEDURE CONSIDERATIONS

3.1 General A pipeline-moving project has three steps, which are to

be performed in the following order:

a. Project planning. b. The actual work of ditching, moving, backfilling, and cleanup. c. Documentation to meet pipeline-operator and regulatory requirements.

Each of the considerations discussed in this section should be taken into account in at least one of these steps.

3.2 Safety Precautions 3.2.1 GENERAL

CAUTION: For safety, the cautions and recommendations described in 3.2.2 through 3.2.7 should be considered and followed.

3.2.2 INTERNAL OPERATING PRESSURE

Prior to the pipe movement, the internal operating pressure of the pipeline should be reduced in accordance with the pipeline operators’ procedures and applicable regulations.

3.2.3 PIPELINE LOCATION

Prior to planning and excavation, the location of the pipeline, including its depth, should be determined.

3.2.4 OTHER UNDERGROUND FACILITIES

Prior to planning and excavation, efforts should be made to determine whether underground facilities may be encountered and, if so, where the facilities are located. The construction area should be checked for utility markers and other evidence of underground facilities. If available, state or local “One Call” systems should be accessed. Otherwise, operators of such underground facilities should be contacted directly so they may locate and mark their facilities. All contacts.

3.2.5 GIRTH WELD INSPECTION

If available, pipe mill test reports and welding inspection records should be reviewed. In addition, consideration should be given to the visual and nondestructive inspection of girth welds once the pipeline is exposed and prior to movement should be considered.

3.2.6 AlTACHED APPURTENANCES

Attachments to the pipeline such as fittings or valves may affect the pipeline movement. Their effect on the movement

should be considered. The movement of pipelines with attached appurtenances is beyond the scope of this recommended practice (see 1.3).

3.2.7 EXCAVATION SAFETY

Excavation presents some unique safety considerations. It should be performed in accordance with the pipeline operators’ procedures and applicable safety regulations. Refer to OSHA trenching and excavation regulations.

3.3 Terrain Terrain refers primarily to the profile of the ground where

the pipeline is located. Terrain affects a pipeline movement primarily by influencing the length of the trench required to move the pipeline.

In flat or gently rolling terrain, a pipeline is often laid by elastically conforming it to the terrain profile. In this case, the movement should be executed to minimize additional stress in the pipeline.

CAUTION: In flat or gently rolling terrain, to limit additional stress and ensure the safe movement of the pipeline, it may be necessary to excavate a longer trench than that required by the trench length equation.

In mountainous or hilly terrain, the pipeline may have permanent overbends or sag bends. In such cases, the physi- cal profile for the moved pipeline should incorporate these bends. Movement operations on the pipeline should be executed to prevent the alteration of these bends.

CAUTION: To maintain safe conditions in difficult terrain such as that found in mountains and hills, movement operations should be treated as special cases and may require a detailed engineering analysis and the use of specialized construction techniques.

3.4 Soil The soil type may determine the cross-sectional shape of

the excavation and how the pipeline will be handled over the ditch.

3.5 Other Considerations CAUTION: All pipeline movement projects should be executed with caution. If the pipeline is in tension and little or no slack is available, the movement will subject the pipe to additional stress due to the weight of the pipe, the weight of the fluid in it, and to seasonal temperature changes. Particu-


A P I RP*lLL7 9 6 m 0 7 3 2 2 9 0 0558365 091 m


lar care should be taken in older pipelines in which the pipe 3.7.2 POINT LOADING connections may be mechanically weak.

For pipelines of known low toughness, additional consideration should be given before pipeline movement operations.

Points for supporting or lifting the pipeline should not be at or near girth welds. The spacing of lift or support points should ensure that load capacity limitations are not

3.6 Trenching Requirements exceeded.

The pipeline excavation should be performed SO as to 3.7.3 SOIL BEARING CApAClTlES reduce the chances of damage to the pipeline its coating system. If necessary, the ditch should be padded before lower- The soil bearing capacities for equipment and temporary ing the pipeline. The bottom of the completed trench should supports should be considered. conform to the design profile for the moved pipeline.

3.7.4 PIPELINE-SUPPORTING METHODS 3.7 supports 3.7.1 CONTROL OF UNINTENDED MOVEMENT Figures 4 through 7 illustrate some pipeline-supporting

methods. Changes in the longitudinal stress in the pipe may cause

unintended movement of it. Such changes in stress may 3.7.5 PIPELINE-MOVEMENT METHODS result from residual stress or temperature changes in the pipeline. To control such movement, the pipeline should be Figures 8 through 10 illustrate some pipeline-movement properly supported and laterally restrained. methods. The differential heights of adjacent supports dur-

ing the movement operation should be controlled so that at no time during the movement does the elastic curvature of the pipeline exceed the expected final elastic curvature of the pipeline due to the movement.

Pipeline

Figure 4-Pig Pen Method of Pipeline Support


í o API RECOMMENDED PRACTICE i í í 7

PiDeline

Seam

Figure &Air Bag Method of Pipeline Support

Figure &Earth Pillar Method of Pipeline Support



Beam or pipe r\

S Figure 7-Sling Method of Pipeline Support

Figure 8-Pipeline-Movement Method Using Two Side Booms


Side boom

c Figure 9-Pipeline-Movement Method Using One Side Boom and One Backhoe

Figure 10-Pipeline-Movement Method in Which Pipe is Slid into Ditch


API RP*LLL7 96 m 0732290 05583b9 737


SECTION 4-INSPECTION

4.1 General 4.4 Inspection for Mechanical Damage prior to the execution of the pipeline movement, the exposed The pipeline should be inspected for mechanical damage.

inspection. A record should then be made of the inspection. with the pipeline operators’ procedures and applicable regu- P”hon of the pipeline be siven a *Omugh Imperfections and defects should be handled in accordance

4.2 Girth Welds lations.

Girth welds identified by 3.2.5 as requiring visual inspec- 4.5 External Coating tion should be visually inspected. 4.5.1 INSPECTION CAUTION: Pipe movement cannot be controlled once started. Note: Successive steps may be required.

The coating should be inspected both before and after a movement.

SECTION 5”CLEANUP

5.1 General good fill dirt, if necessary. No trash should be allowed to CAUTION: Backfilling and restoration should be performed as described in 5.2 and 5.3 so as not to damage the pipe or

get into the ditch. In areas such as streets, driveways, and parking lots, extra compaction may be required.

its coating. 5.3 Surface Restoration 5.2 Backfilling After backfilling is completed, right-of-way contours

should be restored to the original grade, the backfill material

be ‘Onsidered. The next to the pipeline appropriate water diversions should be installed to prevent In backfilling* the use of rock shields Or adequate Padding should be crowned over the excavation for soil settling, and

should be free from rocks and other hard objects. Pipeline washout of the excavation. stress can be reduced in backfilling by ensuring that the pipe is flat on the trench bottom and is padded well with sand or


A P I R P * 1 1 1 7 96 0732290 0558370 459 m

14 API RECOMMENDED PRACTICE 1 1 17

SECTION 6-DOCUMENTATION AND RECORDS

6.1 General d. The pipeline designation. Adequate documentation and records of each pipeline

movement project should be created and retained so that any subsequent operation on the pipeline at the movement site can take into account the adjustments made there. Move- ment records should be retained for the life of the pipeline.

e. The pipeline location. f. Any design calculations. g. The “as built” plan and profile record. h. The dates work was done. i. An observation of pipe behavior during movement. j . The pressure during movement.

1. Record of posting to alignment sheets. m. The locations of adjacent structures and boundaries such as the following:

l . Other pipelines. 2. Roads. 3. Buildings. 4. Fences.

6.2 Alignment Sheets k. The name of the on-site representative. Line-moving projects should be posted to alignment

sheets as soon as practicable. At a minimum, the posting reference should indicate where the details of the design and the “as built” information can be found.

6.3 Files Files should have the following information: 5 . Property lines.

a. The reason for moving the pipe. 6 . Rights-of-way. b. The condition of the pipe. 7. Aboveground and underground utility structures. c. The condition of the coating.


APPENDIX A-NOMENCLATURE

Symbol Description linear coefficient of thermal expansion of steel

mid-span vertical deflection of the pipe vertical deflection of the pipe at distance x inside diameter of the pipe outside diameter of the pipe modulus of elasticity of steel design factor minimum trench length required to reach the mid-span vertical deflection of the pipe (A) minimum trench length required to reach the mid-span vertical deflection of the pipe (A) maximum free span between pipe supports Poisson's Ratio for steel maximum internal operating pressure of the pipe elastic section modulus of the pipe longitudinal stress available for bending longitudinal stress in the pipe due to bending caused by the lowering operation longitudinal stress in the pipe due to existing elastic curvature existing longitudinal stress in the pipe total longitudinal stress in the pipe specified minimum yield strength of the pipe longitudinal tensile stress in the pipe due to internal pressure longitudinal stress in the pipe due to its elongation caused by the moving operation longitudinal tensile stress in the pipe due to a change in its temperature nominal wall thickness of the pipe temperature of the pipe at the time of the installation

ValueAJnits 6.5 X 10-6 inches per inch per "F feet feet inches inches 29 X 106 psi -

feet inches

feet 0.3 psi inches3 psi psi

psi

psi psi

psi psi psi

psi

inches "F

operating temperature of the pipe at the time of the movement "F desired mid-span vertical deflection of the pipe (A) [not the pounds per inch full weight of the pipe and fluid (see Appendix B)] distance along the length of the trench from the starting point feet of the pipe deflection

15


APPENDIX B-DERIVATION OFTHE EQUATION FOR LONGITUDINAL STRESS DUETO BENDING AND OFTHE EQUATION FOR TRENCH LENGTH

Equation 7, the trench length equation, and Equation 4, the equation for longitudinal stress in the pipe due to bending, are derived from AISC beam diagram 15 (see AISC M016) for a single-span, fixed-end, uniformly loaded beam. The desired pipe deflection (Al) is set equal to the mid-span deflection of a fixed-end beam and used to determine the net load (wT) on the beam (pipe) required to cause this deflection. The length (LI) of the beam in which the bending stress (S,) due to the desired deflection is equal to the stress (S,) available for bending is then determined.

Note: All AISC dimensions are in inches.

Setting the desired deflection (Al) of the pipe equal to the maximum deflection of a fixed-end beam,

W&: AI = -

384EI Where:

I = moment of inertia, in inches4.

Rearranging to solve for wT,

384ElAl WT = -

L:

The maximum moment in a fixed-end beam occurs at the ends as follows:

Where:

M = maximum moment in a fixed-end beam, in inch- pounds.

The bending stress in the beam (pipe) at its outer surface is

M C I

M S

SB = -

" -

Where:

C = distance from neutral axis to outside surface of beam, in inches.

Therefore, as expressed in Equation 4, the equation for longitudinal stress in the pipe due to bending,

As shown in Equation 6,

S A = F, SMYS- S E - S S

Equation 5 implies that

SS = 2.67E- A: L:

Setting S, equal to S, and substituting for SS,

Substituting for wT.

384E1A1 = FD S M Y S - SE - 2.67E7 A: 12s L; L,

Simplifying and solving for L: ,

384E1Ah, " - L:( FDSMYS - S E ) - 2.6768: 12s

32E1A1 + 2.67EA: L: = S

FD SM Ys - SE

For a hollow circular pipe (see AISC M01 6),

I = 0.049087(D4-d')

E = 29 x lo6 psi

Substituting for S, I , and E,

32(29x 106)(0.049087)(D4-dl)d

0 . 0 9 8 1 7 5 p y ) L, = 2

FDSMYS-SE

2.67(29 x lo6) A: + FD SMYS - S E

17


A P I RP*1117 Yb 0732270 0558373 Lb8


and Converting to feet, the units used for L in this publication,

L, = FD SMYS - S,

L = F0 S M Y S - SE


APPENDIX C-DERIVATION OFTRENCH PROFILE EQUATION

Equation 8 , the equation for the deflection of the pipe at Rearranging to solve for wT, any point along the trench profile, is derived from AISC beam diagram 15 (see A I X M016), assuming that the beam is fixed at both ends, that the loads are uniformly distributed, and that the units of measure are consistent.

384ElA W 7 = -

L4 Substitution of the right-hand side of the above equation for W , in Equation C-1 and simplification of the resulting equa-

WTX2( L - Ax =

24 EI (C-1) tion show that

Setting the desired deflection of the pipe (A) equal to the Ax = 384EIAx2( L - x ) 2

maximum (mid-span) deflection of a fixed-end beam, 2 4 E l L'

W T L 4 A = - 38481

- - 16x2A( L - x)2 L'

19


APPENDIX D-DERIVATION OF EQUATION FOR LONGITUDINAL STRESS DUE TO ELONGATION

Equation 5, the equation that estimates the longitudinal stress in the pipe due to elongation, is based on the fact that for any given horizontal distance (see Figure D-l), the arc length of a circular curve is greater than the length of the corresponding horizontal line segment.

For any one of the four circular-curve segments of the moved pipe (see Figure D-2), the elongation (6) is the difference in length due to stretching:

6 = A - 1

Figure D-1-Arc Length (A) of a Circular Curve

Where:

S = difference in length of the pipe segment due to stretching caused by movement.

A = arc length of a circular curve representing the pipe segment in its final position, after movement.

1 = original length of the pipe segment, before movement.

The strain ( E ) on the pipe due to its elongation is the difference in length divided by the original length:

S & = - L (D- 1)

Where:

E = strain on the pipe due to its elongation.

Trigonometry indicates that for angles in radians,

A = R8

[ 3! 5 ! o3 o5 1 = R sin8 = R 8-- + --...

Where:

R = radius of curvature.

8 = arc angle, in radians.

For small angles,

Substituting and simplifying,

I I *

v

L

Figure D-2-The Four Circular-Curve Segments in the Preferred Trench Profile of the General Movement

21



In general,

h - = tank] 1

Where:

h = deflection.

Since for small angles,

tan[!] e 2

therefore 2h e = -

1

Since 1 = R sin8

therefore, for small angles, 1zR9

Substitution of the right-hand side of the second line of Equation D-2 for 6 in Equation D-1, reduction of R 8 in the resulting equation to 1 in accordance with the above equation, and simplification show that

/ \ 2

/ \ 2

Since there an four circular-curve segments in each lowering (see Figure D-2),

L = 41

L I = - 4

2 LZ 1 = - 16

As Figures D- 1 and D-2 indicate,

A = 2 h

A h = - 2

2 A’ h = - 4

Rewriting the above equation for E in terms of A and L,

&=”=””” 2h2 2 A216 8A2 3E2 3 4 L’ 3 L’

2

= 2.67 k) Since, by definition,

& = & E

therefore, the stress in the pipe due to its elongation is / \ z

SS = 2 . 6 7 E b )


APPENDIX E-DERIVATION OF EQUATION FOR MAXIMUM FREE SPAN BETWEEN PIPE SUPPORTS

Equation 9, the equation for the maximum free span therefore between pipe supports, is derived from AISC beam diagram 39 (see AISC M016), which is for a continuous beam with W = :[ P s t e e l P - d 2 ) + (Pwuterd2)] four equal spans that are loaded.

Note: All dimensions are in inches.

M,,, = 0.1071 WL:,

= SA S Where:

= maximum free span between pipe supports, in inches.

0.283 D’ - 0.2469d2 1 M, = maximum moment, in inch-pounds. W = full weight of water-filled pipe, in pounds Substituting for W,

per inch.

For a hollow circular pipe,

S = O . o 9 8 1 7 5 p y ]

Substitution yields

M,,, = S A 0.098175 - [ ( . x d 4 ] ]

0.1071 WL:, = SA 0.098175 - [ rid4]] 2

LSI = O. 107 1 W Since

W = Pstee, + Pwuwr Awutcr

Where:

psrrrl = density of steel, 0.283 pound per cubic inch. pwaIer = density of water, 0.0361 pound per cubic inch. A,, = cross-sectional area of steel pipe, in square

A,,,, = cross-sectional area of water in filled pipe, in inches.

square inches.

and

Since

0.1071(:) = 0.084116

therefore

2 s~[1.16714(D~- d4)]

0.238 D[ D2 - 0.8724d2] Ls, =

- \ / - D3 - 0.8724Dd2

and

4.1242SA(D4 - d4) L , =

D3 - 0.8724Dd

Converting to feet, the units used for L$ in this recommended practice,

L, =

23


APPENDIX F-EQUATIONS

Equation No. Description, in Units

S' = S, + S B +SS - total longitudinal stress in the pipe, in psi

PDP s p = - 2t

S, = Ea (T, - T,)

S B = - 12s W,L:

SS = 2 . 6 7 E t J

S, = FD SMYS - S, - S S

longitudinal tensile stress in the ['I pipe due to internal pressure, in psi

longitudinal tensile stress in the

ature, in psi [2] pipe due to a change in its temper-

existing longitudinal stress in the f31 pipe, in psi

longitudinal stress in the pipe due

ment operation, in psi [4] to bending caused by the move-

longitudinal stress in the pipe due [ 5 ] to elongation caused by the move-

ment operation, in psi

longitudinal stress available for [61 bending, in psi

1- [7] reach the mid-span verticle deflec- minimum trench length required to

L = FD SMYS - SE tion of the pipe (A), in feet

A, = 16x2A( L - x)' L4

i 0.0286SA(D4 - d')

D3 - 0.8724Dd' Ls =

verticle deflection of the pipe at [81 distance x, in feet

maximum free span between pipe '91 supports, in feet

S, = longitudinal stress in the pipe due to longitudinal stress in the pipe due existing elastic curvature to existing elastic curvature, in psi

-

25


A P I RP*1117 9b m 0732290 0558380 3 T B W

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api 1117 (1996) movementin-servpipelines

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