vibration fatigue

Guidelines for the Avoidance of Vibration Induced Fatigue in Process Pipework

Publication 99/100

Guidelines for the Avoidance of Vibration Induced Fatigue in Process Pipework

Disclaimer Every reasonable effort has been made to ensure that these Guidelines are based on the best knowledge available up to the time of finalising the text. However, no responsibility of any kind for any injury, delay, loss or damage, whatsoever, resulting from the use of these Guidelines can be accepted by MTD, the sponsors or others involved in its publication.

Published by MTD Ltd, a Charity Registered in England and Wales, Reg. No. 295576 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form by any means, electronic, mechanical, photocopying, recording or otherwise, without prior permission of the publisher. Enquiries should be made to MTD Ltd.

Publication 99/100 © MTD 1999 ISBN 1 870553 37 3

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MTD Guidelines for the Avoidance of Pipework Fatigue

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MTD Guidelines for the Avoidance of Pipework Fatigue

Foreword The project leading to these Guidelines was initiated in response to a growing number of pipework failures in process systems of both offshore and onshore installations. A database of actual and potential failures was compiled and, when analysed, indicated that various contributing factors were present, most importantly changes in process operating conditions and a greater use of thin-walled pipework. The Marine Technology Directorate Ltd (MTD) therefore initiated a Joint Industry Project to produce appropriate engineering Guidelines, with the aim of minimising the risk related to fatigue failure of process piping systems. These Guidelines were prepared under contract to MTD, on behalf of the sponsors, by ATL Consulting Group Ltd and Mitsui Babcock - Technology Centre as the principal consultants, and with assistance from Shell Global Solutions. It was sponsored by the 16 organisations listed below and was managed for MTD by Mr R W Barrett.

Project Sponsors AMEC Process and Energy Amerada Hess Chiyoda Corporation Foster Wheeler Petroleum Development Health & Safety Executive Kvaerner Oil & Gas Marathon Oil McDermott Marine Construction Minerals Management Service (USA) Mobil Technology Company Norsk Hydro Scottish Enterprise Shell UK Exploration & Production Statoil Total Oil Marine Toyo Engineering Corporation

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MTD Guidelines for the Avoidance of Pipework Fatigue

Steering Group A Steering Group comprising representatives of participants, MTD, and the Technical Services Contractors provided the forum for both verbal and written discussion of the content of these Guidelines during its preparation. During the period of the project, the following individuals served on the Steering Group which was chaired by Mr T McMahon (Mobil Technology Company) and latterly Mr C R Howard (Shell UK Exploration & Production): F. Ando

Chiyoda Corporation

G. Appleby

Total Oil Marine Plc

R.W. Barrett

Marine Technology Directorate

W. Bryan

Scottish Enterprise

G. Evans

Foster Wheeler Petroleum Development Ltd

G.E. Goodacre Shell UK Exploration & Production H.I. Haugen

Norsk Hydro as

K. Hollen

Statoil

C.R. Howard

Shell UK Exploration & Production

D. Hughes

Amerada Hess

T. Kiuchi

Toyo Engineering Corporation

K. Knaevelsrud Statoil W.J.G. Little

Mitsui Babcock - Technology Centre

M.J. Marks

Kvaerner Oil & Gas

J.T. Martin

Shell Global Solutions

T. McMahon

Mobil Technology Company

D.H. Mitchell

Mitsui Babcock - Technology Centre

P. Oswald

Marathon Oil UK Ltd

R. Sharma

Health and Safety Executive

B.M.H. Soper

ATL Consulting Group Ltd

C. Stobie

Marathon Oil UK Ltd

R.J. Swindell

ATL Consulting Group Ltd

P. Tring

AMEC Process and Energy Ltd

R. Tyagi

Minerals Management Service (USA)

T. Williams

Scottish Enterprise

J. Young

McDermott Marine Construction

MTD Guidelines for the Avoidance of Pipework Fatigue

Technical Services Contractors The preparation of these Guidelines was undertaken principally by the following organisations and the individuals who worked on its various elements were: ATL Consulting Group Ltd

J. R. Baker W. J. Skailes B. M. H. Soper R. J. Swindell

Mitsui Babcock - Technology Centre

T. Grant W. J. G. Little C. McGlinchey D. H. Mitchell

Acknowledgements A special acknowledgement is due to J. T. Martin (Shell Global Solutions), G. E. Goodacre (Shell UK Exploration & Production), M. Marks (Kvaerner Oil and Gas) and J.P. Graham (Mitsui Babcock Technology Centre) for their additional assistance in the final stages of drafting these Guidelines. A further acknowledgement is made to The Health & Safety Executive for assisting with the database at an early stage of the project.

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TABLE OF CONTENTS

PAGE

1.0 Introduction

1

2.0 Vibration Mechanisms

3

2.1

Excitation Mechanisms and Response 2.1.1 Introduction to Vibration 2.1.2 Flow Induced Turbulence 2.1.3 High Frequency Acoustic Excitation 2.1.4 Mechanical Excitation 2.1.5 Pulsation 2.1.5.1 Reciprocating Pumps and Compressors 2.1.5.2 Periodic Flow Induced Excitation 2.1.5.3 Centrifugal Compressors (Rotating Stall)

3 3 5 5 5 6 7 7 8

2.2

Failure Mode

8

2.3

Likelihood of Failure

8

2.4

Determination of Overall Risk

9

3.0 Assessment Methodology

15

3.1

Overview

15

3.2

Stage 1 - Identification of Excitation Mechanisms 3.2.1 Purpose 3.2.2 Method 3.2.3 Recommended Action

15 15 15 16

3.3

Stage 2 - Detailed Screening of Main Pipe 3.3.1 Introduction 3.3.2 Purpose 3.3.3 Method 3.3.4 Recommended Actions

17 17 17 17 17

3.4

Stage 3 - Detailed Screening of Small Bore Connections 3.4.1 Introduction 3.4.2 Purpose 3.4.3 Method 3.4.4 Recommended Actions

18 18 18 18 19

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4.0 Design Solutions

29

4.1

Overview

29

4.2

Design Solutions for Main Pipe 4.2.1 Flow Induced Turbulence 4.2.2 High Frequency Acoustic Excitation 4.2.3 Mechanical Excitation 4.2.4 Pulsation

29 29 30 30 31

4.3

Design Solutions for Small Bore Connections

32

5.0 Survey Methods

33

5.1

Introduction

33

5.2

Survey Methods 5.2.1 Vibration Based Survey Techniques 5.2.2 Fatigue Direct Strain Measurement

33 33 33

5.3

Interpretation of Fatigue Assessment

34

6.0 References

39

Appendix A1 STAGE 1 IDENTIFICATION OF EXCITATION MECHANISMS

A1-1

1.0 Overview

A1-1

2.0 Questionnaire 1 - Liquid/Multiphase fluid systems

A1-1

3.0 Questionnaire 2 - Gas systems

A1-3

Appendix A2 STAGE 2 - DETAILED SCREENING OF MAIN PIPE

A2-1

1.0

Overview

A2-1

2.0

Method 2.1 Process Information 2.2 Excitation Mechanisms

A2-1 A2-1 A2-2

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MTD Guidelines for the Avoidance of Pipework Fatigue

Appendix A2.1 SCREENING METHOD FOR FLOW INDUCED TURBULENCE IN PROCESS PIPING SYSTEMS

A2.1-1

1.0

Support Arrangement

A2.1-1

2.0

Screening Method

A2.1-2

Appendix A2.2 ADVANCED SCREENING METHOD FOR FLOW INDUCED TURBULENCE IN FLEXIBLE PIPEWORK

A2.2-1

1.0

Overview

A2.2-1

2.0

Calculation Method

A2.2-1

3.0

Limitations

A2.2-2

4.0

Existing lines

A2.2-3

Appendix A2.3 SCREENING METHOD FOR HIGH FREQUENCY ACOUSTIC EXCITATION IN PROCESS PIPING SYSTEMS

A2.3-1

1.0

Overview

A2.3-1

2.0

Method

A2.3-1

3.0

Worked Example

A2.3-4

Appendix A3 STAGE 3 - DETAILED SCREENING OF SMALL BORE CONNECTIONS

A3-1

1.0

Small Bore Connection Modifier

A3-1

2.0

Likelihood of Failure due to the Branch Geometry 2.1 Type of Fitting 2.2 Overall Length of Branch 2.3 Number and Size of Valves 2.4 Main Pipe Schedule 2.5 Small Bore Pipe Diameter

A3-1 A3-1 A3-2 A3-2 A3-2 A3-3

3.0

Likelihood of Failure due to Geometry of the Main Pipe 3.1 Main Pipe Schedule 3.2 Location on Main Pipe

A3-3 A3-3 A3-4

4.0

Small Bore Connection Modifier

A3-4

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MTD Guidelines for the Avoidance of Pipework Fatigue

Appendix B WORKED EXAMPLE

B-1

1.0

Introduction

B-1

2.0

Stage 1 - Identification of Excitation Mechanisms 2.1 Gas systems

B-1 B-1

3.0

Stage 2 - Detailed Screening of Main Pipe 3.1 Flow Induced Turbulence 3.2 Mechanical Excitation 3.3 Pulsation (Reciprocating Compressor) 3.4 Recommended Actions

B-2 B-2 B-3 B-3 B-3

4.0

Stage 3 - Detailed Screening of Small Bore Connections

B-4

Appendix C RECOMMENDED SMALL BORE CONNECTION SUPPORTS

C-1

Appendix D PIPEWORK VIBRATION SURVEY METHOD

D-1

1.0

Aim

D-1

2.0

Background

D-1

3.0

Method

D-1

4.0

Results and Analysis

D-2

5.0

Assessment Technique

D-2

6.0

Interpretation

D-2

7.0

FFT Analyser/Data Logger Setup

D-2

Appendix E RECORD SHEET FOR PIPING VIBRATION PROBLEMS EXPERIENCEDIN SERVICE

E-1

1.0

Problem Details

E-1

2.0

Process Details

E-1

3.0

Piping Geometry Details

E-2

4.0

Contact Details

E-2

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MTD Guidelines for the Avoidance of Pipework Fatigue

List of Figures,Tables and Worksheets PAGE Figure 2-1

Description of vibration using a simple spring-mass system

10

Figure 2-2

Comparison of the amplitude of displacement, velocity, and acceleration as a function of frequency

10

An example of the distribution of kinetic energy due to turbulence generated by flow into a tee

11

Figure 2-4

Turbulent energy as a function of frequency

11

Figure 2-5

Relationship between acoustic natural frequencies and structural response

12

Figure 2-6

An example of ‘Dead Leg Branch’

Figure 2-3

Figure 2-7

An example of Rotating Stall

13 13

Figure 2-8

Criticality matrix linking likelihood of failure calculation from these guidelines and consequence of failure from the user

14

Figure 3-1

Overview of assessment methodology

20

Figure 3-2

Methodology for assessing vibration fatigue in process piping systems and small bore connections

21

Figure 3-3

Stage 1 (Identification of Excitation Mechanism) and Stage 2 (Detailed Screening of Main Pipe) Flowchart

Figure 3-4

Stage 3 (Detailed Screening of Small Bore Connection) Flowchart

22 23

Worksheet 3-1

Stages 1 and 2 of the Guidelines

24

Worksheet 3-2

Stage 3 of the Guidelines

25

Figure 3-5

The basis of default ‘likelihood of failure’ results for process area from database of failures

26

The effect of pipe wall thickness and mass of valve on the natural frequency of the small bore connection

27

The effect of small bore connection schedule (thickness) on the natural frequency of the small bore connection

27

Figure 3-6

Figure 3-7

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MTD Guidelines for the Avoidance of Pipework Fatigue

Figure 3-8

Database extract showing high occurrence of problems where there is a high number of unsupported valves

28

Figure 5-1

S-N curves for different weld classes from BS 7608

36

Figure 5-2

Stress distribution at a typical connection from BS 7608

37

Table A-1

Default Process Data

A2-1

Table A-2

Mechanical Excitation values

A2-3

Figure A-1

Stage 1 (Identification of Excitation Mechanism) and Stage 2 (Detailed Screening of Main Pipe) Flowchart

A2-5

Table A-3

Support Arrangement

A2.1-2

Table A-4

Method of calculating Fv

A2.1-4

Figure A-2

Different support arrangements as a function of span length and outside diameter

A2.1-7

Figure A-3

Fv Curve Fit - Stiff Support Arrangement – 60mm