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8/12/2019 Pages From Research Report Dispersion Modelling and Calculation in Support of EI MCoSP Part 15 Mar 2008

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Research report: Dispersion modellingand calculations in support ofEI Model code of safe practice Part 15: Areaclassification code for installations handlingflammable fluids

2nd edition


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RESEARCH REPORT: DISPERSION MODELLING AND CALCULATIONS IN SUPPORT OF

EI MODEL CODE OF SAFE PRACTICE PART 15: AREA CLASSIFICATION CODE FOR

INSTALLATIONS HANDLING FLAMMABLE FLUIDS

Second edition

March 2008

Published by

ENERGY INSTITUTE, LONDON

The Energy Institute is a professional membership body incorporated by Royal Charter 2003Registered charity number 1097899


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The Energy Institute (EI) is the leading chartered professional membership body supporting individuals and organisations across the

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ENI

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Maersk Oil North Sea UK Limited

Murco Petroleum Ltd

Nexen

Saudi Aramco

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Shell U.K. Exploration and Production Ltd

Statoil (U.K.) Limited

Talisman Energy (UK) Ltd

Total E&P UK plc

Total UK Limited

Copyright 2008 by the Energy Institute, London:

The Energy Institute is a professional membership body incorporated by Royal Charter 2003.

Registered charity number 1097899, England

All rights reserved

No part of this book may be reproduced by any means, or transmitted or translated into a machine language without the written

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The information contained in this publication is provided as guidance only and while every reasonable care has been taken to ensure

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information. The Energy Institute shall not be liable to any person for any loss or damage which may arise from the use of any of the

information contained in any of its publications.

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ISBN 978 0 85293 489 0

Published by the Energy Institute

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RESEARCH REPORT: DISPERSION MODELLING AND CALCULATIONS IN SUPPORT OF EI MODEL CODE OF SAFE PRACTICE PART 15

iii

CONTENTS

Page

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2 Objective and scope of work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

3 Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.1 Investigation of research topics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3.1.1 Sensitivity effects of input parameters on dispersion characteristics . . . . . . . . . 3

3.1.2 Area classification for liquid pools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.1.3 Application of area classification methodology to LNG . . . . . . . . . . . . . . . . . . . 6

3.2 Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4 Validation of previous work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4.1 Release flow rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4.2 Dispersion results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5 Investigation of sensitivity of results to variation of parameters . . . . . . . . . . . . . . . 16

5.1 Variation with weather category (windspeed and stability) . . . . . . . . . . . . . . . . . . . . . 165.1.1 R1distances to LFL (releases at 5 m height above ground) . . . . . . . . . . . . . . . 16

5.1.2 R2distances to LFL (releases at 1 m height above ground) . . . . . . . . . . . . . . . 18

5.1.3 Distance to 0.5 LFL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

5.2 Variation with ambient temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

5.3 Variation with relative humidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

5.4 Variation with surface roughness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

6 Investigation of area classification for liquid pools . . . . . . . . . . . . . . . . . . . . . . . . . . 30

6.1 Spill volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

6.2 Hazard distances: base case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

6.3 Hazard distances: sensitivities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

6.3.1 Variation with ambient temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

6.3.2 Variation with surface roughness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

7 Investigation of application of EI15 methodology to LNG . . . . . . . . . . . . . . . . . . . . . 36

7.1 Liquid rain-out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

7.2 Base case and variation with weather category . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

7.3 Variation with ambient temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

7.4 Variation with relative humidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

7.5 Variation with surface roughness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

7.6 Variation with surface type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44


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Contents Cont... Page

8 Conclusions and recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

8.1 Sensitivity to parameter variations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458.1.1 Fluid category A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

8.1.2 Other fluid categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

8.2 Liquid pools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

8.2.1 Base case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

8.2.2 Sensitivity to parameter variations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

8.3 LNG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Annex A Sensitivity analysis on release angle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Annex B Glossary of terms and abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

B.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

B.2 Glossary of terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

B.3 Glossary of abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Annex C References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Addendum 1:EI Calculations in support of IP 15: The area classification code for

petroleum installations (first edition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Tables:

Table 3.1: Parameter values used for dispersion values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Table 3.2: Pool dimensions modelled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Table 3.3: Example LNG compositions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Table 4.1: Release flow rates from EI15 and DNV Phast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Table 4.2: Comparison of dispersion results (distances to LFL, m) from EI15 and DNV Phast:

Hazard distance R1; release height 5 m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Table 4.3: Comparison of dispersion results (distances to LFL, m) from EI15 and DNV Phast:


Table 4.4: Summary of sensitivity of hazard distance to release angle . . . . . . . . . . . . . . . . . . 14

Table 4.5: Comparison of dispersion results (distances to LFL) from EI15 and DNV Phast:


Table 5.1: Ratios of R1hazard distance to 0.5 LFL/LFL (5 m elevation release) . . . . . . . . . . . . 25

Table 6.1: Spill volumes modelled (m3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Table 6.2: Distances from edge of pool to LFL and 0.5 LFL for base case, concrete . . . . . . . . 31

Table 6.3: Distances from edge of pool to LFL and 0.5 LFL for base case, dry soil . . . . . . . . . 32Table 7.1: Percentage rain-out of LNG (maximum from all weather categories) . . . . . . . . . . . 36

Table 7.2: Summary of base case hazard radii R1to LFL and 0.5 LFL for LNG releases at

5 m height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Table 7.3: Comparison of distances to LFL (m) for fluid category G(i) and LNG . . . . . . . . . . . 37

Table 7.4: Summary of base case hazard radii R1to LFL and 0.5 LFL for LNG releases at

1 m and 0.1 m height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Table 7.5: Distances to LFL for releases at 5 m height at different ambient temperatures . . . 42

Table 7.6: Variation in distances to LFL for releases at 5 m height for different relative

humidities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Table 7.7: Distances to LFL for selected releases at 5 m height onto concrete and water . . . . 44


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Contents Cont... Page

Table 7.8: Distances to LFL for releases at 0.1 m height onto concrete and water . . . . . . . . . 44

Table A.1: Hole diameter 1 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49Table A.2: Hole diameter 2 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Table A.3: Hole diameter 5 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Table A.4: Hole diameter 10 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Figures:

Figure 3.1: Definitions of hazard radii R1and R2for releases at height H (reproduced

from EI15) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Figure 5.1: Example comparisons of R1hazard distances to LFL for different weather

categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 5.2: Example comparisons of R2hazard distances to LFL for different weather

categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Figure 5.3: Example side views of plumes for releases at 1 m height, showing LFL contour

for each weather category . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 5.4: Example comparisons of hazard distances R1to 0.5 LFL for different weather

categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 5.5: Example comparisons of R1hazard distances to LFL between different ambient

temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 5.6: Example comparisons of R1hazard distances between different relative

humidities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Figure 5.7: Example comparisons of R1hazard distances between different surface

roughnesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Figure 6.1: Example comparisons of R1hazard distances between different ambient

temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Figure 6.2: Example comparisons of R1hazard distances to LFL between different surface

roughnesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Figure 7.1: Example side views of plume dispersion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Figure 7.2: Variation of distances to LFL with weather category (release height 5 m) . . . . . . . 41

Figure 7.3: Variation of distances to LFL with surface roughness . . . . . . . . . . . . . . . . . . . . . . 43


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ACKNOWLEDGEMENTS

The technical development project that forms the basis of the second edition of this report was

undertaken by Philip Nalpanis (DNV Energy)1, and assisted by colleagues Dr Phil Crossthwaite, Stavros

Yiannoukas and Jeff Daycock. It was directed by the Energy Institutes Area Classification Working

Group, which comprised during the project:

Howard Crowther Consultant (Chairperson)

Jon Ellis ConocoPhillips

Tony Ennis Haztech Consultants

Geoff Fulcher F.E.S. (Ex)

Kieran Glynn BP International

Martin Hassett M W Kellogg

Peter Murdoch SIRA CertificationSonia Quintanilla Energy Institute (Secretary)

Dr Mark Scanlon Energy Institute

Dr Sam Summerfield Health and Safety Executive

Edmund Terry Sauf Consulting

Mick Wansborough Consultant

Dirk Wong M W Kellogg

The Institute wishes to record its appreciation to the technical direction provided by them.

The Institute also wishes to record its appreciation to the assistance provided by Peter Roberts (Shell

Global Solutions) regarding technical issues in the first edition of this report.

Project management and technical editing were carried out by Dr Mark Scanlon (Energy Institute).

Affiliations refer to the time of participation.

1Philip Nalpanis, Principal Specialist, Det Norske Veritas (DNV) Ltd., Palace House, 3 Cathedral Street, LONDON,

SE1 9DE.


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vii

FOREWORD

The third edition of EIArea classification code for installations handling flammable fluids ('EI15') was

published in July 2005 and incorporated both technical clarifications and editorial amendments.

EI15 is widely used in both the upstream and downstream sectors of the petroleum industry, as well

as in other industry sectors that handle flammable fluids. In addition, it is regarded as a key

methodology for addressing the area classification requirements of the Dangerous Substances and

Explosive Atmospheres Regulations (DSEAR).

In developing the second edition of EI15, some research studies were commissioned to strengthen

its evidence base; this included the research published as the first edition of EI Calculations in support

of IP15: The area classification code for petroleum installations.

Following publication of the third edition of EI15, this research was commissioned to further extendthe dispersion analysis and calculation basis of EI15: the findings are described here in the second

edition of EI Research report: Dispersion analysis and calculations in support of EI15: The area

classification code for installations handling flammable fluids.

The research described here focused on the following technical issues:

Sensitivity analysis of ambient temperature, relative humidity, weather and surface roughness

on dispersion characteristics from point sources for various fluid categories.

Sensitivity analysis of the nature and ambient temperature of the underlying surface (e.g.

concrete, dry soil), weather, and surface roughness on dispersion characteristics from pools of

various diameters and depths, for various fluid categories.

Determination of whether any existing IP15 fluid categories apply to liquefied natural gas (LNG),

or if it requires specific modelling and sensitivity analysis of parameters (hole diameter, release

pressure, temperature, relative humidity, weather, surface roughness, surface type) to determine

dispersion characteristics.

Publication of the new research augments the following technical issues in the first edition:

Work item 2: Shape factors and hazard radii for pressurised releases see Section 3 of EI

Calculations in support of IP 15: The area classification code for petroleum installations (see

Addendum 1).

Work item 4: Liquid pools due to spillage see Section 5 of EI Calculations in support of IP 15:

The area classification code for petroleum installations (see Addendum 1).

In practice, information on these issues in the earlier report is not invalidated, but rather is

augmented in the second edition. Consequently, and because no further technical work has been

carried out on other work items in the earlier report, the first edition is entirely replicated as

Addendum 1.


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viii

The research reported here should be considered independent of the Energy Institutes Area

Classification Working Group, although commissioned and reviewed by them; going forward, they

intend to consider how the findings of the new research affects the continuing technical integrity of

pertinent aspects of the third edition of EI15.

The information in this publication should assist process safety engineers, safety advisors, designers,

or others with responsibility for hazardous area classification to better determine the extent of

hazardous areas in a consistent manner for specific fluid and process, weather and environment

dependent values. The information is internationally applicable provided it is read, interpreted and

applied in conjunction with relevant national and local requirements.

For further information on the suite of EI publications on hazardous area classification see

http://www.energyinst.org.uk/ei15.

The information contained in this publication is provided as guidance only and while every reasonable

care has been taken to ensure the accuracy of its contents, the Energy Institute and the technicalrepresentatives listed in the Acknowledgements, cannot accept any responsibility for any action

taken, or not taken, on the basis of this information. The Energy Institute shall not be liable to any

person for any loss or damage which may arise from the use of any of the information contained in

any of its publications.

This publication may be further reviewed from time to time. It would be of considerable assistance

in any future revision if users would send comments or suggestions for improvement to:

The Technical Department

Energy Institute

61 New Cavendish StreetLONDON, W1G 7AR

e: [email protected]


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Page 1

1 INTRODUCTION

The third edition of EIArea classification code for installations handling flammable fluids

('EI15') was published in July 2005 and incorporated both technical clarifications and

editorial amendments. EI15 is widely used in both the upstream and downstream sectors of

the petroleum industry, as well as in other industry sectors that handle flammable fluids. In

addition, it is regarded as a key methodology for addressing the area classification

requirements of The Dangerous Substances and Explosive Atmospheres Regulations

(DSEAR).

In developing the second edition of EI15, some research studies were commissioned

to strengthen its evidence base; this included the research published as the first edition of

EI Calculations in support of IP15: The area classification code for petroleum installations (see

Addendum 1).

Following publication of the third edition of EI15, this research was commissionedto further extend the dispersion analysis and calculation basis of EI15: the findings are

described here in the second edition of EI Research report: Dispersion analysis and

calculations in support of EI15: The area classification code for installations handling

flammable fluids. This research report sets out project findings: the results obtained from

DNVs analysis and the conclusions that can be drawn in respect of EI15 in the areas

researched.


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Page 2

2 OBJECTIVE AND SCOPE OF WORK

The project has aimed to strengthen the evidence base of EI15 by researching the following

technical issues, as requested by the EI Area Classification Working Group:

1. Sensitivity effects of parameters on dispersion characteristics. EI15 Annex C

sets out atmospheric dispersion results for a range of fluid compositions, modelled

for a single set of atmospheric conditions and other release parameters. The

dispersion modelling included in EI15 Annex C will be repeated as a calibration of

the models to be used. The new research will extend the parameter ranges of

atmospheric temperature, relative humidity, wind speed, reference height, stability,

reservoir temperature and surface roughness. In addition, modelling would be

carried out for both the existing EI15 hazard radius lower flammable limit (LFL)

boundary and a 0.5 LFL boundary.

2. Area classification arising from pools formed as a result of instantaneous

releases. EI15 currently only addresses continuous releases (leaks) for particular

mass flow rates/hole sizes, continuing over a period of time. Additional research is

required to investigate the factors that affect vapour dispersion from gasoline spills

resulting from an instantaneous release that would be subject to area classification.

These factors potentially include pool size, pool depth, confinement by kerbs or

bunds, the nature and temperature of the underlying surface (e.g. concrete, water),

wind speed, and topography.

3. Application of the EI15 methodology to liquefied natural gas (LNG).EI15does not specifically address LNG, a rapidly growing market and a material thatrecent work has shown presents particular challenges in modelling dispersion. The

research for EI15 will determine whether it aligns with any of the existing and well

established fluid categories or warrants separate treatment. In the latter case hazard

radii would be modelled equivalent to those for materials already addressed. The

intent of each of these technical issues was further discussed with the EI Area

Classification Working Group, which led to the agreed approach described in

Section 3. This research report delivering the project findings aims, so far as is

practicable, to align with EI15, to enable the findings to be integrated into any

future edition.