Explosion Modelling In Onshore Facilities - Presentation Slides

SOFTWARE

Explosion modelling in onshore facilities: Considerations for congested and confined regions

22 June 2016

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SAFER, SMARTER, GREENER

Speakers

Kenny Shaba Phast and Safeti Product Manager Senior Consultant DNV GL with extensive experience in QRA for both onshore and offshore assets

Mark Hunter Chartered Engineer in DNV GL’s Advisory business 10 years’ experience of safety related studies in the oil & gas sector

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Agenda  Introduction  Congestion and Confinement defined  Explosion modelling approaches – Multi Energy model – Baker Strehlow Tang model  Considerations for congested and confined regions  Case Study  Q&A Ungraded

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Introduction

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Introduction  Explosions are key hazards due to their significant damage potential

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Introduction  Explosions are key hazards due to their significant damage potential  Key incidents include: – Flixborough 1974

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Introduction  Explosions are key hazards due to their significant damage potential  Key incidents include: – Flixborough 1974 – Pasadena 2000

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Introduction  Explosions are key hazards due to their significant damage potential  Key incidents include: – Flixborough 1974 – Pasadena 2000 – Toulouse 2001

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Introduction  Explosions are key hazards due to their significant damage potential  Key incidents include: – Flixborough 1974 – Pasadena 2000 – Toulouse 2001 – Fluxys 2004

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Introduction  Explosions are key hazards due to their significant damage potential  Key incidents include: – Flixborough 1974 – Pasadena 2000 – Toulouse 2001 – Fluxys 2004 – Texas City 2005

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Introduction  Explosions are key hazards due to their significant damage potential  Key incidents include: – Flixborough 1974 – Pasadena 2000 – Toulouse 2001 – Fluxys 2004 – Texas City 2005 – Buncefield 2005

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Introduction  Explosions are key hazards due to their significant damage potential  Key incidents include: – Flixborough 1974 – Pasadena 2000 – Toulouse 2001 – Fluxys 2004 – Texas City 2005 – Buncefield 2005 – Torrance 2015

– Many others

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Introduction (cont’d)

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Introduction (cont’d)  Diverse research initiatives have advanced our knowledge in this area – Experimental and theoretical/empirical

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Introduction (cont’d)  Diverse research initiatives have advanced our knowledge in this area – Experimental and theoretical/empirical  Notable initiatives/projects include – GAME – GAMES – RIGOS

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Introduction (cont’d)  Diverse research initiatives have advanced our knowledge in this area – Experimental and theoretical/empirical  Notable initiatives/projects include – GAME – GAMES – RIGOS

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Introduction (cont’d)  Diverse research initiatives have advanced our knowledge in this area – Experimental and theoretical/empirical  Notable initiatives/projects include – GAME – GAMES – RIGOS

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Introduction (cont’d)  Diverse research initiatives have advanced our knowledge in this area – Experimental and theoretical/empirical  Notable initiatives/projects include – GAME – GAMES – RIGOS

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Introduction (cont’d)  Diverse research initiatives have advanced our knowledge in this area – Experimental and theoretical/empirical  Notable initiatives/projects include – GAME – GAMES – RIGOS  Experimental work done at Spadeadam – World reknown test site

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Introduction (cont’d)  Diverse research initiatives have advanced our knowledge in this area – Experimental and theoretical/empirical  Notable initiatives/projects include – GAME – GAMES – RIGOS  Experimental work done at Spadeadam – World reknown test site

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Introduction (cont’d)  Diverse research initiatives have advanced our knowledge in this area – Experimental and theoretical/empirical  Notable initiatives/projects include – GAME – GAMES – RIGOS  Experimental work done at Spadeadam – World reknown test site

 Learnings from Major Incidents such as Buncefield (“black-swan” event, controversial, still the subject of immense research effort)

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Introduction (cont’d)  Diverse research initiatives have advanced our knowledge in this area – Experimental and theoretical/empirical  Notable initiatives/projects include – GAME – GAMES – RIGOS  Experimental work done at Spadeadam – World reknown test site

 Learnings from Major Incidents such as Buncefield (“black-swan” event, controversial, still the subject of immense research effort)  Key learning outcome: VCEs with appreciable overpressure are only credible when located within confined or congested areas Ungraded

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Congestion and Confinement defined

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Congestion and Confinement defined

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Congestion and Confinement defined

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Congestion and Confinement defined  Many terms are used here and often used interchangeably – but express different concepts

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Congestion and Confinement defined  Many terms are used here and often used interchangeably – but express different concepts

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Congestion and Confinement defined  Many terms are used here and often used interchangeably – but express different concepts  Congestion – Obstacles present in a configuration which will cause turbulence and accelerate a flame if a flammable cloud is ignited inside it  Confinement – Surfaces that constrain the blast wave from dissipating Ungraded 6

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Congestion and Confinement defined  Many terms are used here and often used interchangeably – but express different concepts  Congestion – Obstacles present in a configuration which will cause turbulence and accelerate a flame if a flammable cloud is ignited inside it  Confinement – Surfaces that constrain the blast wave from dissipating Ungraded 6

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Explosion Modelling approaches  Computational Fluid Dynamics (CFD) – Pros – Considered to be the most technically advanced approach – Cons – Time and resource heavy – Not practical for evaluating hundreds of scenarios  Phenemological models (Key focus of this session – ME and BST models) – Pros – Based on experimental data and CFD calculations – Ability to run large amount of scenarios in relatively short time

– Pragmatic, shorter time to results – Cons – Designed to be conservative as less detail is accounted for

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Poll Question

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Multi-Energy Model - Basis Peak Overpressure P0 Peak overpressure = f(obstructions)

x Vapour Cloud

Central Ignition

Blast Wave Ungraded

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Multi-Energy Model – Blast Curves 

Peak Side-On Overpressure

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Multi-Energy Model – GAME Correlations

Guidance for the application of the Multi-energy model (GAME)  3-D Expansion

 VBR . LP  P0  0.84  D    2-D Expansion  VBR . LP  P0  3.38  D  

2.7

SL D

0.7

2.25 2.7

SL D

0.7

LP – Flame Length D – Characteristic Diameter SL – Laminar Burning Velocity

P0 - Peak Side-On Overpressure VBR – Volume Blockage Ratio Ungraded

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2.75

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BST Model - Basis

 Elevated spherical explosion model  Central Ignition  Zone of combustion with peak overpressure  Outside the zone blast wave decays with distance Ungraded

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Baker-Strehlow-Tang Model (BST) - Flame Speed Table  Degree of confinement (2-D, 2.5D, or 3-D) (no 1D in the 2005 tables)  Congestion (high, medium, or low)  Material reactivity (high, medium, or low)

Degree of confinement 2D

2.5D

3D

Low

Medium

High

High

0.59

5.2

5.2

Medium

0.47

0.66

1.6

Low

0.079

0.47

0.66

High

0.47

5.2

5.2

Medium

0.29

0.55

1

Low

0.053

0.35

0.5

High

0.36

5.2

5.2

Medium

0.11

0.44

0.5

Low

0.026

0.23

0.34

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Congestion

Material reactivity

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Baker-Strehlow-Tang Model (BST) - Blast Curves  Like Multi-energy model, BST model assumes that only the vapour cloud in obstructed region generates significant explosions.  Flame speed is used to select blast curves.

 A flame speed table based on confinement, congestion and reactivity is used to determine flame speed of confined explosions

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Considerations for congested and confined regions

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Considerations for congested and confined regions  1. Definition – Physical definition – Elevated regions – Curve selection/First principle approach – Linked regions

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Considerations for congested and confined regions  1. Definition – Physical definition – Elevated regions – Curve selection/First principle approach – Linked regions  2. Modelling – Releases within regions – Assessing degree of overlap of cloud with region – Separation distances

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Considerations for congested and confined regions  1. Definition – Physical definition – Elevated regions

– Ability to run many cases simultaneously

– Curve selection/First principle approach

– Efficient way to report and view results

– Linked regions

– Quick run time

 2. Modelling – Releases within regions – Assessing degree of overlap of cloud with region – Separation distances

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 3. Practical

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Considerations for congested and confined regions  1. Definition – Physical definition – Elevated regions

– Ability to run many cases simultaneously

– Curve selection/First principle approach

– Efficient way to report and view results

– Linked regions

– Quick run time

 2. Modelling

 4. Uncertainty

– Releases within regions

– Handling uncertainty

– Assessing degree of overlap of cloud with region

– Social consent

– Separation distances

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 3. Practical

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– Sensitivity Analysis

Considerations for congested and confined regions - DEFINITION  Approaches to defining regions of congestion – Original work - GAME(S), RIGOS, Dutch Yellow book  Recent work (Pitblado and Alderman et al, 2014) – Reviewed various approaches and came up with this – it is supported by pictures – Useful for existing facilities, but less so for new build – No new science. The goal of this effort was to reduce the variability – Approach to selecting Severity level given – curve selection or first Ungraded principles 16

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Considerations for congested and confined regions - MODELLING

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Considerations for congested and confined regions - MODELLING  Evaluate if the gas clouds reach the congestion – NB gas cloud is transient, hence not one cloud but many clouds

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Considerations for congested and confined regions - MODELLING  Evaluate if the gas clouds reach the congestion – NB gas cloud is transient, hence not one cloud but many clouds  What happens if a release happens within a congestion? If yes – how much is contained within the congestion?

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Considerations for congested and confined regions - MODELLING  Evaluate if the gas clouds reach the congestion – NB gas cloud is transient, hence not one cloud but many clouds  What happens if a release happens within a congestion? If yes – how much is contained within the congestion?

 Size/degree/extent of gas cloud overlap, used to calculate the amount of flammable gas – Calculate on a volume rather than area basis

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Considerations for congested and confined regions - MODELLING  Evaluate if the gas clouds reach the congestion – NB gas cloud is transient, hence not one cloud but many clouds  What happens if a release happens within a congestion? If yes – how much is contained within the congestion?

 Size/degree/extent of gas cloud overlap, used to calculate the amount of flammable gas – Calculate on a volume rather than area basis  Separation distances/potential for regions to overlap and form a single source – The congested areas are linked?

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Cloud interaction with Obstructed Regions

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Considerations for congested and confined regions - PRACTICAL  Practical considerations – Ability to run many cases simultaneously – Efficient way to report and view results – Quick run time  Characterizing Blast Outputs – Side-on overpressure, Reflected overpressure, Impulse, Dynamic overpressure

 Ability to create cumulative contours to threshold levels of interest e.g. 0.2 barg overpressure – Useful for Facility Siting/Escalation analysis

– Can be used to support Building Damage levels (BDL’s) assesments

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Sample result – Single LNG Train

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Sample result – Single LNG Train

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Sample result – Four LNG Trains

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Considerations for congested and confined regions UNCERTAINTY

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Considerations for congested and confined regions UNCERTAINTY  Handling Uncertainty – Key issue as explosion outcomes are highly dependent on the definition of the congested area

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Considerations for congested and confined regions UNCERTAINTY  Handling Uncertainty – Key issue as explosion outcomes are highly dependent on the definition of the congested area

 Social Consent – Get agreement on the assumptions used

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Considerations for congested and confined regions UNCERTAINTY  Handling Uncertainty – Key issue as explosion outcomes are highly dependent on the definition of the congested area

 Social Consent – Get agreement on the assumptions used  Sensitivity Analysis – Evaluate key assumptions – Quick way – assume the cloud will always come into contact with a congested region e.g. global congestion definition. Approach used in the Netherlands with Safeti NL.

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Why are these important?

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Why are these important?  Robust and detailed evaluation of Explosion threats is key to developing an effective management strategy. Why?

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Why are these important?  Robust and detailed evaluation of Explosion threats is key to developing an effective management strategy. Why?

Control of Risks

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Why are these important?  Robust and detailed evaluation of Explosion threats is key to developing an effective management strategy. Why?

Control of Risks  To control risks you have to manage processes to reduce them

Management

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Why are these important?  Robust and detailed evaluation of Explosion threats is key to developing an effective management strategy. Why?

Control of Risks  To control risks you have to manage processes to reduce them

Management  To be able to manage risks you have to understand them.

Understanding

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Why are these important?  Robust and detailed evaluation of Explosion threats is key to developing an effective management strategy. Why?

Control of Risks  To control risks you have to manage processes to reduce them

Management  To be able to manage risks you have to understand them.  To be able to understand risks you have to analyse the risks.

Understanding

Analysis

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Why are these important?  Robust and detailed evaluation of Explosion threats is key to developing an effective management strategy. Why?

Control of Risks  To control risks you have to manage processes to reduce them

Management  To be able to manage risks you have to understand them.  To be able to understand risks you have to analyse the risks.  If you don’t do the analysis you might not fully understand the issues.

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Understanding

Analysis

Why are these important?  Robust and detailed evaluation of Explosion threats is key to developing an effective management strategy. Why?

Control of Risks  To control risks you have to manage processes to reduce them

Management  To be able to manage risks you have to understand them.  To be able to understand risks you have to analyse the risks.  If you don’t do the analysis you might not fully understand the issues.  If you don’t fully understand, you might not be able to target your effort to reduce risks cost effectively and it will be harder to justify your decisions. Ungraded DNV GL ©

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Understanding

Analysis

Considerations for congested and confined regions - RECAP

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Considerations for congested and confined regions - RECAP  1. Definition – Physical definition – Curve selection/First principle approach

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Considerations for congested and confined regions - RECAP  1. Definition – Physical definition – Curve selection/First principle approach  2. Modelling – Releases within regions – Assessing degree of overlap of cloud with region – Separation distances

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Considerations for congested and confined regions - RECAP  1. Definition – Physical definition – Curve selection/First principle approach  2. Modelling – Releases within regions – Assessing degree of overlap of cloud with region – Separation distances

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 3. Practical – Ability to run many cases simultaneously – Efficient way to report and view results – Quick run time

Considerations for congested and confined regions - RECAP  1. Definition – Physical definition – Curve selection/First principle approach  2. Modelling

 3. Practical – Ability to run many cases simultaneously – Efficient way to report and view results – Quick run time

– Releases within regions – Assessing degree of overlap of cloud with region – Separation distances

 4. Uncertainty – Handling uncertainty – Social consent – Sensitivity Analysis

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Considerations for congested and confined regions - RECAP  1. Definition – Physical definition – Curve selection/First principle approach  2. Modelling

 3. Practical – Ability to run many cases simultaneously – Efficient way to report and view results – Quick run time

– Releases within regions – Assessing degree of overlap of cloud with region – Separation distances

 4. Uncertainty – Handling uncertainty – Social consent – Sensitivity Analysis

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References/Works cited  Van den Berg, A., & Mos, A. (2005). Research to improve guidance on separation distance for the multi-energy method (RIGOS) (TNO Report PML 2002-C50 Prepared for the UK Health and Safety Executive: Research Report 369). Rijswijk: TNO Prins Maurits Laboratory.  TNO (The Netherlands Organization of Applied Scientific Research). (1997). Methods for the calculation of Physical effects due to releases of hazardous materials "Yellow Book" CPR 14E. The Hague.  Mercx, W., Van den berg, A., & Van Leeuwen, D. (1998). Application of correlations to quantify the source strength of vapour cloud explosions in realistic situations. Final report for the project: ‘GAMES’. TNO report PML 1998-C53. Rijswijk: TNO Prins Maurits Laboratory.  Pierorazio, A.J., Thomas, J.K., Baker, Q.A. and Ketchum, D.E., 2005. An update to the Baker– Strehlow–Tang vapor cloud explosion prediction methodology flame speed table. Process Safety Progress, 24(1), pp.59-65.  Pitblado, R., J. Alderman, and J. K. Thomas. "Facilitating consistent siting hazard distance predictions using the TNO Multi-Energy Model." Journal of Loss Prevention in the Process Industries 30 (2014): 287-295.  Alderman, J., Connolley, D., Pitblado, R., Thomas, J. K. “Facility siting Rule set for the TNO Multi-Energy model for Congested volumes (PES) and Severity levels.” Presented at 10th Global Congress on Process Safety, New Orleans, LA, March 30 – April 2, 2014. Ungraded

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Case Study

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Onshore Explosion Modelling – Case Study

 Past project using onshore explosion modelling: an LNG Production Plant.  Analysis was carried out for the FEED stage design.

 Overall study was a full QRA, BRA and FEHA – Many different risk results calculated, – Will concentrate on explosion aspects here.  Study carried out using Phast Risk / Safeti.  Explosions done using ME method, defining congested volumes.

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Plant Layout

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Explosion Modelling  Used Multi-Energy method  Congested volumes based on data & experience

LNG Train

= TNO Curve 6 = TNO Curve 7

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Full Results Produced  LSIR plots  SIMOPS LSIR plots (one or two trains operating)  PLL number for site  IRPA number for worker groups  FN Curve  Escalation plots – Fire – Explosion  Explosion and Impulse exceedance curves for each building  10-4 blast loads at key building locations

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Escalation  Plots produced for  Fire: – 200kW/m2 Jet Fire Heat Flux Frequency at 5 minutes – 37.5kW/m2 Heat Flux Frequency at 20 Minutes  Explosion – 350 mbar – 100 mbar – 50 mbar  10-4 per year Overpressure and Impulse with Derived Pulse Duration calculated and tabulated for buildings – Taken at point building experiences highest potential overpressure

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200kW/m2 Jet Fire Heat Flux Frequency at 5 minutes

10-3 per year 10-4 per year 10-5 per year 10-6 per year 10-7 per year

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37.5kW/m2 Heat Flux Frequency at 20 Minutes

10-3 per year 10-4 per year 10-5 per year 10-6 per year 10-7 per year

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350 mbar

10-3 per year 10-4 per year 10-5 per year 10-6 per year 10-7 per year

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100 mbar

10-3 per year 10-4 per year 10-5 per year 10-6 per year 10-7 per year Ungraded

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50 mbar

10-3 per year 10-4 per year 10-5 per year 10-6 per year 10-7 per year

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Building Overpressure Exceedance Curve Example

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Building Impulse Exceedance Curve Example

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10-4 Blast Loads at Key Locations

Building

Side-On Overpressure (mbar)

Impulse (Ns/m2)

Pulse Duration (ms)

Admin Building A

36

230

128

Admin Building B

43

297

139

Substation 1

457

1616

71

Substation 2

314

1141

73

Field Station 1

467

1829

78

Field Station 2

437

1453

66

Field Station 3

145

634

88

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Summary – Case Study  Results produced here were used to:

– Confirm design acceptability – Determine building protection design levels – Plan SIMOPS activities  For explosions, key model inputs were: – Congested volumes – location, dimensions – Selection of TNO curve level

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