Explosion Analysis of an Onshore Plant with Worked ... · PDF fileQuantitative Risk Analysis, Probabilistic Explosion & MDOF Response Analysis ... onshore installations incl. transport

FABIG TECHNICAL MEETING REVIEW

Explosion Analysis of an Onshore Plant with Worked Examples, Quantitative Risk Analysis,

Probabilistic Explosion & MDOF Response Analysis

Pol Hoorelbeke

Total Petrochemicals

Bob Brewerton/Jerome Renoult

GexCon AS

For further information please contact:Pol HoorelbekeTotal PetrochemicalsTelephone: + 32 02 2883950Fax: + 32 02 2883152E-mail: [email protected]

Jerome Renoult Bob BrewertonGexCon AS GexCon ASTelephone: + 47 55 574330 Telephone: + 44 (0) 1732 465465Fax: + 47 55 574331 Fax: + 44 (0) 1732 469735E-mail: [email protected]@gexcon.com E-mail:

Vapour Cloud Explosion Hazards in Petrochemical onshore facilities

Pol HoorelbekeTotal Petrochemicals HSE

2 20050406, FABIG meeting

ExxonMobil

Shell

BP

Total

ChevronTexaco

ENIConocoPhillips

PDV

Gazprom

Non-OECD based

OECD based

Petronas

Qatar Petroleum

Pemex Saudi Aramco

Saudi Aramco

Adnoc

NIOC

Sonatrach

17%Exxon Mobil

Royal Dutch/Shell

BP

ChevronTexaco

Total

ConocoPhillips

ENI

Pemex

PDV

INOC

KPCAdnocPetrobras

Others NOC

Saudi Aramco

NIOC

OECD based

FSU

China

Non-OECD based

NNPC

Petronas

Libya NOC Sonatrach

Total Petrochemicals is part of the Total group

Oil producers

I.O.C.

N.O.C.

Gas producers

I.O.C.

N.O.C.

17%

Russiaand other

CIS


Total

47 Sites

40 Sites

179 Sites

214 Sites61 Sites

14 Sites

• 110,000 employees

• Turnover: 110 G€

• An energy company Exploration & Production

Gaz & Electricity

Refining & Marketing

Chemicals

555 high risk sites worldwide


Total Petrochemical sites

• Europe: Feluy

Feluy Research

FAO Antwerp

Antwerp Elastomers

Carling

Feyzin

Gonfreville

Notre Dame de Gr.

Lavera Naphta Chimie

Lavera APPRYL

El Prat

Stalybridge

• Middle East Umm Said

“Rass Laffan”

• Asia Sanshui

Singapore

Daesan

Ayutthaya

• USA La Porte

La Porte

Research

Carville

Cosmar

Bayport

Port Arthur

• Others Houston

Brussels

Paris

Lyon

Ets Lacq / Mont

Beijng

Agents

5 20050406, FABIG meetingTypical petrochemical onshore plant


Historical evidence of VCE hazards

• Offshore industry has a relatively recent vapour cloud explosion explosion history: The piper Alpha explosion on the 6th of July 1988 was one of the first

major devastating explosions in offshore. There were 226 people on theplatform at the time of the accident; only 61 survived.

• Onshore Hydrocarbon industry has a much longer vapour cloudaccident history: On the 29th of July 1943 a release occurred from a rail car in the BASF

works at Ludwigshaven. The rail car contained 16,5 te of a mixture of 80% butadiene and 20% of butylene. A vapour cloud formed and ignited. 57 people were killed and 439 injured. The explosion demolished a block 350 m x 100m;

On the 23th of March 2005 a devastating explosion occurred at the BP-Amoco refinery at Texas City. At least 15 people were killed and more than70 injured.


Cracker experience (1975 – 2003)Number of crackers in operation (2002)

78

56

56

37

20

17

6

270

0 50 100 150 200 250 300

Asia

Western Europe

North America

Eastern Europe

Latin America

Middle East

Africa

TOTAL

5564TOTAL

98Africa

191ME

342LA

917EU

1270NA

1288Asia

1458WE

# cracker.yearsRegion

# of major accidents in WE region: 7 Major explosion: 4.8 E-3 per cracker.year

Vapour Cloud Explosions : a real risk in Petrochemicals


• Total Petrochemicals Data Analysis on PE units

ATEC database : 853 PE units in the world

Experience 1987-1996 : 4.979 reactor-line.years

# accidents: 3

99% confidence interval: 7.05 E-5 → 2.29 E-3 per reactor-line.year

Average: 6.25 E-4 per reactor-line.year

• Total Petrochemicals Data Analysis on Low pressure PE reactor-line

experience 1975 – 2003: 6 131 reactor-line.years

3 « Pasadena like accidents » have been identified in this period

99% confidence interval: 5.51 E-5 → 1.79 E-3 per reactor-line.year

Average: 4.89 E-4 per reactor-line.year

Vapour Cloud Explosions : a real risk in Total Petrochemicals

Total Petrochemicals : one VCE every 80 years


Some characteristics of petrochemical onshore installations in relation to VCE hazards

• Large congested areas. A typical congested volume of a large steam cracker could be 150 m x 80 m x 15 m

• Large quantities of flammable materials. A typical major vapour cloud can contain 10 – 50 tons of flammableproducts

• Several zones with dense congestion






VCE approach in onshore industry

• The major concern for onshoreinstallations has been the offsite risk;

• Seveso legislation put emphasis on accident prevention (for onsite andoffsite people) and effect mitigation for off site people

• Simple methods (TNT equivalent, ME, Baker Strehlow, etc.) allow goodpredictions for damage potential in thefar field

Offsite property damage cost

of Toulouse accident is

currently estimated at 1,8 G€

33

31


Simple methods(TNT equivalent, ME) give a goodidea for the far fieldblast load potential

Overpressure-distance for case "a" and case "b"

(ME method & TNT equivalent)

10

100

1000

10000

100000

10 100 1000

Distance (m)

Ov

erp

res

su

re (

mb

arg

)

ME-5a ME-5b ME-7a ME-7b ME-10a

ME-10b TNTa TNTb FLACS


BP-Amoco Refinery Texas City explosion23th of March 2005

1

10

100

1000

0 100 200 300 400 500 600 700 800 900 1000

Distance from Cloud Epicentre (m)

Calc

ula

ted

Bla

st

Overp

ressu

re (

mb

arg

)

ME curve 5

ME curve 6

ME curve 7

ME curve 8-10


Conclusions

• The situation till say 5 years ago was:

Simple methods allowed to cope with the main concerns (i.e.offsiterisk assessment)

Onshore hydrocarbon process industries did not make the sameprofits as offshore facilities and advanced technologies (3D modelling) were expensive

• Even today there is still an important gap between explosion research (theoretical and experimental investigations) andapplication of this research in the plants

• Accidents like Skikda clearly demonstrate the necessity to:

Use advance technology for onshore plants;


Vision of Total Petrochemicals

• Accidents like Skikda clearlydemonstrate the necessity to perform risk assessments ofexplosion effects in the nearfield;

• The near field can only bestudied by means of advancedtechnologies

Technology

Investment

Advanced

modelling

Simple

empirical

correlations

Computational

Fluid Dynamics

• The results of extensive research that has been done over the last 30 yearsshould be applied in the field.

• There is a enormous amount of data and knowledge available but large parts of it remain within a select group of experts;


Skikda, Algeria, Jan 20, 2004

Damage:

23 workers were killed.

9 were missing.

74 were injured.

$800,000,000 (U.S.) estimated property damage.

Quote from LNGWM Alert,

Jan 22, 2004

“The fact that the boiler explosion caused damage to the nearby process equipment raises questions about separation distances in this 1970s vintage process facility”

1 FABIG Technical Meeting – 6th and 7th of April 2005

FABIG Technical Meeting – April 2005

Probabilistic Explosion Analysis

in an Onshore Plant

Presented by Pol Hoorelbeke,

Jérôme Renoult & Robert Brewerton


GexCon is...

Clients

ProcessSafety Dept

International, independent Analyst Alliance Established through Research Institute CMI 1970s Experienced consultants within ATEX/Seveso II, QRAs, EPAs, hazid/hazop and other diciplines Development, sale and support of advanced CFD software with world-wide distribution Protective equipment & system testing and certification

SimulationSoftware

R&DDept

GasExplosion &

Fire Consulting

Dept

Xafe AS(Stavanger)

Lilleaker Consulting

(Oslo)

Associated partnersGexCon AS

A company that offers complete services towards process industries on explosion safety and fire


GexCon provides...• First class competent consultants and project managers

– Cross-diciplinary and fundamental background and approach

– Reputable and in-depth competence – expert level

• Oil and gas safety assessments– QRAs for Topsides, incl. FPSOs/FSOs

– CFD and qualitatively based risk assessments - onshore installations incl. transport systems

– Design Accidental Load (DAL) analysis

• Dust fire and explosion risk– ATEX Explosion Protection Services

– Design Accidental Load

– Area Classifications

– CFD based and qualitative Risk assessments for process facilities and transport systems

• Simulation Software– CFD code FLACS – ventilation, dispersion, explosion/fire, analysis (gas, aerosols, explosives)

– CFD code DESC – ventilation, dispersion, explosion/fire, analysis (dust)

• Experiments & testing (2005)– EU- and JIP-backed activities on gas dispersion, LNG and Hydrogen

– Testing of tools for ’hot work’ in potentially explosive atmospheres

– Independent small to large scale testing of new mitigation principles/systems - certification


The problem

Existing unit

Future unit

What is the risk of escalation in the

future unit in case of an explosion

occurs in the existing unit?


Step by step

The probabilistic explosion analysis is performed based on

advanced CFD simulations using the FLACS code developed by

GexCon. The main steps in the analysis are:

- Build a 3D geometrical model

- Ventilation simulations

- Dispersion simulations

- Explosion simulations

- Explosion risk based on a time dependent ignition model

Structure response analysis

Blast or pressure exceedance curves


Building a 3D model in FLACSBy importing a CAD model (Microstation or PDMS)


Building a 3D model in FLACSFrom drawings and/or photographs


Building a 3D model in FLACSUsing the Anticipated Congestion Method developed by GexCon


Building a 3D model in FLACS


FLACS dispersion simulations

There is an infinite number of possible leak scenarios.

Assumptions need to be made in order to reduce the study to a

limited number of representative scenarios. ≈ 300 simulations are

performed.

Following assumptions are made:

- Ventilation conditions

- Gas composition

- Leak locations

- Leak directions

- Leak rates

- Segment sizes


Ventilation conditionsWind direction frequency

0

5

10

15

20346-015

016-045

046-075

076-105

106-135

136-165

166-195

196-225

226-255

256-285

286-315

316-345

36.5%

22.2% 23.3%

Total = 82%


B HGFEDC QPNML R

Leak locations


B HGFEDC QPNML R

DF402

DF702

R401

E733-S

C701

E733-T

DC301DF401 DF303AE734-S

E309-S

G302A

D723

C301

C401

G722

R202 R201

R200P601A

P301

C302

P702

P705

G720

D720

BE503A

C501

P501

BE705A

D302

G301A

P302

DF201A

Leak locations


B HGFEDC QPNML R

DF402

DF702

R401

E733-S

C701

E733-T

DC301DF401 DF303AE734-S

E309-S

G302A

D723

C301

C401

G722

R202 R201

R200P601A

P301

C302

P702

P705

G720

D720

BE503A

C501

P501

BE705A

D302

G301A

P302

DF201A

Leak locations


46%4%

13%

11% 13% 13%

Leak locations and frequencies


Leak rates and frozen cloud assumption

96 kg/s> 64 kg/s

48 kg/s32 – 64 kg/s

24 kg/s16 – 32 kg/s

12 kg/s8 – 16 kg/s

6 kg/s4 – 8 kg/s

3 kg/s2 – 4 kg/s

1.5 kg/s1 – 2 kg/s

0.75 kg/s< 1 kg/s

Repr. Leak rateLeak rates

Simulated

Estimated


Dispersion simulations

Flammable gas cloud


Dispersion simulations

Flammable gas cloud


FLACS explosion simulations

There is an infinite number of possible explosion scenarios.

Assumptions need to be made in order to reduce the study to a

limited number of representative scenarios. ≈120 simulations are

performed.

Following assumptions are made:

- Gas composition

- Gas cloud sizes

- Gas cloud locations

- Ignition locations


B HGFEDC QPNML R

Gas cloud and ignition locations

7 gas cloud sizes:

4%, 7%, 15%, 22%, 36%, 50% & 100%


Explosion simulations

Pressure



Pressure



Flame


Ignition modelling

• Ignition sources

– Two types of source: continuous and discrete

• Continuous ignition sources will ignite the flammable gas cloud as soon as it reaches the source.

• Discrete ignition sources can ignite a combustible gas cloud at any moment.

– Centre and end ignitions

• Continuous ignition sources are associated to end ignitions only.

• Discrete ignition sources are associated to both centre and end ignitions (50/50).


Ignition modelling

• Ignition intensitiesContinuous Adjustment Factors for Ignition Source Categories # items or sq. meter Adjust Continous

Gas Age Maintenance Manning Technology Overall Module Total

Hot work (# hours per 365*24h) 1.83E-02 1.83E-02

Pump 9.60E-05 Pump 24 0.459 1.06E-03

Compressor 2.30E-03 Compressor 9 0.459 9.50E-03

Generator 3.50E-03 Rotating machinery 0.9 0.85 1 0.6 0.459 Generator 0 0.459 0.00E+00

Electrical equipment * 2.60E-06 Electrical eq. 0.9 0.9 1 0.6 0.486 Electrical eq. * 3000 0.486 3.79E-03

Other equipment * 2.60E-06 Other eq. 0.9 0.9 1 0.6 0.486 Other eq. * 3000 0.486 3.79E-03

Other * 1.30E-06 Other 1 1 1 1 1 Other * 3000 1 3.90E-03

Personnel * 3.00E-06 Personnel 1 0.95 0.6 1 0.57 Personnel * 3000 0.57 5.13E-03

* per m2 exposed to gas SUM 4.54E-02

Discrete Adjustment Factors for Ignition Source Categories # items or sq. meter Adjust Discrete

Gas Age Maintenance Manning Technology Overall Module Total

Pump 2.10E-07 Pump 24 0.459 2.31E-06

Compressor 5.10E-06 Compressor 9 0.459 2.11E-05

Generator 6.20E-06 Rotating machinery 0.9 0.85 1 0.6 0.459 Generator 0 0.459 0.00E+00

Electrical eq. * 2.70E-08 Electrical eq. 0.9 0.9 1 0.6 0.486 Electrical eq. * 3000 0.486 3.94E-05

Other equipment * 2.10E-09 Other eq. 0.9 0.9 1 0.6 0.486 Other eq. * 3000 0.486 3.06E-06

Other * 1.70E-08 Other 1 1 1 1 1 Other * 3000 1 5.10E-05

Personnel * 4.00E-08 Personnel 1 0.95 0.6 1 0.57 Personnel * 3000 0.57 6.84E-05

* per m2 exposed to gas SUM 1.85E-04


Ignition modellingProbability of exceedance – Sensitivity cases

– Offshore philosophy for shutting down ignition sources

• Gas detection = low alarm 15s after leak start, high alarm 30s after leak start

• ESDV = closed 60s after detection

• Continuous ignition sources start to shut down on gas detection, and are closed

2min after gas detection

• Discrete ignition sources reduced to 25% (pump, comp. and equip.) and 50% (elec.) on high alarm, personnel evacuated 30s after high alarm

– Onshore philosophy for shutting down ignition sources

• ESDV = closed 120s after detection

• Continuous ignition sources are not shut down, except for hot work (120s after

leak start) and personnel (120s after leak start)

• Discrete ignition sources: see model


Ignition modelling

Offshore philosophy "

Onshore philosophy " No reduction, except for hot work and personnel

Reduction of continuous ignition sources

0

0.2

0.4

0.6

0.8

1

1.2

0 30 60 90 120 150

Time (s)

Re

du

cti

on

fa

cto

r (-

)

Rotating Machinery

Electrical eq., other eq., personnel


Ignition modellingReduction of discrete ignition sources

0

0.2

0.4

0.6

0.8

1

1.2

0 15 30 45 60 75 90 105 120 135 150

Time (s)

Red

ucti

on

facto

r (-

)

Rotating machinery

Electrical eq. & other eq.

Personnel

Offshore philosophy "

# Onshore philosophy

Reduction of discrete ignition sources

0

0.2

0.4

0.6

0.8

1

1.2

0 300 600 900 1200 1500 1800 2100 2400 2700 3000

Time (s)

Re

du

cti

on

fa

cto

r (-

)

Other sources

Personnel


Explosion frequenciesFrequency of ignited gas clouds

1.00E-09

1.00E-08

1.00E-07

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1 2 3 4 5 6

Gas cloud category (-)

Cu

mu

lati

ve f

req

uen

cy (

n/y

)

Leak 1

Leak 2

Leak 3

Leak 4

Leak 5

Leak 6

Total


Probability of exceedance

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

0.00 0.10 0.20 0.30 0.40 0.50 0.60

Pressure (barg)

Pro

ba

bilit

y (

n/y

)

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

0.00 0.20 0.40 0.60 0.80 1.00 1.20

Time (s)

Pre

ss

ure

(b

arg

)


Example of projectsFeluy (Total) – Polymers

Kollsnes (Statoil) – Gas treatment

Snøhvit (Statoil) – Liquified natural gas

Gonfreville (Total) – Petrochemicals

Page 1

1 Fabig seminar Jan 2005

1) MDOF Explosion response analysis of large refinery plant

By R W Brewerton (GexCon) and C Izatt ( Ove Arup & Partners). April 2005

•Large pressure vessel on high saddles•70m high multi-Loop Reactor •More complex equipment: (future)

www.gexcon.com


2) The problem

Existing unit

Future unit

What is the risk of escalation in the future

unit in case of an explosion occurs in the

existing unit?

Page 2


3) Selected equipment

Raised Vessel 11.5m longx 3.3m dia(MDOF)

Loop reactor 70m high(MDOF)

?


4) Pressure vessel 11.5m x 3.3m dia: Meshing for DYNA analysis

Concrete part

Steel part

Page 3


5) Saddle and shell elements for NLFEA


6) DLM* Method for explosion loading on large obstacles

• DLM = Direct Load Monitoring

• Dominant loading is often like inertia component of wave loading on submerged structures.

Source: HSE OTO 1999-046 ch 6 and FABIG TN8.

Page 4


7) Selection of explosion loading

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

0.00 0.10 0.20 0.30 0.40 0.50 0.60

Pressure (barg)

Pro

bab

ilit

y (

n/y

)

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

0.00 0.20 0.40 0.60 0.80 1.00 1.20

Time (s)

Pre

ss

ure

(b

arg

)


8) Loading Method

501 502

503 504

505

506•Select deterministic load case(s), in this example

for 10-4 return event

•Select upstream and downstream monitor points

(X & Y loads)

•Find pressure at each point (in time domain)

•Calculate differential pressure (eg 504-503, 502-

501) and 506-505

•Decide on pressures on saddle supports

Page 5


9) Point pressure-time histories

•Evaluation of other factors: reflection possibility, saddle

loads, attached pipes, what load factor (1.0, 1.5?)

•Decide whether negative phase to be included: look at the

deflection response for this:

10-4 blast pressures on PP4 - D302

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

0.75 0.80 0.85 0.90 0.95 1.00 1.05Time [s]

Pre

ss

ure

[b

ar]

Point 501

Point 502

Point 503

Point 504

Point 505

Point 506


•Judge movements particularly in relation to pipe

flexibility and stresses.

10) Response: deflections (positive loading phase only)

Page 6


11) Response: Stresses and deflections


•Max Von Mises stress 103

MPa, UF approx 0.4 hence

OK.

•Obtain force plot and:-

•Code check the support

bolts eg to EC3 (hand calcs)

•Code check concrete and

foundation eg to EC code or

ACI

12) Response: Saddle stresses

Page 7


13) Concrete saddle supports

Moment range for D302 support


14) Loop reactor model

Page 8


15) Explosion Loading on medium - small obstacles (DLM or drag Method)

Source: HSE OTO 1999-046 ch 6.

• The monitor points are far from the obstacle .

• Either: use smaller control volumes at the obstacle or use drag method

• In far-field include blast overpressure impulse (with reflection effect)


16) Drag Coefficients CD

Source: Baker, W E, Cox, P A Westine, P S, Kulesz J J and Strehlow R A (1983)

Explosion Hazards and Evaluation, Elsevier Scientific Publishing Company.

•“Drag” pressure = 0.5 V2.

•Pipe design load = 0.5 CD V2 * D

where D is pipe diameter including insulation.

Page 9


•Drag varies with height

•Use CD value of 1.2

17) Drag pressure – time histories


•Peak overpressure is twenty times as high as drag pressure

at this distance (much more equal in near field)

•Treat as Zero-rise-time impulse, with shock reflection factor

of 2.0 and clearance times according to “Explosive shocks in

air” by Kinney and Graham (Springer Verlag Berlin, New York).

18) Explosion overpressure time histories

Fieldpressure

Net force applied to member,(positive phase only)

duration depends on member size

Page 10


•Natural period 1.4 secs therefore response is in “Impulsive”

regime.

•Low DLF for primary: secondary modes will be important.

19) Response: deflections


•Plot max value from dynamic

simulation.

•Assess member resistance.

•Member is a large (hot) coaxial

pipe in steam jacket and both

are structural.

•Nodes are full-strength

gussetted H beam to steam

jacket spool - good for ductility

as in seismic design.

20) Response: Beam forces (max)

Page 11


A201 concrete columns - Moment-axial force demand interaction

--- Bending-axial demand

--- Bending-axial ultimate capacity

21) Response: Concrete column resistance & UF (max)


22) Tank and support structure: relative displacements (important for interconnecting pipes)

•15.5mm max

Page 12


23) Response animation: deflections x 50


24) Response animation: deflections (x50) & beam forces

Page 13


25) Response: deflections (x50) & beam forces at tank


26) Future study: 60 pipe pipe-rack pipe forces: drag

or overpressure dominating?

?

Page 14


27) Recommendations & discussion points

• MDOF analysis is the most reliable method for complex plant.

• Response is like seismic response. Dynamic resistance will not happen on its own: it needs to be built in at early design stage.

• Loading needs careful definition.

• For avoidance of unacceptable domino effects criteria such as10-4

return have to be used carefully.

• Maintain load factor >1.0 (eg 1.5) through design. Only allow 1.0 for final design and ALARP decisions.

• Implement load factor through difference between assessed probable loading and specified design resistance.

Documents

Explosion Analysis of an Onshore Plant with Worked ... · PDF fileQuantitative Risk Analysis, Probabilistic Explosion & MDOF Response Analysis ... onshore installations incl. transport