Assessment of Hydrocarbon Fire Risk and Explosion

7/28/2019 Assessment of Hydrocarbon Fire Risk and Explosion

1/33

1

Assessment of Hydrocarbon Explosion and Fire Risks

by

Professor Jeom Paik

The LRET Research Collegium

Southampton, 11 July 2 September 2011


2/33

Assessment of Hydrocarbon Explosion and Fire Risksin Offshore Installations:

Recent Advances and Future Trends

Prof. Jeom Kee Paik, DirectorThe LRET Research Center of Excellence

at Pusan National University, Korea


3/33

New Paradigm for Robust Design of Ships and Offshore

Design Formula

Experimental InvestigationExperimental Investigation

Past Experience First PrinciplesFirst Principles

Deterministic ProbabilisticProbabilistic

Mathematical Algor ithm

( )21 1

!lim

! !

m n

xi j

n

r n rx x

= = +

Limit States/RiskLimit States/RiskAllowable Stress

EngineeringEngineering

Various Ocean Environmental Phenomena

Traditional Future


4/33

Trend in Offshore Oil & Gas Production Systems

Fixed type in shallow waters Floating type in deep waters Ship-shaped offshore unit, Semi-sub, Spar, TLP

Pipeline infrastructure Multiple functions such asproduction, storage and offloading


5/33

Vessel (hull), topsides (process facility), mooring, risers/flow lines, subsea, and export system

FPSO for Oil and Gas Production


6/33

Oil/Gas Leak Resulting in Explosion and Fire

Source: HSE


7/33

6th July 1988, UK

167 people ki lled

Property damage of 1.4billion US$

Risk based engineering became mandatory since the Pipe Alpha accident

Pipe Alpha Accident


8/33

20thApril 2010, Gulf of Mexico

11 people killed, 17 people wounded

Environmental damage of approx. 30 bill ion US$

Deepwater Horizon Accident

Oil spil l


9/33

Hydrocarbons can explode through ignition when combined with

an oxidiser (usually air). Thus, when the temperature rises to the point

at which hydrocarbon molecules react spontaneously to an oxidiser,

combustion takes place. This hydrocarbon explosion causes a blast

and a rapid increase in overpressure.

Fire is a combustible vapour or gas that combines with an oxidiser in

a combustion process that is manifested by the evolut ion of l ight, heat,

and flame.

The impact of overpressure from explosions and that of elevated

temperature from fire are the primary concern in terms of the actions that

result from hazards within the risk assessment and management

framework.

Hydrocarbon Explosions and Fires


10/33

Gas burns

Volume

increases

Gas flowincreases

Turbulence

Gas expands

Larger volumepushes unburnt gas

ahead

Unburnt gas pushed

around obstacles

Flame front wrinkled,burning surface greater,increased mixing, faster

burning

BLAST

CONGESTION? CONFINEMENT?

Mechanism of Gas Explosion Depending on Topology and Geometry


11/33

Factors Affecting Explosions and Fires

Wind direction

Wind speed

Leak rate Leak direction

Leak duration

Leak position (x)

Leak position (y)

Leak position (z)

Type of oil or gas (molecules)

Concentration ratio Temperature of oil or gas

(LNG Cryogenic -163 degree C)


12/33

Risk Based Design Process

Hazard

identification (Step1)

Risk

assessment (Step2)

Decision making

recommendations (Step5)

Risk control options

(Step3)

Cost benefit assessment

(Step4)


13/33

What is Risk? How to Manage Risk?

i i

i

R F C=

Asset risk

- Damage to structures and equipment

- Duration of production delay (downtime)

Environmental risk

- Amount of oil that spills out of the offshore installation

Personnel risk

- Loss of l ife


14/33

Trends in Risk Assessment

Qualitative Quantitative

Past Experience Simulation

Experiment,

Deterministic Probabilistic

Specific Scenarios All Possible Scenarios


15/33

API Procedure for Risk-based Design

Does

the facility

meet screenin g

criteria?

Establish performance

criteria

Implement measures to

reduce fire and blast risk

Arenom inal load cases

applicable?

Assess impact o n saf ety

criti cal elements

Are

performance

criteria met?

Assessm ent co mplet efor th e facility

Consider fire and b last risk

Event-by-Event

Risk matrix

Reconsider

or modify conceptor reassess risk wit h

more rigorou s

approach

Modify or select new

concept o r reassess risk

Implement measures to

reduce fire and blast risk

Risk matrix

Assess load and

response for t he event

Are

performance

crit eria met?

Are furt her

risk reduction options

available?

Assessm ent co mplet e

for t he event

As sessm ent co mplet e

ensure goo d practice

Redesign

Yes

No

Yes

No

Yes

Yes

No

Low

Low

Yes

No

NoYes

Medium or Higher

Medium or Higher

Method 1

Designaccording to

guidances is

sufficient if low

consequences

are expected

Method 2

Possibili ty to

omi t load assessment

in certain cases

Method 3

Scenario based

load and

consequence

assessment


16/33

Simulation-based Procedure for Risk-based Design

Dead and live loads Nominal loads Design guidance

System d escriptio n

Definit ion of scenarios

Loads assessment

Design load

Consequence Frequency

Risk evaluation

Risk acceptable Risk unacceptable

Design com plete

Mitigation

Redesign

Performance

acceptance

criteria

Risk

acceptance

criteria

A

B

A: Limi t s tates based des ignB: Risk based design


17/33

Joint Industry Projects


18/33

EFEF JIP - 27th JIP in the WorldExplosion and Fire Engineering of FPSOs

Coordinators:

- Pusan National University, Korea

- Nowatec AS, Norway

Partners:

- DSME, SHI, HHI, ABS, KR, LR- Gexcon, CompuIT, USFOS, UK HSE, NTUA


19/33

Quantitative Gas Explosion Risk Assessment and Management (1/2)


20/33

Selection of credible scenariosinvolving PDF parameters of

leak and environment conditions


gas cloud condition

Explosionfrequencyofexccedance

(perFPSOyear)

Overpressure (MPa)

0 0.02 0.04 0.06 0.08 0.1

0.00001

0.0001

0.001

0.01Large cylindrical vessels (Point 171 )

CAD modelCFD model

Gas dispersion analysis

Explosion CFD simulation Design loads with exceedance curve Nonlinear consequenceanalysis under explosion

EFEF JIP Procedure for Explosion Risk Assessment and Management (2/2)

Latin hypercube sampling technique


21/33

EFEF JIP Fire Risk Assessment and Management (1/2)


22/33


leak and environment conditions

EFEF JIP Procedure for Fire Risk Assessment and Management (2/2)

CAD modelCFD model

Fire CFD simulationDesign loads with exceedance curve

Nonlinear consequenceanalysis under fire

Temperature(K)

Excee

dancefirefrequency(perFPSOyear)

200 400 600 800 1000 1200

0.00001

0.0001

0.001

0.01

0.1

Mean temperature(Point20 and Point31)

Mean temperature(Point41 and Point52)

Latin hypercube sampling technique


23/33

Applied Example: VLCC Class FPSO Topsides


24/33

Effect of Gas Cloud Volume on Maximum Overpressure Comparison between EFEF JIPand Exist ing FPSO Practices

Overpressure(MPa)

Equivalent volume (m3)

0 2000 4000 6000 8000 10000 12000

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

FPSO A

FPSO B

EFEF JIP


25/33

E

xplosionfreq

uencyofexceedance

(perFPSOyear)

Overpressure (MPa)

0 0.02 0.04 0.06 0.08 0.1 0.12

0.00001

0.0001

0.001

0.01

Top process deck(Point 226 & 274)

Solid process deck(Point 76 & 124)

Above the middle process deck(Point 161)

Process decks

Design Explosion Loads with Exceedance Curves


26/33

0 0.02 0.04 0.06 0.08 0.10 0.12 0.14

0

0.02

0.04

0.06

0.08

0. 10

0.12

0.14

RiskacceptedloadFPSOC,D(

MPa)

Risk accepted loadEFEF JIP (MPa)

EFEF JIP vs. FPSO C

EFEF JIP vs. FPSO D

Design Explosion Loads Comparison between EFEF JIP and Existing FPSO Practices


27/33

Temperature(K)

Exceedancefirefrequency(perFPSOyear)

280 300 320 340 360 380

0.0001

0.001

0.01

0.1

0.00001

Separation train 2(Point 77)

Oil inlet(Point 96)

Gas compressor(Point 75)

Surrounding separation train1

Design Fire Loads with Exceedance Curves


28/33

Nonlinear Structural Consequence Analysis Escape Route


29/33

Trends in Risk Assessment

Qualitative Quantitative

Past Experience Simulation

Experiment

Deterministic Probabilistic

Specific Scenarios All Possible Scenarios


30/33

CFD Explosion Simulations

(barg)


31/33

Gas Explosion Tests with or without Water Sprays (1/2)- Importance of Risk Management

Source: The Steel Construction Institute, Fire and Blast Information Group

Without water sprays With water sprays


32/33

0.0

2.0

1.5

1.0

0.5

700100 200 300 400 500 600

Time (ms)

TNO PI-10, Test 10, LDN Nozzles

TNO PI-10, Test 11, MV57 Nozzles

TNO PI-10, Test 12, No Deluge

Source: The Steel Construction Institute, Fire and Blast Information Group

Gas Explosion Tests with or without Water Sprays (2/2)- Importance of Risk Management


33/33

Explosion and Fire Test Facil ities under Construction in Korea

Assessment of Hydrocarbon Fire Risk and Explosion

Documents

Transcript of Assessment of Hydrocarbon Fire Risk and Explosion