Challenges with

Fire & Gas detection and Emergency Shutdown

systems for the modern LNG plants

Presented by: Fabienne Salimi @

BEYOND REGULATORY COMPLIANCE, MAKING SAFETY SECOND NATURE

2010 Mary Kay O’Connor Process Safety Center International Symposium

October 26-28, 2010

LNG Codes

EN 1473 (European code)

NFPA 59A (American code)

AS-3961 (Australian code)

LNG plants are top tier installation according to SEVESO II

(COMAH) classification and their design shall comply at least

with one of the following codes:

Hazardous Materials in LNG Plant

• Condensate

• Methane (Natural gas & LNG)

TNT efficiency: 10%

• Ethane (gas & liquefied)

• Propane (gas & liquefied)

TNT efficiency: 100%

• Butane (gas & liquefied)

• Mixed Refrigerant (gas & liquefied)

Hazardous Material Release

Hazardous Material Release

• 2D Gas dispersion model

• Open door simulation without any

congestion

• Gas and pressurized liquids (>4 barg)

releases in form of directional jet gas or fine

aerosol clouds

AS-3961

2.5.1 Where required an emergency shutdown system shall be

incorporated into any installation that:

(a) includes an atmospheric tank; or

(b) exceeds 300 m3 total capacity; or

(c) includes LNG pumps, compressors or liquefaction plants; or

(d) involves the loading of LNG into tankers.

When operated, such a system shall isolate, shut down, depressurize or otherwise

make safe any equipment whose continued operation could add to or continue an

emergency.

• introduce further hazards, or

• cause damage,

2.5.2 Exceptions

Where the shutdown of particular equipment could:

the shutdown of such equipment may be omitted from the emergency shutdown

system provided that the effects of continued release of flammable or combustible

fluids.

EN 1473

Shutdown Requirement

ESD activation shall be automatic from the fire and gas system with

supplementary activation from local ESD station or central panel.

Exception

ESD activation shall neither cause a new hazard situation nor damage a

machine or other equipment.

How to interpret?

ESD-0

ESD-1

ESD-2

ESD-3

Through telemetry Abandon

ESD-1 of all fire zones

SD-2 of all units in fire zone

SD-3 of all eauipment in unit

Loss of Communication

link

Activate

Fire-f

ightin

g o

n

Equ

ipm

en

t

Unit S

hutd

ow

n a

nd

Trip

all

Equ

ipm

en

t

Perm

issiv

e t

o B

low

do

wn

(+

Part

ial B

D a

re r

ele

va

nt)

Activate

Fire-f

igth

ing

in f

ire

zo

ne

Insta

llatio

n B

lack o

ut

(excep

t E

me

rge

ncy lig

ht)

Clo

se E

SD

V's

Ele

ctr

ica

l Is

ola

tion

(N

orm

al

& e

ssen

tial co

nsu

mers

)

To

tal E

lectr

ica

l Is

ola

tion

(excep

t co

ns.

Suita

ble

fo

r

zo

ne

1)

(1)

PSD-2 Unit Shutdown

PSD-3 Equipment Shutdown PSD-3 Gas PSD-3 Fire

Op

en

BD

V's

Clo

se D

am

pe

rs a

nd

Shu

tdo

wn

HV

AC

Op

en

Equ

ipm

en

t B

DV

's

(as r

ele

bva

nt

and

if

any)

Op

en

/Clo

se S

DV

's

Equ

ipm

en

t S

hutd

ow

n

Ele

ctr

ica

l S

hutd

ow

n o

f

Equ

ipm

en

t

Eq

uip

. F

au

lt

Fire

De

tectio

n

(sp

ecific

eq

uip

me

nt)

Fire

De

tectio

n

(sp

ecific

eq

uip

me

nt)

To

ES

D-1

(6

)

Pro

ce

ss f

au

lt

Po

we

r fa

ilure

PS

LL

/ L

SL

L (

7)

LS

HH

Fla

re d

rum

(5

)

Un

it d

ep

ressu

ratio

n

PS

LL

Fu

el g

as (

3)

Emergency Control

Center

ESD-1 Gas ESD-1 Fire

Fire

de

tectio

n

in F

ire

Zo

ne

ESD-0 Total Black Shutdown

UP

S B

atte

ry L

ow

vo

lag

e (

4)

ESD-1 Fire Zone Emergency Shutdown

Oth

er

Fa

ults

Esse

ntia

l U

tilit

ies if a

ny

Ga

s d

ete

ctio

n

in T

ech

. R

oo

m

Ga

s d

ete

ctio

n

in F

ire

Zo

ne

OROROR

PB

PSSPB

PSS

PB

ESDPB PB

ESD

OR

OR

T

(2

)

T

PB

F&GPB

OR

T

OR

PB

F&G

PBPB

ESDPB

• Safety concept of LNG plants is based on prevention.

• Safety distance and Passive fire protection are the most

effective measures to protect against BLEVE.

• F&G detection coverage is not effective and less than 60%

gas releases are detected.

• Instrumented based safety systems are complicated and operator

may not be able to understand them well.

• Spurious trips are frequent with gas detectors specially when they are exposed to sun or

welding.

• Maintaining F&G system is a headache and we have a steady stream of false alarms despite

our best efforts. IR3 and LOS detectors are more reliable but they are expensive and need

high maintenance.

• Spurious trips are costly and hazardous.

• LNG plants need to time to come down and get back up safely due to the wide temperature

differences between the process and the ambient. Too many shutdown and start-up will

introduce equipment fatigue stresses due to (thermal cycling) and potential failures.

• Quick closure of ESD valves and stop pumps processing the liquefied gas may lead to high

surge pressure and vacuum. Normal relief valves are not quick acting and cannot relief such

pressures. This may lead to further catastrophic ruptures.

• Well trained Operator is reliable. With a good coverage of CCTV operator can respond to fire

in less than 3 minutes or so.

• Operators are always present in plant on 24/7 basis.

ESD-1 is NOT require because:

SD-3 of all eauipment in unit

Activate

Fire-f

ighting o

n

Equip

ment

Unit S

hutd

ow

n a

nd T

rip a

ll

Equip

ment

Perm

issiv

e to B

low

dow

n (

+

Part

ial B

D a

re r

ele

vant)

PSD-2 Unit Shutdown

PSD-3 Equipment Shutdown PSD-3 Gas PSD-3 Fire

Clo

se D

am

pers

and

Shutd

ow

n H

VA

C

Open E

quip

ment B

DV

's

(as r

ele

bvant

and if any)

Open/C

lose S

DV

's

Equip

ment S

hutd

ow

n

Ele

ctr

ical S

hutd

ow

n o

f

Equip

ment

Eq

uip

. F

au

lt

Fire D

ete

ction

(specific

equip

ment)

Fire D

ete

ction

(specific

equip

ment)

To E

SD

-1 (

6)

Pro

ce

ss f

au

lt

Po

we

r fa

ilure

PS

LL

/ L

SL

L (

7)

LS

HH

Fla

re d

rum

(5

)

Un

it d

ep

ressu

ratio

n

PS

LL

Fu

el g

as (

3)

OROROR

PB

PSSPB

PSS

PB

ESDPB PB

ESD

• Material Selection (9% Nickel SS alloy)

• Seismic classification

• Separation of fuel and ignition Sources

• Minimal congestion

• Minimization of flanges

• Impounding basin

• Hazardous area classification/ATEX compliance

• Process trips

• Pressure relief

• F&G detection

• ESD (minimization of isolatable

section)

• Blowdown

• Passive Fire Protection

• Active Fire protection

• There is statutory obligation

• LNG plant works under high pressure and large

inventories. If ESD-1 is not activated on confirmed medium

and large releases then gas cloud certainly which reach a

source of ignition and cause explosion.

• If ESD-1 is not activated on confirmed medium and large

releases then jet fires will damage the unprotected

equipment and structures in less than 15 min and cause

escalation including BLEVE.

• ESD-01 includes numerous executive actions with proper

order and time delays. These actions include isolating the

ignition sources, close the valves, stop machineries and

activate the fire protection systems.

• Due to the low probability of emergency events operators

can have little familiarity with the tasks that they have to

perform. This results in increased likelihood of error. Stress

also increases the likelihood of error.

• Data on human behaviour in fires in buildings shows that

80% - 90% of people assume a fire alarm to be false in the

first instance

• Efficiency of F&G can be improved by better design

including fire & gas mapping, use of diverse detectors and

voting system.

ESD-1 is a MUST because: Through telemetry Abandon

ESD-1 of all fire zones

SD-2 of all units in fire zone

SD-3 of all eauipment in unit

Loss of Communication

link

Activate

Fire-f

ightin

g o

n

Equ

ipm

en

t

Unit S

hutd

ow

n a

nd

Trip

all

Equ

ipm

en

t

Perm

issiv

e t

o B

low

do

wn

(+

Part

ial B

D a

re r

ele

va

nt)

Activate

Fire-f

igth

ing

in f

ire

zo

ne

Insta

llatio

n B

lack o

ut

(excep

t E

me

rge

ncy lig

ht)

Clo

se E

SD

V's

Ele

ctr

ica

l Is

ola

tion

(N

orm

al

& e

ssen

tial co

nsu

mers

)

To

tal E

lectr

ica

l Is

ola

tion

(excep

t co

ns.

Suita

ble

fo

r

zo

ne

1)

(1)

PSD-2 Unit Shutdown

PSD-3 Equipment Shutdown PSD-3 Gas PSD-3 Fire

Op

en

BD

V's

Clo

se D

am

pe

rs a

nd

Shu

tdo

wn

HV

AC

Op

en

Equ

ipm

en

t B

DV

's

(as r

ele

bva

nt

and

if

any)

Op

en

/Clo

se S

DV

's

Equ

ipm

en

t S

hutd

ow

n

Ele

ctr

ica

l S

hutd

ow

n o

f

Equ

ipm

en

t

Equip

. F

ault

Fire

De

tectio

n

(sp

ecific

eq

uip

me

nt)

Fire

De

tectio

n

(sp

ecific

eq

uip

me

nt)

To

ES

D-1

(6

)

Pro

cess fault

Pow

er

failu

re

PS

LL / L

SLL (

7)

LS

HH

Fla

re d

rum

(5)

Un

it d

epre

ssu

ration

PS

LL F

uel gas (

3)

Emergency Control

Center

ESD-1 Gas ESD-1 Fire

Fire d

ete

ction

in F

ire Z

one

ESD-0 Total Black Shutdown

UP

S B

attery

Low

vo

lage (

4)

ESD-1 Fire Zone Emergency Shutdown

Oth

er

Faults

Essential U

tilit

ies if any

Gas d

ete

ction

in T

ech. R

oom

Gas d

ete

ction

in F

ire Z

one

OROROR

PB

PSSPB

PSS

PB

ESDPB PB

ESD

OR

OR

T

(2

)

T

PB

F&GPB

OR

T

OR

PB

F&G

PBPB

ESDPB

It's better to be Safe rather than

Sorry !

Can gas detection get better can better using:

• 3D Gas mapping

• IR Camera

• Acoustic gas detectors

• Cold detection

• Low pressure detection at process

• Diversity, voting system and quantitative SIL

assessment

• Risk based inspection and maintenance

3D Gas mapping

From Shell Global Solution

FLIR Infrared Camera

http://www.flir-press.com

3D Gas Mapping

IR fixed Camera

Gassonic ultrasonic (acoustic) gas leak detectors

http://www.gassonic.com

Sensornet Cold detection

http://www.sensornet.co.uk/

Acoustic gas detectors

Cold detectors

Initiation by operator ≠ No need for ESD-1

Gas detection

Initiates ESD-1 Alarm in CCR

Operator initiates ESD-1

ESD-1 actions• Isolate quickly sources of ignition

• Close ESD valves to isolate source of fuel

• Open the Blowdown valve to send fuel to safe location

• Activate fire protection systems (deluge, CO2, etc.)

Release Time (sec)

Rele

ase

Ra

te (

kg

/se

c)

A

B

C

A = Continuous release by the time that ESDV close the inlet and out lets of isolatable section.

B = Release to accident area between the closure time of the ESDVs and activation of blowdown valve.

C = Release to accident area and release to safe location via vent/flare when

both ESDVs and Blowdown valves are activated

Release Time (sec)

Rele

ase

Ra

te (

kg

/se

c)

A

B

C

A = Continuous release by the time that ESDV close the inlet and out lets of isolatable section.

B = Release to accident area between the closure time of the ESDVs and activation of blowdown valve.

C = Release to accident area and release to safe location via vent/flare when

both ESDVs and Blowdown valves are activated

Relief calculation according to

API 521

API 521 provides guidelines for pressure relief when vessel is exposed to pool

fires.

Liquid pools can be formed by all hydrocarbon products containing pentane

and heavier components but also by butanes/butenes at sub-zero ambient

temperature and low pressures (<4 bara).

9.6 kW/m2 Thermal Radiation

Contour

Fire

X

Fire F

ire

Fire

Jet fire & Escalation

• Intensity of jet fires is much higher

than pool fires.

• For jet fires impingement is the

main concerns and not thermal

radiation.

• Jet fires are directional. . .100

Open pool fires

Large or confined pool

fires

Open Jet fires

Confined Jet fires

.200

.300

.400

Total incident Heat flux (kW/m2)

Fir

e t

yp

e a

nd

se

ve

rity

Fire case

Relief ValveBDV

To Flare

To Flare

Re

ce

ive

r

So

urc

e

9.6 kW/m2 Thermal Radiation

Contour

Receiver Contains Liquefied Gas

Step 1- Fire case relief valve on Receiver opens to protect against

overpressure

Fire case

Relief ValveBDV

To vent

To Safe location

Re

ce

ive

r

So

urc

e

9.6 kW/m2 Thermal Radiation

Contour

Step 2- Following relief liquid level decrease in receiver and vapour part

of vessel is exposed to jet fire.

Receiver Contains Liquefied Gas

Fire case

Relief Valve

BDV

To Flare

To Flare

So

urc

e

Step-3: If Receiver is not protected by passive fire protection it will fail in

less than 15 min and cause BLEVE.

Receiver Contains Liquefied Gas

• Safety distance: distance

between the source & receiver >

jet fire length @ 15min

• Duration of jet fire < 15 min

• Blowdown content of source to

safe location in 15 min

• Relief valve on receiver relief

pressure to reach at 7 bar in 15

min

• Passive fire protection on

receiver to increase the failure

rate of receiver to more than

duration of fire

Need Analysis based on Medium Release

(20 mm)

Thank you for

your kind attention!

For more information contact: fabienne@adepp.com

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