This presentation adhere to the concept of FLNG processing facility and also shows different hazards associated with it and possible consequences. Assessment of fire impacts by computational fluid dynamics.

1. SEMINAR
Fire Impact Assessment in FLNG
Processing Facilities using
Computational
Fluid Dynamics (CFD)
Presented By-
ADITYA PRAKASH
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2. CONTENTS
 INTRODUCTION
 PROPOSED METHODOLOGY
 APPLICATION OF THE METHODOLOGY
 RESULTS AND DISCUSSION
 RISK ASSESSMENT
 CONCLUSION
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3. INTRODUCTION
 Process facilities are usually equipped with diverse
equipment, control systems and operating procedures.
 Any process deviations from normal operating conditions,
due to:
 errors in the interaction of equipment,
 human factor,
 management and organizational issues make process plants
susceptible to process failures and or accidents.
 After analysing previous major accidents, many lessons were
learnt and safety regulations and designs have been
upgraded.
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 Fires account for 59.5% of the accidents in process industries.
 Need for an efficient means for combating potential fire
accidents.
 Accident modelling relates the causes and effects of events
that lead to accidents is required.
 Accident modelling supports:
a) gathering relevant data
b) creating realistic scenarios of the accident sequence
c) summarizing the gathered data into meaningful information
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 Various models are available, namely :
 Semi-empirical models
 Integral models
 Zone models
 CFD models.
 Analytical models do not represent real condition.
 CFD model is recognized as one of the most powerful tools.
 CFD also helps to visualize effects of the system under various
conditions at different time intervals.
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7. What is FLNG?
 Floating Liquefied Natural Gas
 Emerging technology which is foreseen to be one of the most
promising technologies for exploiting remote and stranded
offshore gas fields.
 FLNG concept is obtained from a mixture of
• land-based LNG
• offshore oil and gas
• marine transport industries.
Function:-
 In FLNG processing facilities, natural gas is treated, processed,
liquefied, stored and offloaded to LNG carriers in the form of
LNG.
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8. ADVANTAGE:-
 Economic
 Environmental advantage due to its distant offshore location
 Better security
DISADVANTAGE:-
 Compact layouts leads to difficulty in:
 emergency evacuation & rescue,
 potential risks to assets and on-board personnel
 Hazardous properties of LNG adds more risk due to its:
cryogenic temperature, flammability and vapour dispersion
 Lack of past experiences or references.
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9. PROPOSED METHODOLOGY
 The overall framework of the methodology –
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10. Steps in Proposed Methodology:
Step 1:
 Developing various credible fire accident scenarios in an FLNG
facility.
 In an offshore processing facility such as an LNG FPSO,
unfavourable events that may escalate to loss of containment
are:
 Gas leak from feed gas & LNG tank rollover
 Vapour, liquid leak from LNG cold box area & jetty line failure
 Gas or liquid leak from refrigeration circuits
 External fire in refrigeration circuits
 Leak from LNG tank & loading arm connection failure
 Liquid spill from LNG tank
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11.  Risks involved are:
 Flash fire, pool fire or jet fire
 VCE or BLEVE
Step 2:
 Identify More credible fire accident scenarios considering
inherent hazards existing in each scenario.
 Various methodologies available for hazard index calculation:
 Dow fire and explosion index.
 Mond fire, explosion and toxicity index.
 Mortality index.
 Hazard Identification and Ranking System (HIRA).
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12.  The MCAS methodology incorporates two studies:
i. Probable damage caused by an accident
ii. Probability of occurrence.
 A more damaging and frequently occurring accident will have
higher credibility.
Step 3:
 CFD simulation of the most credible accident scenarios is
performed.
 CFD model is effective to analyse complicated accident scenarios.
 FDS uses Navier-Stokes equations.
 Effects of thermal loads and temperature on surrounding is
analysed.
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13.  FDS has the capability of simulating :
 Fire and smoke development
 Thermal flow predictions and
 Concentrations of toxic substances released during the fire
Step 4:
 The effects of the fire event are assessed on:
1. Fire impact on humans:
• At different locations, probabilities of having first degree burn,
second degree burn and death are calculated using Equations
where, D= thermal dose
c₁ and c₂ are probit coefficients
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15. 2. Fire impact on assets:
• Based on thermal loads and adiabatic surface temperature.
• Heat load transfer takes place by the combination of
radiation and convection.
• Fires cause structural failure mainly by reducing strength due to
heat and thermal stresses.
• Equipment damage occurs at the heat flux of 37.5 kW/m2 and
the minimum heat intensity for ignition and melting of plastic is
12.5 kW/m2.
• At higher temperatures, the yield strength and the modulus of
elasticity of the steel decrease and the rate of creep increases
significantly. 15

16. • The maximum yield strength and the modulus of elasticity at any
elevated temperatures are:
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17. • Materials used in the process industries lose their 40% of their
strength at temperatures higher than 670 K (396.85 C)
• Lose 80-90% of their strength at temperatures higher than 850 K
(576.85 C).
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18. Step 5:
 In order to estimate the severity of risk, the probabilities of first
degree burn, second degree burn and death are assigned with risk
scores (Si)
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19. APPLICATION OF THE METHODOLOGY
 Scenario Development:
• Scenarios are developed on the basis of inherent hazards.
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20.  Selection of the MCAS:
 Credibility values greater than 0.5 are considered as the MCAS.
 The three most credible fire accident scenarios in decreasing
order of their credibility are as follows;
1. LNG spill due to overfilling or leakage of the tank and forms a
pool with immediate ignition.
2. LNG liquid leak under pressure from a pipe in Mixed Refrigerant
(MR) Module of the liquefaction process, forms a pool and
ignites immediately.
3. Treated two phase hydrocarbon is released under pressure
from a valve and immediate ignition occurs with a pool fire. This
occurs in the PMR module 1.
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21. RESULTS AND DISCUSSION
 Asset Impact:
• Heat flux contour of 37.6 KW/m² in scenarios 1, 2 and 3.
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22. • Adiabatic surface temperature contour higher than 538 C in
scenarios 1, 2 and 3.
• Storage Area 1 contains LNG is more likely to undergo BLEVE.
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23.  Personnel impact:
• Probabilities of human impacts against distance of receptor from
the flame surface in the three scenarios.
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24. • Comparison of fire risk to personnel in (a) scenario 1, (b) scenario 2
and (c) scenario 3.
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25. • This suggests that the scenario 2 may cause more severe
consequences to both assets and personnel than other considered
scenarios.
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26. RISK ASSESSMENT
• Thermal radiation contours are converted into corresponding
risk contours using risk scores.
• Range of these values varies from 1 at the furthest distance
from the fire location to the maximum value of 10 at the flame
surface.
• It is evident that higher risk is available in scenario 2.
• Contrary to the result of MCAS methodology, scenario 2 has
higher impact and risk level than that of scenario 1.
• Credibility assessment , BLEVE is considered.
• In CFD simulation BLEVE is Not considered.
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27. CONCLUSION
 The above methodology can be applied for better
• safety measure design
• fire suppression systems
in order to mitigate or avoid the potential impact of
fire events.
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