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FHA / FRA of an LNG Tanker:

FHA / FRA of an LNG Tanker - Nithin Simon

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Purpose and Methodology: Conduct FHA/FRA of an ocean going LNG tanker and recommend the fire protection/mitigation Identify the potential fire hazards. Analyze the potential hazards to identify the impact on personnel and environment . Recommend fire protection/prevention methods.

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Brief Outline of LNG carrier Arrangement of LNG ship is similar to any other cargo ship except the cargo tanks which is uniquely constructed to store the LNG in liquid stage at - 160°C cargo tanks are located inside the inner hull and are capable to maintain the LNG at atmospheric pressure and at extreme low temperature. Mainly two types of cargo containment systems Moss Spherical Tank and Membrane system

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Advantages of Moss Spherical Tank Spherical tanks are more difficult to puncture than membrane tanks unless hit at a vulnerable spot or a bigger explosive charge is used . Greater resistance to sloshing forces In general, spherical tanks are more resilient than membrane tanks Brief Outline of LNG carrier

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Advantages of Membrane System More capacity vs. spherical ship of similar size Suez Canal toll advantage Faster cool-down of tanks Lower cost due to inherent cost of the system and increased competition due to greater shipyard capacity Brief Outline of LNG carrier

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Properties and Characteristics of LNG –Typically ~ 95% methane (CH4) with small amounts of ethane, propane, butane and nitrogen Colorless , odorless, non-toxic, non-carcinogenic and in liquid form is 45% the density of water Vapors will rise under normal atmospheric conditions Can be stored and transported in insulated tanks at standard atmospheric pressure Flammable when mixed with air concentrations between 5% - 15% Has a boiling point of −161 °C (−257.8 °F) at a pressure of one atmosphere

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Potential Fire Hazards Major and Minor Fires In this context a minor fire is defined as a fire in accommodation or Engine room and a major fire is that in the cargo area which cause the LNG to burn

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Accommodation/Deck area Fire hazards Fire from galley b) Fire from smoking in non designated areas c) Fire from short circuits d) Fire from the use of electric heaters, electric iron and the like in non designated places . e) Fire from electric heaters in pantries f) Use if intrinsically unsafe portable equipments on the deck g) Fire from deteriorated insulation for electric cable laid on the deck, mast, and posts . h) Fire from electrostatic discharge Potential Fire Hazards

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Machinery/Engine room area Fire Hazard Faulty ventilation system in cargo pump or compressor rooms causes vapor to accumulate and can caught fire from any ignition source . b) Fuel oil/ lube oil leakage in Engine room getting fire . c) Boiler fire d) Main Engine fire e) Transformer fire Potential Fire Hazards

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Cargo tank area fire hazard Possible cargo leak and fire hazards from any ignition source include Accidental Collision with other ships b) Cargo tank leakage from fatigue structural damage c) Grounding of the ship and bottom damage d) Cargo valve failure/overflow e) Terrorism act Potential Fire Hazards

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Potential fire scenarios The major potential fire scenarios in this case is obviously the cargo (LNG) fire Other Minor fire scenarios are not discussed here in detail as the risk associated with those are comparatively minor when compared to the cargo fire. But it should be noted that if those small fires are not dealt with properly those can lead to the ultimate cargo fire.

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Rapid phase transition (RPT) Pool fires Potential fire scenarios Vapor cloud explosion

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Potential Impact Burning LNG emits thermal radiation that, if intense enough, can cause skin burns on humans exposed to the radiation and can ignite combustible materials on buildings. The more intense the radiation , the shorter is the exposure time needed to cause a skin burn or combustible material ignition . Study by Sandia National Laboratories, New Mexico

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Potential Impact

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Fire Risk Assessment Risk = Pt (threat occurring) x Ps (system failure/threat) x Consequences ; Where: Pt = the probability of an accidental or intentional threat, Ps = the probability that preventive or mitigating measures fail, and Consequences = usually expressed in fatalities or costs.

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Sandia Laboratories Qualitative Risk Assessment

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Fire Protection Recommendations Major Fires (Cargo Fire) Protection Traffic control, safety zones around the vessel while in transit within a port . Escort by Coast Guard vessels, and coordination with local law enforcement Redundant offshore mooring and offloading systems Following the standards designed to prevent groundings, collisions, and steering or propulsion failures . The use of ESD system minimizes potential risks during the transfer of liquefied gases between ship and shore loading and unloading installations. The best way to protect fire is to avoid happening it in first place, mitigation strategies include:

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It is almost impossible to extinguish an LNG spill fire because the fire will be extremely huge, Hence before attempting to tackle a large fire, you should seriously consider allowing the fire to burn itself out. If the fire is to be extinguished Do not use water Use combination of firefighting foam and dry chemical agents Foam of choice here is Hi-Expansion foam Foam must be applied in very large quantities in a very short time Utilize better emergency response systems to reduce fire and dispersion hazards Major Fires (Cargo Fire) Protection Fire Protection Recommendations

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Smoking should only be permitted under controlled conditions . No Fire Except in Designated Places Portable electrical equipment should not be used outside of accommodation spaces unless it is intrinsically safe. Main radio transmitters should not be used and the main aerials should be earthed during cargo . Use of Anti-electrostatic Clothes and Shoes. Use of Electrostatic Discharge Plate Cargo vapor, whether toxic or flammable, should be vented to atmosphere with extreme caution, taking account of regulations and weather conditions. Minor fires in accommodation and Engine room area can lead to major LNG fire, hence protection from that is also equally important. Sources of ignition and precautions can prevent these fires to happen to a great extent Minor Fires Protection Fire Protection Recommendations

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Minor Fires Protection Lighting systems in cargo machinery rooms must be certified flame proof. Gas-tight bulkhead gland seals and air lock doors to cargo machinery electric motor rooms should be carefully checked and maintained to ensure that cargo vapor does not enter . Proper maintenance and inspection of gas detection system In case of accommodation fire or engine room fire the appropriate fire extinguishers must be used depending on the type of fire and extinguish it as early as possible. LNG Tankers are designed with utmost importance fire safety and this is the reason why there are very few accidents happened on LNG tankers. Fire Protection Recommendations

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Standard Active and Passive protections on an LNG carrier Detectors : Standards and codes require that combustible gas detectors and low temperature detectors are located at places where an LNG release might occur and where LNG or low temperature vapors might accumulate. In Europe, the main code is: EN 1473 . In the US, they are: NFPA 59A; 49; CFR Part 193.2507 , Subpart I and 49 CFR Part 127.201-3. These detectors are continuously monitored. They also have alarms set just above the detection levels and automatic shutdowns at hazard levels. Gas-tight bulkhead gland seals and air lock doors to cargo machinery electric motor rooms should be carefully checked and maintained to ensure that cargo vapor does not enter . ESD: IGC Code requires an ESD system. These comprise manual trip points and automatic fire sensors that can initiate remote closure of emergency shutdown valves “for shutting down liquid and vapor cargo transfer between ship and shore” and require that this emergency trip, when activated, must also stop cargo pumps and compressors. Fire Protection Recommendations

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Thank You !