Refinery fires: Firefighting strategies and tactics

Refinery fires: Firefighting strategies and tactics

Petroleum refineries are most hazards industries due to their characteristic of handling, processing and storing different types flammables materials at or above flash point and ignition temperature. There are number of hazards including flammability, toxicity, explosion, physical hazard, noise, ergonomics, electrical hazard, etc. (To know more about types of hazard, click here)

Amongst all the type of hazards, fire, explosion and toxicity hazard are the major concerns in the petroleum refineries. Petroleum refineries fire and explosion can cause massive damage to company installations, loss of life and health hazards to the neighborhood.

Although there are many different hazards in oil refineries but this article provides a detail knowledge on firefighting strategy and tactics for fighting refinery process unit fire, heat exchanger fire,  heater fire, furnace fire, vent fire, sewer fire,  oil terminal/gantry fire, oil tanker fire, storage tank fire, LPG fire, Natural gas fire, etc

Fire hazards in petroleum refinery

Petroleum refinery inherently possess high risk of fire and explosion due to processing and storing highly flammable material. Crude oil is blend of number of hydrocarbons itself hazardous due to its flammability property and toxic contents. In refinery process, the high temperature and pressure adding the risk. Petroleum products are handled in pipeline, exchangers, pumps, vessels and columns at or above their autoignition temperature, thus in case of any leakage, immediately catches fire.

Gas like hydrogen is highly flammable, only 0.019 mJ ignition energy required to fire or explosion. All the hydrocarbon vapors are heavier than air and forms vapour cloud, during leak may cause explosion after getting ignition. As per Lewis and von Elbe, minimum ignition energy required to ignite vapours of hydrocarbon like butane, propane, motor spirit (gasoline) and gases like methane and ethane is about 0.1 mJ.

There are explosion hazards in exchanges, reactors, furnace, columns and vessels due to high temperature and pressure.

During refinery maintenance or catalyst replacement work, there is always risk of pyrophoric fire due to traces of ferrous sulfate formation.

Hydrogen sulfide is deadliest gas in petroleum refinery due its characteristic of flammability and toxicity.

Bulk storage of crude oil, finished product like motor spirit, diesel, ATF, kerosene, ethanol, intermediate products and highly flammable liquefied petroleum gas (LPG) adding the risk of fire and explosion in oil refinery.

Other fire hazards are electrical equipment, appliances, cables, oil field transformers, coal or fuel in captive power plants, UPS batteries, open flame in refinery flare, hot work inside refinery operating units, etc.

Below are the special fire and explosion hazards in oil refinery

Boiling Liquid Expanding Vapour Explosion (BLEVE):  It is an explosion of container (sphere, vessel, tanker, cylinder, etc) containing flammable liquid/liquified gas caused by over pressurization due to boiling of the liquid. This usually occurs due to the prolonged heating of the container and liquid/ liquified material reached at its boiling point, therefore the conversion rate from liquid  to vapour is higher than the release rate through safety relief valve/ vent, which increases the pressure inside the container. In addition, when the liquid converted to gas, it expands and creates more pressure inside the container, for example, expansion ratio of LPG from liquid phase to vapour phase is 1: 270 (i.e. 1 liter of liquid expands to 270 liters of vapour/gas).

BLEVE

Three main factors responsible for BLEVE, one is the over pressurization due to the boiling of liquid, the second vaporization rate is more than venting and the third is material loose it’s tensile strain due to prolong heating by an external flame.

These three factors resulted in a catastrophic rupture of container and the pressurized flammable vapour released suddenly in the form of massive explosion called BLEVE.

A secondary fire in nearby facility can be caused by shock wave and propelled pieces of container.

Unconfined vapour cloud explosion (UVCE): It is a delayed explosion of released flammable vapor/ gas away from point of leak source after the formation of flammable mixture in an unconfined area.

UVCE occurred when flammable gas released into the atmosphere, after some delay, forms a vapour cloud and ignited by ignition source away from its point of leak source resulted into deflagration.

In UVCE, the flame propagate at an ultrasonic velocity thus produces shock waves and destroys the entire installation covered under the cloud.

A secondary fire in the facility can be caused by shock wave and direct contact of fire and explosion.

If the gas is heavier than air (LPG, vapours of gasoline, diesel, kerosene and other hydrocarbons), the flammable cloud covers more area whereas lighter gas (hydrogen, methane, etc) forms less flammable cloud because it disperses easily.

Flash fire: It is the ignition of flammable vapour/gas mixture within its flammable range immediately after it’s released from the source. This type of fire doesn’t cause an explosion, but the flame burns back against vopour cloud.

Pool fire: Spillage of flammable / combustible liquid forms pool on surface and ignites by an ignition source, such fires called as pool fire. It is surface fire in vapours of liquid. The flammable liquid layer can be on the direct surface of the ground or float on another liquid such as water.

Jet fire: The release of gas, vapor, or liquid from the container above atmospheric pressure and causes a fire due to ignition, called as jet fire. It is a 3D fire in the form of a jet.

Boil over: Boil over is a violent eruption of viscous liquid such as crude oil from the storage tank due to an extended fire scenario.

Boil-over in crude oil storage tank

Due to the prolonged fire in storage tank of viscous oil such as crude oil, the lighter product pushed up whereas heavier product pushed down due to density difference in the form of heat wave. The temperature of hot oil is approximately 350 degree Celsius which forms the heat wave and travels downward at a speed of about 15 to 20 inches per hour. When this heatwave reaches the bottom of the tank, it heats the water available there. The water get boiled and converted into steam, as the water to steam conversion ratio is 1:1700, the steam pushing the oil in the form of bubbles but viscous fuel resists to release it from its surface and thus building tremendous pressure. The steam gives a piston effect and finally it erupted with large volume of liquids and forms a fire ball. The erupted oil spreads beyond the dyke wall and causes secondary fires.  This event occurred several hours after the combustion of oil in a storage tank.

Slope overs:

Slope over in oil storage tank

At initial stage of oil storage tank firefighting operation, when foam encounters hot surface of the burning oil, a sudden expansion of the oil occurs, increases the volume and begins to overflow, this phenomenon is called as slope over.

Fire due to spontaneous ignition: When pyrophoric material exposed to air, it starts burning without any external ignition source, this fire called as fire due to spontaneous ignition.

During shutdown activities in refinery and petrochemical, pyrophoric material (iron sulfide) can be found accumulated at inner surface of equipment, columns and vessels handling oil with sulfur contains. When it exposed to air, spontaneous ignition occurs even at low temperatures.

Ground fire due to refinery flares: During process upset, a heavy load of hydrocarbon vapours is diverted to the flare system,  knock out drum (KOD) gets overfilled with condensed liquid as well as water seal system can be failed thus liquid reaches at the tip of the flare and burning liquid spreads near the flare area causing ground fire.

Fire safety in refinery and petrochemical industries

National and international standards are available for refinery and petrochemical fire safety systems which provides the detail guideline on designing and installation of complex. Modern technology provides the PLC base safety systems including various interlocks, blow down system, venting systems, etc.

There are two types of fire safety systems, passive and active. Passive fire protection system is as-built system which prevent the occurrence of unwanted events or minimizes the consequences without much human intervention. Active fire safety system may be automated or manual and comes into action after the occurrences of event. Typically, passive fire safety system is for prevention and active fire safety system is for protection.

Refinery fire protection system

Refinery fire protection system is broadly divided into two category, passive and active.

Typically, passive fire protection system is provided to protect the system or structures from failure, for example, fire proofing of steel structures, columns, pipe rack, vessels, etc.  Separation barrier or fire wall is provided to prevent the spread of fire and to protect the nearby facility/ equipment from thermal radiation.

Dyke wall around the storage tanks is also an important passive fire protection system in oil refinery. Dyke wall is provided for storage tanks to contain the leaked oil. Compartmentation provided in building area to prevent the spread of fire and smoke. Trip interlock is also one of the types of passive fire protection system provided in process units for various systems and equipment to safely isolating or shutdown the equipment. It is also provided in HVAC system to activate the dampers.

Active fire protection system is broadly divided into four categories and can be used to control the fire, extinguish the fire, and/ or provide exposure protection to prevent domino effects. Active firefighting system in oil and gas industry is maintained by dedicated company fire department.

1. Portable firefighting equipment: It includes portable fire extinguishers, fire buckets, hose reel, foam trolley, etc. Adequacy and placement can be done with reference of NFPA-10.

2. Fixed fire protection systems: here are the fixed fire protection systems widely used in refinery and petrochemical industries. 

2.1 Water based fixed fire protection system: It includes, Fire water pumps with fire hydrants and fire monitors, medium velocity water spray system (MVWS) for exposure protection, high velocity water spray system (HVWS) for extinguishing the fire, sprinkler system is for exposure protection as well as extinguishing the fire, fixed foam injection and pouring system, water mist system, etc. Deluge system is not a separate system, it is component of water spray system. Deluge valve is provided in water spray system to activate the system automatically or remote manually. API 2030 provides the detail guideline on water spray system.

2.2 Clean gas fire protection fixed system: It can be total flooding type or/and local application system type. These systems are suitable for protecting control rooms, satellite buildings, generator rooms, battery rooms, cable cellars, etc. NFPA 2001 provides detail guideline of clean agent fire extinguishing system.

2.3 DCP based fixed protection system: This type of system can be used to protect transformers, electrical motors and pumps, hot oil pumps, reactors flanges, heat exchanger flanges and other hot equipment where application of water is restricted to prevent thermal effect.

2.4. Fixed steam fire protection system

This type of system can be used to protect the flanges of hot oil handling equipment, vessel and columns like reactor flange, exchanger flanges and hot oil pump flanges where application of water is restricted to prevent thermal effect.

2.5 Rim seal fire protection system: It is a fixed type automatic fire protection system intended to protect the rim seal area of the floating roof tank, the detection ring and the foam pouring nozzles are placed between the primary and secondary seal of the floating roof and foam modules are mounted on the roof. The fire is detected by the detection / sensor ring and activates the foam modules, so the foam is poured between the primary and secondary ring and extinguishes the fire at its incipient stage.

3. Semi-fixed fire protection system: This type of system has fixed piping but requires supply of fire extinguishing media from external sources, for example, the foam pourer system on floating roof and fixed roof storage tank have fixed piping with collecting head at outside the dike wall. In the event of a fire, fire vehicles are used to feed the foam solution into the system in order to apply it to the surface of the hot oil in the tanks or in the area of the rim seal of the floating roof tank.

4. Mobile fire protection system: It includes fire engines/ tender (fire trucks), Trailer mounted pumps, Trailer mounted high-volume long-range monitors, Trolley mounted DCP units and foam units.

Fire trucks are of various type like Foam fire tender, water tender, water bowser, Foam nurser, Combine fire tender, crash fire tender, DCP fire tender, etc.

Firefighting strategies and tactics

Refinery Process unit firefighting method

Without isolating the source or cutting off the fuel supply, it is very difficult to extinguish refinery process unit fires. Starvation (elimination of fuel) is the best technique to fight process unit fires.

This can be achieved by making operational changes to reduce the flow, volume and pressure. Steam can be introduced in the affected systems or equipment to minimize the fuel concentration and by blow down the sections of the unit as required.

Appropriate and effective firefighting method, strategies and tactics should be decided taking into account the location, type of equipment on fire, process parameters, type of fuel and the intensity of a fire.

Small fires can be fought with dry chemical powder, CO2, steam or foam depending on the type and class of fire.

Water in the form of spray is most effective on large area of intense fire which threaten to damage support structures and adjacent equipment. However, the use of water may cause flanges and joints to leak due to thermal shock and my responsible for adding fuel to the fire. Adjusting the water stream to spray or fog will reduce this danger.

Note: Foam should only be used if it can cover burning fuel or leaking hydrocarbon liquid / which has spilled on the ground, i.e. a pool fire.

You may interested to read more on Basic process control system and SIL calculation

 Click here to read other article - Layer of protection analysis (LOPA)

Refinery Exchanger and transfer line firefighting techniques

In most cases, exchanger and transfer line fires are the result of abrupt changes in process parameters viz temperature and sometime pressure too. Therefore, make an effort to restore the normal operating temperature of the equipment.

Heat Exchange fires

Apply steam or DCP or both together to the point of leak to extinguish the fire. If the fire cannot be extinguished using portable equipment due to accessibility problem, use DCP fire tender (DCP fire engine). 

Apply water spray to the immediate vicinity of the leak to prevent fires from radiant heat. The deluge water spray system can be used to cool the nearby structure and equipment, but the decision should be made in coordination with operations manager. However, the use of water can cause flanges and joints/seals to leak due to thermal shock and may responsible for adding fuel to the fire.

Inaccessible pipe rack, structures, and other nearby equipment including vessels and columns that are not provided with fixed water spray system and exposed by flame impingement, can be protected by applying water spray from ground fire water monitors and handlines. Fire water monitors and hand line nozzles should be in spray mode.

Apply firefighting foam to the ground/trenches where burning oil may accumulate. To prevent the spread of fire in the sewer drain, it should be immediately covered. Avoid working above sewer drains or near fire traps as there is a risk of explosion.

Maintain adequate drainage of the fire area and must notify the waste water treatment plant of its preparation.

Firefighting strategy for open Relief valve vent fires

Extinguish the fire by applying Dry chemical powder (DCP). If there is evidence that a relief valve has opened and will not reset, shutdown the equipment ie. take the equipment out of service and depressurise it.

If the liquid hydrocarbon overflows from the vent, apply high pressure water fog/spray working upwards from the lowest flames.

Apply water spray to the entire structure engulfed in the flame to the point of advantage around the base of the structure to avoid heat damage to structural elements.

Electrical Machinery firefighting method

Machinery on fire must be switched off and start the standby machine, if possible. Apply carbon-dioxide or DCP to extinguish the fire. Do not use water or fire fighting foam as it may cause electrocution. De-energise the circuit, if possible.

Refinery Pump and compressor firefighting strategies and techniques.

In case of fire in oil pump or compressor, equipment should be shut down and immediately changeover to standby machines. Equipment should be drain out and depressurised the connecting lines, if conditions permit.

Apply steam or dry chemical powder (DCP) from portable extinguishers to the point of leak to extinguish the fire. If the fire is large and portable extinguishers are inadequate to fought the fire, cover the fire area with water spray and direct the jet of high pressure water on the source of fuel until the operators have succeeded in stopping the flow of fuel.

Apply firefighting foam to the ground/trenches where burning oil may accumulate. To prevent the spread of fire in the sewer drain, it should be immediately covered. Don’t work above sewer drains or near fire traps as there is a risk of explosion. Maintain adequate drainage of fire area.

Use deluge water spray system for compressor area to protect the structure from failure. Operate HVWS for firefighting of oil pumps.

Refinery furnace header or tube rupture firefighting method

A header box fire is normally the result of a radical operating change. Injection of steam into the header box will usually extinguish a fire. If it is of significant size and cannot be extinguished with steam, this fire must be treated as a tube rupture fire.

Tube rupture firefighting technique

Preference should be given to removal of hydrocarbon by isolating the supply fuel and depressurise the system. Inject steam into furnace tubes, fire box and header box to inert the atmosphere. Fire can be extinguished by application of dry chemical powder which also help to avoid the reignition.

Water sprays can be used to protect the structural members outside the fire box threatened by flame. As the firefighting foam is ineffective, do not use it.  

Trench or Pit Firefighting techniques

Priority should be given to locate and stop the source of leakage into the trench or pit. Apply steam, CO2 or dry chemical powder to the fire area to extinguish the. If this is not successful, apply medium expansion foam to cover the area faster.

Nearby structures and equipment must be protected by operating the water spray system. In absence of fixed water spray system, use high pressure water spray from fire engines or use water monitors in spray mode.

Avoid overflowing trenches or pits with water since this may cause spread of fire. Don’t allow any person to work near fire traps.

Refinery sewer firefighting method and tactics

Fighting sewer fires in refinery is challenging as there is always a risk of explosion. This type of fire can affect many process units as they may be connected internally though sewer. During the explosion, covers of the sewer manholes can blow out and damage the neighbouring facility.

Steam lancers should be used to inject the steam into the sewers. Other steam hoses can also be directed to sewer outlets in all gaseous areas. All working peoples and emergency personnel must ensure that no one is standing or working on or near the manhole cover and sewer outlets.

Remove the manhole cover at farthest point to release the built-up pressure during application of dry chemical powder from manhole where the flame is visible. High expansion foam can be injected from sewer manhole to extinguish the fire. If foam injection is not possible then direct the water streams into affected trenches to maintain flow.

Refinery firefighting strategy and techniques for oil spill fires

Many vessels and equipment in refinery are mounted aboveground on steel structure platform. The underneath of these equipment, there may also be other equipment handling flammable materials.

Oil spill fires - above ground level

The source of leak must be identified and isolated immediately as early as possible. Equipment should be shutdown, isolated and depressurised to prevent further leakage and to prevent the addition of fuel to the fire. It can be purged with steam if possible.

A small fire can be put out by applying dry chemical powder. Steam lancers can be used, if available.

The deluge water spray system should be used to protect the structure and nearby equipment against radiation heat. In absence of deluge system, water can be applied by fire water monitors and fire hydrants in spray mode.

If an oil leak forms pool at above ground level in oil catch pit area or forms pool at ground level, then firefighting foam must be used to extinguish the fire. Keep in mind that foam is ineffective on 3D fire. If there is pool fire or surface fire, foam may be applied.

Oil spill fire - ground level

The source of the leak must be identified and stopped immediately. If the leak could not be stopped and continue, then system should be shut down and affected part of the system must be put out of service. This affected part of system must be drained, depressurised and purged with steam.

To put out the small fire, steam or dry chemical powder can be used immediately. If the fire spreads over a large area, apply the firefighting foam on pool to blanket it. Foam is the most effective firefighting agent to put out the pool fires.

There may be a risk of fire spreading in the trenches and pit, foam may be applied to control these fires. The nearby steel structure and equipment must be protected from radiation heat by the application of water spray. Water spray can be applied via deluge system or fire engine or ground water monitors or hoses with nozzles. Flooding of fire water can be prevented by maintaining adequate drainage of the fire area.

Firefighting strategy for refinery laboratory fire

This type of fire requires different combating procedures because of glass- ware and special types of apparatus and equipment involved.

Use carbon-di-oxide, DCP portable extinguishers on small fires.

In case of large spills of flammable material whether ignited or not, evacuate personnel from the building and cut off fuel, air gas and electrical services to the building. Cut off any other outside source of fuel.

Use water fog or water spray only on fires, which threaten damage to the building structure.

All fire responders must ensure self-content breathing apparatus. Entry is restricted in smoke-filled area without appropriate respiratory protection.  Laboratory supplies include many chemicals which may emit toxic vapours when exposed to fire.

Firefighting strategy and tactics for fighting storage tank fires

Oil storage tank firefighting strategy

Before attempting to extinguish the fire in the oil storage tank, fire in the surrounding area i.e. in the dyke should be extinguished first to prevent heating of stored fuel.

To know more details about firefighting strategy and techniques for large diameter storage tank full surface fires, read below article

FULL SURFACE STORAGE TANK FIRE FIGHTINGSTRATEGY

Cooling of adjacent tanks (within the same dyke those are not on fire but exposing to radiation heat) must be ensured by operating tank shell water spray system. this will help to minimize the vaporization of oil and to reduce the risk of fire spread. It means that water cooling system must be operated for both tanks, those on fire and adjacent tank without fire too.

If the adjacent tank is floating roof type, then it is important to apply firefighting foam on seal area of adjacent tank as precaution to prevent ignition.

Burning surface of crude oil in tank develops a heat wave which may travels downwards at a rate of 15 to 40 inches/hr. Temperature of oil may reaches to 260 to 350 0C. When this heat wave reaches to the tank bottom, where some settled water is generally present, it will cause a violent “Boil-Over.”

Burning oil first erupts and then falls, spreading even beyond the dyke of the tank. The columns of the flame can be very widely spread at the base. The beginning of a boil over is indicated by both increase in height and in brightness of the flames prior to actual eruption of the boiling oil. In such scenario, all personnel including firefighters must be immediately evacuated from that area.  

In case of explosion in fixed roof tank, the semi-fixed foam system is liable to get damaged and use of foam may get waste. Under such circumstances, the only option is to apply the foam over the tank using HVLRM.

Storage tank firefighting - Fixed roof tank fire

(Light to Heavy Oils)

Prioritize the firefighting operation in case of tank fire along with fire in dyke. Extinguish the dyke fire first by applying medium expansion foam to reduce heat input to tank contents.

Operate tank shell cooling water spray system or apply cooling water streams to tanks shell by use of ground water monitors. Precautions should be taken to prevent the entry into the tank either from run-off or from the water stream since it will destroy the foam blanket.

Apply firefighting foam inside the tank either through fixed foam chamber connections or through other available equipment.

Adjacent tanks cooling systems must be operated to protect them from radiation heat exposure.

Observe the accumulation of firefighting water in tank dyke, open tank dyke valves, to avoid flooding of the tank dykes, if required. However, care should be taken to prevent spread of spilled hydrocarbon.

Oil tank firefighting - Fixed roof tank fire

(FO tanks)

FO tanks are heated and operated at temperatures above 150⁰C and therefore foam cannot be used in these tanks. Precaution should also be taken while using water to cool the pipeline so that no water enters the tank.

Start steam rings in case of failure of breather valve on top of Tank only & combat the Fire using DCP Fire extinguisher. Stop heating coil and reduce internal product temperature.

Extinguish the fire by operating DCP extinguishers (if fire is less than 4 sq. mtr.). If involved fire area is more than 4 sq m. then fire shall be extinguished in combination with DCP tender.

Use water monitors for water curtain, firefighting foam can be used to fight the full surface tank fire.

Firefighting strategy for floating roof tank fire

Floating roof rim seal fires should be extinguished by applying foam through fixed foam system or through foam branch from the top platform.

Firefighting personnel should not go down on the floating roof of a partially filled tank except in extreme circumstances. In case it as absolutely necessary proper safety appliances such as safety belt, lifeline, and fire suit must be used.

Actuate cooling water spray system, in absence of this, apply water jet streams on the affected tank as well as adjacent tanks as required. However, precaution should be taken to avoid water stagnation on the floating roof since it may cause the float unbalanced.

Avoid directing heavy streams of water into the flammable material of the roof edge. This may splash burning product into the roof and increase the seriousness of the fire.

Open Tank dyke drain valves as required to avoid flooding of the dyke area. Care should be taken not to spread hydrocarbons to surrounding areas.

In case of full surface fire, use high capacity HVLRM from two direction, if feasible, to cover the surface of burning liquid.

More details on full surface large diameter tank firefighting strategies, you may read below article

FULL SURFACE STORAGE TANK FIREFIGHTING STRATEGY

Firefighting strategy and tactics for LPG fire

A large leakage of the LPG can form a vapour cloud that can travel up to 1500m, while vapour from the open surfaces of gasoline is not known to travel beyond 50m.

Approach the fire or gas leakage area from upwind or crosswind. All fires (Process Heaters etc.), down wind of leak should be put off or water curtain should be provided immediately.

Evacuate the area within the range of vapour clouds as quickly as possible. In case, escaping LPG is not on fire, activate the ROV to cut off the source of LPG. Water spray is effective in dispersing LPG vapours. The spray stream should be directed across the normal vapour path.

Do not attempt to extinguish the LPG fire unless the source of the leak cut off. A small LPG fire can be extinguished by Dry chemical powder. The extinguishing agent should be directed to the point of vapour release. Immediately start water spray on the leaking LPG to avoid re-ignition.

Application of water spray to control LPG fire

The best method is controlled burning of leaking LPG as it prevents the formation of vapour cloud. The application of sufficient quantity of water to keep the shell of the vessel and piping cool will allow the fire to consume the products without risk of causing failure. It is desirable that the leaks cannot be controlled after extinguishing fire and wherever the leak can be controlled, attempt to extinguish the fire.

Firefighting strategy for LPG storage vessel fire

Do not extinguish the flame except by elimination of fuel, as the accumulation of leaking gas forms a flammable vapour cloud and increases the risk of explosion due to accidental ignition.

Stop the movement of the product in and out of the tank by activating ROVs, etc.

Use the water spray system to cool the shell of LPG vessel/ sphere, if this seems ineffective, use ground water monitors to cool the vessels. Do not apply a solid jet directly on the shell of the LPG vessel/sphere. Always make sure that water application must be in spray mode.

In the event of a fire in the bottom section, apply water spray through fixed/mobile water monitors to the piping assembly/supporting structure. Water cooling should be carried out on the adjacent storage vessels.

Water cooling on the affected vessel should be continued even after the flame has been extinguished until all danger of re-ignition of the hot surfaces or other sources has been eliminated.

Control burning of LPG and water spray for cooling

Water spray protection for fire fighters should be provided continuously as long as the danger of vapour cloud persists.

If possible, pump water into the vessel to float the flammable material above the leak point in the vessel/sphere. This will extinguish the flames if the rate of water pumping exceeds the rate of leakage (an attempt should only be made when competent to do so).

If a shell failure occurs below the liquid level in the vessel/sphere and results in a leak that exceeds the capacity of the water pumping facility, several solid streams of water should be directed on the shell surrounding the leak.

Try to form a curtain of water spray and maintain it until all flammable material i.e. LPG has been consumed and the vessel has become gas-free by natural ventilation or by the addition of steam in the vapour space of the sphere/vessel.

Before resuming the plant operations after the end of firefighting, a gas test should be carried out in pits, trenches or dykes where gas or heavy vapours could accumulate. Portable gas detectors should be used to check for the presence of flammable gas. Similar precautions and firefighting operation must be followed in the event of fire in the LPG recovery Unit.

Secured the site for preserving the evidences of incident which may help during process safety incident investigation as part of process safety management

Firefighting strategy and techniques for hydrogen fire

The hydrogen flame is smoke-free and is not visible during the day time. Necessary precaution should be taken during approaching the hydrogen fire.

Hydrogen is extremely flammable and ignites with very less energy (0.02 micro joule). The hydrogen fire turnout should be accompanied by DCP tender/ engine. The fire tender/engine must be parked in the upwind direction and firefighting operation must be initiated from upwind /cross wind.

Actuate the deluge system manually for all adjacent as well as  H2 spheres which is on fire, if it is not activated automatically.

Stop the transfer/ receive of H2 by shut down the compressor & try to close all associated valves.

Operate fire water monitors for additional cooling & shielding for firefighters. Use hand lines for the water curtain to protect from radiation heat.

After fighting the fire, check the LEL at the point of leakage. Continue to cool the sphere/compressor/ pipeline for an additional 30 minutes.

If the gas is leaking from the pipeline/source without burning , measures must first be  taken to stop the leak, the water fog or spray is effectively used to disperse the explosive mixture.

If the gas is already burning , it can be dangerous to extinguish the flame and allow the gas to flow and burn , otherwise an explosive mixture may form with air which , if ignited , can cause considerable damage more important than if the original fire had been allowed to burn . The best method to extinguish a gas fire is to stop the gas flow.

Firefighting method for natural gas fire

The appropriate extinguishing medium is dry chemical powder (DCP) and the water is intended for cooling in spraying mode. The Leak will form explosive mixtures which may travel to source of ignition and cause a flash back. The compressor and piping may be exposed to fire and may vent and release flammable gases through pressure relief devices. The pipeline can explode when heated.

Gas fires must not be extinguished unless the flow of gas is stopped.

Fire crews must wear a self-contained breathing apparatus (SCBA) and a multilayer nomex suit.

Natural gas is lighter than air and will vent upward, but special consideration should be paid to areas that may trap or contain explosive concentrations, including areas of potential migration underground or through structures.

Water spray can be used to cool surrounding structures, including the compressor, pumps, pipeline, etc.

Firefighting strategy and tactics for rail wagon fire (Liquid Fire)

All the loading and unloading operations must be suspended immediately in the affected area and isolate the respective lines to minimize the risk of fire escalation.

Close the cover/ domes of all unaffected wagons as much as possible.

Isolate the tanker/ wagon on fire from other tankers those are not involved in the fire by using water spray through hose lines.

Apply cooling water spray streams through hose lines/fixed water monitors to the fire affected wagon, adjacent wagons and other nearby equipment.

Remove unaffected wagons from the fire areas as quickly as possible. Use a water screen to protect against radiation heat for undertaking wagon removal or other operations.

Extinguish all ground fires before attempting to extinguish the fire on tanker/ wagon.

After containing the fire on the wagon, use firefighting foam or dry chemical powder to extinguish the fire. Water spray should be continued for some time after the fire has been extinguished to prevent re-ignition.

Salvage as much un-burnt liquid as possible.

Firefighting strategy and tactics for rail wagon fire (LPG)

In the event of LPG wagons fire, similar precautions to those of LPG storage vessels should be followed, whenever possible. However, the DCP should only be used to extinguish the fire and water for cooling.

Stop all pumping/loading operations.

Close block valves on pipelines to affected wagon, LPG vessel/sphere as well as loading lines to gantry.

Isolate the burning LPG wagon from other wagon trucks that are not yet involved in the fire.

Apply cooling water in spray mode from fixed water monitors as well as hose lines to completely cool the wagon trucks.

Protect adjacent refinery equipment and other tank trucks with a cooling water stream.

When the fire is contained using water spray streams, apply DCP and foam to extinguish the flames. The cooling streams must be maintained even after the flame has been extinguished until all danger of re-ignition of the hot surfaces has been eliminated. Salvage as much un-burnt oil as possible.

Firefighting techniques for sulphur fire

Evacuate the area and fight the fire from a safe distance with self-contained breathing apparatus (SCBA)  and full protective gear.

During a fire, irritating and highly toxic gases may be generated by thermal decomposition or combustion.

Dust may present an explosion hazard when exposed to heat or flame. Water spraying is effective in dispersing the explosive dust cloud.

Flammable solid, can burn rapidly with flaring effect, may re-ignite after the fire is extinguished. For large fires, use water spray, fog or regular foam. 

Do not disturb the fire by using a water jet. CO₂, DCP, Steam may be used to extinguish the fire in molten sulphur.

Conclusion

Oil refinery and Petroleum industries  inherently possess high risk of fire and explosion due to processing and storing highly flammable material. In this article we have discussed various firefighting method, strategies and tactics to manage the fire and explosion hazards to save the life and property. Process fires can be extinguished effectively by ensuring adequate and effective firefighting strategies and techniques, but the major control is to isolate the fuel supply. Crude oil storage tank fire is challenging as possess boil over hazard and required effective firefighting strategy with numerous resources.  Exchanger fires possess explosion hazard and application of water may lead to thermal shock therefore DCP/steam are the best firefighting media to extinguish the fire. Flammable gas fire should not be attempted to extinguish as it may cause vapour cloud and increase risk of vapour clod explosion. 

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