flammable liquid fires

7/30/2019 Flammable Liquid Fires

1/5

Flammable Liquid Fires: Measures to Minimise the Hazards Oct 2007 issue page 1/5

Flammable Liquid Fires: Measures to Minimise the Hazards

When controlled, flammable liquids can fuel a vehicle, coat furniture, dissolve soap scum,lubricate a drill press or adhere two plastic pieces. Uncontrolled, they can destroy entire facilities infires and cause tens of millions of pounds in damage and business interruption, as well as harm soiland water supplies through runoff.

Mr Kai Foo Chan, Chief Engineering Technical Specialist of FM Global, gives practical tips on howto minimise fire hazards with flammable liquids and dispels some myths that mislead and couldresult in confusion and human error.

It takes so little just a spark of static electricity to ignite vapours from a flammable liquid leakingout of a ruptured container. Once ignited, burning vapours engulf the entire amount of releasedliquid, producing extremely high temperatures. Within seconds, fire temperature and flame heightcan reach their peaks overtaxing your fire protection system.

Learning from Losses

The following two losses illustrate the extent of damage that can result:

A US$27 million estimated gross loss occurred in a manufacturing plant when workers usingan acetylene soldering torch ignited insulation soaked with heat transfer fluid. Fearing anaccidental discharge, a worker put the fixed automatic CO2 extinguishing system on manualoperation before soldering began. The system failed during the fire because it was installedimproperly. Fire, smoke and water damaged equipment in a sterile production area.

A US$44 million estimated gross loss resulted when a 620MW generator sustained alubricating oil fire. Failure to shut off or bypass oil flowing to the filters of the hydrogen seal oilsystem caused the fire. While cleaning the filters, an employee removed some bolts whichcaused the seal to rupture and release lubricating oil at 70-90psi (483-621kPa). Oil spewedout of the opening, contacted hot piping, and ignited. The generator, two LP turbine sections,steam pipes, oil piping and isophase bus bars sustained extensive damage. The roof over the

turbine generator unit sagged over about a 929sqm (10,000sq ft) area pulling the walls inabout 1.5m (5ft).

Neglect and Lack of Knowledge Two Most Common Human Factors

You cannot change the properties of flammable liquids that create such sudden and intense fires.And it is impossible to exaggerate the nightmare of sustaining a major fire. But no one is powerlessto prevent losses.


2/5


An effective loss prevention programme begins with ensuring that personnel will handle and storethese flammable liquids safely at all times. Employee training is crucial because neglect and lackof knowledge are the two most common human factors in almost every major loss.

Fire severity is the worst hazard of flammable liquids. With fire protection for solids, the goal is tocontain the fire to its point of origin. That cannot be done with liquids. When liquid is pouring acrossthe floor you cannot stop the flow. As the surface area grows, so does the heat release rate.

Three scenarios are typical of flammable liquid fires.

Hot spray fires are the worst. When liquid sprays it produces millions of droplets, each with asurface area; droplets maximise the total surface area available to burn.

Three-dimensional spill fires, typified by a spill falling to the floor from a leaking container,have less surface area than airborne droplets and are thus less severe because the available

surface area is smaller.

Pool fires are the least severe. Liquids are released from a leaking or spilled container and theliquid is contained in a dike.

How to Minimise Hazards

The four best-known methods for curtailing damage are:

1. Drainage2. Isolation

3. Cooling4. Confinement

1. DrainageA well-arranged drainage system on the floor is the best protection you can buy. Ideally itshould be like a trench drainage system designed to remove fuel and all water discharge fromthe building. Drainage protects the building by removing the fuel and protects the environmentby controlling the released liquid and sprinkler discharge. Without drainage, burning fuelspreads inside the building and contaminated water is released to the environment.

2. IsolationFlammable and combustible liquids present a significantly greater fire hazard than most solid

materials. If flammable liquids are secondary to the main process, the best way to minimisethe exposure is to isolate excess quantities of flammable liquid storage.

A separate low-value building or a cutoff room with 1 hour-rated walls (minimum) isrecommended. In cutoff rooms, provide some way to prevent liquids from escaping into themain plant areas. When designing the isolation plan, carefully consider liquid transport routesfrom the point of delivery to the cutoff room; transporting flammable liquids through a facilitypresents the same severe fire hazard as liquid storage or use. Ideally, cutoff rooms should belocated next to the point where liquids are expected to enter a facility.


3/5


3. CoolingThe wet pipe automatic sprinkler system is your first line of defence for controllingtemperatures in a flammable liquid fire; all other protection is supplementary. Sprinklers

extinguish fires that involve high flash point liquids above 93C (200F). They cool the area toprevent structural and equipment damage and dilute water-miscible liquids such as methylalcohol and acetone until they are no longer flammable. Sprinklers also smother fires thatinvolve liquids heavier than water.

Sprinkler discharge will not extinguish fires that involve liquids with low flash points. A fixedspecial protection system such as total flooding to protect an entire room or area, or localapplication for localised hazards may be needed. Available systems include:

Water spray Carbon dioxide and other gaseous suppression systems Dry chemical

Aqueous film-forming foams (AFFF) High expansion foams

4 ConfinementConfine flammable liquids and their vapours inside equipment and piping to prevent vapoursfrom leaking and contacting any ignition source. Provide rapid shutoff in case liquids release.Equipment should hold the weight of the liquid and be able to resist fire, impact, vibration,corrosion and erosion. Process vessel supports should either be made of fire-resistantmaterials such as concrete or protected steel, or be protected with water spray.

Provide open vessels such as dip tanks and some mixers with devices to minimise entry ofsprinkler water. Use emergency bottom drains to direct the flow to a safe disposal point.

Provide open tanks with automatic closing covers. Also provide automatic and remote manualmeans for shutting off product flow in case of equipment failure or fire.

Exploding the Myths

Protecting business property from flammable liquid fires is an enigma even for experts whoregularly test these volatile materials. These recommendations are only guidelines for a basic lossprevention programme. It is up to you to flesh it out. Beyond the basics, myths that mislead usersand codes that can cause confusion lead to the worst threat of all human error.Wrong assumptions contribute heavily to major flammable liquid fires. Many users know theseverity of fire but do not take the threat seriously until it happens. They may be unaware of the

hazards of combustible containers and high flash point liquids, or wrongly assume codes areadequate or fire protection agents on the market are sufficient.

Five myths result from such assumptions:

1. Storage guidelines applicable years ago are still validRecent Factory Mutual Research testing has called for changes in FM Global Property LossPrevention Data Sheet 7-29 flammable liquids in Drums and Small Containers that willaffect several protection methods people have been used to. The new, more stringent criteriainvolve:


4/5


Water-miscible flammable liquids in plastic containers. The former data sheetsprotection for 16oz (500ml) and smaller containers was found to be inadequate.

Solid pile/palletised and rack storage of vegetable and motor oil in small plastic containers.Full-scale testing has uncovered new alternatives including early suppression, fastresponse (ESFR) sprinkler technology.

ESFR protection for small, relieving-style metal containers filled with flammable liquids.

2. Intermediate bulk containers (IBCs) can be protected like 0.21m3 (55gal) metal drumsIf IBCs filled with flammable liquids were only used in transit their exposure would beminimal, but the risk increases greatly when IBCs are stored in warehouses, especiallybecause they can contain up to 2.5m3 (660gal), or an average of 1.14 to 1.51m3 (300 to400gal) of flammable liquid.

Previously called tote tanks and consisting of non-combustible construction, today, IBCs canbe metallic, plastic or some composite of both. Some are simply cardboard boxes with plasticbags inside. IBCs have become popular because they can be filled quickly, moved easily withforklift trucks, are great space-savers and less expensive to ship.

However, when exposed to fire they fail (melt and burn), even with automatic sprinklerprotection, and present a serious risk. Once ignited, this immense fuel load can easily takedown a large building. If many of these containers are stored and one leaks and then ignites,there is potential for cascading failure of the others and an uncontrollable hazard.

Non-combustible metal containers protected by automatic sprinklers will generally not fail andwill not add more liquid to a fire. Preventing or limiting liquid release and removing released

liquid quickly are key elements of flammable liquid fire protection. In a storage area, metalcontainers provide such fuel control.

3. High flash point materials are less problematicMany codes and standards support this idea by calling high flash point liquids combustibleliquids instead of flammable liquids. The reality is flash point does not define the fire hazardis presented by a liquid that will burn. On the contrary, recent loss experience points to manylarge losses involving materials with high flash points such as heat transfer fluids, cutting oilsand mineral oil-based hydraulic fluids. When heated above their flash points, these materialsare just as dangerous as those with low flash points.

People have more respect for low flash point materials. They tend to provide more protection

and use more vigilance. Following FM Global property loss prevention guidelines for high flashpoint materials will minimise damage from a fire just as much as following FM Globalrecommendations for low flash point materials will.

4. New alternative agents workMany have not been tested. You need to know the limitations of these agents and use onlythose that are listed in the current edition of the Factory Mutual Research Approval Guide orare Factory Mutual Research-Approved for a given application. Advertisements, promotionalmaterials and manufacturers literature do not always fully disclose the limitations of theseagents.


5/5


Training is Essential

The myths will prevail as long as people are uninformed. Employee training programmes should be

provided to inform employees about:

Overall impact of a flammable liquid leak from processing equipment or storage containers.

All new and existing hazardous processes.

Step-by-step procedures for carrying out a process, including initial startup, normal operation,temporary conditions, emergency operations (including shut-downs), normal shutdowns, andstartups following outages.

Mechanical integrity. Employees are shown how to maintain mechanical integrity of processequipment to ensure flammable or toxic materials do not escape from equipment. They are also

trained in methods to minimise ignition sources.

Managing change. Changes in storage arrangements or processes must be identified andreviewed before they are implemented.

Incident investigation. All incidents including major accidents and near misses must beinvestigated within a specified time. A system must be established to assure compliance withrecommendations from the investigation.

Ongoing training. All employees who handle flammable liquids should have regular trainingand updates in business changes or new requirements that could affect handling or storage.

In conclusion, trained employees will be well-versed in safe handling procedures and know-how tocontrol ignition. They will be continually updated on guideline changes and involved withmanagement in pre-fire planning and spill response programmes. These employees will beempowered to take prompt, corrective action as needed to minimise flammable liquid hazards andprevent losses.

flammable liquid fires

Documents