Fighting Storage Tank Fires

OISD WORKSHOP THEME: SAFETY CONCERNS & CHALLENGES IN MARKETING

FIGHTING STORAGE TANK FIRES

ByS.K. KAUSHIK

Chief Manager(HSE)Indian Oil Corporation Limited, CO

Date : 15TH FEBRUARY 2013

Causes of tank Fires

Common Fire Scenarios

• Overfill Ground fires/Dyke fires

• Vent fires

• Rimseal fires

• Obstructed full Liquid Surface fires

• Un-obstructed full Liquid Surface fires

Common Fire Scenarios Overfill Ground fires/Dyke fires

• Common in tank farm fires. Jaipur terminal fire &Buncefield fires are examples on this type of fires.

•Result from Piping/valve or tank leak

•If leak occurs without ignition- Isolate all ignition sources.- Cover the spill with foam blanket.

• If ignition does occur treat the fire as a largepool fire & cool the nearby tank, if required.

Common Fire Scenarios Vent fires

• Typically associated with fixed roof tankssuch as cone & internal floating roof tanks.

• Main cause is lightning strike that ignite fugitivevapours. However electric arcing , static dischargeand human activities around the tank can alsocause ignition.

• These are generally less severe type of fires.

• Can be extinguished by Dry Chemical fireextinguisher or by reducing pressure in the tank.

Common Fire Scenarios Rim-seal fires

• Most common in floating roof tanks. 0.16% of all tankswith rim-seal experience a rim-seal fire every year.

• Lightening is the primary cause of Ignition. It isestimated that 95% of rimseal fires are result of lightningstrike.

• Risk of rim-seal fires can be reduced by ensuring tightfitting primary & secondary seals.

• Fire extinguishment can be achieved by rim-seal fireprotection system, semi fixed/ fixed foam pourers orhand lines.

Common Fire Scenarios Obstructed surface fire

• Surface fires where portion of the burning surfaceis blocked by the roof or pan.

• This happens when roof sinks.

• Roof sinking can occur due to variety of reasons suchas :- Rain build up on the roof where there is inadequate

drainage either from plugging or rain amountexceed the design.

- Pontoon gets filled with tank liquid due to leak.- Improper application of fire fighting material during

rim-seal fire.

Roof sunk inside the tank

Common Fire Scenarios Un-Obstructed full surface fire

• Full surface of the fuel in tank is on fire.

• Happens generally in fixed roof tanks when roofgets lifted off the tank. May happen in floating rooftanks also incase of roof sinking.

Common Fire Scenarios Un-Obstructed full surface fire

Largest successfully extinguished full surface fireoccurred on 8th June 2001 in Noroco, Louisiana where82m. Dia. tank was struck by lightning. The tank wasextinguished in 65 minutes of suppression activity. Fireextinguished after 13 hrs of occurrence.

Fire can be handled by using foam pourers & highcapacity foam monitors.

Handling Storage Tank Fires

Pre-Incident Response Planning

• Tank Fires are complex events.

• Well planned & tested pre-incident planning is needed.

• If plan is not achieving desired result during a fire,change the strategy & tactics to achieve safety & success.

Handling Storage Tank FiresPre-Incident Response Planning

Pre-Incident Response Planning involves following points :

1.Construction :Collect construction details of tanks & tank-farm, piping in the area. Inter-distances of the tanks to find out requirement of cooling.

It is now accepted theory that you should not cool the tank unless you can cool it evenly all around. Uneven cooling may result into failure of tank shell.


2. Occupancy : - Witn-in Tank farm and other facilities nearby. - Capacity Size & Number of tanks etc.

3. Apparatus & Staffing :- Is your fire dept equipped to perform fire fighting on storage tanks.

- How much foam do you carry.- What size & type of monitors available(portable/fixed)- How many persons respond from your dept. Are they adequate to deploy the resources required.


4. Life Hazard : - Should be given topmost priority . - Consider employees as well as surrounding community.- Employees on duty including contract persons.- What are usual work area & how accounting shall be

done. 5.Terrain:

- Area around tank-farm & its suitability for deployment fire fighting equipment.

- Size & width of the approach roads to the facility & within the facility for large fire fighting appliances.

- Containment & control of water run-off. Water run off may also contain flammables.


6. Water Supply :- Ensure adequate supply of water for extinguishment,

cooling & vapour suppression. - Ensure consistent water supply. - Additional resources available nearby and means of transport of water like large diameter hoses, pumps etc.


7. Training & Deployment:- SOP’s for operating fixed/ semi fixed fire protection

system.- Indentify the persons who will operate fixed/ semi fixed

fire protection system.- Practice it thru’ mock drill.

8. Weather : - Weather conditions can effect fire fighting operation especially at large tank fires.

- Anticipate & Prepare for heavy winds, rains , fog , extreme cold & hot conditions.


9. Exposures:- Exposures in downwind to be protected first. - Cooling water should be conserved as it may lead to

problem of water shortage, effluent water going out of the facility.

- Cooling water on the exposures should be applied as long as it produces steam on the surface.

- As a thumb rule cooling water on a exposed tank can be calculated as follows :

• Atm. tank upto 30m dia : 1800 LPM• Atm. tank between 30m - 50m dia. : 3500 LPM.• Atm. Tank above 50 m dia. : 7500 LPM.


10.Extent of Fire :- Fire protection facilities & preparedness to be designed for worst case scenario of largest tank fire.

- Take into account possible scenarios of dyke fires, manifold fires in the vicinity.

11. Time :- Time of day may affect response.- Take into account the slow response during non-

operational/ night hours.- Ensure adequate lighting in night hours.- Traffic congestion may block access of emergency response vehicle during peak hours.


12. Height of the tank:- May affect the operation. - Trajectory of foam monitors should reach the tank.- Safe distance for fire fighting operation should be more.

Remember the more information you can gather prior to the incident, the easier is to develop the incident action plan.

Response Considerations

Response Considerations • Type of fire(vent fire/rimseal/ full surace) shall determine

resources required & necessary incident action plan.

• Before attack the fire establish adequate water & foamsupply. A common mistake is to try to extinguish thefire with inadequate resource. If fire is notextinguished with resources, it will continue to burn &destroy the foam blanket already in place.

• Protect exposures such as tank & associated piping and pumps.

• Never attempt to enter dyke area unless it is safe to do so. Check for any spill potential which can fill the dyke.

Response Considerations Rim-seal Fires

• Rim-seal fires can be extinguished using semi fixed/ fixedfoam system, if these are installed & usable. If foam pourersare not usable fire can be extinguished using hose lines &foam monitors.

• Foam Application rate of 18 LPM/m2 of rim-seal areashould be considered.

• Generally following Capacities of fixed/mobile foammonitors are sufficient for rim-seal fires :250 GPM for tanks up-to 30 m. dia.500 GPM for tank from 30 to 60 m. dia1000 GPM for tanks above 60 m. dia

Response Considerations Full Surface Tank Fire

• As per the statistics of full surface tank fires, fixed /semifixed foam system has been found un-usable.

• Over the top application using fixed/portable foam monitorshave been found successful method to extinguish large fullsurface fires.


Full Surface Tank Fire

•In the event of a fire, cease tank operations to eliminateturbulence in the tank contents. These activities may beinitiated later as a part of the fire fighting strategy.

•Pumping out the product of the tank may worsen the fire if thesides have been distorted and the roof does not lower evenly.

•If a foam blanket is used as a precautionary measure avoidplunging of the foam streams into the liquid. Static charge candevelop and cause ignition of the stored materials. Foamsolution should preferably be applied through the foamchambers to avoid the risk of static build-up.



•While using cooling streams on the tank exterior, apply coolingstreams on the Fuel lines within the dike area.

•Cooling streams on adjacent tanks should be applied asneeded only.

•Cooling stream should periodically be applied to the exposedtank. If stream is given off, the cooling stream applicationshould be continued until steam is no longer apparent.



• Attempt Fire Fighting only when foam, Fire Water Network,Fire Water storage, Fire Water pumps, Foam monitors, foamproportionators & hoses capable to meet the requirement offoam application are in place.

• Ensure that equipment & foam solution brought in by mutual aid members are compatible to existing at the facility.


In the event of a crude tank fire:

•Crude oils fire if last for longer periods have the potential fora Boil Over.

• Boil Over covers approximately 7 times the tank area andextends into the air approximately 10 times the tank diameter.


In the event of a crude tank fire:

•Consumption rate of crude oil due to burning is approximately12-18 inches per hour.

•The heat wave advances from the top of the liquid towards thebottom of the tank at approximately 24-36 inches per hour.

• Cooling stream may be periodically applied to the side of thetank to help determine the location of the heat wave in the tank.

•Evacuation of the area should be considered as the heat waveapproaches the bottom few feet of the tank.


• Minimum foam application rates vary based on :- Fuel flash point- Water immiscibility- Type of foam- Application device

• 3% foam concentrate is most widely used for fires involvinghydrocarbon. However some industries are now-a-daysusing 1% concentrate also due to ease of handling.

• On polar solvents 3%/6% AR foam shall be needed.


• Foam application rate will vary depending on the tankdiameter(Surface area). For larger tank higher applicationrate is required.

• As per NFPA an application rate of 8.1 LPM/m2 of the fuelsurface area should be considered for large full surface tankfires.

•However tests carried out by LASTFIRE Group recommendthat 60 % higher application rate may be needed while usingportable/mobile foam monitors due to loss of foam by heat &thermal currents.


• Generally following application rate are recommended :

Tank Diameter Application rate(lpm/sq.m)upto 50 m. 6.550 to 65 m 7.365 to 80 m 8.180 to 100 m 8.9Above 100 m 9.8

Response Considerations Foam Concentrate & Water for full surface Tank Fire

As per OISD‐116/117 & NFPA‐11

Typical Calculations for a 60 m. diameter tank

Liquid surface area = ¼ x 3.14 x D2

= ¼ x 3.14 x 60 x 60 = 2826 m2

Consider Foam application rate : 8.1 LPM/m2

Foam solution application rate = 8.1 x 2826 = 22890.6 LPMFoam Application time : 65 minutesFoam Concentrate Required : 0.03 X 22890.6 X 65 = 44636.7 Ltr.

Water Flow : 0.97 X 22890.6 = 22203.9 LPM = 1332.2 m3/hr.Water storage : 1443.2 m3

(Add water required for exposure protection)


• Consider additional hazards which may arise due to :

- Slopeover - Frothover

• Carefully consider the location of incident command post, equipment placement, medical camp in safe zone.


Teasing the Fire

Before attacking the full surface tank fire pass theextinguishing stream over the top of the tank, it will result intoincreasing the intensity of fire. Continue it till violent reactionof fire settles down. This technique is called teasing the fire.

This technique shall prevent more violent reaction of firewhen extinguishing media is directly applied on the hot fuelsurface.


• Do not position the extinguishing streams around the tank for multiple points of application.

•Position the foam monitors at one location. This will help to achieve a stable foam blanket ore quickly.

•Do not be tempted to move the foam streams to other positions.

•If fire intensity do not reduce for considerable time, increase application rate.


Large tank Fires can be extremely costly in terms of - Life Safety- Property Damage- Environmental Concerns & - Public Impact.

Large tank fires require : - Large Commitment- Implementation of plans- Preparation & Proper use of resources & equipment - Logistics & co-ordination.

Documents

Fighting Storage Tank Fires