Fire in a storage tank is a challenge to both tank operators and fire fighters. Value of the material adds to the risk of life-threatening damage in a storage tank fire.
For more information, please visit our website.
Modern technology has made fire protection options easily available to tank designers and operators. Proper selection of right equipment and designs can make a difference between disaster and safe operation.
The spacing and layout of tank, its design, material and construction of bund walls influence the choice of equipment.
Standards of Fire Protection System:
NFPA (National Fire Protection Association) decides tank fire protection guidelines in the USA. These include specifications of foam delivery layout, rates and spacing. The contents of the tank fix the foam application rates that range between 4 liters/m2/min to 12 liters/m2/min.
Foam Concentrates
Firefighting foam is an integral part of tank fire protection system. The foam concentration must suit different tank content and application systems. Fluor protein foams are best for hydrocarbon risks and Alcohol Resistant Aqueous Film Forming Foam (AR-AFFF) for water miscible risks or polar solvent.
Foam Induction
Foam induction proportioning system plays the lead role in tank protection system. In simple words, correct amounts of water and foam are necessary for a perfect mix.
Foam delivery device decides foam solution amount. For constant foam solution demand, fixed inline inductors are the best choice.
For variable foam solution demand, you can choose any among the two: balanced pressure proportioned with balanced valve on foam skid and balanced pressure foam proportioner with bag tank.
Foam skids function well with water, diesel or electric driven motor foam pumps. Single or multiple skids can feed the foam systems. Thus, they aren&#;t always readily available.
Water Cooling
Radiated heat is a huge risk for storage tanks. Cooling water can minimize its effect. A mushroom nozzle can cool the roof and other nozzles can cool the tank walls. For additional cooling of the surface area, oscillating monitors are great to go with.
Bund Protection
The bund walls generally get neglected as tanks steal the limelight. But the casualties won&#;t be any less if bund walls get affected.
A fire in this area can result from leaking valve or tank or fractured pipe. These can also cause major accidents. A medium expansion foam system can protect the walls from fire and vapor suppression.
Rim Seal System
Sometimes it becomes tough to detect a fire in rim seal system, especially when the floating roof is at its lowest level. Early detection is necessary to reduce loss. The design needs to be wind-resistance. Strategically fitted fixed monitors are also helpful to supplement the rim seal system.
GSC Tanks is a leading tank production company of the USA that follows all of the required safety measures while building any storage tank. Our API and ASTM certified tanks are made following advanced techniques. We are committed to ensure the best storage tank production service.
Contact us on 470-589- or write to us at for more information.
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Sizing fire protection water storage tank
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(Mechanical)
(OP)
24 Aug 09 17:26When sizing a water storage tank for exclusive fire protection use, and fed by a fire pump, should the tank be sized on 150% of pumps rated capacity (at the req'd duration)or just the fire sprinkler demand + inside hose?
(Specifier/Regulator)
24 Aug 09 20:16Fire sprinkler demand + inside hose x duration= tank capacity. If u have any dry pipe or preaction system then as per NFPA 13 u have to add the gpm required to fill the systems for your total gpm for the tank.
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Fire Sprinklers Save Firefighters' Lives Too!
(Specifier/Regulator)
24 Aug 09 20:17Also if u have any hydrants connected to the tank u need to add this demand too.
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Fire Sprinklers Save Firefighters' Lives Too!
(Mechanical)
(OP)
24 Aug 09 20:24Thanks LCREP!
(Mechanical)
25 Aug 09 06:40If you have standpipes per NFPA 14, you have to consider the flow/duration for those - if it exceeds what the sprinklers require.
(Mechanical)
25 Aug 09 10:43It is my opinion that the water tank is to be sized for the greatest demand. If you have hydrants, that is often your greatest demand. Second is usually standpipes, followed by sprinklers. If you have a pump taking suction from the tank, you want to be sure you have enough water in the tank to be able to complete the pump test.
Travis Mack
MFP Design, LLC
www.mfpdesign.com
(Mechanical)
(OP)
25 Aug 09 19:34Travis, so what do you think in this case - make the tank able to supply 30 minutes at 150% capacity + 30 minutes at 100% capacity and compare that with the sprinkler + hose demand at 60 minutes and see which is greater?
gpm pump @ 150% = gallons X 30 minutes = 67,500 gallons
+
gpm pump @ 100% x 30 minutes = 45,000 gallons
---------------------------------
= 112,500 gallons
compared to sprinkler demand (+ hose stations inside) = 1,642 gpm X 60 minutes = 98,520 gallons
Of course the pump test durations were just arbitrary - not that anyone is going to need the pump running at 150% for 30 minutes to test it... but it would be embarassing to run out of water for the pump test and the above seems to dictate at least a 100,000 gallon tank.
What do you think?
(Specifier/Regulator)
26 Aug 09 01:24I'm late to the party but I have a question: What is the fire flow? Travis stated this, but sprinkler demand is not the same as firefighting water demand, and that's the question in my arena.
Travis answered it, and the original poster neglected to even raise the question.
Without all the facts this is not a simple question. We don't know if this a community fire pump, a building fire pump, a campus fire pump or what the heck you are trying to protect. Tell me what is "exclusive" as you originally asked.
(Mechanical)
(OP)
26 Aug 09 10:43Stookey, pump & tank are for fire sprinklers and inside hose stations- exclusively. No hydrants, no domestic, no nothing - but fire sprinklers.
(Mechanical)
26 Aug 09 11:34I don't see why you would need to run the fire pump for 30 minutes at 150% and 30 minutes at 100%. It looks like your sprinkler demand is going to be the driving force.Does this tank have an automatic float for refill. You can even use that to reduce the size of the tank if needed.
Travis Mack
MFP Design, LLC
www.mfpdesign.com
(Specifier/Regulator)
26 Aug 09 12:17Oremus,
I stand corrected. I should have read the question more closely.
(Mechanical)
26 Aug 09 17:33NFPA 851/850 (protection for power plants) states that the design water capacity of the system should able to be refilled in 8hrs or less, is there a similar requirement for just sprinkler-internal hose systems water tanks as per Oremus case?
(Mechanical)
26 Aug 09 19:20When you run your pump test can't you run your hoses back to the tank so you don't have to refill the tank after your annual pump test? I've done this on a few projects and doing this combined with using a flow meter makes the pump test easy.
(Specifier/Regulator)
26 Aug 09 20:54DavidNFPA 22, .4.2 The means to fill the tank shall be sized to fill the tank in a maximum time of 8 hours.ChevyWhy bother with hoses, use a flow meter into the tank and make it easy it is permitted by NFPA 25,08 see below.8.3.3 Annual Tests.8.3.3.1.2.2 Use of the Pump Discharge via the Bypass Flowmeter to Drain or Suction Reservoir. Pump suction and discharge pressures and the flowmeter measurements shall determine the total pump output.8.3.3.1.3 Where the annual test is conducted periodically in accordance with 8.3.3.1.2.3, a test shall be conducted every 3 years in accordance with 8.3.3.1.2.1 or 8.3.3.1.2.2 in lieu of the method described in 8.3.3.1.2.3.
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Fire Sprinklers Save Firefighters' Lives Too!
(Mechanical)
9 Sep 09 20:03How about a solved example that everyone agrees with ?
(Mechanical)
14 Sep 09 14:20If fire flows are an issue I could calculate it for my own purposes but would want verification by a PE or FPE before proceeding. After reading everything about it I could find I concluded ISO fire flows are an area sprinkler layout technicians aren't qualified to navigate. What the heck, a set of plans with $300 or so on a $10 million project could save me a lot of headache down the road so why take the risk?
Why the gpm pump on a project that requires but a 30 minute supply? Sounds light hazard to me unless there are ISO fire flows involved.
From NFPA #20 appendix A-2-3
A stationary pump for fire protection should be selected in the range of operation from 90 percent to 150 percent of its rated capacity. The performance of the pump when applied at capacities over 140 percent of rated capacity can be adversely affected by the suction conditions. Application of the pump at capacities less than 90 percent of the rated capacity is not recommended.
Seems a 500 gpm pump would handle anything up to OH2.
My understanding the correct way is to calculate total sprinkler demand plus hose stream allowance for whatever time requirement there was. 400 gpm sprinkler + 250 hose = 650 gpm which would call for a 39,000 gallon water storage regardless of the pump size.
Personally I like to size the tank for the pump at 150% for whatever time is required. In the case of a 500 gpm pump I prefer to size the tank at 750 gpm for 60 minutes and provide a 45,000 gallon tank. Come on, the cost difference between a 39,000 gallon and 45,000 is very minimal. What are we talking about, $6,000 more on a project that might be sellign for $10 million?
I've always been able to offer it to the owner as an alternate which they always accept when you explain the larger tank would take care of any additions or a density increase should something change down the road.
But the answer to the question (not addressing ISO fire flows) is sprinkler demand plus inside and outside hose stream allowance if any.
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