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Finite Element Analysis: Introduction, Method, and Application by: Trung Nguyen

DESIGN-SELECTION FIRE PUMP SYSTEM

PETROVIETNAMENGINEERING J.S.C

PETROVIETNAMENGINEERING J.S.C

1

FIREWATER PUMPNFPA20Standard for the Installation of Stationary Pumps for Fire ProtectionPresented by: Nguyen Thanh Tin

PETROVIETNAMENGINEERING J.S.C

Purpose of a Fire Pump

To protect lives and properties against fire by supplying an adequate water supply to automatic sprinklers or standpipe systemsTo meet building codes and insurance requirements

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Listing AuthoritiesUnderwriters Laboratories (UL)Factory Mutual Research Corporation (FM)

PETROVIETNAMENGINEERING J.S.C

Codes and StandardsNFPA PhilosophyA fire pump system should operate irrespective of any damage it may cause to itselfNo element of the system under emergency conditions should: Prevent a fire pump from turning onCause a fire pump to turn offChanges to the code must be substantiated by data or experience (actual scenarios)

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Water SupplyWhere fire pumps are installed on a city main, a fire flow test should be performed to determine minimum and maximum supply pressures as well as suitability of supply for the fire protection systemWhere adequate city supply water is unavailable, a suction tank or pit should be installedTank sizing must consider 150% of the fire pump rated flowTotal water requirements are defined in NFPA13 (Sprinkler Systems), NFPA14 (Standpipe Systems), NFPA15 (Spray or Mist Systems), Mains)

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Pump RequirementsCentrifugal fire pumps shall be listed for fire protection service.Pumps shall furnish not less than 150% of rated capacity at not less than 65% of total rated head. The shutoff head shall not exceed 140% of rated head for any type pump.

PETROVIETNAMENGINEERING J.S.C

Pump Requirements100%150%

140%100%

65%%Rated Head%Rated Flow

Max Shutoff Head

PETROVIETNAMENGINEERING J.S.C

Pump SizingA 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. The selection and application of the fire pump should not be confused with pump operating conditions. With proper suction conditions, the pump can operate at any point on its characteristic curve from shutoff to 150 percent of its rated capacity.

PETROVIETNAMENGINEERING J.S.C

Pump Sizing100%150%

100%

HeadFlow

Pump Design Flow90%Pump Rated Flow

PETROVIETNAMENGINEERING J.S.C

Pump RequirementsFM & UL require that fire pumps have packing sealsPacking requires periodic adjustment and replacement as it hardens over timeThe packing gland should be tightened until the seal leaks 30 drips per minuteIf the gland is tightened to much, the seal receives no lubrication and will burn

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Allowable Pump TypesHorizontal Split CaseVertical In-LineEnd SuctionVertical Turbine

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Horizontal Split Case Fire Pumps

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HSC Fire PumpsBENFITSAvailable in a wide flow and head rangeServiceable without disturbing piping or driverAvailable in electric or diesel driveDRAWBACKSLarge floor space requirementRestricts mechanical room layout due to direction of rotationMore costlyMore difficult to service

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Diesels have the particularity to provide less HP at high elevations. It is important to keep that in mind before quoting a project where site elevation is above 300ft.

14

Vertical In-Line Fire Pumps

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Armstrong will prepare a complete package ready for site installation.

Vertical in line packages are the most compact.

15

VIL Fire PumpsBENEFITSCompactServiceableReliableCost EffectiveDRAWBACKSOnly available up to 1500GPMElectric Drive OnlyRequires suction strainer

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End Suction Fire Pumps

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End Suction Fire PumpsBENFITSModerate floor space requirementFlexibility in mechanical room layoutAvailable in electric or diesel driveServiceableDRAWBACKSOnly available up to 1500gpmSingle suction design limits hydraulic efficiency

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Vertical Turbine Fire Pumps

Used where a flooded suction cannot be maintainedUnderground water sources or below ground tanks with above ground pump room

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Vertical Turbine Fire PumpsBENFITSWill operate under suction liftAvailable in electric or diesel driveAvailable over wide flow and head rangeDRAWBACKSMore costlyMore difficult to service and install

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Typical Application Wet Pit - Electric Motor Driver

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Typical Application Wet Pit - Diesel Engine Driver

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NFPA Required Pump Accessories

Suction & DischargeGaugesAir Release ValvePressure Relief Valve

PETROVIETNAMENGINEERING J.S.C

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NFPA Required Pump AccessoriesSuction gauge must be of the compound type (capable of reading negative pressure or vacuum)Discharge gauge must read two times the working pressure of the pump and not less than 200psi

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Air Release Valve1/2 Air Release Valve is required Exception: top centre-line discharge end suction and vertical fire pumps

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Automatic Air Release and Pressure gauges

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Circulation relief valve

A circulation relief valve allows a small amount of water to discharge from the pump to keep the fire pump from overheating when operating at no flow or very low flows.

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Relief Valve3/4 up to 2500usgpm1 over 3000usgpmShould be set between the maximum suction pressure and minimum suction pressure plus the closed valve pressure of the pumpPiped before the fire pump discharge check valve

PETROVIETNAMENGINEERING J.S.C

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Eccentric tapered reducer at suction inlet

When the pump suction pipe is larger than the pump suction flange, an eccentric tapered reducer is required to minimize the possibility of air pockets forming at the pump suction.

PETROVIETNAMENGINEERING J.S.C

Isolation ValvesSuction OS&Y Gate ValveDischarge Butterfly ValveBoth must be supervisedDischarge Butterfly Valve Installed after Test Tee and pressure sensing line

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Isolation Valves

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Hose Valve SystemsProvides testing meansSized by pump rated capacityThere are hundreds of different thread types depending on jurisdiction - type should be specified on projects

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Flow MetersDoes not replace a hose valve systemFlow meters must be listed for fire protection serviceGauge reading is a minimum of 175% the pump rated flowProvides a testing means without wasting waterFlow meter is installed in bypass back to suctionMust be installed with isolation valves per manufacturers specificationsRULE OF THUMB:Annular Type - 10 upstream - 5 downstreamVenturi Type - 7 upstream - 5 downstream

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PETROVIETNAMENGINEERING J.S.C

Flow measuring device

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PETROVIETNAMENGINEERING J.S.C

Main Relief Valves and Waste ConesSized by pump rated capacitySpring or pilot operatedWaste cone provides visibility of flow through the valveWhen it is used:1) Diesel driven systems2) Electric systems ???

PETROVIETNAMENGINEERING J.S.C

Main relief valve is usually used with diesel systems. It will prevent the pressure from increasing above the system pressure limits if the diesel overspeeds.

The main relief valve would open and discharge into a discharge cone to waist. The size of the cone and valve are determined by NFPA20 according to the pump flow.

Outside headers are installed outside a building with hose valves. Firefighters would connect to the hose valves in case of fire.

The size and quantity of hose valves are recommended by NFPA20.

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Main Relief Valves and Waste Cones

Recommended on all diesel driven systemsNot required on diesel if maximum supply pressure plus 1.21 x closed valve pressure does not exceed system pressure ratingNFPA allows piping back to suction - NOT recommendedRelief valve should be set below maximum pressure rating of the system

PETROVIETNAMENGINEERING J.S.C

NFPA Fitting Sizing

Piping, Relief Valves, Metering Devices, and Hose Valves should be sized according to Table 2-20 on Page 20-13.

PETROVIETNAMENGINEERING J.S.C

NFPA Required Pump Accessories

PETROVIETNAMENGINEERING J.S.C

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