Fire Detection and Suppression

Chapter 4Fire Pumps

Fire Pumps

Fire Pump FunctionsThe main function of a fire pump is to increase the pressure of the water that flows through it.Inadequate or nonexistent municipal water supply system Sprinkler systems and standpipe systems

Fire Pumps

Common Fire Pump TypesSplit-case pumps (see Fig. 4.2 in manual) Horizontal: not self-priming(Continued)

Fire Pumps

Common Fire Pump Types Horizontal: not self-priming

(Continued)

Fire Pumps

Common Fire Pump Types

Single-stage and multiple-stageMaintenancePacking gland Wear rings

Fire Pumps

Common Fire Pump TypesSplit-case pumps (cont.)Vertically mounted

Fire Pumps

Common Fire Pump TypesVertical shaft turbine pumps

(Continued)

Fire Pumps

Common Fire Pump Types

Pressurized water source

Fire Pumps

Pump DriversEngines or motors used to turn the pumpPower requirementsTypesElectric motorsRequired power

(Continued)

Fire Pumps

Pump Drivers

Mounting(Continued)

Fire Pumps

Pump Drivers

Mounting (cont.) Maintenance(Continued)

Fire Pumps

Pump DriversTypes (cont.)Diesel engine driversEngine powerGear drivesEngine requirementsCooling systemFuel storageMaintenance(Continued)

Fire Pumps

Pump DriversTypes (cont.)Steam turbinesHorizontal and vertical shaftLimited feasibility

Fire Pumps

Pump ControllersGovern pump operationControllers for electric motor-driven pumpsSwitchesMultiple pumps connected in parallelManual shutdown (Continued)

Fire Pumps

Pump Controllers (cont.)Diesel engine controllersMain function is to close the circuit between the storage batteries and the engine starter motor.Alarm and signal devices(Continued)

Fire Pumps

Pump Controllers (cont.)

Pressure recording deviceManual shutdownWeekly startup

Fire Pumps

Pump Installation Components and AccessoriesPipe and fittingsMaterialsValvesStandardsSuction piping: NFPA 24, Standard for the Installation of Private Fire Service Mains and Their AppurtenancesDischarge piping: NFPA 24 and NFPA 13, Standard for the Installation of Sprinkler SystemsSizing (Continued)

Fire Pumps

Pump Installation Components and Accessories (cont.)Relief valvesPrevent pressures that are high enough to damage system piping or fittingsRequired only if pressure at churn is high enough to damage system componentsSizing (Continued)

Fire Pumps

Pump Installation Components and Accessories (cont.)Circulation relief valve: provides enough water flow into and out of the pump to prevent the pump from overheating when operating at churn against a closed systemTest equipmentTest manifoldGPM metering device(Continued)

Fire Pumps

Pump Installation Components and Accessories (cont.)

Pressure maintenance pumpsPrevent false starts due to fluctuations in pressure of water supply to pumpSmall-capacity, high-pressure pumps that maintain constant pressure on system(Continued)

Fire Pumps

Pump Installation Components and Accessories (cont.)GaugesHorizontal split-case pumps and vertical shaft pumps One gauge near discharge port One gauge near intakeVertical turbine pump: single gauge on discharge side(Continued)

Fire Pumps

Pump Installation Components and Accessories (cont.)Component arrangementTypical arrangement(Continued)

Fire Pumps

Pump Installation Components and Accessories (cont.)

Additional bypass line

(Continued)

Fire Pumps

Pump Installation Components and Accessories (cont.)

Horizontal-shaft pump installation (See Fig. 4.23 in manual)Vertical-shaft pump installation (See Fig. 4.24 in manual)Standard performance specifications: NFPA 20, Standard for the Installation of Centrifugal Fire Pumps

Fire Pumps

Testing, Inspection, and MaintenanceTesting fire pumpsPiping: hydrostatic testingAcceptance testingCertified shop test curvesStandard performance points:1.Maximum of 140 percent of rated pressure at 0 gpm.2.Minimum of 100 percent of rated pressure at 100 percent of rated flow.3.A minimum of 65 percent of rated pressure at 150 percent of rated flow.(Continued)

Fire Pumps

Testing, Inspection, and MaintenanceEquipment needed for pump testsOne section of 2 1/2-inch or larger hose for each hose connection on the test headerOne Underwriters playpipe for each hoselineMethod for safely securing playpipesPitot tube and gaugeMethod of measuring pump speedVoltmeter and ammeter(Continued)

Fire Pumps

Testing, Inspection, and MaintenanceConversion of velocity pressure to gpm:Q=(29.83)(Cd)(D2)(P)Where: Q=Flow in gpmCd=Coefficient of dischargeD=Discharge orifice diameterP=Nozzle pressure(Continued)

Fire Pumps

Testing, Inspection, and Maintenance (cont.)Acceptance test on an electric horizontal split-case pumpStep 1:Calculate the expected pitot pressure for 100 percent and 150 percent of the rated flow.Step 2:Connect all the hoselines and nozzles.Step 3:Close the indicating control valve that separates the pump from the fire system.(Continued)

Fire Pumps

Testing, Inspection, and MaintenanceAcceptance test on an electric horizontal split-case pump (cont.):Step 4:Connect the ammeter and voltmeter to the test leads in the controller or at any other appropriate location.Step 5:If using a handheld revolution counter to measure pump speed, remove end plate of motor for access to shaft. (Continued)

Fire Pumps

Testing, Inspection, and MaintenanceAcceptance test on an electric horizontal split-case pump (cont.):Step 6:If end of shaft is not accessible, use a strobe-type tachometer.Step 7:Start the pump.Step 8:Open the control valve in the line leading to the test header and open the hose valves for the first gpm measurement.(Continued)

Fire Pumps

Testing, Inspection, and MaintenanceAcceptance test on an electric horizontal split-case pump (cont.):Step 9:Open and adjust sufficient lines to exact required pitot pressures for 100 percent of rated flow.Step 10:When all readings are complete and recorded, open and adjust additional hoselines to the exact required pitot pressures for 150 percent of the rated flow.(Continued)

Fire Pumps

Testing, Inspection, and MaintenanceAcceptance test on an electric horizontal split-case pump (cont.):RepetitionsManually controlledAutomatically controlledElectrically driven pump (Continued)

Fire Pumps

Testing, Inspection, and MaintenanceAcceptance test on an electric horizontal split-case pump (cont.):Evaluating dataPerformance curvesPump speedVoltage and current for electrically driven pumpAcceptance test on a vertical shaft electric pumpAcceptance test on a diesel driven pump

Fire Pumps

Instructors note: Include the additional details below in your discussion of steps 13.

Step 1:Calculate the expected pitot pressure for 100 percent and 150 percent of the rated flow by algebraically manipulating Equation 4.6.

Step 2:Connect all the hoselines and nozzles. Make sure that all nozzles are securely fastened in place All hose valves should be closed, and the control valve in the pipe to the test header should be closed.

Step 3:Close off the indicating control valve that separates the pump from the fire system. This will allow testing of the pump without subjecting the system piping to possible water hammer.

Instructors note: Include the additional details below in your discussion of steps 4 and 5.

Step 4:Connect the ammeter and voltmeter to the test leads in the controller or at any other appropriate location.

Step 5: If a handheld revolution counter is being used to measure pump speed, the end plate of the motor should be removed for access to the shaft. Because both the motor and the pump will be rotating at the same speed, measuring the speed of the motor also gives the speed of the pump. Proper attention to safety is critical with respect to any rotating equipment. Loose fitting clothing or ties should not be worn.Instructors note: Include the additional details below in your discussion of steps 68.

Step 6: If the end of the shaft is not accessible, a strobe-type tachometer can be used. To establish the speed of the pump using the tachometer, the shaft may be marked with a piece of chalk and the strobe impulse adjusted until the rotating chalk mark appears to be standing still. The pump speed can then be read from the tachometer dial. Several modern styles of digital tachometers are available. The most common variety uses a small strip of reflective tape that is placed on the shaft. The handheld sensor counts the rate of reflections as the shaft rotates.

Step 7:With everything ready, the pump can be started. Initially, the pump should be operating against a closed system with no valves open and with no water flowing. This is the churn or shutoff phase. The pump can be started manually or, if equipped to start automatically, should be started by bleeding off the water pressure. Once the pump is operating, both the suction and discharge pressures should be read and recorded, the rpm measured, and voltage and current readings taken. While the pump is operating at churn, the circulation relief valve should have opened automatically and be flowing a solid stream of water. If water is not flowing, the relief valve can be adjusted with a crescent wrench until water begins to flow.

Step 8:Open the control valve in the line leading to the test header and open the hose valves for the first gpm measurement.Instructors note: Include the additional details below in your discussion of steps 910.

Step 9:Sufficient lines must be opened and adjusted so that the exact required pitot pressures for 100 percent of the rated flow is read on the pitot gauge. While the velocity pressures are being measured outside, the rpm, voltage, current, discharge, and suction pressures are to be measured inside the pump room. When the first line is opened, the circulation relief valve should again be checked. When the first line was opened, the relief valve should have closed off. If it continues to flow a solid stream, further adjustment is needed.

Step 10:When all readings are complete and recorded, the additional hoselines are opened and adjusted to the exact required pitot pressures for 150 percent of the rated flow. This usually requires flowing all of the hoselines to achieve 150 percent of the rated flow. It is important to calculate ahead of time what pitot pressure is needed at each nozzle to give both the 100 percent and the 150 percent points. It is convenient if the total flows required are divided by the number of hoselines to be used to determine the flow required from each line. In this way, the pitot reading required at each nozzle will be identical.