INTERNATIONAL FIRE PROTECTION 33

FIREWATER PUMPS

The capability of the water supply to meet thewater flow and pressure requirements forfixed installation extinguishing systems is of

paramount importance and is determined by theextinguishing system design. Where this cannot beadequately achieved, it is necessary to incorporatefire pumps within the system.

Globally, there is a vast range of local, regionaland international standards in existence for pumpsystem design and selection. For example, withinEurope nearly every country currently has its ownnational sprinkler and fire pump standardsalthough much effort is being applied to introducea harmonised European Standard EN12259 ofwhich Part 12 will apply to fire pumps. Ultimately,

when formally adopted as an EC Directive, theharmonised standards will supersede the currentEuropean national standards. However, theNational Fire Protection Association Standard NFPANo. 20 (Standard for the Installation of StationaryPumps for Fire Protection) has progressively andpositively evolved since 1896 and is currentlylooked upon as the standard which is most widelyknown and adopted internationally.

In addition to designing and manufacturing tocomply with the relevant codes and standards, firepump producers also commit their products toextensive testing to obtain approvals from recog-nised organisations such as Factory Mutual (FM),Underwriters Laboratories (UL), Loss Prevention

By James Shipman

Sales Manager,Patterson Pump IrelandLimited

Fixed InstallationFirewater PumpPackagesInternationally, there is a continuing movement towards installing more fixedinstallation fire sprinkler/hydrant/water-mist/deluge systems into a wider varietyof sites ranging from schools and hospitals to shopping centres, manufacturingplants and distribution warehouses. Fixed fire extinguishing installations are avital component within any overall facility design to protect life and property andtheir more widespread use provides facility owners with further benefits in termsof risk insurance premium reductions and reduced facility downtime in the eventof an incident.

Certification Board (LPCB) Great Britain, VdSGermany, etc. to enable their equipment to beinstalled and accepted on particular projects.These approvals are the attestation that the manu-facturer has complied with the appropriate codesand standards, operates effective quality systemsand provides correct product support for theirequipment.

Fire pumps can work in a variety of configur-ations – boosting town mains water pressuredirectly or from intermediate water storage tanks,either above or below ground. Generally, forabove ground water supply applications, ‘endsuction’ or ‘horizontal split case’ centrifugalpumps are used. Below ground water applicationscan use an underground storage tank, river oreven the open sea as their water source and forthese installations ‘vertical turbine’ or ‘sub-mersible’ pumps are generally used. Irrespective ofthe configuration, the final intention is to producea certain volume of water at a certain pressure – inother words its design duty.

The capacity of the fire pumps required for aparticular installation is determined by theextinguishing system design requirements andstandards and these can typically range from 550litres per minute (150 US Gallons per minute) to19000 litres per minute (5000 US Gallons perminute) at pressures from 2.75 barG (40 psi) to 26 barG (390 psi). Depending on the risk insurer’sphilosophy, the required system design duty maybe provided by a single pump system or may beshared between, say two pumps (known as 50%duty pumps) or more. Frequently, two 100% dutypumps will be installed and each one either desig-nated as ‘duty’ or ‘standby’. All reputable firepump manufacturers will assist the sprinkler designconsultants with determining the optimum pumpsystem selection and specification as required.

Fire pump design and construction is developedaround reliable operation. Many fire pump designsavailable on the market have evolved from manu-facturers’ proven continuous service process pumpdesigns which have been subsequently adapted

for fire pump applications. Although under normalcircumstances it may only be run for 30 minuteseach week for test purposes, when called on to‘operate in anger’ it must start and perform flaw-lessly and provide firewater to the seat of theincident. This not only means installing andmaintaining a reliable fire pump but also its driver,control system and accessories which form part ofthe overall fire pump package and must be equallyas reliable.

Drivers for fire pumps comprise diesel engines,electric motors and steam turbines. Generally,spark-ignition internal combustion engines are notpermitted. The popularity of using a diesel engineversus an electric motor as the fire pump driverdepends on where you are. In North America it isestimated that 80% of fire pumps are electricmotor driven whereas in Europe the converse istrue and diesel engines account for 80% of all firepump drivers. It is true that electric motor drivensystems provide for lower overall maintenance andrelatively low emissions in a more compact pumproom floor area but a diesel engine driven systemis virtually independent of reliability on externalpower sources.

Selection of the correct driver for the fire pumpagain depends on the codes and standards the firepump package is being designed to. Whilst thecorrect pump speed is fundamental, the driverpower rating will need to be sized to accom-modate the absorbed power rating of the pump –for some codes this is only at the pump designcapacity but for the more rigorous codes it needsto cover pump end of curve performance whichdemands a considerably higher power rating.

Diesel engine drivers specifically developed forfire pump applications are available. These areusually proprietary well tried and tested brandsand models of diesel engines which are thendressed or customised and tested to meet specificcodes and approval body requirements. Usually ade-rating factor of 10% is applied to the grossavailable power when used for fire pump drivesbut further de-ratings will need to be applied if

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FIXED INSTALLATION FIREWATER PUMP PACKAGESFIREWATER PUMPS

the engine is installed in ambient temperaturesabove 25°C (77°F) or 91 metres (300 feet) abovesea level to compensate for reduced engine perfor-mance. Nearly all codes and standards call for dualredundant battery electric starting systems. This isto ensure reliable starting in the event of one setof batteries failing. Although radiator-cooledengines are permissible, heat exchanger cooling isthe usual method with cooling water being takendirectly from the discharge of the running pumpvia the exchanger and returned to waste or to thewater storage tank.

Another essential component within the firepump system is the automatic controller. The prin-ciple of this is to detect a fall in the firemain waterpressure when a sprinkler head ruptures, delugevalve operates or a fire hydrant is opened. This isachieved via a pressure switch or pressure trans-ducer and, when the controller is in ‘automatic’mode, initiates the starting sequence and oper-ation of the fire pump. Controllers also providelocal manual operation overrides for the automaticstarting system as well as remote alarm circuits toenable pump status to be monitored in a perma-nently manned position such as a gatehouse,reception area, building monitoring system or bythe local fire brigade.

Controllers for electric motor fire pumps arerelatively straightforward in design and usuallyemploy direct-on-line (across the line) or star delta(wye delta) open transition motor starting tech-niques. However, when there are mains supplypower limitations, more diverse starting methodsare available such a primary resistor, auto-transformer or electronic soft start.

Controllers for diesel engine driven fire pumpsare necessarily more complex in nature. Mostly,they will include a cyclic cranking feature to alter-nate between the dual redundant battery electricstarting systems. A crank termination feature isalso included to withdraw the starter motor fromfurther cranking once the engine has started. Inaddition, both battery systems are catered for byfully automatic battery chargers operating fromthe pump room AC power supply ensuring thatthey are always in a full state of charge ready forthe pump set being called into operation. Engineprotective devices are limited but usually engine oilpressure and cooling water temperature aremonitored with audiovisual alarms and certaincodes require the inclusion of an engine overspeedprotection alarm and safety trip circuit.

More and more frequently,fire pump manufacturers arebeing called on to provide com-plete pre-packaged fire pumphouses. These are fully manu-factured at the fire pumpmanufacturer’s facility on aunitary baseplate including allsuction and discharge valving,test lines and are ready to installimmediately on delivery to thework-site. They can be suppliedwith (or without) a pre-fabricatedpump house building fullywired out with electrical system,lighting, heating and ventilationsystem. Smaller capacity unitscan be fabricated using cus-tomised shipping containers.

The increasing popularity of the pre-packagedpump house system is without doubt due to thespeed and convenience of installation, requiring justfixing to the pre-prepared support base, attachingof suction and discharge lines, electrical supply andthe unit is then ready to be commissioned and startits working life. A further major benefit is the elimi-nation of site building costs associated with theconstruction of a conventional ‘bricks and mortar’pump room and its subsequent fitting out costs.

Whilst purchasing and installing any type offixed extinguishing system is an extremely wisemeasure in reducing fire risks to life and propertyand the associated disruption to a business whena fire incident occurs, it is absolutely essential toensure that the fire pump system is correctlyinstalled and commissioned. Incorrect installationcan lead to serious problems later on; for examplecoupling failure due to incorrect or mis-alignmentof the coupling halves. Reputable fire pumpsystem manufacturers will provide local trainedengineers to carry out this work to the acceptanceof the facility owner and his risk insurer’srequirements and also to put into effect the manu-facturer’s equipment warranties.

Pump system testing should be conducted bythe facility owners on a weekly basis and recordsaccurately maintained. Any abnormalities with itsoperation should be rectified without delay.

It is also imperative that correct regular main-tenance is carried out on the system. Most firepump system manufacturers and risk insurersrequire equipment to receive servicing and mainte-nance annually.

Remember – fire pump systems are provided forlife-saving and property protection and are notsomething to fit and forget! IFP

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FIXED INSTALLATION FIREWATER PUMP PACKAGESFIREWATER PUMPS