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Selecting the optimum pressure proportioner system

AcomparisonbetweenanelectronicallycontrolledpressureproportionersystemandaFireDosadmixingsystemshowedthatthefollowingworkingrangescanbeachievedinpractice:

Wettingagent Foam1% Foam3%

no no yes

Wettingagent Foam1% Foam3%

yes yes no

Wettingagent Foam1% Foam3%

yes no no

Wettingagent Foam1% Foam3%

yes yes yes

Wettingagent Foam1% Foam3%

yes yes yes

Wettingagent Foam1% Foam3%

yes yes yes

Manufacturer‘sdataforanelectronicallycontrolledpressureproportionersystem:

„waterflowratefrom50to2000l/min“„admixturerate0.1to3%“

Thefacts:

With a water flow rate of 50 l/minthe admixture rate* is 2 to 9.9%

With a water flow rate of 1000 l/minthe admixture rate* is 0.1 to 1.9%

With a water flow rate of 2000 l/minthe admixture rate* is 0.05 to 0.95%

* The admixture pump of the examined pressure proportioner system delivers foaming agent at 1 to 19 l/min.

Manufacturer‘sdataforaFireDosbasedontheFD1600/0.1-3-APP-Fwithreductionoftheminimumwaterflowrate**:

„waterflowratefrom40to1600l/min“„admixturerate0.1to3%“

**A wide range of FireDos admixing systems is available, covering water flow rates and admixture rates for practically every application.

Thefacts:

With a water flow rate of 40 l/minthe admixture rate* is 0.1 to 3%

With a water flow rate of 1000 l/minthe admixture rate* is 0.1 to 3%

With a water flow rate of 1600 l/min the admixture rate* is 0.1 to 3%

* The admixture pump of the FireDos pressure proportioner system examined delivers foaming agent at 0.04 to 48 l/min.

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Selecting the optimum pressure proportioner system

Amoredetailedexaminationofthepracticalapplicationdataforthetwopressureproportionersystemswhichwerecomparedleadstothefollowingquestions,whichshouldbeputtoanypersonproposingsuchproducts:

Whatarethedifferencesbetweenthevariouspressureproportionersystems?Thevariouspressureproportionersystemsavailableonthemarkethavedifferentprinciplesofoperation.Theseinfluencetheperformanceoftheproductsandtheapplicationsforwhichtheycanbeused.Thefollowingnotesprovideanoverviewofimportantcriteriatobeconsideredwhenselectingapressureproportionersystem.

Whatarethemaximumandminimumwaterflowrateswhichthepressureproportionersystemwillhandle?Theworkingrangeofapressureproportionersystemdependsontheapplicationandthemainrequirementsofthefirebrigade’swork.Aparticularlyimportantfactoristheflowrateofthefoamingagentatmaximumandminimumwaterflowrates.

Herearetwoperformancegraphsforcomparison:

Working range of an electronically controlled system Working range of a FireDos admixing system

TheadmixtureraterequiredcanbeachievedTheadmixtureraterequiredcannotbeachieved

admixturera

te[%]

waterflowrate[l/min] waterflowrate[l/min]

admixturera

te[%]

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Theelectronicallycontrolledsystemunderconsiderationwillnotoperateifthewaterflowrateisbelow100l/min.Anadmixturewillnottakeplace.Manysuchsystemscannotdrawfoamingagentatlessthan1l/min.Thus,iftheadmixtureraterequiredtogeneratethewettingagentis0.1%,thewaterflowratemustbeatleast1000l/min.

Attheotherextreme,thelimitedperformanceoftheelectricaldriveunit(whichispoweredfromthevehicle’selectricalsystem)meansthatelectronicallycontrolledsystemscanoftennotdrawmorethan19l/minoffoamingagent.Iftheadmixtureraterequiredis3%,thiscanbeachievedonlywithwaterflowratesupto633l/min.

CanfoamANDwettingagentbothbegeneratedwithintheworkingrangeofapressureproportionersystem?Fromthediagramquotedbeforeitcanbeconcludedthat,dependingonthead-mixturerate,foamcanbegeneratedonlyatwaterflowratesofuptoapproximate-ly600l/min.Wettingagentshowevercanbegeneratedonlyatwaterflowratesof1000l/minandabove.Therangeofapplicationofelectronicallycontrolledsystemsisthusveryrestricted.WithFireDostheentirespectrumofadmixtureratescanbeachievedatanywaterflowratewhichcanbehandledbytheFireDosadmixingsystem.Foamandwettingagentcanbothbegeneratedwithoutrestriction.

Howdoesapressureproportionersystemreacttochangesinthewaterflowratepassingthroughthesystem?Electronicallycontrolledsystemssometimestakeasignificantamountoftimetoreachthedesiredadmixturerate.Thecontrolsystemsnormallyemployedwillstartatthemaximumpossibleadmixturerateandthencorrectthisdownwards,stepbystep.Eachtimethereisachangeinthewaterflowrate,orifthereisawatersurgeorachangeinpressure,thisprocessstartsalloveragain.Inpracticethisresultsinexcessivelyhighadmixturerateswhichhaveanegativeeffectespeciallyonthequalityofthewettingagentwhichisgenerated.

Thefollowingdiagramillustratesthiswiththeresultsofacomparisontest:

Selecting the optimum pressure proportioner system

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Withanadmixtureratesetat0.3%theelectronicallycontrolledsysteminfactachieves0.65%asanaveragefigurefromthisveryirregularadmixture.Thuseventheaveragedeviationis116%andthemaximumdeviationismuchhigher.Bycomparison:withanadmixtureratesetat0.33%theFireDosachievesanaver-ageadmixturerateof0.39%.Theadmixingsystemreactsinstantaneouslytoanychangesinthewaterflowrate.Asthediagramshows,theadmixturerateisalwaysmaintainedataconstantlevel.

Howdoesapressureproportionersystemreacttofluctuationsinpressure?Pressurefluctuations,whichcanoccurasaresultofreleasingextinguishingwaterintermittentlyorwithvariationsintheflowrate,haveidenticaleffects.Thecomparisonquotedabovethereforealsoappliestopressurefluctuationsinthewatersupplyline.

waterflow

rate[l/min]

Reaction of the pressure proportioner system to fluctuations in water flow rate

Admixtureratewithanelectronicallycontrolledsystem

AdmixtureratewithFireDos

Fluctuationsinwaterflowrate

Selecting the optimum pressure proportioner system

time

Adm

ixturera

te[%

]

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Whatisthepowerrequirementofthepressureproportionersystemonavehicle’selectricalsystem?Thepowerrequirementwhichelectronicallycontrolledsystemsplaceontheve-hicle‘selectricalsystemdependsonthedemandgeneratedbytheirelectricdrivemotors.Forthisreasonthedrivemotorisgenerallynotaspowerfulasitshouldbeinordertopowertheelectronicallycontrolledsystemwithoutanylimitations.FireDosadmixingsystemsplacenoelectricalloadingonthevehicle‘selectricalsystem,becausetheyworkcompletelywithoutelectricity.Theelectricalpoweravailableisthereforeneveralimitingfactor.

WillthesystemshandleALLcustomaryfoamingagents?Modernpressureproportionersystemsmustbeabletoprocessallcustomaryfoamconcentrates.However,thelimitedperformanceoftheelectricaldrivesusedinelectronicallycontrolledsystems(operatingfromthevehicle‘selectricalsystem)meansthattheyquicklymeettheirlimits,particularlywherehigh-viscosityfoamingagentsareinvolved.

FireDosisnotaffectedbylimitedelectricalenergy.Itsmotorispoweredex-clusivelybythewaterusedtofightthefireandthisprovidesalltheperformancerequired,nomatteroftheviscosityofthefoamingagent.

Whatisthequalityofthefoamwhichisgenerated?Giventheloadonthevehicle’selectricalsystem,itisnotpossibletoprovideelectronicallycontrolledsystemswithadequatepowerforeverypossibleap-plication.Insuchcircumstancestheadmixtureratewithhigh-viscosityfoamingagentsislowerthanthesettingrequired.Furthermore,withchangesinwaterflowrateand/orifpressurefluctuationsoccur,theadmixturerateissometimesfartoohighandirregular.Ineithercasethequalityofthefoamsuffers.

FireDosiscompletelyunaffectedbyanysuchoperatingconditionsbecauseofitsuniqueprincipleofoperation.Thequalityofthefoamisalwaysconsistent.

Selecting the optimum pressure proportioner system

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Isthefoamingagentheatedbythepressureproportionersystem?Insomeelectronicallycontrolledsystemsthedesignconceptrequiresthefoamingagenttocirculate.Thiscausesthefoamingagenttoheatup,particularlyifthelevelinthefoamingagenttankdropstoalowlevel.However,ifthetemperatureofthefoam-ingagentexceeds50°Ctheextinguishingeffectdecreases.InaFireDosadmixingsystemthefoamingagentdoesnotcirculate.Theadmixturepumpalwaysdeliversonlythequantityrequiredatonetime.Thismeansthatthefoamingagentcannotbecometoowarm.

Whatisthequalityofthewettingagentproducedbythepressureproportionersystem?Manyelectronicallycontrolledsystemscannotdeliverfoamingagentatlessthan1l/min.Thus,ifanadmixturerateof0.1%isrequiredinordertogeneratewettingagent,thewaterflowratemustbeatleast1000l/min.Ifthewaterflowratedropsbelowthisfigure,theadmixturerateincreasesandthesystemgeneratesfoaminsteadofwettingagent.AFireDosadmixingsystemwillmaintaintheadmixtureratewhichhasbeenselected,evenatlowwaterflowrates.Thereforeitistheonlypressureproportionersystemwhichgenerateswettingagentsreliably,nomatterwhatthewaterflowrateis.

Howmuchtrainingisrequiredinordertooperatethepressureproportionersystem?Eachfireisastresssituation.Insuchsituationstrainingisrequiredifafire-fighteristohandleanelectronicallycontrolledsystemquicklyandexpertly.AFireDos admix-ing system,ontheotherhand,worksonapurelymechanicalprinciple.Assoonastheextinguishingwaterstartstoflow,allitneedsistheturnofasingleballvalvetostarttheadmixture.

Whatadditionalfeaturescanbeofferedforthepressureproportionersystemtoextendtherangeofapplication?Withelectronicallycontrolledsystemsitiseithernotpossibletodrawanextinguishingadditivefromanexternalcontaineratthesametime,orthisfeatureisnotprovided.Eventheuseofanindependent,portableunitisnotgenerallypossibleorprovidedforwithelectronicallycontrolledsystems.

WewouldwelcometheopportunitytodemonstratetoyouhowFireDos admixingsystemsprovidealltheserequirements.

Selecting the optimum pressure proportioner system