fuel dispensers

2/6/2015 Fueldispensers

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Verification of Fuel Dispensing Pumps

Part IV of Eighth Schedule, The Legal Metrology (General) Rules, 2011

Specific provision: Part 2 Rule 5(1)

Adispensingpumpisameasuringinstrumentusedinconjunctionwith a storage tank for effecting delivery of liquid products byspecified volume. The instrument should be able to measurecontinuously, memorize and display the volume of liquid passingthroughthemeasurementtransducer.

A fueldispensing system contains several sets of components toperform a number of interrelated functions. Some componentsmaintain hydraulic continuity regulate the direction of flow andfluid pressure. Others put the pressure on the fuel to move it

through thesystem.Someothercomponentsareresponsible formetering the liquid fuel,registering accurately the quantity delivered, and computing the price of the delivery.Thesecomponentsaresubjecttometrologicalcontrol.Anothersetofcomponentscontroltheoperationof the system, switch itonandoff, resets thevolumeandprice indicators,andregulatesthedelivery.Resettingofindicatorsanddeliveryregulatingcomponentsarealsosubjecttometrologicalcontrol.

Hydraulic part of a dispenser

When a dispenser is switched on, theelectricmotorisactivated,andbeginsdrawfuel from its outlet. This displacement ofthe liquid creates a partial vacuum at thepump inlet. When the discharge nozzleremains closed, the vacuum is relieved byfuel circulating continuously through theunit. But when the nozzle is opened,suction pressure is transferredinstantaneouslyfromthepumpinlettothestorage tank through the pipe line. There,atmosphericpressureforcesthefueltoflowthrough a check valve toward thedispenser.

Beforeenteringthepumpingunit,itpassesthroughastrainerorfilter,whichremovesanysolidparticles.Smallquantitiesof trappedair and fuel vaporarealso removed from thefuelthroughanairseparatorchamber.

Thenthe fuel, freeofairandvapor,passes to theautomaticcontrolvalvewhichpermitsfuel to flowonly in thedirectionof themeter,neverback to thepump.Nowadays, thecontrolvalveisreplacedbyasolenoidandpilotvalve.

The Metering and the Registering part

Working principle of mechanical and semi mechanical units

While the hydraulic part of a dispensing unit will remainmore or less similar, working

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principleofthemeteringandregisteringpartofmechanical,semimechanical(Ztypesforexample)andelectronicunitsaretotallydifferent.Requirementforsealingofthoseunitswillalsobedifferent.

Metering part for both the types are similar. But, mechanical dispensers employmechanical registering unit of analog display while a semimechanical dispenser uses adigital display unit. In the former type themetering unit is connected to the registeringunit through a gear box while in the later type a sensor (a device which transformsmechanicalforceintoelectronicsignals)isusedfortheconnection

Metering Unit

The main components are the Adjustment wheel by which the delivery is controlled(calibration),theCylindersandtheGearBox.

Meteringdevicesmostlyusepistonmetersandarepositivedisplacement.Apistonmovingthrough a cylinder filled with liquid will displace a quantity of liquid which will bedeterminedbytheboreofthecylinderandthestrokeofthepiston.Usuallyfourcylindersareused.Thepistonsoperatemayoperateinahorizontalplaneorinaverticalplaneandconvert their toreciprocatingactiontoarotaryshaftoutput todriveeitherasensororamechanicalcomputer(gearbox).

The metering units are calibrated at the factory.Normally,thecalibrationisofhighaccuracyandreliable.However, meters may need adjustment after period ofusage or deliberate maladjustment to cross the MPElimit.

Theseadjustmentscanbemadeinverysmallquantityaslittle as 3/10,000 part of volume. The adjustingmechanismmaybelocatedonthetopofthemeterorononeofthepistoncaps.Itmaybea knurled knob, keyed disk, or calibrated wheel or have some other but immediatelyidentifiabledesign.Thediscorwheeloranyotheradjustingdevicemusthavelockingpinsorfixedperforatedscrewsforsealing.

Inside and outside of two common types of gear box

Gearboxesandadjustmentwheelsaremajorcomponentswhicharemanipulatedmostlybyunscrupulousdealers.

Extraprecaution is required for sealing theGearBoxand theAdjustmentwheel.All thethreecomponentsaresealedindividuallywithonelongmultithreadedwire.

The Registering Unit



The rotary shaft output of themeteringunit drives a registeringunit,whichmaybe oldfashionedmechanicalcomputer,orasensororpulserinelectricalinstallations.

In mechanical registers the display isanalog. It has two panels of computinganddisplay.Thelowerpanel indicatesthevolumedeliveredwith1/10thdivisionsofalitre,inanoperation.Thedisplayhastoberesettozerobeforethenextoperationcanbegin. The upper panel, known astotalizer, registers the total volumedispensed by the unit. The indication must be irreversible and is sealed to prevent anychangeindisplay.

Suchregisteringunitsarestillfoundinsmalltownsandmainlyintheruralareas

In semimechanical registering units, a sensor isused to convert the mechanical energy og themetershafttoconvertitintoelectricalsignal.Theoutput of the sensor is sent to the digital displaypanel.Thepanelshowsboththevolumedisplayedin an operation and also the total volumedispensed by the unit. Here again, the volumeindicator is set to zero before the next operationcan begin and the totalizer is irreversible. Thesensor box is need to be sealed to prevent any

unauthorizedadjustment.

Such type of units are found in semiurban or rural areas and are known as Zseriespumpsbecauseoftheirdesign.

Working Principle of Electronic Multiple Product Dispensers

Electronic Multiple Product Dispensers (MPD) devices used for measuring andtransferringaspecifiedvolumeofanumberofliquidfuelsfromasingleequipment.Apartfromtheintroductionofsolenoidvalve,whichiscontrolledbythemicroprocessor,restofthehydraulicsectionismoreorlessthesameasthoseinoldermechanicalunits.

The electronic Device

The heart of the system istheCentralProcessingUnit(CPU), a microprocessorwith an inbuilt memorychip. It controls the entireset of measuring, display,delivery and associateddevices of preset keypad,receiptprinteretc.

AnMPD,beinganelectronicdeviceusesatransducer,generallycalledapulser,whichiscoupled directly to the meter shaft. The pulser converts the mechanical force of therotating shaft intodiscreet electricalpulses.Thesepulses are transmittedas input to theCPU. The CPU recognizes not only pulse signals but electrical signals from other inputdevise zero reset,priceadjustment,presetmechanismetc.Afterall the informationareprocessed, the CPU sends appropriate signal to the display panel (through the display



card),totheprinter, ifconnectedandalsotothesolenoidvalvetocontrolrateofflowofliquid through the meter. The rate increases in the beginning, remains steady in themiddleandslowsdowntowardstheendofdelivery.

Thepresetkeypadisusedtotransmitthepresetthequantitiesortotalpriceoffueltobedeliveredandalsocreditcarddetails.

The display panel normal bears the following information price per litre, quantitydeliveredandprice.There isalsoa totalizer to register totalquantityof fueldeliver fromtheunit.

Upper Chamber

The Upper Chamber holds theelectronic part of the unit. Itcontains the main mother boardof the processor along withmemory chip, connected to allinput devices and output devices.TheallimportantDIPswitchBox,alsoknownasBlackBox,usedforelectronic calibration, is locatedhere.OthermajorcomponentsareCalibration Card, Display Cardand Unit and Totalizer.Calculating device PresetKeyboard andPrintingDevice are

alsoconnectedtothemotherboard.

ComponentsofthischamberwhichrequiresealingareDipSwitchBox,DisplayUnitandtheTotalizer.

Ina chamber theremaybeasmanyas fourunits, two in each side, oneunit each for4typesoffuelsHighSpeedDiesel,SuperDiesel,UnleadedPetrolandnormalPetrol.

Functioning of the Calibration Card

Calibration means the process of adjusting the calibration mechanism of a measuringinstrumentsothatitfunctionswithinitsstandardaccuracy.

InanMPDoranelectronicdevice,CalibrationCard is themost importantcomponentofthesystemsystembecauseitcontrolstheactualquantityoffuelsuppliedtothenozzle.Onthe card, there is a black box inside which the Dual Inline Package (DIP) Switch isplaced.ThisswitchisrequiredtobesetONforcalibratingthepumpforcorrectdelivery.Naturally, this box needs additional protection. After, switching on the DIP, thecalibrationismadethroughthepresetcalculatorthroughaseriesofcommands,asmaybegivenintheusermanual.However,thelimitofadjustmentthroughthecalibratingcardis150mlin5l.Changeindelivery beyond that is possible through rotating the adjustment gear or turning theadjustmentrodinsidethemeter.

Electronic Calibration

The DIP Switch Box on the PCB (Printed Circuit Board), or somewhere near, is

openedandswitchedon.

Entercalibrationmodeusingacodenumber.

EnteruserPIN.

Calibratefor5lor20l.(Thecalibrationcanchangedeliveryupto150mlin5l.)



Manual Calibration

Whenthecalibrationcannotbemadeuptoadesiredlevelbyelectronicmethod,manualcalibration is done. This is done though calibrating the meter either by rotating theadjustmentgearorturningtheadjustmentrodafterliftingtheadjustmentknobtofreeitfromthemetershaft.

Caution

It is not enough to guard the Calibration Device through a PIN Code only. Under theprovisionofRule2(20)(ii), inaninstrumentmeantforsellingtothepublic,thereshouldalso be a Hard Key, a locking device. The device should be sealed so that it cannot beopenedunauthorizedly.

Calibration History

Thememorychipmaintainsahistoryof lasttenattemptsofcalibration.Itcanberetivedbytypingappropriatekeysofthekeyboardasgivenintheusermanual.It isveryhelpfulto detect any attempt of unauthorized calibration. The history consists of Calibrationfactor of the nozzle. no of calibrations attempted and the Totalizer reading after thecalibration.Thesefiguresmaybenotedforanyfuturecomparing.

Verification Procedure

Equipment

1.Certificate/sofmodelapproval.2.Appropriateworkingstandardsofmeasurementas(a)Avolumemeasureofatleast10Lcapacitysuitablefordeliveriesatmaximumflowratespecified for the dispenser. The measure should be suitable for deliveries greater thanthree times the minimum measured quantity (Vmin) specified for the dispenser. For

dispensersgreaterthan60L/minuseameasurewithavolumeequivalenttoatleast1mindeliveryforbothmaximumandminimumflowrate.(b)Asmallcapacitymeasureverifiedatrelevant intervals for testswheresmallmeasuresarerequired.

Preparation

The first fill into a dry standard volumemeasure may produce erroneous results if theinternal walls of the measure are not wet with the liquid to be measured. Hence, it isessentialthatallworkingstandardvolumemeasuresbeconditioned(wettedanddrained)beforebeingused.Thisprocedureisonlyneededontheinitialtestrun,andisnotrequiredonsubsequentdeliveriesaslongasthemeasureremainsconditioned.

Test Procedures

The following series of test procedures determine if the performance of a fuel dispensermeets requirements andwhether the dispenser requires adjustment or service. Each testprocedure is explainedasadiscrete test.However tests canbecombined toexpedite thetestingprocedure.

Unless specified otherwise in the certificate of approval, all dispenserswith amaximumflowratenotgreaterthan60L/minshallhaveaVminof2L.

1. Checking Facility for Electronic Indicating Devices

Thecheckingfacilityforanelectronicindicatingdeviceshallprovidevisualcheckingoftheentiredisplay,whichshallmeetthefollowingdescription(Part2,clause4.3.iv.b):



displayingalltheelements(eightstest)

blankingalltheelements(blanktest)and

displayingzeros.

Thistestcanbecarriedoutinconjunctionwiththetestforzerosetting.

1.Removethenozzlefromitshanguppositionandcheckthatthe:displaytestisperformedand

displaysegmentsarenotfaulty.

2.Determinewhetherthedispenserhaspassedorfailed.

2. Zero Setting

ThezerosettingdevicesofthepriceindicatingdeviceandofthevolumeindicatingdeviceshallbedesignedinsuchawaythatzeroingeitherindicatingdeviceautomaticallyinvolveszeroingtheotherPart2,clause3.3.v)

Thezerosettingdeviceshallnotpermitanyalterationofthemeasurementresultshownbythe price/volumeindicating device other than by making the result disappear anddisplayingzeros(Part2,clause3.2.iv.b)

Once the zeroing operation has begun it shall be impossible for the price/volumeindicating device to show a result different from that of themeasurement that has justbeenmade,untilthezeroingoperationhasbeencompleted.Theprice/volumeindicatingdevice shall not be capable of being reset to zero during measurement (Part 2, clause3.2.iv.c)

Determinewhether zero setting ismechanical or electronic and conduct theappropriatetestasfollows:

2.1 Mechanical Reset Mechanism

Formechanicalindicatingdevices,theresidualvolumeindicationafterreturntozeroshallnot be more than half the minimum specified volume deviation (Emin), e.g. 10 ml for

dispenserswithaVminof2L(Part2clause3.2.iv.d).

Likewise,theresidualpriceindicationafterreturntozeroshallnotbemorethanhalftheminimum specified price deviation (MSPD) where MSPD = Emin X unit price (Part 2,

clause3.3..viii).

Removethedeliverynozzlefromitshangupposition.

IfaprevioussaleremainsontheindicatormovethestartinglevertotheONposition

andensurethatthepumpmotordoesnotstartorthedispenserisnotactivated.Ifthe

pumpmotordoesstartorthedispenserisactivatedthentheinterlockmechanismis

faulty.

Resettheindicator/stozeroandcheckthatthevolumeindicator/sis/arezerowithin

0.5Eminandthepriceindicator/sis/arezerowithinEminXunitpriceX0.5.

Move the starting lever slowly and gently towards the ON position until themotor

starts (or the dispenser is activated) and then slowly and gently towards the OFF

positionuntilthemotorstops(orthedispenserisdeactivated).

MovethestartingleverslowlyandgentlytowardstheONpositionandcheckthatthe

interlockhasengagedandpreventsthemotorfromstartingorbeingactivated.

ReturnthestartinglevertotheOFFposition.

Determinewhetherthedispenserhaspassedorfailed.

2.2 Electronic Reset Mechanism



Forelectronicindicatingdevices,theprice/volumeindicationafterreturntozeroshallbezerowithoutanyambiguity(Part2,clauses3.2.iv.eand3.3.ix).Remove the nozzle from its hangup position and ensure that the display test is

performed and the price and volume displays are on zero before any delivery of

productispossible.

Carefullyreturnthenozzletoitshanguppositionandensurethatwhenthenozzleis

then removed no further deliveries are possible without the segment test being

initiatedandtheindicationsreturningtozero.


3. Price Computing

Thepriceindicatedshallequalthepricecalculatedfromthevolumeandunitprice.

Thistestcanbedoneatanytimeduringatestdelivery,e.g.accuracytestornozzleshutofftest.Resetthedispensertozero.

Makeadeliveryofaconvenientvolume.

Calculatethetotalpricefromtheunitpriceandtotalvolumeindicated.

Comparethiscalculatedpricewithalldisplays.


4. Nozzle Cutoff

Where the hose is fitted with an automatic cutoff nozzle the nozzle should closeautomaticallywhenthesensingportofthenozzlecomesincontactwithliquidorfroth.

Thistestcanbedoneduringaccuracyorantidraintesting.Makeadeliveryatnormalflowrate.

Allowthesensingportofthenozzletocomeincontactwithliquidorfroth.

Ensurethenozzlecutsoff.

Repeatsteps1to3twicemore.


5. Interlock

The use of the same indicating device for the indications of several measuring systems(whichhaveacommonindicatingdevice)isauthoredprovideditisimpossibletouseanytwoofthesemeasuringsystemssimultaneously(Part2,clause2.9.vi).

Inmeasuringsystemsintendedtodeliverliquids,nomeansshallbeprovidedbywhichanymeasuredliquidcanbediverted(Part2,clause2.16.i).

The selected unit price shall be displayed by an indicating device before the start of themeasurement(Part2,clause3.3.ii)

These requirements are interpreted to mean that no fuel can be dispensed unless it ismeasured and that the unit price indicated corresponds to the unit price of the fuelselectedanddelivered.

Determinewhetherthehoseshaveacommonindicatororwhethertheyshareapumpingunit,andconducttheappropriatetestasdocumentedbelow.

5.1 Hoses Sharing a Common Indicator

Selectandauthorizeonehoseandremovethenozzlefromitshangupposition.

Check that thepriceandvolume indications for thehose selected reset to zero, and

fordispensers:

withseparateunitpricedisplay:



theunitpricedisplayforthetypeoffuelselectedistransferredtothemainindication

withoutseparateunitpricedisplay:the unit price display for the hose selected is displayed and all other unit price

displaysdisappearuntilthedeliveryhasbeencompleted.

Check that all other hoses sharing the same indicator are disabled by removing the

othernozzlesfromtheirhanguppositionandconfirmingthattheydonotauthorize.


5.2 Hoses Sharing a Pumping Unit

Selectandauthorizeanyhosethatsharesacommonpumpingunit.

Whilethepumpingunitisoperating,attempttomakeadeliveryfromanyotherhose

connectedtothesamepumpingunitwithoutallowingtheindicatortoresettozero.

Check that it is not possible to make a delivery from any other unauthorized hose

connectedtothesamepumpingunit.


6. Preset Indications

Measuring systemswithapriceindicatingdevicemayalsobe fittedwithaprice/volumepresettingdevice,whichstopstheflowoftheliquidwhentheprice/quantitycorrespondstothepresetvaluePart2,clause3.6.x).

Thistestcanbecombinedwiththepresetaccuracytestandoneresultrecorded.Resetthedispensertozero.

Enterasuitablepresetvalueusingthepresetfacility.Makesurethepresetamount

appearsonthedisplay.

Commenceadelivery into thecontainerwith thenozzle fullyopenallowingthepre

setfacilitytoslowdownandcompletethedeliveryautomatically.

Check that the price/volume indication on the display corresponds to the preset

amount and for selfserve remains on the display or is stored in memory until the

transactionisfinalized.


7. Maximum Flow Rate

Themaximumachievable flow rate shall bewithin theapproved range (Qmin toQmax)markedon thedataplate.This test is only indicative that themaximumachievable flowrate is within the approved range and can be performed during one of the fast flowaccuracytestdeliveries.

Determine whether the hoses have their own pumping unit or whether they share apumpingunit,andconducttheappropriatetestasspecifiedbelow.

Hoses with their own Pumping Unit

1.Commenceandtimeadeliveryatthemaximumachievableflowrate.2.Stopthedeliveryafteratleast10s.3.Notetheindicationonthedispenserandcalculatetheflowrate.4.Determinewhetherthedispenserhaspassedorfailed.

Hoses Sharing a Pumping Unit

This isarequirementat initialverification/certification,whenanysitechangesoccur,orat thediscretionof the trademeasurementauthority.Refer to thecertificateofapprovalforspecifictests.

1.Selectandauthorizeanumberofhosesconnectedtothesamepumpingunit.



2.Withallhosesoperatingatthemaximumachievableflowrate,timethedeliveryforoneofthehoses.3.Stopthedeliveryafteratleast10sandcalculatetheflowrate.4.Determinewhetherthedispenserhaspassedorfailed.

8. Accuracy

ItisrecommendedthattestingbecarriedoutatthemaximumachievableflowrateandatQmin (asper theprocedure)and the resultsanalyzed todetermine if themeter requiresadjustment.

1.Conditiontheworkingstandardvolumemeasure2.Makeadeliveryatmaximumachievableflowrate.Recordthevolumeindicatedbythefueldispenser(VFD)andthevolumeindicatedbytheworkingstandardmeasure(VREF).

3.Calculateandrecordtherelativeerror(EFD).

EFD=(VFDVREF)/VREFX100

4.Repeatsteps2to3twicemore.5.Makeonemoredeliveryatminimumflowrate.Recordthevolumeindicatedbythefueldispenser(VFD)andthevolumeindicatedbytheworkingstandardmeasure(VREF).


7.DetermineifalltheresultsarewithintheallowableMPE.Ifnot,analyzetheresultsandassesswhetherornotthemetercanbeadjustedsothatalltheresultsarewithinMPE.8.Ifmeteradjustmentsaremade,circulateaquantityoffuelandrepeatsteps2to7.

9. Accuracy of Preset

Apresetaccuracytestisonlyconductedwhenitisnecessarytochecktheaccuracyofthepresetdeliveryvolume.

1.Conditionthestandardvolumemeasure.2. Enter and record a suitable preset value using the preset facility. This preset valueshoulddeliverclosetothevalueofthereferencestandardmeasurebeingused.3.Makeadelivery atmaximumachievable flow rateuntil thedelivery stops.Record thevolume indicated by the fuel dispenser (VFD) and the volume indicated by the working

standardmeasure(VREF).


EFD=(VFDVREF)/VREFX100

5.DetermineiftheresultiswithintheMPE.

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