Final Program EXPRES 2012 - Conferences

III.RESULTS OF MEASURMENTSEach measurement was repeated 30 times (There is aremark in the chart key if this number was between 5 and20).TABELE 2.ERROR RANGES OF WATER METER MEASURING FOR CALIBRATEDDISCHARGES IN THE FUNCTION OF WATER METER READING ACCURACY(CLASS B, RATED DIAMETER OF 20 MM AND DISCHARGE OF QN=1,5M3/H),FOR A DURATION OF 0,5 MINUTES FLOWG (%)65432Accuracy of water meter readings: 2,5 centilitrespermitted error limitmethod without switching off the water meterfrom 1,2 to 2,8%from 1,4 to 2,1%from 1,5 to 1,9%from 1,6 ro 1,8% - 10 datafrom 1,6 to 1,8% - 10 datafrom 1,6 to 1,8% - 10 dataReading Dis- Error range (%)accuracy charge For both methods During calibration2,5 centilitres Q min from -7,4 to 32,1Q t from 2 to 8,5Q n from 1,2 to 3,31 decilitre Q min from -25,9 to 56,9 ±5Q t from -2,9 to 12,1 ±2Q n from 1,6 to 3,2 ±2G (%)100 0.5 1 1.5 2 2.5 3 3.5 4 4.5654321t (min)Accuracy of water meter readings: 1 decilitrepermitted error limitmethod without switching off the water meterfrom 1,6 to 3,2%from 1,6 to 2%from 1,4 to 2%from 1,6 to 1,8% - 10 datafrom 1,6 to 1,8% - 10 datafrom 1,6 to 1,8% - 10 data00 0.5 1 1.5 2 2.5 3 3.5 4 4.5t (min)Figure 3. Error in water meter measuring at Q n flow during waterflow shorter than the time for which the meter was calibrated (4 min.)in the function of water meter reading accuracyIt means that during consumption shorter than the timethe water meter was calibrated for, measuring by themeter is unreliable in 95% of the consumption shorter than1 minute. During a discharge of 0,5 minutes, the errormay be even 56,9%.V. CONCLUSIONFor calibration discharges, foreseen by the Protocol,through the testing of class B flow meter with 20 mmrated diameter and discharge of Q n =1,5 m 3 /h, it has beenestablished, that:• in the case, when consumption time was shorter thanthe time the meter was calibrated for, at discharges of, the range of the meter measuring error exceeded therange of permitted errors, and• the biggest errors occur at Q min – for example, atdischarge lasting for 0,5 minute, the error may beeven 32,1% (for water meter reading accuracy of 2,5centilitres), or even 56,9% (for water meter readingaccuracy of 1 decilitre).Since it concerns 95% of water consumptionmeasurement, such testings are necessary for all types ofwater meters used in the supply networks of this country.IV.DISCUSSIONBoth methods of testing provide similar ranges ofwater meter measuring errors for flows Q min and Q n . AtQ t flow, the method without stopping the water meterprovides larger errors than the method with stopping themeter:• the most significant allowance (up to 4,7-2,8=1,9%)was registered during the 2 minute long flow, while• during the time for which the meter was calibrated,the error exceeded (up to 2,2-2=0,2%) the permittedvalues.In the case, when consumption time was shorter thanthe time the meter was calibrated for, the range of themeter measuring error exceeded the range of permittederrors.REFERENCES[1] Arregui, Francisco; Cabrera Jr., Enrique; Cobacho, Ricardo 2006Integrated Water meter Management. IWA Publishing, London.http://www.iwaponline.com/wio/2007/01/pdf/wio200701RF1843390345.pdf[2] Buchberger, Steven G.; Wells, Greg J. 1996 Intensity, Duration,and Frequency of Residential Water Demands. Journal of WaterResources Planning and Management 122(1), 11-19.[3] Hovanj, Lajoš 2010 Minimalno vreme između dva očitavanjavodomera. Zbornik radova Građevinskog fakulteta, Subotica 19,105-113.[4] ISO 4064-3:2005(E) Measurement of water flow in fully chargedclosed conduits – Meters for cold portable water and hot water.Part 3: Test methods and equipment.[5] OIML R 49-2: 2006 (E) Water meters intended for the metering ofcold potable water and hot water. Part 2: Test methods.[6] Pravilnik 1986 Pravilnik o metrološkim uslovima za vodomere. –Službeni list SFRJ, Beograd 51, 1509-1513.[7] SRPS EN 14154-3: 2010 (en) Merila protoka vode. Deo 3: Metodeispitivanja i oprema.65