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Proposal <br /> Comprehensive Water Distribution System Audit <br /> <br />~ Al[0wing air to enter the process flow, resulting in Volumetric Calibration <br /> The volumetric calibration method consists of timing the <br />metering error, increase or decrease in water volume in a tank or basin of <br />~ Failuretopropedygroundtheinstruments, resulting known geometry. Thetechniquerequiresthatthegeometry <br /> of the volumetric tank be we!l-known, that the change in <br />in induced error in the electronic components, water surface elevation can be determined relatively <br />~ Installing a meter that is over-sized for the flow to be accurately, and that the time behNeen different elevations <br /> can be measured with reasonable accuracy. <br />measured. <br /> When performed correctly, volumetric calibration is among <br /> · ' installing the meter in a location that makes future the most accurate methods for calibrating flow meters. The <br /> maintenance impossible, method is oJcen referred to as the "bucket and stop watch" <br /> procedure, which is descriptive terminology, but does not <br /> Meter Aocuracy indicate the relative complexity of the procedure. The <br /> The accuracy of flow meters is a common problem procedure involves the measurement of three separate <br /> encountered in the water industry. The science that deals parameters: the volume of the tank, the change in water <br /> withaccuracyinmeasurementsismetrology, andtherehave surface elevation, and the time. For the procedure to be <br /> been numerous books written on the issues associated with accurate, all three measurements must be preformed with <br /> obtaining measurements that are both accurate and precise, reasonable accuracy. <br /> In the United States, the National institute of Science and <br /> TechnoJogy(NJST),whichusedtobeknownastheNational Tracer Dilution IVlethod <br /> Bureau of Standards, is the organization that is charged The tracer dilution method of in situ calibration consists of <br /> with supporting mehology at the national scale. Therefore, adding a known amount of the tracer to the process flow <br /> inapurestsense, all measurementsshouldbetraceableto and determining the concentration in the process flow <br /> NIST. downstream ofthe meter to be calibrated. Figure4shows <br /> a typical tracer ddutJon set up, and the equipment <br /> ErrorJnflowmeteringsystemsisintroducedbyeacheJement requirementsareminimal. A calibrated container for the <br /> used in the flow measuring process. Consider a venturi tube tracer is required to confirm the rate at which the metering <br /> s~tem that consists of the venturi tube, the differential pumpisaddingthetracertotheprocessflow. There must be <br /> pressure transmitter, and the indicator/recorder. Each of two tops [n place, one through which to add the tracer, and <br /> the three devices has some internal error that contributes to the other from which to collect the downstream sample. <br /> the overall error of the measured flow. it is important to <br /> realize that these errors are multiplicative, not additive. The flow in process is calculated from the following simple <br /> equation: <br /> In Situ Meter <br /> Calibration qxC, = (Q+q) xC? <br /> Several techniques can be used to perform in situ meter <br /> calibration, or to check the accuracy of meters that are whereqistheflowrateofthetracer, C~ isthe concentration <br /> of the tracer in the tracer solution container, Q is the process <br /> currentlyin service. Thetechniquesthat are most applicable <br /> to the City of Paris' project are discussed in the following flow rate, and C: is the concentration of the tracer Jn the <br /> downstream sample. <br /> paragraphs. <br /> <br /> Carter Burgess ~ 7 <br /> <br /> <br />