5313 Parshall Datasheetl Db 02 0027

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  UF_Parshall_DB_02_0901.doc Reprint of texts or text extracts requires prior written authorization of Badger Meter Europa GmbH. Misuse of texts, pictures or company logo will be prosecuted. Parshall flumes Description The Parshall flume is one of a large class of open channel primary elements known as critical flow venturi flumes. A distinguishing characteristic of the Parshall flume is the downward sloping invert of the throat. This feature gives the Parshall flume its ability to operate at higher ratios of downstream to upstream head than any other such device. The Parshall flume is a monolithic fiberglass reinforced polyester structure to assure maximum strength and accuracy of dimension while minimizing installation time. Its weight is light, the installation easy and there is no need for special tools. Its short length makes the installation possible in areas, where further constructions are limited. Application The Parshall is recommended for those applications in which moderate concentrations of sand, grit or other heavy solids exist and fluid velocities entering the flume are subcritical. The flume operates with a small energy loss or change in channel grade, about one-fourth that of weirs having the same crest length. The flume is ideally suited for fluid measurement in irrigation channels or sewers. Features ã   Accuracy ±3% ã   Self-cleaning construction ã   Available from DN75 – DN915 ã   Measuring range from 0,77 l/s to 1577 l/s ã   Short delivery time ã   Own manufacture Calibration The Parshall flume exhibits reproducible head rise/flow rate characteristics throughout its size range. In order to assure the accuracy of the device, adherence to all dimensions for construction as well as free flow hydraulic conditions are required. Factory made Parshall flumes can be calculated with an accuracy of ±3% of nominal value. Sizing Selection of a Parshall flume should be made on expected flow rates or on the maximum flow rate and on the width of influent and effluent channel, which must at least have the dimensions mentioned in column B (see table on back side). For single point measurement to be valid, the design hydraulic gradient must insure that free flow conditions exist at all flow rates. Thus, the downstream fluid level must not exceed the values in figure 2 or single point measurement will not produce acceptable values. Badger Meter Europa GmbH Nürtinger Str. 76 72639 Neuffen (Germany) Tel. +49-7025-9208-0 Fax +49-7025-9208-15 www.badgermeter.de badger@badgermeter.de  UF_Parshall_DB_02_0901.doc Reprint of texts or text extracts requires prior written authorization of Badger Meter Europa GmbH. Misuse of texts, pictures or company logo will be prosecuted. Sizing Performance data and dimensions of standard sizes Minimum downgrade in the channel: 0,2 – 0,5 % Discharge curves for Parshall flumes with free flow and with submerged conditions. The Parshall flume is an empirically derived and rated measuring device. The discharge capacities are rated for free flow conditions. As the downstream depth increases, flow condition is no longer critical, thus two depth measurement readings (at Ha and Hb) are necessary to obtain the correct discharge under these conditions. The following graph presents these corrections necessary to ensure true discharge values. Throat Measuring range max level Dimensions W L/s h1 Length Width Height mm inch min max mm mm mm mm 75 150 230 305 455 610 915 3 6 9 12 18 24 36 0,77-5 1,50-11 2,50-18 3,32-24 4,80-35 12,10-44 17,60-69 0,77-54 1,50-114 2,50-284 3,32-473 4,80-757 12,10-1009 17,60-1577 462 465 661 780 805 799 812 915 1524 1626 2867 2943 3020 3169 323 461 639 973 1154 1335 1700 667 724 876 1143 1143 1143 1143 Flow Flow Level floor Inlet Outlet Throat
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