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6.G. - Page 164 of 238 <br />The system loop error for the secondary metering equipment is determined by connecting <br />its output to the differential pressure transmitter and adjusting the dead weight tester to 5 <br />places over the full range of flow: 0%, 25%, 50%, 75% and 100%, while all instruments <br />in the loop are connected. For water level transmitters, provide simulated test head equal <br />to full range of the transmitter being calibrated, comparing the simulated test head to its <br />4-20 milliamp output signal to determine transmitter error and calibration requirements. <br />The system loop error for the secondary metering equipment may not exceed +/-2%. The <br />individual components of the secondary metering equipment shall also be tested at the <br />same 5 input levels and calibrated as necessary to ensure the error of the system and <br />individual components does not exceed +/- 2%. <br />b) Annual Pitot Tube Testing and Calibration. Annual Pitot tube testing shall be conducted <br />for a comparison of flow totalized by the Pitot tube test equipment and the totalizer used <br />by the SFPUC for water measurement and billing purposes. Annual Pitot tube flow <br />testing shall be performed on all flow meters for assessment of Venturi error using the <br />Annubar continuous flow method at 22% of the pipe radius. Pitot tube now testing must <br />be conducted continuously for a minimum of 30 minutes per test. <br />The Pitot tube flow tests are first performed before any of the secondary metering <br />instruments are calibrated to determine the total system error (system consisting of the <br />primary metering device and secondary metering equipment). Once the total system loop <br />error has been established, perform secondary loop instrument testing and calibration as <br />per the quarterly testing and calibration procedures described in 4.a above. If the total <br />system error exceeds +/- 2% after calibration of the secondary metering equipment, <br />minor adjustments to the differential pressure transmitter shall be made to correct <br />(calibrate) the error in the Venturi meter. Repeat Pitot tube testing must be performed <br />after the individual instrument calibration and differential pressure transmitter <br />adjustments have been performed to establish that total system loop error is within +/- <br />2%. <br />WE <br />March 1 l , 2009 <br />495 <br />