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Division 2.5.1 Positive displacement pump (PDP)

United Kingdom

Original text. Later amendments are not shown.

All the parameters related to the pump shall be simultaneously measured along with the parameters related to a calibration venturi which is connected in series with the pump. The calculated flow rate (in m3/s at pump inlet, absolute pressure and temperature) shall be plotted versus a correlation function which is the value of a specific combination of pump parameters. The linear equation which relates the pump flow and the correlation function shall be determined. If a CVS has a multiple speed drive, the calibration shall be performed for each range used.

Temperature stability shall be maintained during calibration.

Leaks in all the connections and ducting between the calibration venturi and the CVS pump shall be maintained lower than 0,3 % of the lowest flow point (highest restriction and lowest PDP speed point).

The airflow rate (qV CVS) at each restriction setting (minimum 6 settings) shall be calculated in standard m3/s from the flowmeter data using the manufacturer's prescribed method. The airflow rate shall then be converted to pump flow (V 0) in m3/rev at absolute pump inlet temperature and pressure by means of equation (7-69):

V 0 = q V CVS n × T 273,15 × 101,325 p p (7-69)

where:

qV CVS

  • airflow rate at standard conditions (101,325 kPa, 273,15 K) [m3/s]

    • T

  • temperature at pump inlet [K]

    • p p

  • absolute pressure at pump inlet [kPa]

    • n

  • pump speed [rev/s]

    • To account for the interaction of pressure variations at the pump and the pump slip rate, the correlation function (X 0) [s/rev] between pump speed, pressure differential from pump inlet to pump outlet and absolute pump outlet pressure shall be calculated by means of equation (7-70):

    X 0 = 1 n × Δ p p p p (7-70)

    Where:

    Δp p

  • pressure differential from pump inlet to pump outlet [kPa]

    • p p

  • absolute outlet pressure at pump outlet [kPa]

    • n

  • pump speed [rev/s]

    • A linear least-square fit shall be performed to generate the calibration by means of equation (7-71):

    V 0 = D 0 –m · X 0 (7-71)

    with D 0 [m3/rev] and m [m3/s], intercept and slope respectively, describing the regression line.

    For a CVS system with multiple speeds, the calibration curves generated for the different pump flow ranges shall be approximately parallel, and the intercept values (D 0) shall increase as the pump flow range decreases.

    The calculated values from the equation shall be within ± 0,5 % of the measured value of V 0. Values of m will vary from one pump to another. Particulate influx over time will cause the pump slip to decrease, as reflected by lower values for m. Therefore, calibration shall be performed at pump start-up, after major maintenance, and if the total system verification indicates a change of the slip rate.