Document ID: chunk:federal_register_of_legislation:F2023L00129:reg:13:p49
Version: federal_register_of_legislation:F2023L00129
Segment Type: reg
Provision Reference: reg 13 (pt 49/56)
Character Range: 428225–431080

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 per cent of the lowest flow point (highest restriction and lowest PDP speed point).
9.5.2.1. Data analysis
 The airflow rate (qvCVS) at each restriction setting (minimum six 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 (V0) in m3/rev at absolute pump inlet temperature and pressure as follows:
                      (85)
 Where:
qvCVS  is the airflow rate at standard conditions (101.3 kPa, 273 K), m3/s
T is the temperature at pump inlet, K
pp is the absolute pressure at pump inlet, kPa
n is the pump speed, rev/s
 To account for the interaction of pressure variations at the pump and the pump slip rate, the correlation function (X0) between pump speed, pressure differential from pump inlet to pump outlet and absolute pump outlet pressure shall be calculated as follows:
  (86)
 Where:
                    pp is the pressure differential from pump inlet to pump outlet, kPa
                    pp is the absolute outlet pressure at pump outlet, kPa
 A linear least-square fit shall be performed to generate the calibration equation as follows:
  (87)
                    D0 and m  are the intercept and slope, respectively, describing the regression lines.
 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 (D0) shall increase as the pump flow range decreases.
 The calculated values from the equation shall be within ±0.5 per cent of the measured value of V0. 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.
9.5.3. Calibration of the critical flow venturi (CFV)
 Calibration of the CFV is based upon the flow equation for a critical venturi. Gas flow is a function of venturi inlet pressure and temperature.
 To determine the range of critical flow, Kv shall be plotted as a function of venturi inlet pressure. For critical (choked) flow, Kv will have a relatively constant value. As pressure decreases (vacuum increases), the venturi becomes unchoked and Kv decreases, which indicates that the CFV is operated