ASTM D2624 method for electrical conductivity of aviation and distillate fuels
CONTINUOUS IN-LINE CONDUCTIVITY
14. Apparatus
14.1 Continuous measurements can be made where suitable precautions have been taken to remove static charges before the representative fuel stream is passed through the in-line measuring cell. A controlled, continuous flow through the cell prevents ion depletion, thereby providing the equivalent of rest conductivity as a continuous measurement.
15. Installation
15.1 In general, the equipment is designed for permanent installation in the fuel distribution system. Follow the manufacturer's recommendations concerning installation and flow control, particularly with respect to the provision of adequate relaxation time. Install the sample tapping point at least 30 m downstream of any additive injection system, unless a mixing device is used which has been shown to give adequate mixing of the additive concerned prior to sampling. A thermometer having a suitable range for measuring fuel temperature in the field should be installed downstream of the test cell.
16. Calibration
16.1 The specific calibration procedure detailed in Annex A4 is an essential part of the general procedure and should be completed prior to initiating automatic monitoring and control of continuous fuel streams. If fitted, the high- and low-level alarm circuits should be calibrated as recommended by the manufacturer.
17. Procedure
17.1 Flush the cell thoroughly by initiating a controlled flow of the fuel to be measured. Purging of air from the cell and adequate flushing is normally achieved in a few minutes but a longer flush is recommended when calibrating the instrument. The controlled flow must conform to the manufacturer's recommendation. Too fast or too slow a flow will result in inaccuracies in the conductivity measurement.
18. Measurement
18.1 After calibration, select the instrument scale of the approximate range anticipated for the fuel stream and initiate continuous measurements of fuel conductivity. Make measurements at the test cell temperature (indicated by the installed thermometer), which should approximate the temperature of the fuel in the system.
19. Report
19.1 Report the electrical conductivity of the fuel and the fuel temperature at which measurement was made (see Note A1.1).
20. Precision and Bias
20.1 Repeatability - Repeatability of the continuous meter has been established to be within the range given for the portable instruments (see 13.1.1).
20.2 Reproducibility - Reproducibility has not been established.
20.3 Bias - Since there is no accepted reference material or test method for determining the bias of the procedure in this test method, bias cannot be determined.
21. Apparatus
21.1 Continuous measurements can be made using a sensor that utilized alternating current measurement technique. In this type of instrument, the constant rotation of the applied electric field prevents the formation of polarization impedances on the electrodes. The sensor then yields the equivalent of dc-type resting conductivity readings.
22. Installation
22.1 The JF-1A sensor should be used as specified in the "Installation and Safe Use Manual, Ref. A440-010" that is provided with the instrument. The JF-1A has an integral temperature measurement channel.
23. Calibration
23.1 The specific calibration procedure detailed in Annex A6 is an essential part of the general procedure and should be completed prior to initiating automatic monitoring and control of continuous fuel streams.
24. Procedure
24.1 Use instrument in accordance with the manufacturer's procedures (see item 22).
25. Measurement
25.1 Model JF-1A provides means to read a 4 to 20 mA current loop output that is proportional to conductivity and a second loop output that is proportional to fuel temperature. Alternately, serial ASCII data is available for direct interface to a computer or other logging device.
NOTE 8 - Current loop outputs are nominally scaled to 0 to 500 pS/m. The unit can be field programmed for other ranges up to 0 to 2000 pS/m.
