ISO 6297:1997 pdf download – Petroleum products -Aviation and distillate fuels -Determination of electrical conductivity.
7 Sampling
To avoid errors in the measurenteitt of fud conductivity, either carry out the measurements in situ, or take samples using the procedures specified in ASTM D4057 or Iso 3171. The following additional precautions arc also rcquired:
a) the sample size shall be as large as practicabic and not less than I litre;
b) containers shall be fully epoxy-lined cans or of polytetrafluoroethylenc (PTFE) only (see note 3);
c) prior to sampling, all containers and their closures shall be rinsed at least three times with the fuel being sampled;
d) samples shall be tested as soon as possible after sampling.
NOTE 3 — Test method results are known to he sensitive to (race contamination during the sampling operation and from sample containcrs. New containers are recommended, but whcn only used containers are available they shall he thoroughly rinsed with cleaning solvent, propan.2.ol (5.1). followed by toloene 5.2). and dried with a stream of air.
8 Procedure
8.1 Calibration
Carry out calibration procedures in accordance with the equipment manufacturer’s instructions immediately prior to use of the apparatus.
8.2 in situ field measurements in tanks, tank cars, trucks, etc.
4 -— For field measurements portable conductivity meters arc considered suitable. In order to satisfy local safety regulations they should be certified as intrinsically safe for usc in hazardous locations. Each meter has, or can be equipped with, an extension cable to lower the ccli into the tank.
5 — High impedance handheld meters are susccprihlc to electrical transients caused by the extension cable flexing during measurements. Failure to hold the apparatus steady may result in significantly reduced precision.
8.2.1 Check the calibration and earth (ground) the meter to the tank. Lower the conductivity cell into the tank to the desired level, taking care to avoid partial immersion or contact with tank water bottoms, if present. Move the conductivity cell in an up-and-down motion to remove air and previous fuel residues.
CAUTION – To prevent static discharge between a charged fuel and a conductive probe inserted into a tank, the appropriate safety precautions of earthing (grounding) and waiting for charge diss-ipation should be observed. It is recommended that a 30mm interval he allowed after pumping into a storage tank before an operator mounts a tank to insert a sampling device. This will ensure that the Fuel is electrically at rest.
NOTE 6 — If the cell is in contact with water and the instrument is switched on. an immediate oil- scale reading will he obtained. If the cell has been in contact with water, it should be thoroughly rinsed with cleaning solvent, and dried with a stream of air. In hot, humid conditions, condensation on the cell can occur, which can also cause high icro, calibration and sample readings. This can be avoided by storing the cell at a temperature 2 C to 5 ‘C in excess of the maximum ambient temperature.
8.2.2 After flushing the cell, hold it steady and, alter activating the instrument, record thc highest reading after initial stabilization.
NO’[h 7— Stabilization should occur within 3 s.
On instruments with more than one scale range, select the scale which gives the greatest sensitivity for the conductivity value being determined. Record the ftiel conductivity and temperature.
8.3 Laboratory and field measurements on sampled fuels
8.3.1 Prepare containers in accordance with 7 c).
8.3.2 Rinse the conductivity cell and measuring vessel with the fuel under test to remove previous fuel residues. Transfer the fuel to the nieasuring vessel. check the metel calibiatioti. immerse the conductivity cell to the depth given in the manufacturer’s instructions and measure the conductivity of the sample iii accordance with 8.2. Ensure that the bottom of the conductivity cell does not touch the sample container, whatever the material of construction. Record the fuel conductivity and temperature.
8.4 Continuous in-line conductivity measurements
8.4.1 Ensure the conductivity cell is thoroughly purged of air.
8.4.2 Check the calibration and select the appropriate scale range for the fuel stream whose conductivity is being measured. Record the fuel conductivity and temperature.
9 Expression of results
Express the results either in picosiemens per metre (pS!m) to the nearest unit shown on the instrument used, or as less than I pS/rn if the instrument reads iero: also the temperature of measurement to the nearest 1C.