BS 15938:2010 pdf download – Automotive fuels — Ethanol blending component and ethanol (E85) automotive fuel — Determination of electrical conductivity
8 Procedure
8.1 Preparation of the measuring device 8.1.1 General The device manufacturer’s instructions shall be followed for the preparation and operation of the conductometer (6.1) and the measuring cell (6.2). The thermostat (6.5) is connected with the sample vessel (6.4) and set to achieve a temperature of (25 ± 0,1) °C in the sample vessel.
8.1.2 Cleaning of the sample vessel Before the measurement, the sample vessel (6.4) is rinsed several times with ethanol (5.1). The rest of the ethanol used for rinsing shall be dripped off. If the sample vessel (6.4) has been used before for saline samples, it shall additionally be cleaned thoroughly with water (5.3) prior to using it for ethanol or ethanol fuel. Subsequently, it is dried in the drying oven at min. 80 °C. Afterwards it is rinsed once more using ethanol (5.1). If there are any visible contaminations (e.g. stains) on the inner glass surface of the sample vessel (6.4), the vessel shall not be used.
8.1.3 Cleaning of the measuring cell The measuring cell (6.2) is also cleaned by rinsing it thoroughly with ethanol (5.1). If the measuring cell (6.2) had been used before for saline samples, it shall be cleaned thoroughly with water (5.3) prior to using it for ethanol or ethanol fuel. Subsequently, it is thoroughly rinsed with ethanol (5.1). If there are any visible contaminations (e.g. stains) on the inner surface of the measuring cell (6.2), the cell shall not be used.
8.1.4 Filling the sample into the sample vessel The sample is filled into the sample vessel (6.4) by pouring it directly from the sample container into the vessel. Should an intermediate vessel be required for transferring, this vessel shall first be cleaned thoroughly using water (5.3), and dried in the drying oven at min. 80 °C. Before the intermediate vessel is used, it is rinsed with ethanol (5.1). Subsequently it shall be dripped off. Rubbing its inside with a fibrous cloth shall be avoided. The size of the intermediate vessel shall be chosen such that it is filled up to at least half its height. If there are any visible contaminations (e.g. stains) at the surface of the glass on the inside of the vessel, the vessel shall not be used.
8.2 Calibration
8.2.1 Interferences The measurement values of the electrical conductivity can very strongly be influenced by contaminations in the sample as well as by pollutions of the measuring cell (6.2) (suspended matter, grease or oil). Such interferences cannot easily be detected in routine operation; therefore, the cell constant should regularly be checked by means of a reference solution or the calibration solution (5.2).
8.2.2 Checking the cell constant The cell constant is determined at (25 ± 0,1) °C using the calibration solution (5.2), and stored in the device and recorded. In order to enable a fast measurement, the calibration solution (5.2) should be pre-adjusted to a temperature of 25 °C. NOTE The cell constant is a parameter of the measuring cell. The conductometer (6.1) automatically works out this value with calibration solution (5.2). The measuring cell (6.2) and the sample vessel (6.4) are cleaned of any adhering rinsing ethanol (5.1). To do so, the sample vessel (6.4) is filled with the calibration solution (5.2) and, after the measuring cell (6.2) has been immersed in the solution, the solution is stirred for at least one minute. Subsequently, the sample vessel (6.4) is emptied und refilled with the calibration solution (5.2). The measuring cell (6.2) is immersed in the solution, and the lid is closed. In order to achieve a homogeneous temperature distribution, the solution is gently stirred. As soon as a constant temperature of (25 ± 0,1) °C has been achieved in the solution, the calibration measurement can be started. The determined cell constant is stored in the device in accordance with the manufacturer’s instructions and recorded rounded to the nearest 0,001 cm –1 . Following the calibration of the conductometer (6.1) the first measurement using the calibration solution (5.2) is carried out. The sample vessel (6.4) is emptied and refilled with the calibration solution (5.2) without another intermediate cleaning step. The measurement result shall not deviate by more than 2 % relative from the conductivity * 25 σ of the calibration solution (5.2).