BS EN 15751 Automotive fuels - Fatty acid methyl ester (FAME) fuel and blends with diesel fuel - Determination of oxidation stability by accelerated oxidation method
5 Reagents and materials
Use only reagents of analytical grade and distilled or demineralised water.
5.1 Ternary solvent mixture, consisting of methanol/toluene/acetone 1:1:1 (by volume)
5.2 Alkaline laboratory glass cleaning solution
5.3 2-Propanol
6 Apparatus
Usual laboratory equipment and glassware, together with the following:
6.1 Device for the determination of oxidation stability, comprising the following parts (see Figures 1 and 2).
NOTE An instrument for determining the oxidation stability is commercially available.
6.1.1 Air filter, comprising a tube fitted with filter paper at the ends and filled with a molecular sieve (6.6), connected to the suction end of a pump.
6.1.2 Gas membrane pump, with an adjustable flow rate of (10 +/- 1.0) l/h.
6.1.3 Reaction vessels of borosilicate glass, provided with a sealing cap.
The length of the reaction vessel depends on the measuring equipment and shall exceed the depth of the oven by at least 130 mm, in order to reduce evaporation losses to a minimum by condensing, volatile fuel components at the cold vessel walls outside the oven.
EXAMPLE Total length of the test tube for the Metrohm Rancimat 743 L = 250 mm, for the Omnion OSI Instrument L = 300 mm.
The sealing cap shall be fitted with a gas inlet and outlet tube. A few centimetres below the top, the vessel shall preferably have a slightly reduced inner diameter in order to break any emerging foam. An artificial foam blocker (e.g. glass ring) may also be used for this purpose.
6.1.4 Closed measurement cells, of approximately 150 ml capacity, with a gas inlet tube extending to the bottom inside of the vessel. The cell shall have ventilation holes at the top.
6.1.5 Electrodes, for measuring conductivity within a range of 0 µS/cm to 300 µS/cm aligned with the dimensions of the measurement cell (6.1.4).
6.1.6 Measuring and recording apparatus, comprising:
a) an amplifier, and
b) a recorder registering the signal of each of the electrodes (6.1.5).
6.1.7 Thyristor and contact thermometer graduated in 0,1 °C or Pt 100 element to measure the block temperature, with attachments for relay connection and an adjustable heating element; temperature scale 0 °C to 150 °C.
6.1.8 Heating block, made of cast aluminium, adjustable to a temperature up to (150 +/- 0.1) °C. The block shall be provided with holes for the reaction vessels (6.1.3) and an aperture for the contact thermometer (6.1.7).
Alternatively, a heating bath may be used, filled with oil suitable for temperatures up to 150 °C and adjustable to the nearest 0.1 °C.
6.2 Certified and calibrated thermometer or Pt100 element, with a temperature range up to 150 °C, graduated in 0.1 °C.
6.3 Measuring pipettes and/or measuring cylinders
6.4 Oven, adjustable to a temperature up to (150 +/- 3) °C.
6.5 Connecting hoses, flexible and made of inert material [polytetrafluoroethylene (PTFE) or silicone].
6.6 Molecular sieve, with moisture indicator, pore size 0.3 nm, dried in an oven set at 150 °C and cooled down to room temperature in a desiccator before use.
