This standard specifies determination method for oxidation resistance of inhibited mineral turbine oils and is applicable to other oil products like the oil for hydraulic system.
Note: This method may be also used to petroleum products specification and the measured value may be used to evaluate the oxidation stability of the turbine oil. But one point should be noted, namely the oxidation stability of the oil products measured in a single method may be different from that in the actual operating conditions.
2 Normative References
The following standards contain provisions which, through reference in this text, constitute provisions of this standard. Unless otherwise specified in the standard, the standards below shall be valid and current.
GB/T 514 Liquid in Glass Thermometers for Petroleum Products-Specification
GB/T 3141 Industrial Liquid Lubricants-ISO Viscosity Classification
GB/T 6682 Water for Analytical Laboratory Use-Specification and Test Methods
GB/T 11415 Laboratory Sintered(fritted) Filters-Porosity Grading, Classification and Designation
3 Summary of Method
Put oxidation tube filled with specimen (oil-soluble iron naphthenate, copper naphthenate catalyzer have been added in the specimen) into a 120℃ heating bath and get through the oxygen for 164h, and after the test, measure the volatile acid value, soluble acids value and sludge content. The time (induction period) when the volatile acid runaway rate is added obviously may be determined by daily determination of volatile acid value and drawing the acid value-time curve.
4 Apparatus and Materials
4.1 Apparatus
4.1.1 Oxidation tube: made of the borosilicate glass or neutral glass in accordance with dimension in Figure 1.
4.1.2 Absorption tube: identical to oxidation tube; at an interval of 150mm±50mm between central axes of two tubes, two tubes connected with silicon rubber as short as possible and absorption tube fixed out of the heating bath.
4.1.3 Heating bath: aluminum alloy heating bath (see Figure 2) or oil bath, capable of automatic temperature control to keep the temperature of the specimen in the oxidation tube at 120%±0.5℃ and the temperature is measured by thermometer (5mm from the bottom of test tube) inserting into the test tube filled with specimen. The specimen in the test tube shall be filled at the immersion line of the thermometer and put the thermometer into the heating bath. The upper surface of the heating bath shall remain at 60℃±5℃ to eliminate the slight influence on the determination results due to the change of ambient temperature. This temperature is measured by the thermometer in the bored aluminum block which shall be protected by the heat insulator except the surface in contact with the upper surface of the heating bath. This block shall be close, to the largest content, to the holes used for insertion of the test tube and within the area of aluminum alloy heat block.
In case of application of aluminum alloy aluminum alloy heating bath, oxidation tube shall be inserted into a 150mm deep hole. The depth for aluminum alloy heat block shall be 125mm at least; the metal ring through the heat insulation cover and surrounding each oxidation tube makes the 150mm long oxidation tube to be heated. In case of oil bath, the immersion depth of oxidation tube in the immersion depth is 137mm of 150mm total depth. In case of two heating baths, the length of the oxidation tube above the upper surface of the heating bath is 60mm where the oxidation tube will be exactly inserted into the hole in such a diameter; in case of relaxation, cover a 25mm diameter O-type ring on the tube which shall be compressed tightly on the heating bath surface .
