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RPVOT RBOT The RPVOT (formerly referred to as RBOT) test is a measure of an oil’s ability to resist oxidization. However, ASTM D2272 advises that the test is not intended to compare one new oil formulation to another: “4.1 The estimate of oxidation stability is useful in controlling the continuity of this property for batch acceptance of production lots having the same operation. It is not intended that this test method be a substitute for Test Method D943 or be used to compare the service lives of new oils of different compositions.” Oxidization is one of the primary contributors to oil degradation. The process of oxidization produces acids and by-products that form varnish and sludge, coat bearing surfaces, narrow clearances or clog passages, all preventing lubricants from performing effectively. The RPVOT may be used to monitor the depletion of oil antioxidants over time and estimate the oil’s remaining useful life. Due to the time required and the expense of the tests, it is usually performed on large capacity oil reservoirs (as in steam turbines), on an annual basis. The test is performed by placing an oil sample in a a pressure vessel with water and a copper catalyst, then pressurizing the vessel with pure oxygen while rotating the sample. As the antioxidants in the oil react and are consumed by the pressure, rotation and oxygen, the pressure in the vessel begins to drop. The time it takes for the pressure to drop to the specified end point of the test is recorded in minutes as the RPVOT.
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