The compatibility of oils can be important for users of oil-lubricated equipment. It is well known that the mixing of two oils can produce a substance markedly inferior to either of its constituent materials. One or more of the following can occur:
5.1.1 A mixture of incompatible oils most often forms a precipitate.
5.1.2 The precipitate will form unwanted deposits in the lubrication system, plug filters and oil passageways.
5.1.3 Such events can lead to catastrophic equipment failures.
Because of such occurrences, lubricant suppliers recommend evaluating compatibility of lubricating oil of different formulations and sources prior to mixing. Equipment users most often do not have the resources to evaluate oil compatibility and must rely on their suppliers. Mixing of oils is a highly imprudent practice without first determining the compatibility.
Although new turbine oils may be compatible, in-service oil of the same type may be degraded or contaminated to such an extent that the new oil added may not be compatible with the system oil. In-service oil compatibility with new oil additions should be evaluated on a case by case basis.
The oxidation resistance of different oils of the same type can vary widely, and compatibility does not imply equivalent performance.
1.1 This practice covers the compatibility of mixtures of turbine lubricating oils of the same ISO VG grade and type as defined by Specification D 4304. The Tier 1 method compares the visual appearances of specific mixtures with those of the neat oils after storage at specified conditions.
1.2 If the current in-service oil is causing problems or if circumstances indicate the need for additional testing, a Tier 2 method compares selected performance properties of the mixture and its constituent oils.
1.3 The Tier 1 and Tier 2 methods can be used to evaluate new (unused) lubricant compatibility or the effects of adding new (unused) lubricant to in-service lubricant in the system.
1.4 This method does not evaluate the wear prevention characteristics, load carrying capacity, or the mechanical shear stability of lubricants mixtures while in service. If anti-wear (AW), extreme pressure (EP), or shear stability are to be evaluated, further testing of these parameters may be required.
1.4.1 Tier 1 Mixtures of the two constituent oils to be evaluated are prepared at specified proportions, stored in an oven at 65176;C for 168 h, and then evaluated for changes in physical appearance.
1.4.2 Tier 1 - Mixtures of the two constituent oils to be evaluated are prepared at specified proportions, stored in an oven at 65176;C for 168 h, and then evaluated for changes physical appearance and parameters detailed in 7.3.
1.5 Mixtures of the two constituent oils are evaluated in a primary testing protocol using the following standards:
1.5.1 For compatible mixtures, a supplemental (nonmandatory) testing scheme is suggested when circumstances indicate the need for additional testing the beyond Tier 2 primary recommended tests.
Note 0The oxidation stability test method should be selected based on the product type and in agreement with the lubricant supplier (see for options). Unlike other tests described in this practice, the impact on oxidation stability may not be easily interpreted with a pass/fail rating. The user is encouraged to contact the lubricant supplier for assistance in the evaluation of the data.
1.6 Sequential or concurrent testing is continued until the test requestor or user is satisfied that the intent of this practice has been met. If any mixture fails the Tier 1 visual appearance method or any of the Tier 2 primary tests, when requested, the oils are incompatible. If all mixtures pass the Tier 1 or Tier 2 tests, the oils are considered compatible by those methods.
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