ASTM D6224 Standard Practice for In-Service Monitoring of Lubricating Oil
ASTM D6224 Standard Practice for In-Service Monitoring of Lubricating Oil for Auxiliary Power Plant Equipment
9. Monitoring Program
9.1 A sound monitoring program is based on four factors:
(1) obtaining representative samples and testing at appropriate intervals; (2) logging, trending, and interpretation of test data; (3) action steps; and (4) insurance of maintenance follow-up.

9.2 Sampling and Testing of Oil Samples - Schedules should be tailored to the individual facility depending on the criticality and severity of usage of the equipment. The schedules included in Table 2 are typical and should only be used as a guide. Refer to the OEM (original equipment manufacturer) instructions or other regulatory guidelines for lubricant testing requirements. In addition to the tests in Table 2, any deposits found in the oil or removed from the system should be examined and identified (if possible).

9.2.1 Recommended (R) tests represent the minimum level of monitoring. These tests provide the most information about the quality of a particular fluid and about the condition of the equipment in which the in-service fluid is used. (Alternate testing devices which indirectly measure these properties may be substituted at the discretion and risk of the user.)

9.2.2 Optional (O) tests are those which may provide additional information on the oil or equipment condition. These tests may be beneficial in certain but not all facilities. If sample amount or analysis time is limited, omitting these tests would generally have less impact than omitting recommended tests.

9.2.3 As needed (AN) tests may provide information about operational problems. For example, the foaming characteristics test would determine whether a foaming problem was due to the oil or mechanical reasons. As needed tests may also be performed based on results from other tests. For example, a wear debris analysis may be performed when the wear particle concentration is above a certain level.

9.3 Logging, Trending, and Interpretation of Test Data - It is important to keep accurate records of test results and make-up. Graphical representations are highly recommended for key parameters such as acid number, oxidation inhibitor, wear particle concentration, base number, wear metals, and RBOT. In this way, unusual trends become apparent and better estimates made of remaining service life. Interpretation of test data should take into account such factors as oil addition (make-up or replacement oil), possible intermixing of oils, newly installed parts, and recent system inspections. Guidelines for warning levels are provided for various lubricant types in Table 3. Oil supplier and/or original equipment manufacturer (OEM) guidelines supersede Table 3. These warning levels should also be considered with trending information.

9.4 Action Steps - The main purpose of a monitoring program is to ensure long trouble-free operation of the equipment. This can only be achieved by prompt and proper action steps when necessary. Such action steps must be based on a correct interpretation of test results (see Table 4), usually gathered over a period of time. Corrective action should generally never be taken on the basis of one test result since it may be incorrect due to poor sampling or faulty testing. Resampling and retesting is recommended before proceeding. Actions recommended by the oil supplier and/or original equipment manufacturer supersede those in Table 4.

9.5 Possible sources of wear metals, additive elements, and contaminants are presented in Table 5. This table is a compilation of information from industry. It is intended as a guide and should not be considered to be all encompassing. Any additive element from a lubricant other than the desired lubricant could be described as a contaminant.

9.6 Maintenance Follow Up - When maintenance is performed on equipment included in the oil monitoring program, the records of work performed and problems found should be documented and made available to those responsible for interpreting the oil test data. In this way, the test data interpreter can (1) ensure that recommended maintenance was performed, (2) make better recommendations, and (3) learn better how test data correlate with equipment problems.

10. Keywords
10.1 auxiliary power plant equipment; lubricating oil; monitoring program