| 4 Maintenance procedures
Specifications for all measurements taken on a component, such as oil pressure and compression readings, should be available to the maintenance staff as it is necessary to know whether or not the result is acceptable. It is possible to trend the readings within the specifications to obtain even more information on the health of the machine.
| 5 Regular sampling
Intervals between samples should not be too long. The recommended periods should be in the region of 250 hours (10,000 km) for engines, and 500 (20,000 km) for other components. If samples are not taken regularly, a wear problem could degenerate from borderline to critical, and failure could occur with no apparent warning.
| 6 Sample quality
Oil analysis depends entirely on the integrity of the sample. If the sample has been taken incorrectly and is contaminated or taken from an incorrect sampling point, the results will not be representative of the main body of oil and erroneous conclusions will be drawn.
The sample must be taken hot and well mixed. Oil samples can be taken from the drain plug as the oil is drained, or a thief gun can be utilized. Another method is to use the sampling valve which should be located at a well selected point on the component, i.e. not after a filter or on a dead leg.
Samples taken at failure cannot be taken with the machine running and this could lead to an unrepresentative sample being submitted.
| 7 Sample information
To obtain the best results from the program, information supplied with the sample must be accurate and complete. If all the relevant facts are not available to the diagnosticians when they interpret sample results, an incorrect diagnosis could be made. Critical information includes:
The fleet or serial number and the component need to be correctly identified. If the clerk transposes the fleet number or writes left instead of right, the results will be recorded against the incorrect piece of equipment.
In the event of the results indicating a problem, the wrong component will be stripped and will probably show no fault. This could make oil analysis appear unreliable.
Service meter reading
This is important information as a new component will wear differently from and old one. If the diagnostician does not know the age of a piece of equipment, he is unable to give an accurate assessment of the results.
Length of time oil has been in use
This is necessary as the levels of wear metals increase with time and what is normal for 500 hours could be critical for 100 hours.