Preventive maintenance receives a great deal of attention from everyone in the field of diesel engine operation, since letting an engine run as long as it will run and fixing it only after a breakdown occurs is not only foolish, but extremely costly. On the other hand, you would be just as foolish to constantly tear down an engine just to inspect it. You should know that vital parts of an engine last longer and operate better if they are not tampered with unnecessarily. Therefore, an attempt must be made to find a happy medium between these two forms of maintenance.

One way to determine the condition of an engine is by monitoring its operation. This is done by regularly obtaining certain engine operating data and by studying, analyzing, and comparing it with previous data. This information is then reduced to a form that all engineering personnel can interpret and decide whether the engine needs to be overhauled or just temporarily shut down for simple maintenance. For more detailed procedures, refer to NAVSEA S9233-C3- HBK-010/010, Diesel Engine, Over 400 BHP, Trend Analysis Handbook

SPECTROGRAPHIC ANALYSIS

Spectrographic analysis is a method of determining engine or equipment wear by analyzing engine oil and hydraulic oil samples for chemicals and particles not found in new oil or hydraulic fluid. This analysis is done in laboratories on samples provided by ships according to instructions given in their sampling kits.

Ships must maintain accurate records of operating hours since major overhauls, oil changes, and samplings to provide the testing facility with the information requested in the sampling kit. (COMNAVSURFLANT uses the services of the Charleston Naval Shipyard, and COMNAVSURFPAC uses intermediate maintenance activities (IMAs) for analyzing oil samples from machinery employing closed lube oil/hydraulic systems.) In addition, ships must maintain a record of conditions found and repairs made as a result of laboratory recommendations.

When the shipyard or IMA laboratory receives the oil sample, a physical test and a spectrometric analysis are performed. The physical test consists of the following actions:

1. All samples are tested for fuel dilution, and a report by percent volume is provided to all concerned.

2. All samples are tested for solids by being spun in a centrifuge. Solids will settle at the bottom of the sample.

3. Allowable use limits are tested and recorded. When the physical test is completed, the shipyard/IMAs will make a spectrometric analysis of each used oil sample, then report to all concerned the concentrations of the following elements in parts per million (ppm). Additional information on trend analysis and oil spectrometric analysis is contained in COMNAVSURFLANTINST 9000.1C or COMNAVSURFPACINST 4700.lB.