CHAPTERI VOL. Ul SECTION 6 SECTION 6. BOOK 4 ELECTRICAL GENERATION AND DISTRIBUTION In general, preventive and corrective maintenance of diesel engines was accomplished after 300 hours of operation. At this time the units were secured and opened for the removal of carbon accumulation on the ports and in the exhaust system. During the period of shut down all operating parts were checked and adjusted, and repaired or replaced as found necessary. The windings of the alternators were cleaned; brushes were checked and properly adjusted. During operating periods these units were under constant observation by the operators for unusual mechanical noises, overheating, scorching odors and smoking exhaust. Supervisory personnel checked the operating logs for signs of malfunctioning of equipment. All of the foregoing measures, combined with continuous checking of the fuel and lubricating oil consumption records, afforded data for the determination of the need of adjustments, replacement or repair, A maintenance history of each unit was maintained in which all items of maintenance work performed were entered. Oil stoves were installed in the off-island inactive plants. These stoves were kept in continuous operation and thereby kept the windings dry. In addi- tion, the units of these plants were operated once a week and drying was further accomplished by passing a current at low voltage through the windings. Before reactivating these plants, the units were operated in this manner for approximately 72 hours, at the end of which insulation resistance measurements were sufficiently high for full operation. The following non-routine items of maintenance work were required: (1) Relining of engines where piston clearances exceeded allowable tolerances resulting from normal wear. This was generally required after approximately 8,000 operating hours. (2) Rewinding of Generator 1 on Fred due to having grounded out because of excessive dampness of the windings. The grounding out occurred when the unit was first started after return to the site after the Evacuation Period, during which all doors and windows of the plant had been left opened, as a measure of security of the building against excessive blast pressure. (3) Extensive repairs to the diesel engine of No. 2 Engine on Yvonne. The apparent failure of one main bearing and the stoppage of the lubricating system was the cause of considerable damageto this engine.