Cargo hatch cover opening and closing operations are supplied by an electrohydraulic power unit. The system consists of an electric motor-driven hydraulic pump mounted on a hydraulic fluid reservoir tank and an air-driven hydraulic intensifier. Adjacent to the power unit is a hydraulic fluid control valve panel. An emergency air-hydraulic pump is also provided with the system. Fluid pressure is transmitted to either the undogging or dogging side of the hydraulic cylinders. You must read the specific manufacturers manual or NAVSEA 0916-LP-018-2010, Hydraulic Operated Cargo Hatch Cover, to understand the full details of the system. Along with this, you should trace the system in your ship and complete the required PQS. During repairs, follow the procedures specified by the PMS.

BOAT DAVITS

Gravity davits are found on most Navy ships. Figures 8-1, 8-2, and 8-3 illustrate the types of gravity davits that you will be maintaining.

For general information about boat davits, read Boatswain's Mate, Volume 1, NAVEDTRA 10101. You, as the maintenanceman, must also be familiar with the proper operation of the boat davit. Some common problems with the boat davit are rusting of parts, loss of lubrication, contaminated oil in the gearcase, and faulty centrifugal brakes. Because of the location of the boat davit on the weather deck, the machinery is highly exposed to sea spray, even though it is covered by protective covering. You must lubricate the boat davit and winch after adverse weather conditions. For maintenance and repair of the boat davit, follow the PMS assigned for this machinery. If your ship is equipped with a double-pivoted link davit and a 50-hp winch, NAVSHIPS 0920-072-1013 provides information concerning maintenance instructions. Your work center PMS Manual 43P1, under Maintenance Index Page should provide you with the correct reference publications for each piece of equipment.