LUBRICATING OIL SYSTEM

Diesel engine lubricating-oil systems
Fig. 23.18 shows representative lubricating-oil systems for a low-speed diesel engine. The lubricating-oil requirements are divided between two systems: cylinder oil, which is consumed within the cylinders and must be continually replaced; and circulating lubricating-oil, which lubricates and cools the bearings, and (usually) the pistons. The circulating oil is continuously cleaned by the lubricating-oil purifier.

Figure 23.18: Main engine lubricating oil systems for a motorship

The lubricating-oil circulating system draws suction from the engine sump tank, which is built into the ship's double bottom. The suction bellmouth is located slightly above the sump bottom to avoid drawing in any settled water or sediment. The oil is drawn through a suction strainer by the lubricating-oil circulating pump, and then discharged through a finer strainer and the lubricating-oil cooler. A lubricating-oil cooler bypass valve is fitted to control the temperature of the oil supplied to the engine. The lubricating oil is then fed to the bearing-oil manifolds, the turbocharger bearings, and the hydraulic governor and control circuits.
The cylinder-oil system is used on crosshead engines and some trunk-piston engines. The cylinder oil is high-viscosity oil used to lubricate the piston rings and cylinder liner. It has a total base number...