81.  State general requirements of lubricating oil system?

- There must be separate lubricating oil systems for each of the engines.

- The engines must be continually lubricated in every condition.

- Each of the main engines must have at least two LO supply. To lubricate the engines before starting, a hand pump, a gravity tank or a pump driven by an electric motor should be used.

- Amount of the lubricating oil that is stored, must correspond to amount of the fuel oil on the ship. Oil receiving connectors must be arranged in both sides of the ship…

- Pressure and temperature of the lubricating oil in the system must be set and can be adjusted.

- The system must be easy to operate, to clean and to renew lubricating oil when necessary.

- The system must be equipped with indicators, alarm devices such as level gauges, thermometers, pressure gauges, pressure switches, and temperature switches...

82.  State requirements of lubricating oil heater and lubricating oil pump?

LO pump:

In the lubricating oil system, gear pumps or screw pumps are normally used. The lubricating oil pump is driven either by the engine or by an electric motor. Besides this, there must be a LO stand by pump for the main engine in the system.

This pump is driven by an electric motor. In addition, there may be a hand pump in the system. When the lubricating oil pump is directly driven by the engine, it must be equipped with non-reversible valves (non-return valves).

Before starting the engine, the lubricating oil pump that driven by the electric motor or by hand must be run to supply the lubricating oil to the working surfaces of the engine. The same work should be done after the engine stopped.

Lubricating oil heater:

Its function is to heat the lubricating oil before separating or starting engines in cold climate. The lubricating oil can be heated either by steam or by electric.

83.  State the other requirements of the lubricating oil system?

They include:

Regulators: for adjusting pressure and temperature of the lubricating oil.

Indicators: thermometers, pressure gauges, flowmeter, level indicators…

Safety device, alarm device

84.  List the name and explain function of all main components of lubricating oil system?

1-      System oil tank (Sump. Tank)

2-      Primary filter

3-      Lubricating oil heater

4-      Lubricating oil purifier

5-      Lubricating oil circulating pump

6-      Lubricating oil cooler

7-      Secondary filter

8-      Flowmeter

9-      Cylinder lubricators

10-  Cylinder lubricating oil tank

11-  ME system oil tank

12-  DG oil tank

13-  Strainer

85.  State the operational of the typical lubricating oil system?

A perfect lubricating oil system consists of three small component systems:

- Lubricating oil-transferring system: It consists of tanks, transfer pumps (make up pump) and pipeline...

- Lubricating oil-purifying system: It consists of purifier, strainers, heater, LO sludge tank, alarm device and pipe line...

- Lubricating oil-supplying system: It consists of LO circulating pump, filters, LO cooler, alarm device, safety device and pipe line...

86.  What kind of cooling substances are used in marine propulsion plant? State functions of each cooling substance?

Its function is to reduce temperature of the lubricating oil to the proper temperature before coming to the engine. Cooling substance normally used in the lubricating oil cooler is seawater. There are two kinds of cooler used in the system they are plate type and tube type.

The tube type cooler is normally used on the ships. It consists of many tubes fixed on two tube plates. For the tube type cooler, the lubricating oil flows outside of the tubes while water flows inside of these tubes. Normally, the lubricating oil pressure is higher than water pressure.

The plate type cooler consists of many identical plates. In the plate type cooler, two kinds of liquid flow in opposite direction and in alternate passages between plates.

87.  State functions of cooling system in marine propulsion plant?

Cooling diesel engine (ME and DG).

It reduces the temperature of the diesel engine parts to the suitable temperatures. During the operation of the diesel engine, the fuel-air mixture is burned in the combustion chamber so its temperature is very high. With such a high temperature, the parts of the diesel engine (such as cylinders, cylinder covers, piston crowns...) are heated. Therefore, these parts need to be cooled to prevent cracking due to heat.

Cooling lubricating oil at the lubricating oil cooler.

While lubricating the working surfaces of the diesel engine, the lubricating oil gets the heat that is created by friction at the working surfaces so its temperature is raised and its viscosity is reduced. This is not beneficial for the diesel engine. That is why the lubricating oil must be cooled.

Cooling supercharged air at the air cooler.

When compressed to a high pressure, the temperature of the supercharged air is very high and its specific gravity is decreased. So the supercharged air needs to be cooled before entering to the cylinders. The purpose of this cooling is to increase the mass of fresh air entering to the cylinders.

Cooling other machinery:

Such as air compressors, hydraulic oil system, stern tube and stern bearings, intermediate bearings and thrust bearing, condensers of provision refrigerating system, air conditioner and auxiliary boiler...

88.  State requirements of sea chest box and cooling water pump?

Sea chest box:

These must be at least 2 sea chest boxes in cooling system. They are high sea chest and low sea chest. The former in used when ship sailing at shallow water area and the later is used when ship sailing at deep sea.

Cooling water pump:

There must be two main pumps in the system, one is cooling fresh water pump, and other one is cooling seawater pump. Besides these, the system must also have two emergency cooling water pumps: one for fresh water, other one for seawater. In addition, there may be auxiliary machinery cooling water pumps. Centrifugal pumps are widely used in the cooling system and it is designed so as velocity of water in the delivery pipe is about 3-5(m/s)

89.  State requirement of temperature control valve and pipe line of the cooling system?

Control valve

- When load of the engine changes, the difference of the cooling water temperature in comparison with the preset value must be lower than 5o C.

- When load of the engine is static, the difference of the cooling water temperature in comparison with the preset value is about 1¸2o C.

- When load of the engine changes, the control time of the cooling water temperature to preset value must be short.

Pipe line and fitting

When designing the pipeline we must pay attention to following requirements:

- Expansion of water in the system is smallest.

- Evaporation of water is smallest.

- The expansion tank must be arranged in the system for expanding of the fresh water.

- Steam is not existed in the system, if air or steam appears in the system, it needs to be quickly purged. For this purpose, air purge valves must be arranged at high positions in the system.

- The leakage of the system is smallest.

- The hunting of pressure in the system is smallest.

90.  State features of open cooling system?

In this system, seawater outside of the ship is taken in through the seachest valve and is pumped to cool the lubricating oil, the supercharged air, the diesel engines, the compressors and so on.

After carrying out its duty, the seawater goes out to overboard. In this case the seawater contacts directly with the diesel engine and surfaces of the parts that need to be cooled.

To regulate the seawater temperature in the system, a three ways-valve is used. Three ways-valve can be set in auto or manual mode.