61.  Explain all compositions in the formula of critical revolution:

Lmax: maximum length of the shaft

q: weight of the shaft on a unit of length

E: Elastic modulus

I: inertial modulus of the shaft

P: thrust force of the propeller

63.  Classify systems of marine propulsion plant?

Fuel oil system.

Lubricating oil system.

Cooling system.

Compressed air system.

Bilge system.

Ballast system.

Fire-water system.

Sanitary washing water system.

Ventilation system.

Air conditioner system.

66.  State general regulations about interconnection pipes:

The fuel oil piping must be completely independent with others unless there are devides which protect fuel from mixing with other liquid during operation

The lubricating oil piping must be completely independent with other

The fresh water feed pipes of steam boiler or service water pipes must be completely independent with others to avoid pollution due to oil or oily water

Slide connection on pipe is not permitted to use in cargo hold, deep tanks and difficult approaching tank unless allowing of class society

Technical solutions to strengthen structure for pipes which go through bulkhead, decks, upper plating lower plating, and deep tank side plating

67.  State general regulations about valves on the bulkhead?

Screw down valves, butterfly valves such as drain valve which Is not a part of any piping system is not installed on the bulkhead

Valves which go through the bulkhead must be remotely operated from upper deck and secured tighten to the bulkhead. However, these valves can be installed behind bulkhead with condition that it is easy for handling and installing place is not cargo hold. In this case, remote control for this valves may not be necessary.

The weight of devides which control the valves from dry deck of main deck mustn’t burden on valves

68.  Classify the fuel oils for diesel engine?

Fuel for diesel engine is used in liquid form. Depending on properties, fuel oil can be classified into three kinds: gas oil (GO), marine diesel oil (MDO) and heavy fuel oil (HFO)

Gas oil is highest quality distillate fuel normally supplied for commercial marine purposes

Marine diesel oil is basically a distillate but it contains a small proportion of residual fuel. The grade can be black in colour due to delivery through piplines used for HFO.

Heavy fuel oil (HFO) is all residual fuels available at any particular port.

69.  State properties of fuel oil for diesel engine?

1. Density

Density of fuel oil is ratio between specific gravity of fuel oil (g/cm3) at standard condition (15o C) and specific gravity of fresh water at 4o C.

2. Viscosity at 50o C (cst)

Viscosity of fuel oil is unit for measure of resistance to flow of fuel oil.

3. Water and sediment

These impurities are obviously not useful to diesel engine operation. Water is the primary cause of corrosion in fuel storage tanks and equipment especially cylinder liner. Sediment causes a wear in plunger and clog filters, injection valve.

4. Flash point (o C)

The temperature at which the fuel oil vapors (formed on surface of the fuel oil) can be burned by an open flame.

5. Pour point (o C)

Pour point is the temperature at which fuel oil ceases to flow.

6. Ash content (%)

Ash content of fuel oil is that material remaining after fuel oil has been burned at a high temperature.

7. Carbon residue (%)

It is solid carbon left after fuel oil is burned with a fixed amount of oxygen.

8. Sulfur content (%)

 This harmful substance always remains in the fuel. Maximum sulphur content pemitted for commercial fuel is 4.5%.

70.  State function of fuel oil system?

- To receive fuel oil into the ship.

- To store fuel oil in tanks.

- To transfer fuel oil between tanks.

- To clean fuel oil.

- To supply fuel for the main diesel engine, diesel generators, aux. boiler.

- To indicate fuel oil level in tanks, fuel oil consumption...