Chapter SYSTEM OF MARINE PROPULSION PLANT Introduction Marine propulsion plant is supported by many systems These systems have a closed relation to each other On board, they can be classified as follow: 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 5.1 Fuel oil system I Fuel for Diesel engine Fuel for diesel engine is used in liquid form Depending on properties, fuel oil can be classified into two kinds: first one is diesel oil (or DO) and other one is heavy fuel oil (or FO) They are characterized by following properties Density Density of fuel oil is ratio between specific gravity of fuel oil (g/cm3) at standard condition (15 oC) and specific gravity of fresh water at 4oC Viscosity at 50oC (cst) Viscosity of fuel oil is unit for measure of resistance to flow of fuel oil 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 Flash point (oC) The temperature at which the fuel oil vapors (formed on surface of the fuel oil) can be burned by an open flame Pour point (oC) Pour point is the temperature at which fuel oil ceases to flow Ash content (%) Ash content of fuel oil is that material remaining after fuel oil has been burned at a high temperature Carbon residue (%) It is solid carbon left after fuel oil is burned with a fixed amount of oxygen Sulfur content (%) II 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 III Requirements of the fuel oil system General requirements of the fuel system: - The system must ensure normal working of all engines even when the ship rolling 15o and pitching 5o - Fuel pipe must not be arranged near exhaust pipe, silencer, electric panel, and cabin or through fresh water tanks - Fuel is normally stored in double bottom tanks or wing tanks Capacity of all tanks must be enough for continuing operation of the ship in estimated time with some percentage of fuel for stand by - There must be interconnection between tanks The valves should be arranged so that it is easy for operation, checking and repairing - There must be separated pipes for receiving and delivering fuel on each tank Besides this, vent pipe, drainpipe, overflow pipe (with sight glass), sounding pipe (or sounding device), manhole for inspection and repairing must be installed - Diameter of vent pipe is normally equal to receiving pipe The upper end of vent pipe is placed on upper deck with a copper net to prevent dust and fire from falling into fuel tanks Diameter of vent pipe in any case must not be smaller than 50 mm - The system must be provided with international flanges for receiving and discharging pipe and placed on both sides of the ship (Port & Starboard side) - The system must be equipped with remote control device for emergency shut down of delivery valves of each fuel tank in case of fire or flooding in the engine room - There must be indicators, alarm devices such as: pressure gauge, thermometer, viscometer, flow meter, and low-high level alarm to increase the safety of the system - In case of using FO, FO purifier must be provided in the system FO must be heated in storage tanks, settling tank, service tank before transferring and purifying Heating coil of the tanks should be arranged about 25 cm from bottom of the tanks If use steam for heating, steam pressure must be smaller than kg/cm2 Fuel pipe must be heated and insulated to maintain FO temperature The heating temperature of FO before entering the engine depends on kind of fuel and engine This temperature can be adjusted Figure 5.1: Fuel oil tank and fitting 1- Receiving pipe 2- Delivery pipe 3- Venting pipe 4- Overflow pipe 5- Drain valve 6- Thermometer 7- Level indicator 8- Heating coil 9- Manhole DO fill line DO store DOtank store tank FO fill line DO service tank DO purifier FO settling tank FO service tank FO purifier FO heater Figure 5.2: FO & DO purifier system of the marine engine practical room Requirements of fuel injection system of diesel engine - Fuel must be injected to combustion chamber at proper timing The beginning time of injection in degrees of crankshaft before top dead center must be the same for all cylinders and can be adjusted - Amount of fuel delivered to each of the cylinders must be the same - There must be a suitable rate and pressure of injection The fuel mass per degree of crankshaft travel must be the same for all the fuel injection pumps - The fuel must be properly atomized - The fuel must be distributed over the volume of the combustion chamber For auxiliary boiler, fuel sprayed into combustion chamber must be in good atomization corresponding to the load of boiler Air reservoir - There must be at least two main air reservoirs and one auxiliary air reservoir - Capacity of the main air reservoir must be designed to start continuously the main engine at least twelve times with the direct reversing engines and six times with the nonreversible engines while the air compressors are idle Capacity of the auxiliary air reservoir must be enough for six starts of the diesel generators Air reservoir (Air both) - Besides the charge and supply valve, the air reservoirs must be provided with safety valve, pressure gauge, drain valve; manhole for inspecting and repairing On some ships, the air reservoirs can be provided with pressure switch to control the start and stop of the air compressors - Pressure test must be carried out before using or after working period of the air reservoirs *When the maximum air pressure is smaller than 20 KG/cm2 and for the welding air reservoirs: P Test = 1.6 P max, for other: P Test = 1.5 P max *When the maximum air pressure is higher than 20 KG/cm2: P Test = P max + 14 Pressure test interval: years/time Inside check: years/time Compressed air pipe - Non welding high-pressure pipes and zinc galvanized are used in the system - Air pressure in the system depends on different duties: For starting engines: P = 18 ÷ 30 KG/cm2 For the control system: P = -11 KG/cm2 No.2 Air tank No.1 Air tank M/e No.1 Reducing valve DRYER No.2 Cont a i R Serv air No.1 d/g main Air comp No.2 d/g Emer D/g EMER AIR TANK Compressed air system EMER AIR COMP Air tank No1 D/G No1 D/G No2 Distributor Press Reducing valve CompressorNo1 Air tank No2 CompressorNo2 M/E 5.5 ballast system • Function of ballast system • Its function is to increase stability for the ship; it ensures the balance for the ship in every condition • The ballast system is used when the ship is sailing in ballast, loading of cargoes on the ship is not balanced, or in some special cases To aft peak tk No.1 p No.2 p To Fore Peak tk Over board pump No.1 s To other system No.2 s The main components in the ballast system a Ballast tanks - The ballast tanks are used to store water for purpose of adjusting the balance of the ship - The ballast tanks are fore and aft arranged at the bottom of the ship and symmetrically with the keel of the ship - Capacity of tanks depends on displacement of the ship Each tank is provided with a suction and discharge valve, vent pipe, sounding hole, manhole for checking and cleaning b Ballast pump Duties of the ballast pump: - To fill up the ballast tanks when the ship is sailing in ballast - To dry up the ballast tanks when the ship is loading - To transfer water between tanks to adjust the balance when the ship is heeling A centrifugal pump, which has a high capacity, is normally used in the ballast system c Valves and pipe line Workshop Control room Tank No1 Tank No2 To fire station Fire, bilge & ballast pump Overboard GS pump Strainer From sea chest Hose connection Hose connection Boiler room 5.6 bilge system Function of bilge system The bilge system is used to: - Dry up bilge water in the engine room, separate oil from bilge water and discharge cleaned water out to the sea - Store waste oil - Transfer oil residue to shore or to a reception facility Mixture of water and oil in the engine room is called "bilge water" The bilge water is formed due to leakage of oil and water from systems, equipment, stern tube, and cleaning cargo holds 2.The main components of bilge system a Tanks - Bilge water tank - Bilge separator oil tank - Waste oil tank - Sludge tank b Bilge pump A piston pump is normally used in the bilge system In some cases, the ballast pump can be used as a bilge pump c Oily water separator A content below 15 ppm of oil in discharge water is required for this oily water separator d Valves and pipe line Non-return valves are normally used in the bilge system To overboard Solenoid valve B.W Oily water separator Bilge pump To overboard To incinerator W.O.T B.W S.W valve B.W.T Sludge.T k B.S.O.T B.S.O T B.W