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| Illustration 1 | g00753379 |
(1) Overboard discharge (2) Generator air cooler (3) Overboard discharge (4) Orifice (5) Fuel (6) Fuel cooler (7) Engine oil (8) Combined heat exchanger (9) Jacket water (10) Sea water (11) Sea water pump (12) Sea water strainer (13) Orifice (14) Orifice (15) Emergency connection (16) Sight glass (17) Flushing connection | |
The sea water cooling system for the 3608 engine is made up of the following major components. The sea water pump is driven by the engine. The sea water pump draws sea water from the ship's sea chest. The sea water pump discharges sea water to the sea water strainer. The sea water flows through a plate type heat exchanger that cools both the engine's jacket water and the engine oil. The sea water also flows through a second plate type heat exchanger that cools the engine's fuel before discharging to the ship's overboard connection.
There are also lines that provide sea water to the air cooler that is for the generator before discharging through a separate overboard connection. An emergency connection is also provided to the ship's auxiliary cooling system. These major components are mounted on the generator set base in front of the engine.
The total sea water that is required for the 3608 generator set is2374 L/min (627 US gpm) at rated speed of 900 rpm. This requirement drops to approximately 1136 L/min (300 US gpm) at the idle speed of 450 rpm. Since the unit is not under load at idle speed very little heat is generated so this quantity is sufficient. The sea water that is required for the engine oil and the jacket water heat exchanger and the heat exchanger that is for the fuel is approximately 1995 L/min (527 US gpm). The sea water that is required for the air cooler that is for the generator is approximately 379 L/min (100 US gpm).
The pressure drops were calculated through the system in two circuits. The first circuit supplies the heat exchangers for the engine. The second circuit supplies the air cooler that is for the generator. The head losses exist between the pump suction connection and the ship's overboard piping connection. The head losses are subtracted from the pump head in order to determine the pressure drop in the ship's piping. When the engine is operating at rated speed, the amount of available head pressure after losses is equal to following conditions:
- The head pressure from the heat exchangers is 33.8 feet. This is with 2374 L/min (627 US gpm) at the pump suction connection and 1995 L/min (527 US gpm) at the plate type heat exchanger.
- The head pressure from the air cooler that is for the generator is 25.7 feet. This is with 2374 L/min (627 US gpm) at the pump suction connection and 379 L/min (100 US gpm) at the air cooler that is for the generator.
Note: The head pressure includes the total that is available for suction loss plus discharge loss.
When the engine is operating at idle speed, the amount of available head pressure after losses is equal to following conditions:
- The head pressure from the heat exchangers is 6.7 feet.
- The head pressure from the air cooler that is for the generator is 5 feet.