3304 & 3306 – Keel Cooling System (Jacket Water Aftercooled – JWAC)

COOLING SYSTEM SCHEMATIC (Jacket Water Aftercooled – JWAC)
1. Outlet line. 2. Bypass valve. 3. Bypass line. 4. Expansion tank. 5. Pressure cap. 6. Outlet line. 7. Water cooled manifold. 8. Regulator housing. 9. Aftercooler housing. 10. Outlet line. 11. Water cooled turbocharger. 12. Bypass filter. 13. Inlet line. 14. Inlet line. 15. Cylinder block. 16. Cylinder head. 17. Internal bypass (shunt) line. 18. Duplex strainer. 19. Keel cooler tubes. 20. Water pump. 21. Engine oil cooler. 22. Aftercooler inlet line. 23. Bonnet. 24. Auxiliary oil cooler. 25. Aftercooler outlet line. 26. Turbocharger inlet line.

Water pump (20) is on the left front side of the engine. It is gear driven by the timing gears. Coolant from the bottom of expansion tank (4) goes to the water pump inlet. The rotation of the impeller in water pump (20) pushes the coolant through the system.

The coolant flow from water pump (20) is divided. Some of the coolant flow goes through the engine oil cooler (21). The remainder of the coolant flow goes through aftercooler inlet line (22) into the core of the aftercooler. The core of the aftercooler is a group of tubes. These tubes are in position inside aftercooler housing (9). The coolant goes through the tubes. The inlet air for the engine goes around the tubes. This cools the inlet air. The coolant comes out at the rear of the engine and goes through aftercooler outlet line (25) to bonnet (23). In bonnet (23), the coolant from the aftercooler mixes with the coolant flow from engine oil cooler (21).

The coolant flow which comes through engine oil cooler (21) goes through bonnet (23). If the engine has a water cooled turbocharger (11), some of the coolant flow from engine oil cooler (21) goes through turbocharger inlet line (26). The coolant flow goes in at the bottom of water cooled turbocharger (11) and comes out at the top. It goes through outlet line (10) to the top of water cooled manifold (7). It goes through water cooled manifold (7) to the front of the engine. It comes out through outlet line (6) and goes into regulator housing (8). The coolant flow mixes with the rest of the coolant from the engine.

The remaining coolant flow through bonnet (23) goes into one side of auxiliary oil cooler (24). At the bottom, the coolant flow turns and goes up the other side of auxiliary oil cooler (24) and into bonnet (23) again. The bonnet sends this flow into cylinder block (15).

Inside cylinder block (15) the coolant goes around the cylinder liners and up through the water directors into cylinder head (16). The water directors send the flow of coolant around the valves and the passages for exhaust gases in cylinder head (16). The coolant goes to the front of cylinder head (16). Here the water temperature regulator controls the direction of the flow. If the coolant temperature is less than normal for engine operation, the water temperature regulator is closed. The only way for the coolant to get out of cylinder head (16) is through internal bypass (shunt) line (17). The coolant from this line goes into water pump (20) which pushes it through the cooling system again. The coolant from internal bypass (shunt) line (17) also works to prevent cavitation (air bubbles in the coolant). When the coolant gets to the correct temperature, the water temperature regulator opens and the coolant flow is divided. Some goes through keel cooler tubes (19) for cooling. The rest goes through internal bypass (shunt) line (17) to water pump (20). The proportion of the two flows is controlled by the water temperature regulator.

NOTE: The water temperature regulator is an important part of the cooling system. It divides the coolant flow between keel cooler tubes (19) and internal bypass (17), as necessary, to maintain the correct operating temperature. If the regulator is not installed, there is no mechanical control, and most of the coolant will take the path of least resistance thru internal bypass line (17). This will cause the engine to overheat in hot weather. In cold weather, even the small amount of coolant that goes thru the keel cooler tubes (19) is too much, and the engine will not get up to normal operating temperature.

Internal bypass (shunt) line (17) has another function when the cooling system is being filled. It lets the coolant go into cylinder head (16) and cylinder block (15) without going through water pump (20).

Keel cooler tubes (19) are normally installed on the bottom of the hull. They are usually made of a metal which has resistance to corrosion because they give off heat from the engine coolant to the sea water which the hull is in. The efficiency of this action is in relation to: the surface area of keel cooler tubes (19), the rate at which sea water goes around the outside of keel cooler tubes (19), the temperature of the sea water, and the rate of flow of the engine coolant through keel cooler tubes (19).

After going through keel cooler tubes (19), the coolant goes to an expansion tank (4). Expansion tank (4) is a reservoir for the coolant. It is the highest place in the cooling system. It is the place where the volume of the coolant can change because of heating or cooling without causing too much or too little coolant for the cooling system. Expansion tank (4) has a pressure cap (5) to control the pressure in the cooling system for better operation.

Some cooling systems have a duplex strainer (18) installed in the line from keel cooler tubes (19). Duplex strainer (18) has two sides. Each side has a strainer which is large enough for the full flow of the cooling system. When the pressure drop across one of the strainers starts to get an increase, the full flow can be changed to the other strainer without stopping the engine.

Some cooling systems also have a bypass filter (12). This is installed between the inlet and outlet lines for keel cooler tubes (19). In this position a small part of the coolant flow goes through bypass filter (12). This flow removes the particles which are too small for removal by duplex strainer (18).

Many cooling systems have a bypass valve (2) and bypass line (3) installed as shown. The bypass valve can be either manually adjusted or automatically adjusted. Both kinds of valves have the same function. They control the temperature of the coolant which goes to the inlet of water pump (20). The valves control the temperature of the coolant by controlling the amount of the coolant which can go through bypass line (3) instead of through keel cooler tubes (19). The coolant which goes through bypass line (3) is hot. It mixes with the coolant from the keel cooler tubes as it goes into the water pump inlet. Correctly adjusting the flow through bypass line (3) keeps the coolant temperature hot enough for good engine operation and at the same time, cool enough for good aftercooler operation. This adjustment is important for maximum engine performance.

Leave a Reply

Your email address will not be published. Required fields are marked *