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| Illustration 1 | g01822615 |
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Cooling system schematic of a sea water aftercooled system (1) Fuel cooler (2) Heat exchanger (3) Gear oil cooler (4) Water temperature regulator (5) Exhaust riser (6) Exhaust manifold (7) Jacket water pump (8) Turbocharger (9) Charge Air Cooler (CAC) (10) Cylinder head (11) Auxiliary sea water pump (12) Cylinder block (13) Engine oil cooler (14) Sea water inlet (15) Sea water outlet | |
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| Illustration 2 | g01822616 |
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Schematic of a keel cooled separate circuit aftercooled system (16) Auxiliary engine mounted expansion tank (17) Jacket water engine mounted expansion tank (18) Jacket water keel cooler (19) Fuel cooler (20) Auxiliary water pump (21) Water temperature regulator (22) Jacket water pump (23) Exhaust manifold (24) Exhaust riser (25) Auxiliary keel cooler (26) Turbocharger (27) Charge Air Cooler (CAC) (28) Cylinder head (29) Gear oil cooler (30) Cylinder block (31) Engine oil cooler | |
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| Illustration 3 | g01824395 |
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(32) Expansion Tank with a pressure relief cap
(33) Recovery Bottle with a vented cap | |
This engine has a pressure type cooling system that is equipped with an expansion tank (32) and a recovery bottle (33).
A pressure type cooling system offers two advantages:
- The cooling system can operate safely at a temperature that is higher than the normal boiling point of water.
- The cooling system prevents cavitation in the water pump.
Cavitation is the sudden formation of low pressure bubbles by mechanical forces in liquids. The formation of air or steam pockets is more difficult within a pressure type cooling system.
The shunt line prevents cavitation by the water pump. The shunt line provides additional flow of coolant to the water pump inlet.
The recovery bottle (33) provides space for expansion of the coolant volume while the engine is running. Also, the recovery bottle provides space for expansion during the warm up cycle. The recovery bottle also provides a means for checking the coolant level.
In many instances, a separate cooling source is used to supply coolant to the aftercooler. The coolant supply can be fresh water, or the coolant supply can be sea water. Because of the possible unknown composition of the cooling water, a special pump is needed to move the coolant through the system. Two types of pumps are available for use in the raw water circuit.
- A bronze impeller and/or a rubber impeller pump is used to flow sea water through the cooling system. These types of pumps will resist the corrosive action of the coolant that passes through the pump.
Raw water is drawn in through the inlet of the auxiliary water pump . The raw water is forced out of the pump and into the aftercooler. The raw water flows through the aftercooler in order to cool the inlet air. The raw water then exits the aftercooler and travels through the heat exchanger that cools the jacket water and fuel if the engine is equipped with a fuel cooler. The raw water is then discharged or passed through the gear oil cooler (if equipped) and then discharged.
Water pump (7) is located on the right front corner of the cylinder block. The water pump is gear-driven from the crankshaft.
Coolant from the heat exchanger is pulled into the inlet of the water pump by impeller rotation. After the water exits the water pump, the water is dispersed to the following components: engine oil cooler , cylinder head, cylinder block and turbochargers. Coolant also flows from each cylinder head and each turbocharger to each of the exhaust risers and from the exhaust risers to the exhaust manifolds. Next, the coolant flows through a deaerator in the rear frame of the heat exchanger in order to purge excess air from the coolant to the expansion tank. The coolant is then directed by the water temperature regulator either to the bypass back to the jacket water pump or to the heat exchanger to be cooled.
Note: The water temperature regulator controls the direction of flow. When the coolant temperature is below the normal operating temperature, the water temperature regulator is closed. The coolant that is leaving the cylinder heads and exhaust manifolds is redirected to the inlet of the jacket water pump. When the coolant temperature reaches the normal operating temperature, the water temperature regulator opens. Coolant then travels to the heat exchanger for cooling.
Note: The water temperature regulator is an important part of the cooling system. The water temperature regulator divides coolant flow between the heat exchanger and the bypass in order to maintain the normal operating temperature. If the water temperature regulator is not installed in the system, there is no mechanical control, and most of the coolant will travel the path of least resistance through the bypass. This will cause the engine to overheat in hot weather and the engine will not reach normal operating temperature in cold weather.
The coolant recovery bottle adds volume for expansion of the coolant in the engine cooling system. The coolant recovery bottle also provides a convenient way to check the coolant level. Coolant is forced into the bottle during the warm up cycle. Coolant returns to the heat exchanger from the coolant recovery bottle during the cool down cycle through the seal pressure cap on the heat exchanger.
Air vents are provided on the top of each turbocharger. The air vents aid in removing air from the system during the initial filling of the cooling system. The air vents also aid in removing air from the system after a flushing process.
There are two types of systems for heat dissipation that are recommended for use with Caterpillar marine engines. These systems for heat dissipation involve the use of either inboard mounted heat exchangers or outboard mounted keel coolers. This engine offers configurations for both types. The inboard mounted heat exchanger is a plate type heat exchanger that is composed of stacked plates with seals between each plate allowing raw water and jacket water in order to alternate between the plates and the heat that is to be exchanged during the cooling process. Keel cooled systems have coolers mounted on the outside of the hull bottom, using the flow of sea water around the outside surface of the keel cooler to remove the heat from the jacket water which is flowing though the inside of the coolers. Systems that are cooled with a inboard heat exchanger require a sea water pump in order to circulate sea water through the plate type heat exchanger. Keel cooled systems require the use of an auxiliary pump to flow the coolant thru the keel cooler system. Heat is transferred from the hot jacket water coolant to the cool sea water in both systems allowing the engine to maintain an acceptable operating temperature.