Thursday, October 9, 2008

CAT Engine Course(Part 4) Cooling System

Cooling System


COOLING SYSTEM SCHEMATIC
This diagram shows the basic cooling system. We can use it to see the components of the system and see how they are connected. In the diagram, we see the engine block, cylinder heads (separate heads for each cylinder), coolant manifold, housing of the temperature regulators (thermostats), water outlets bypass line from regulator housing to water pump, water pump, water inlet from radiator or heat exchanger, coolant line to the aftercooler, and the oil cooler.
1. water pump
2. oil cooler
3. cylinder heads
4. water manifold (right side)
5. aftercooler
6. temperature regulator housing
7. bypass line from regulator housing to water pump.



COOLING SYSTEM FLOW
Coolant flow comes from the elbow which is connected to the radiator or other heat exchanger into the center of the water pump. The cooler flow is divided at the outlet of the water pump. One partflows to the aftercooler; the other part to the oil cooler.
Coolant sent to the aftercooler goes through the aftercooler and is sent by an elbow into a passage in the block near the center of the vee at the rear of the block. The coolant sent to the oil cooler goes through the oil cooler and flows into the water jacket of the block at the right rear cylinder. The coolant mixes and goes to both
sides of the block through distribution manifolds connected to the water jack of all the cylinders.
The main distribution manifold is located just above the main bearing oil gallery.


COOLING SYSTEM FLOW
The coolant flows up through the water jackets and around the cylinder liners from the bottom to the top. Near the top of the cylinder liners, where the temperature is the hottest, the water jacket is made smaller. This shelf (smaller area) causes the coolant to flow faster for better liner cooling. Coolant from the top of the liners goes into the cylinder head which sends the coolant around the parts where the temperature is the hottest. Coolant then goes to the top of the cylinder head and out through an elbow, one at each cylinder head, into a manifold, one for each back of cylinders. Coolant goes through the manifold to the thermostat housing.



The water pump is gear driven at 1-1/3 times engine speed for the 1300 to 1800 rpm high speed engine and 2 times engine speed for the 1300 rpm low speed engines.


Coolant comes from the aftercooler and goes into this
elbow and into the engine block.


After the coolant goes through the oil cooler, it is sent into the engine block at the right rear cylinder. Coolant from the oil cooler and aftercooler mix (comes together) in the block and goes through the cylinder heads to the left and right water manifolds in the “vee” of the engine.



The bypass line goes from the temperature regulator housing to the inlet of the water pump. The regulators in the housing control coolant flow to the radiator or heat exchanger to regulate the temperature in the cooling system. When the coolant temperature is not high enough to open the regulators, the coolant will flow through the bypass line (bypassing the radiator) to circulate through the engine for quick warm-ups.



Four temperature regulators are in the thermostat housing.The housing has an upper and lower section. The sensing bulbs of the four temperature regulators are in the coolant in the lower section of the housing. Before the regulators open (upper inset), cold coolant is sent through the bypass line to the inlet of the water pump. As the temperature of the coolant increases to 88°C (180°F) and the regulators start to open (lower inset), coolant flow in the bypass line is stopped and coolant is sent through the outlets to the radiator or heatexchanger.
Coolant capacity is given in the Operation Guide for the engine only. Total system capacity will depend on the size of the radiator or heat exchanger. To prevent the coolant from freezing, it should have a mixture of 50 percent pure water, 50 percent
permanent antifreeze and a 3 to 6 percent concentration of corrosion inhibitor.



Here we see the housing for the temperature regulators (thermostats) and the four sleeve-type temperature regulators. The housing of the temperature regulator is above the front gear cover and supported by a compartment connected to the right and left water manifolds that are located above the cylinder heads.
Each of the regulators is positioned in a counterbore and has a lip-type seal.



Here the temperature regulator and seal have been removed from the housing. The smaller barrel portion of the regulator is the part that comes in contact with the seal.



When the regulator is closed (engine cold) coolant goes through the regulators. The coolant returns to the inlet of the water pump by way of the bypass
pipe (which is fastened to the opening in the front of the housing)
and does not get to the radiator.
When the regulator is open (engine hot) coolant goes through the
regulator out the side of the housingand then to the radiator for
cooling. On marine applications, the position of the regulator housing
will be upside down from the position in the photo.



The seals can be removed and replaced. To replace the seals, a seal driver must be used. To replace a seal, remove the old seal and clean the counterbore. Now install the seal in the housing with the lip of the seal away from the regulator.

Use a 1P529 Handle and a 1P489 Drive Plate to drive the seal into position in the housing.
When regulators and seals are replaced, the machinedsurfaces of the housing and cover must becleaned and a new gasket installed.



COOLING SYSTEM GENERATOR SET
On the right, we can see the coolant outlet line and the coolant inlet line at the bottom. The outlet line and inlet line are connected to a radiator outside the building.


The bypass line goes from the top of the thermostat housing to the inlet side of the water pump. We can also see the fuel filter housing and oil filter
housing on this generator set arrangement.
Read More

CAT Engine Course (Part 3)Air Induction System




Clean each crankcase breather element every 1000
service hours or oil change. Wash the breather
with clean solvent or clean diesel fuel.

Air Induction system



AIR INDUCTION AND EXHAUST SYSTEM
In this diagram of the air induction and exhaust system, we seethe turbochargers (two), the air inlet system piping, theaftercooler, the air inlet plenum and elbows, the inletport and intake valves, the combustion chamber, the exhaust valves and the exhaust manifolds.
The location of the air inlet system, exhaust manifolds, turbochargers, piping, aftercooler and air plenum are all in the center of the vee of the block.

Intake air comes through the air cleaners (not shown) and into the compressor inlet of each turbocharger.

Velocity of the air is increased by the turbocharger compressor impeller. The air is sent through the piping into the aftercooler inlet where it has increased in pressure and temperature.

The air then goes down through the aftercooler into the plenum chamber in the center of the vee. The air is cooled by jacket water in theaftercooler.
The decrease in temperature of the air can
range from 38º to 93ºC or 100º to 200ºF.



AIR INDUCTION AND EXHAUST SYSTEM
From the plenum chamber, the air goes throughpassages along the sides of the aftercooler, through aluminum elbows into the inlet ports, inlet valves and into the combustion chambers.
After the combustion or power stroke, the exhaust gases go out through the exhaust
valves, exhaust manifold, through theturbocharger turbine and goes out into the
outside air.


This arrangement of the 3512 Engine has two turbochargers and an aftercooler.

The location of the turbochargers and aftercooler on the vehicle arrangement is in the vee of the banks of cylinders.


The two turbochargers send air into the aftercooler air inlet.



The air inlet system, exhaust manifolds, turbochargers, piping, and aftercooler are all located in the center of the vee.
From left to right are the:
1. coolant manifold (left)
2. exhaust manifold (left)
3. aftercooler
4. rear lifting bail (eye)
5. exhaust manifold (right); and the
6. coolant manifold (right)



Watercooled manifolds and turbochargers are available on marine engines and are available as attachments on the industrial and generator sets.
On 3500 Engine Arrangements with water cooled exhaust manifolds, the coolant manifolds will be (combined with) the exhaust manifolds.


Here we see a generator set arrangement.
The air filter housing and turbochargers are on the rear of the engine. We can also see the:
1. emergency shutoff system
2. premium instrument panel; and the
3. air starting system with filters



This is the rear of the engine. On the industrial generator set engines, the turbochargers are mounted on the rear of the engine.



Here we see the electrical connections for the solenoid of the emergency air shutoff valve.

A sensor in the control panel activates the emergency shutoff system when the engine overspeeds (engine rpm goes higher than the maximum rpm setting).

Other sensors activate the fuel shutoff solenoid and STOP engine operation, when conditions of low oil pressure and high coolant temperature exist.
The remote shutoff also activates the fuel shutoff solenoid to STOP engine.


This is the air inlet reset control of the emergency airshutoff. This is one style. There is another style.



With the pointer in the vertical up position, it is set to RUN. When the solenoid is activated, thevalve goes down closing off the inlet air, and the pointer goes to the STOP position.



This must be RESET (set again) to RUN manually before the
engine is started again and after the problem has
been corrected.
Read More

CAT Engine Course (Part 2)





CRANKCASE EXPLOSION RELIEF VALVES
Crankcase explosion relief valves, seen here, are normally attachments but are required on marine engines. They are available for industrial and generator set arrangements. These valves relieve the pressure of an explosion in the crankcase. An
explosion is possible when combustible gases start to burn because of heat or sparks. A common cause of ignition is heat from a failed bearing. Explosion relief valves open to release the pressure of an explosion - then close to prevent a second cycle of combustion. Basically they stop oxygen from getting in, which would permit further combustion.



This is the idler pulley used on some arrangements to tighten or loosen the belts. To tighten the fan (drive) belts, loosen the bolts that hold the bracket of the idler pulley. Move the idler pulley out until the tension of the belt is correct and tighten the bolts.
Install new belts if they show signs of too much wear. Belts come in sets. If one belt is bad, install a new set of belts. If only one new belt is installed, the new belt will carry the load and all belts will fail rapidly.


Some engine arrangements have a bracket with a bolt or a hydraulic cylinder with a grease fitting to tighten the belts. Either
(1) loosen the nut on the adjustment bolt and turn it until the belt tension is correct, then tighten the bolt. Or,
(2) put grease into the fitting with a grease gun until the tension on the belts is correct. After the fan belts are tightened correctly, check the
tension of the alternator belts.


The alternator is located on the right front side and has
two drive belts which must be adjusted
periodically.


To check the tension of the alternator drive belts, push
down in the belts half way between the center of
the pulleys. If the tension is not correct, tighten
the belts.



To make an adjustment to the alternator belts, loosen
the outside nut on the support bracket bolt
several turns. Turn the inside nut until the belt
tension is correct. Then tighten the nut on the
adjustment bolt that holds the bracket.



Two governors will be available on the 3500 Engines.
The Caterpillar 3161 shown will be standard on the Vehicle, Industrial and Marine engines. The Generator Set and Marine Auxiliary will use the Woodward 2301 Governor.
The standard location for the governor or actuator is on the right front timing gear housing. As as option, the 3161 Governor may be located on the left side of
the front housing. The actuator for the 2301 Governor is available only on the right-hand side.



The 3161 Governor is driven by a 2400 rpm gear.
The speed is reduced to 1370 rpm through a bevel
gear set in the governor drive.
The governor has a hydraulic unit inside which has its own oil supply.
The 3161 Governor has a boost-activated smoke limiter.
A manual shutdown liver is provided on the engine.
An electric solenoid or hydraulic cylinder operated
shutdown is also available.
The electric solenoid operated shutdown is used on Vehicle, industrial
and Marine arrangements.
The hydraulic operated shutdown is used with hydramechanical
shutoff or at customer request.



WOODWARD ELECTRIC GOVERNOR
For some applications such as generator sets and marine
auxiliary engines, a Woodward electric governor and
actuator are used.
Here we can see:
1. governor actuator (EG-10P)
2. control rod from actuator to fuel control shaft
3. shaft (control) lever
4. governor drive housing
5. control cable to 2301 governor



The crankcase breather group is normally on the front
left side of the engine. When it is necessary to
locate the governor on the left side, the breather
group location is on the front right side.
Read More