Locomotive Water Cooling System - How Water Cooling System of Locomotive Wok
WATER COOLING SYSTEM
1.0 INTRODUCTION
During the combustion of fuel
and air, enormous amount of heat is produced inside the engine cylinder and the
temperature as high as 1200ºF may be reached.
The temperature is so high that it will break the lubricating film
between the moving parts of the engine parts.
Hence this temperature must be reduced to the working condition of the
engine.
2.0 ENGINE COOLING
The temperature is so high that
it will break the lubricating film between the moving parts of the engine
parts, weld the moving parts or may cause any mechanical breakage to the engine
parts. Hence this temperature should be
reduced by some means to such a value, of 65º-90ºC, at which the engine may
work efficiently. Too much cooling would however, lower the thermal efficiency
of engine. Thus the purpose of the cooling system is to keep the engine temperature
within the operating range. About 30 to
35% of the total heat produced is to be removed by the cooling system. When the
combustion takes place, the cylinder walls, cylinder head, piston and valves
are heated.
The cooling system should cool
rapidly when the engine is too hot, and it cools slowly or not at all, when the
engine is cool or is warming up. Most
engines are designed to operate in a definite temperature range which will ensure
correct clearances between parts, promote vaporization of the fuel, keep the
oil at its best viscosity and prevent the condensation of harmful vapour. Thus, the duty of the cooling system is to
keep the engine temperature within the desired limits.
Cooling beyond permissible
limits is not desirable because it decreases the overall efficiency due to the
following reasons.
1. Thermal efficiency
is decreased due to more loss of heat to the cylinder walls.
2. The vaporization of
fuel is less, it decreases combustion efficiency.
3. Viscosity of lubricant increases at low temperature, it increases fiction.
Although more cooling improves volumetric efficiency, the above factors results in decrease of overall efficiency.
3.0 PROPERTIES OF AN EFFICIENT COOLING SYSTEM
1. An efficient
cooling system removes 30 to 35% of the heat generated in the combustion
chamber. Too much removal of the heat
decreases thermal efficiency of the engine.
2. It removes heat at
a fast rate when the engine is hot and at a low rate when the engine is started
until the engine reaches at its normal operating temperature.
4.0 METHODS OF COOLING
There are following four methods of engine
cooling.
1. Air cooling
2. Liquid cooling
3. Steam
cooling
4. Water
cooling
1. AIR COOLING
In this method of cooling, the
heat is dissipated directly to the air after being conducted through the
cylinder walls. Fins and flanges on the outer surfaces of the cylinders and
heads serve to increase exposed area to the cooling air and so raise the rate
of cooling.
2. LIQUID COOLING
In this method of cooling,
instead of water other liquids having higher boiling points are used for
cooling. Glycerine (boiling point 290ºC
and ethylene glycol (boiling point 86ºC) are examples of such liquids. Due to their higher boiling point these
liquids have increased capacity to carry heat and hence the weight of coolant
and radiator is decreased.
3. STEAM COOLING
In this method of cooling, steam
is used for cooling. The cooling system
consists of the same components as
for water cooling, except the radiator.
The radiator is in the form of condenser in this system. The circulation
of water is made by a pump. The water in the cylinder jackets is converted into
steam, which flows out at the top of the engine block and goes to the bottom of
the radiator. The steam is condensed in
the radiator and the water thus formed is again circulated by the pump.
4. WATER COOLING
In this method of cooling,
water is circulated around the cylinder liners, cavities of inlet and exhaust
and injector cooling sleeves. The
circulating water when passes into the engine block and cylinder head, takes
the heat of the combustion. When it
passes through the radiator, it is cooled by air drawn through the radiator by
a fan. After passing through the
radiator, the water again goes into the engine block.
There are
two systems of water cooling:
b. Pump circulating system.
a. THERMOSIPHON SYSTEM
In this system of water
cooling, the circulation of water is obtained due to the difference in
densities of hot and cold regions of the cooling water. There is no pump to circulate the water. The hot water from the engine block being
lighter, rises up in the hose pipe and goes in the radiator from the top
side. It is cooled there and hence goes
down at the bottom side of the radiator; from there it goes again in the engine
block. The system is quite simple and
cheap but the cooling is rather slow. To
maintain continuity of the water flow, the water must be maintained upto a
certain minimum level. If the water
level falls down, the circulation will discontinue and the cooling system will
fail.
b. PUMP CIRCULATION SYSTEM
In this system of water
cooling, the circulation of water is obtained by a pump. The pump is driven by means of extension
shaft gear on the engine. The
circulation of water becomes faster as the engine speed increases. There is no necessity of maintaining the
water upto a correct level.
5.0 COMPONENTS OF WATER COOLING SYSTEM
1. Radiator
2. Water
Pump
3. Eddy
current clutch,
4. Right Angle Gear Box
5. Fan Drive Assembly
5.01 Radiator
Radiator
is a device having a large amount of cooling surface to air so that the water
circulating through it is cooled efficiently.
It consists of upper and lower headers and between them a core. The upper header is connected to the water inlet
from the engine and the lower header is connected to the outlet side. The core is a radiating element, which cools
the water.
|
RADIATOR |
No.
of cores |
No.
of tubes in each core |
No.
of tubes may be dummied |
|
Rt.
1 + Lt.1 |
628 |
20
3% (Approximately) |
Radiator core testing pressure 30 PSI.
There
are two basic types of radiator cores: Tubular type and Cellular type. In tubular type core, the upper and lower headers
are connected by a series of tubes through which water passes. Fins are placed around the tubes to improve
heat transfer. Air passes around the
outside of the tubes, between the fins, absorbing heat from the water. While passing inside. In a tubular radiator, if one tube becomes
clogged, the cooling effect of the entire tube is lost, because the water
passes through all the tubes in series.
Radiators
are also classified according to the direction of the water flow through
them. If the water flows from top to
bottom, they are named as down flow type
radiator. Our Radiators are down flow
radiators. Radiators are usually made of
copper because of their high heat conductivity.
The various sections of the radiator are almost completely joined
together by soldering.
5.02 WATER PUMP
It is a centrifugal type water
pump mounted on the left side free end bottom of the engine and is driven by
the extension shaft gear. The pump draws the water from the radiator at the
centre (auxiliary), then pumps radially to the system. The pump bearing housing
is connected to the engine through a flanged connection. Suction and discharge piping are directly
connected to the suction and discharge flanges of the pump.
PARTS OF THE WATER PUMP
1. Gear nut
2. Clamp
screw and locking wire
3. Gear
key
4. Gear
5. Thrust
bearing retainer
6. Bearing
frame
7. Pump
shaft
8. Lifting eyebolt
9. Nut
10. Nut
and locking wire
11. Casing
12. Split
eyebolt
13. Washer
14. Castle
nut
15. Impeller
16. Water
seal unit
17. Seal
plate
18. Gasket
19. Oil
slinger
20. Oil
seal
21. Radial
bearing
22. Thrust
bearing
23. Cap screw and locking wire
5.03 EDDY CURRENT CLUTCH
It is coupled together with the
Right Angle Gear Box. It is having
spider coupled with Right Angle Gear box shaft and the drum coupled with
extension shaft drive. Spider is mounted
inside the drum. Spider is a core wound
with coil and is connected with temperature control circuit. When the crankshaft starts rotation the
crankshaft extension shaft also rotates.
As and when the spider gets electrical supply, core getting magnetized
and starts rotating along with the drum.
Since the spider rotates Fan starts rotates.
5.04 RIGHT ANGLE GEAR BOX
It is mounted at the middle of
the Radiator Room on a stand. It
converts horizontal rotation from the extension shaft into vertical rotation to
the Radiator Fan Drive Assembly.
The parts of the Right Angle
Gear Box are as under:
Gear Rate between Horizontal &
Vertical gears YDM4/4H: 1:1.11
1. Gear Box casing
2. End Cover
3. ECC side cover
4. Vertical Carrier
5. Top cover
6. Horizontal Shaft
7. End Bearing
8. Small Bearing
9. Horizontal
Bevel Gear
10. ECC side large bearing
11. Oil Catcher
12. Horizontal Bevel shaft nut.
13. Vertical shaft.
14. Bottom small bearing
15. Vertical Bevel Gear
16. Vertical Large Bearing
17. Oil Catcher
18. Hub and Nut ( Note : All the above bearings are single row roller bearing)
20. Parts of Fan Drive Assembly:
a) Fan bearing
b) Fan shaft
c) Single row ball bearing 2 Nos type
(broad) 4 Nos. type (small). It is a sealed bearing, no need for greasing.
5.05 RADIATOR FAN
The radiator fan gets drive
from extension shaft from engine through compressor, eddy current clutch, right
angle gear box and universal shaft. Fan
will not run continuously along with the engine. As the water temperature raises to 68ºC, a
temperature switch TS1 picks up and energies the Eddy Current Clutch, making
the radiator fan to rotate at slow speed.
When the water temperature reaches 74°C, TS2 picks up and make the radiator
fan rotate at full speed through electrical circuitry.
When the Radiator Fan starts
running, atmosphere air is supplied through the radiator core fins, cooling the
radiator tubes and the water passing through the tubes. The hot air is then exhausted through the
Radiator Fan.
As the water temperature drops to
66ºC, the relay cuts off supply of 72 V from Auxiliary Generator to the Eddy
Current Clutch. As the ECC loss magnetic effect and the fan stops running.
6.0 COOLING WATER SYSTEM (YDM4/4A)
In the cooling water system a
water circulating pump of the centrifugal type draws the water from the
radiators and discharges to the lube oil cooler. From the lubricating oil cooler the water
enters the engine block. It circulates
around the cylinder liners. It then goes
up getting lighter due to heat transfer through the drilled holes in the block
and through the jumpers, enters the cylinder heads at the bottom. It then raises to the top of the cylinder
heads through the raiser pipes and enters the water outlet header. From this header it passes through on to the
bubble collector and then to the radiator on top and collect at the bottom in
sequence, thereby passing through the elements and getting cooled. It again finds its way ultimately to the
suction side of the pump. Thus the water
is cooled for recirculation through the system.
 |
| Cooling Water System of Locomotive |
A pipe is taken at the discharge side of the pump to the turbo for cooling the turbo casing. It returns through another pipe from top of the turbo casing to the inlet side of the pump.
EXPANSION
TANK
There is a tank at the top of the compressor
room. This tank provides expansion of
water and stores make up water to compensate the loss due to evaporation. A float chamber is incorporated inside the
tank to hold the low water switch. This
switch consists of a float and an electrical contact. This switch operates when the water level
reduces to 1” from the bottom of the tank and shuts downs the engine through
the electrical circuit and governor.
7.0 ENGINE COOLING WATER TEMPERATURE CONTROL
The Engine water temperature is
controlled by the radiator automatically.
The speed of the radiator fan is automatically changed to two speeds by
the temperature of the cooling water.
When the temperature of the water leaving diesel engine reaches 68ºC the
switch TS1, picks up by the action of the temperature sensitive element. This action (closing of the switch energises
the relay R1. The contacts of R1 closes and excites the field of eddy current
clutch through a resistance allowing the fan to rotate at a medium speed. When the temperature drops down to 66ºC,
switch TSI break off. Thus bringing the
fan to a stop.
When the temperature of cooling water reaches 74ºC another switch
TS2 picks up and energies the coil of R2 thereby making contacts to close. This excites the field of eddy current clutch
without the resistance causing the fan to rotate at full speed, TS2 breaks off
at 72ºC.
7.1 TEMPERATURE SETTING & ITS FUNCTIONS
|
Temperature
Switch |
Pick
up at |
Drops
at |
Fan
Conditions: |
|
TS1 |
68ºC |
66ºC |
Minimum
speed |
|
TS2 |
74ºC |
72ºC |
Maximum
speed |
|
ETS
1 |
85ºC |
83ºC |
Max.
speed +Hot Engine+ alarm + |
|
ETS
2 |
90.5ºC |
88ºC |
Max.speed+Hot
engine alarm+indication light Engine comes to idle in YDM4 or YDM4 A only. |
7.2 HOT ENGINE ALARM
There is a provision made in
the engine cooling system to indicate the driver a warning light (red) and
alarm if the temperature of the water reaches 85ºC. This is done by ETS1 (Engine Temperature
Switch). When the water temperature
reaches 90.5ºC, ETS 2 picks up and brings the engine to idle. (When the
throttle handle is in 5th or 6th notch, engine will shut down)
The minimum water level in an
expansion tank is always necessary. This
is to safeguard the engine cooling with sufficient flow from the pump. If sufficient water is not available for
circulation, it may lead to hot engine condition. To prevent these, a float switch is provided
on the expansion tank. When the water
drops to a specified level (1” below from the bottom of the tank) the float
comes down and closes the switch. It
results in action on the Governor clutch coil. (G.E.) The Governor in turn brings
the fuel control shaft to no fuel position and engine stops. The engine will not be able to start if there
is not enough water in expansion tank.
8. TROUBLES AND CAUSES IN WATER COOLING
SYSTEM
|
Sl.No |
TROUBLES |
|
POSSIBLE
CAUSES |
|
1. |
External leakage |
1. |
Loose victaulic or armoured couplings |
|
2. |
Damaged radiator tubes |
||
|
3. |
Water pump water seal defective |
||
|
4. |
Flange joints leaking/defective gaskets |
||
|
2. |
Internal leakages |
1. |
Cylinder Head, Cylinder liner or Turbo Super
Charger crack. |
|
3. |
Water running down |
1. |
Boiling |
|
2. |
External or internal leakages |
||
|
3. |
Restricted radiator |
||
|
4. |
Poor circulation |
1. |
Water pump drive shaft cut at gear |
|
2. |
Water pump drive shaft cut at impeller side |
||
|
3. |
Extension shaft Gear damaged |
||
|
4. |
Restriction in the system |
||
|
5. |
Corrosion |
1. |
Outstation topping up of Hard water |
|
2. |
Not using the chromate compound with distilled
water |
||
|
6. |
Overheating |
1. |
Poor circulation of water |
|
2. |
Radiator fins checked |
||
|
3. |
Incorrect injection timing |
||
|
4. |
Incorrect tappet clearance |
||
|
5. |
Clogged exhaust system |
||
|
6. |
Engine over loading |
||
|
7. |
Brake binding |
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