GM Locomotive Water Cooling System PDF

Water Cooling System of GM Locomotive  Introduction The engine mounted water pumps, draw cooling water from the expansion tank and lube oil cooler assembly, and pump it into the engine.  The heated water leaves the engine, and flows through two radiator assemblies whe...

Water Cooling System of GM Locomotive  Introduction The engine mounted water pumps, draw cooling water from the expansion tank and lube oil cooler assembly, and pump it into the engine.  The heated water leaves the engine, and flows through two radiator assemblies where it is cooled. The cooled water then returns by way of the oil cooler to repeat the closed loop cycle.  Part of the water from the water pumps is piped to the air compressor. There are no valves in this line, air compressor cooling is provided whenever the engine is running.  Flow diagram of water cooling system Electronic temperature sensing probes Two electronic temperature sensing probes (ETP-1&-2) are located in the water line from the oil cooler to the inlet of the water pump on the engine left side, near the water temperature gauge.  Engine temperature feedback failure If the EM2000 computer detects that either temperature probe has failed, it sends a crew message ENGINE TEMPERATURE FEEDBACK FAILURE to the EM2000 display screen and also stores the message in Archive memory.  If it is detects that both probes have failed, it ignores both probes signals, fans remain in last operations status, engine speed goes back to idle and the NOT LOADING ENGINE TEMPERATURE FEEDBACK FAILURE message stored in Archive memory.  Radiators and cooling Fans During circulation through the diesel engine, air compressor and oil cooler, the coolant picks up heat which must be dissipated. Water temperature is controlled by means of radiator banks and AC motor driven cooling fans. The radiators are located in a hatch at the top of the long hood end of the Locomotive. Each radiator bank consists of two quad length radiator core assemblies, bolted end to end.  Headers are mounted on the radiator core to form the inlet and outlet ends of the radiator assembly, A bypass line is provided between the inlet and outlet lines in order to reduce velocity in the radiator tubes.  The cooling water from the engine is piped to the headers of each radiator bank. The discharge from the radiators enters the oil cooler. From there, the water returns to the water pumps for re- circulation.  RADIATOR FANS The 8 blades 52”cooling fans are controlled by the computer which acts on the contractors. The computer also controls the fan sequencing duty cycle and speed (low & high) to ensure even fan and contractor wear.  The two speed cooling fan system consists of two full speed contractors (FCFA & FCFB) and one slow speed contractor (FCS) per cooling fan motor. The system maintains the coolant temperature within a predetermined range of 79degree c to 85degree c.  For fuel efficiency, each cooling fan is driven by a two speed AC motor, which in turn is powered by the companion alternator. As the engine coolant temperature rises, the fans are energized in sequence by the control computer (slow speed). As additional cooling is required, the fan switch to full speed in progression as coolant temperature drops, the fans switch off one at a time.  Speed due to cold engine during engine idle conditions If the ETP 1 & 2, detects the temperature is below 46degree c, the engine speed will be raised to TH-2. The engine will continue to run at TH-2 for as long as the temperature stays below 52degree c. Once the temperature goes above 52degree c, the engine speed will again be reduced to idle. The isolation switch must be in RUN position for this speed up to occur. The reason for this speed up will be displayed to the crew as ENGINE SPEED INCREASE – low water temperature.  HOT ENGINE CONDITION The engine cooling water temperature is sensed at the water pump inlet. When the temperature becomes excessively high, the computer will display the HOT ENGINE- THROTTLE 6 LIMIT message.(Temp.-97deg.c) In addition to the message, the computer will limit engine loading when operating in throttle position 7 or 8. This condition will remain in effect until the temperature returns to a safe limit. Temp.-101deg.c- Power & RPM 6th Notch Temp.-101deg.c- for 5 Min.- Engine comes Idle  A temperature gauge is also located on the inlet line to the water pump. The gauge is colour – coded to indicate COLD (blue), NORMAL (green), and HOT (red).  Cooling System Pressurization The cooling system is pressurized to raise the boiling point of the coolant. This in turn permits higher engine operating temperatures, with a minimal loss of coolant due to boiling. Pressurization also ensures a uniform water flow, and minimizes the possibility of water pump cavitations during high transient temperature conditions.  A pressure cap, which is located on the water tank filler pipe, opens at approximately 20 PSI. By relieving excessive pressure, this prevents damage to cooling system components. The pressure cap is also equipped with vacuum breaker. This minimizes the possibility of system damage, which could be caused by pulling a vacuum on the system as the system cools. Filler valve handle Pressure cap Filler Pipe  OPERATING WATER LEVEL An operating water level instruction plate is provided next to the water level sight glass. It indicates LOW (minimum) and FULL (maximum) water levels, with ENGINE RUNNING, or DEAD (stopped). The water level should not be permitted to go below the applicable LOW water mark. A water level switch (float type) is installed in the cooling system water tank. This switch is connected to DIO 1 input channel 7 labeled NO LWL. While the engine is running, if the low water level switch opens for 10 seconds a crew message “ LOW ENGINE WATER LEVEL DETECTED” will be displayed and the alarm bell will ring for 60 seconds to alert the crew. The fault will be archived if the low water level condition is detected while the engine is shut down. The engine will not be allowed to start and a crew message “ENGINE WATER LEVEL DETECTED” will be displayed for 60 seconds.  Coolant The coolant is circulated through the engine to transfer heat from the engine components to the radiators. Engine coolant is composed of water, corrosion inhibitor, and when considered necessary, antifreeze. Coolant samples should be taken and analyzed at prescribed intervals to maintain the proper solution of corrosion inhibitor. To be suitable for use in EMD engines, a coolant must meet four basic requirements:- 1) Adequately transfer heat energy through the cooling system. 2) Not form scale or sludge deposits. 3) Prevent corrosion inside the cooling system. 4) Can’t deteriorate seals or gaskets in the cooling system.  Corrosion Inhibitor The main type of corrosion inhibitor for EMD engines is the borate – nitrate type. Borate – nitrate is available in powder, and liquid form. Powder and pellet form inhibitors should be dissolved in water in a separate container before being added to the cooling system. The level of the borate –nitrate should be maintained in a concentration above 5625 parts per million. WATER PUMP The two engine cooling water pumps (one on 8 cylinder engines) are self draining centrifugal pumps, which rotate in the opposite direction of the engine crankshaft. The pump drive shaft is supported by two permanently sealed grease lubricated ball bearings which require no maintenance.