Cooling System PDF

C c c c c G c c c G c c c G cd G Cooling System c G G G Introduction G The engine cooling system consists of engine driven centrifugal water pumps, c replaceable inlet water manifolds...

C c c c c G c c c G c c c G cd G Cooling System c G G G Introduction G The engine cooling system consists of engine driven centrifugal water pumps, c replaceable inlet water manifolds wit8 an individual jumper line to each liner, cylinder head discharge elbows, and an outlet manifold through which cooling water is G circulated. The centrifugal water pumps (one on an 8 cylinder engine) are mounted on the accessory drive housing and are driven by the governor drive gear. A representative G illustration of the engine cooling system is shown in Figures 5.1A and 5.1B. ci G G G c, c c c1 G Figure 5.1A Cooling System Pictorial Diagram G ITS Locomotive Training Series - Student Text c 51 I c  3 bll Coolant is drawn from the expansion tank through an aspirator by the water pumps. Pump outlet elbows conduct the water from the pumps to the water inlet w I manifolds located in each air box. Each manifold is connected at the rear end plate to an aftercooler water inlet pipe. Radiators Water PressurdLow Water Detect Turbocharger Aftemooler Manifold Figure 5.1B Cooling System Schematic Diagram Each cylinder liner is individually supplied with coolant from the water manifold through a water inlet tube assembly. A deflector is used at each liner water inlet to divert the water and prevent direct impingement on the t inner liner wall. The coolant flows upward in the cylinder liner water jacket and enters the cylinder head through 12 discharge holes at the top of the liner. A counter-bore around each hole accommodates a heat dam and a water seal. A water discharge elbow is bolted to each cylinder head to provide a water passage to the water discharge manifold which extends along the top of the crankcase. The crankcase has two “built-in” siphon tubes inside the water discharge manifold to provide for engine cooling water draining in the event the enginemnot level. Figure 5.1C Coolant Flow through Power Assembly I 5 2 ElectrdvlotiveModel 567,645 & 710 Series Diesel Engines I C c... -.'......... G G c In addition to the engine cylinder assemblies, on turbo engines, coolant is also , c circulated through the aftercooler cores. One condition that has a dramatic effect on engine performance is the temperature of incoming air for combustion.'As inlet air I' temperature is reduced, engine performance is increased. Past EMD engines used 2 pass aftercoolers as illustrated in Figure 5.2A to cool intake air after it had been ' G I compressed by the turbocharger. The coolant was taken off the rear of the main cooling manifolds after the power assemblies. : G ! G c c c c G c c c G Figure 5.2A Two Pass Aftercooler Figure 5.tB Four Puss Aftercooler (li 6) Coolant temperature for the after coolers therefore was limited to the same level as required for the power assemblies. Because the cores were equipped with only two G flanged connections, the coolant flow patterns were different from side to side of the engine resulting in an airbox temperature imbalance between the two banks, c EMD in partnership with Young Radiator has developed a four pass aftercooler c which recycles the water through the cooler before discharge to provide a higher G cooling capacity. The cores have been equipped with four connection flanges to allow for the application of any four pass core to either the right or left engine bank and keep G the coolant pattern the same between banks. c Coolant from the power assemblies and the aftercoolers is collected in the main water chamber in the top center of the engine. From the engine, water is directed out c the 'Y" pipe to the radiator assemblies. Electrically driven cooling fans move air G through the radiators, which absorbs heat from the coolant. Water temperature control is facilitated by the use of temperature switches that control fan and shutter operation. c Newer systems use temperature sensors, and fan and shutter control is handled by a microprocessor. G The coolant returns from the radiators to the lube oil cooler where it absorbs some c of the excess heat from the lube oil. The cooler consists of a radiator section mounted in 0 a steel tank. 'Q G ITS LocomotiveTraining Series - Student Text c 5-31 c  3 From the cooler, the coolant goes back to the aspirators to repeat the cycle. When the engine is first started, coolant is drawn from the expansion tank as there is no return from the radiators at this point. When there is sufficient return flow, the water level in the tank stabilizes. Note that part of the water from the engine mounted pumps is piped to the air compressor. There are no valves in the line, thus cooling will be provided whenever the engine is running. Upon leaving the air compressor, water is piped back to the water tank for re-circulation Blower Type Cooling System The cooling system of the blower type engine is identical to the turbo type except for the absence of the aftercoolers and the associated piping. The blower type cooling system is shown in Figure 5.3. 1. W.1.r Pump 4. IdelTube 7. Dirchug.Elbow 2. Outlet Elbow 5. U w Water 8. Syatan h.in V.hn 3. Inlet Manitold 6. Cyl1nd.r nud 0.wohvg.M.nHold Figure 5.3 Blower Type Cooling System Cooling System Pressurization On most newer systems, the cooling system is pressurized to increase the boiling point of the coolant, prevent cavitation at the water pumps during high transient temperature conditions, and to provide uniform cooling throughout the operating range of the diesel engine. The expansion tank has a pressure cap that regulates system pressure at 7,12, or 20 psi (48,82or 138 KPu) depending on engine requirements. Older switcher locomotives and older marine installations use unpressurized systems. 1 54 ElectrMotive Model 567,645 & 71 0 Series Diesel Engines  Operating Water Level An operating water level instruction plate, Fig 5.3, is provided next to the water level sight glass. The instructions indicate minimum and maximum water lever with the engine running or stopped. The water level mark should not be permitted to go below the applicable “low” water level mark. Progressive lowering of the water in the gauge glass indicates a water leak in the cooling system, and should be reported. Normally, there should be no need to add water to the cooling system, except at extended intervals. Figure 5.4 Water Level Plate 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 analysed 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: adequately transfer heat energy through the cooling system not form scale or sludge deposits prevent corrosion inside the cooling system can’t deteriorate seals or gaskets in the cooling system Water The water in some areas contain elements such as excessive solids, hardness salts, or corrosive elements such as chlorides that make it unsuitable for use in the cooling systems of EMD engines. Water from these sources should be processed by softening, de-ionizing, or distillation to make it suitable for cooling system use. Corrosion Inhibitor The main type of corrosion inhibitor for EMD engines is the borate-nitrate type. Borate-nitrate is available in powder, pellet, 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 borate-nitrate should be maintained in a concentration above 5625 parts per million. ITS Locomotive Training Series -Student Text 551  L, 4 rj) Antifreeze d Specifications for the use of antifreeze in EMD engines is available in M.I. 1748. 0 d Water Pumps ". r XI...,. " 1 1. Water Sllngu 8. Water Pump 8h.R 15. Cubon 8ul 2 S u m HMIIing O.ahn&uK.y 16. Impdlr Hwdng 3. ou Inl.1 10.DdwOur 17.ot.tlwry Buahing 4. BWng R. l r i m Rlng 11. W n g Auunbly 18. outwsul 6.&up Rlng 12. Oil outl.1 19. Sad RaWnu Spring 8. Owr W n r W & r 13. Rdl Ph and Spring 20. lmpdlu 7. Gu W n l n g Nu( 14. Baaing S p s w 2l. Impdlw Rotalnw Koy Figure 5.5 Water Pump Cross Section Description The two engine cooling water pumps (one on 8 cylinder engines) are selfdraining 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. The components of the water pump are d identified in Figure 5.5. 3 3 3 1)- Electro-Motive Model 567,645 & 710 Series Diesel Engines LJ c a C &A c4 G c Carbon Shell c Inner Seal c G G c c Spring Outer Seal , looking up beside each liner through the inner air box opening). c c Check the water manifolds the entire length of the engine both sides for cracks or leaking "0"rings. G c FiW Dnin V.hn mDnlnVahm &HI &Turn To Dnin c c c; c c G G Figure 5.12 Strainer Housing Drain Valves ci c c ITS Locomotive Training Series -Student Text 515 a A G  3 Drain the lube oil strainer housing (by rifling and turning strainer housing druin valve), when the oil level drops below the oil cooler inlet line check for water running down from the lube oil cooler. On turbo engines, check the aftercooler cores for leaks. If equipped with a exhaust manifold screen inspection port, check turbo screen and exhaust manifold for signs of dried corrosion inhibitor or "washed" areas. After making all these checks, and no leaks are found, it may be necessary to a hot water 2Spsi hydro-test. Drain the engine, refill with hot water apply 2 5psi water pressure, and repeat all the proceeding checks. Block Check, Power Assembly Removed: On some occasions a suspected leaking power assembly will be removed, and after examination, no obvious cause of the leak is found. Inspect the exhaust port for a crack, dried coolant inhibitor, or water. If nothing is found, apply a blanking saddle to the water manifold outlet of the removed assembly and an expansion plug to the water discharge hole in the block. Refill the engine with hot water, reapply the 25psi hydro test, and check for water leaking down the exhaust port. If water is seen running down the exhaust port but the source cannot be seen, the exhaust manifold section for that cylinder will have to be removed to locate and repair the leak (usually u crack in the exhaust scroll to engine top plate weld). Figure 5.13 "Blanking Saddle" and "Expansion Plug" 9Opsi Block Test In some cases, where an engine has been inspected with 25psi cold and hot hydro- tests, and no water leaks are found, it becomes necessary to apply a 9Opsi (620kPa) test to the isolated engine block. Usually this is done when an engine has a history of oil contaminated by water, or loosing water with no leaks being found. 516 Electro-MotiveModel 567, 645 & 71 0 Series Diesel Engines A  13 r3 High Coolant Temperature c3 On an engine experiencing high coolant temperature, make the following suggested checks: 3 Check the coolant level in the expansion tank, and refill if low. If the 3 engine is continually using cooling water check for internal and external 3 water leaks. 3 0 Veri@that the shutters are operating properly using the temperature switch test button. Check the temperature switch operation by running the 3 engine until the switch closes, or by removing the switch and testing it in a 3 pan of heated water with a thermometer. kd Check for the proper operation of all cooling fan motors and temperature control switches. r3 Remove the radiator access panels and inspect all radiators for restriction of 3 air flow. Clean the radiators if necessary using the procedure on Pg.5-8. 3 0 Inspect all water pump and radiator vent lines for proper connection, k3 loose fittings, or damage to the lines. Loose water pump vent lines can cause cavitation of the water pump and a resulting loss of coolant 3 delivery pressure. Damaged or improperly connected radiator vent lines can cause air binding in the radiators resulting in a loss of cooling efficiency. 3 3 Low Coolant Pressure 3 Low coolant pressure can be a cause of high coolant temperature. Install a pressure gauge in the expansion tank and run the engine until it reaches operating temperature. Compare the gauge reading to the pressure stamped into the expansion tank pressure 3 cap. If the pressure is low, make the following checks. 13 Test the expansion tank vent valve by placing the end of the expansion tank vent line in a bucket of water. If bubbles are released through the water, the 3 expansion tank vent valve is not seating properly and must be replaced. 3 With the engine shut down and the cooling system pressure relieved 3 by opening the manual vent valve, remove the pressure cap and inspect the filler neck. If the sealing surface is damaged or distorted, replace the neck +d assembly with a new one using a new tank to neck gasket. 3 Inspect the pressure cap for proper seating of the snifter valve, and check 3 for a cracked, hardened or damaged gasket. Test the cap on an external pressure tester. Replace the cap if any defects are noted. 3 I518 Electrdvloti Model 567.645 81710 Series Diesel Engines A