Fujian Southchina Heavy Machinery Manufacture Co.,Ltd

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32 Tons 32t LNG Heavy Forklift

32 Tons 32t LNG Heavy Forklift

HNF-320 Rated load: 32,000 kgs Load center:1250 mm Operating weight: 41,000 kgs Wheel base: 4,800 mm Email: claire@socmachinery.com

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    Email: claire@socmachinery.com 


    32 tons 32t LNG heavy forklift


    The overheating of the working oil temperature of the forklift torque converter is a common fault, and the failure of the loading machine is weak. At the same time, the high oil temperature also accelerates the oxidation and foaming of the hydraulic oil, so it loses the lubrication performance of the sports parts, causes the damage of the seal, and affects the normal work of the machine. Through examples, several reasons for the malfunction are analyzed in detail, and corresponding solutions are put forward.

     

     

     

    After the use of a certain forklift after overhaul, it is used for the culvert to produce the ballast. After less than one month's use, it is found that the torque converter system has been working for half an hour. The oil temperature of the torque converter has reached 120 degrees centigrade, obviously feeling the weakness of the bucket. At this time, the variable speed oil pressure gauge shows 1.1 MPa, indicating that the variable speed oil pressure is normal. In order to find out the cause of the fault accurately, the factors which may lead to the temperature rise of the torque converter oil are investigated one by one from the transmission oil cooling machine and so on.

     

    32 tons 32t LNG heavy forklift




    1. The composition and heat dissipation principle of torque converter and transmission hydraulic system.

     

    The heat generated by torque converter and transmission is mainly solved by circulating cooling of transmission oil. As shown in the picture, the transmission gear pump suck oil from the transmission oil bottom through the hose and filter, and enters the pressure regulating valve (1.1 ~ 1.6 MPa) after filter filter, and then the pressure oil is divided into two ways: one way through the clutch shut-off valve enters the variable speed control distribution valve and enters the I, the second gear and the inverted hydraulic cylinder according to the different position of the variable speed valve stem. The other way enters the torque converter through the buried tube on the box wall and comes out of the torque converter through the hose to the radiator. After cooling, the low pressure oil is lubricated to the planetary clutch of the overrunning clutch and the transmission and then flows back to the oil pan.  The pressure valve controls the inlet pressure of the torque converter from 0.4 to 0.55MPa, and the oil pressure is 0.3 to 0.45 MPa. The heat dissipation of the transmission oil is mainly caused by the cooling of the radiator and the heat dissipation in the shell.

     

     

     

    Fault analysis on high oil temperature of forklift torque converter

     

    2. Several factors leading to high oil temperature in torque converter

     

    2.1 system oil inlet pressure is insufficient


    32 tons 32t LNG heavy forklift



     

    Through the heat dissipation principle of the torque converter one transmission system, it is known that the transmission pump, after absorbing the working oil through the pressure regulating valve from the transmission oil bottom, enters the torque converter, and then goes back to the oil pan after the radiator is cooled, and the other way into the transmission. If the oil pressure of the system is insufficient, the pressure of the working oil into the torque converter is too small, so that the oil intake is insufficient and the oil is too small to enter the cooler, so that the oil can not be cooled fully in the system, the temperature of the oil will rise quickly and the transmission temperature is too high. The main reasons leading to insufficient oil pressure are:

     

    (1) improper system pressure. The pressure regulating valve is an important part of the hydraulic transmission system, which controls the pressure of the oil entering the system. If the spool valve core wear leakage or the torque converter pressure valve failure, stagnation, can not play the role of adjustment, will cause the torque converter shortage of oil supply, pressure reduction.

     

    (2) the wear of the gearshift pump causes the gap between the gear and the end cover to be larger, the leakage is serious and the oil supply is insufficient; the system pressure is too low, the oil of the torque converter is insufficient; if the leakage of the pump into the oil pipe or the low oil level of the oil bottom, the pump inhaled air will also cause the shortage of the oil supply.

     

    (3) Because of excessive wear and tear of hydraulic piston seals in transmission, the pressure of hydraulic system drops, the clutch slips and the oil temperature rises.


    32 tons 32t LNG heavy forklift


     

    2.2 the oil level is too low or too high

     

    (1) when the oil level is too low, the oil circulation in the work is accelerated. The residence time of the transmission oil in the oil pan and the natural heat dissipation time is short and the heat dissipation is poor. It causes the transmission of the transmission and also causes the transmission pump to absorb the air, which leads to the pressure drop in the system.

     

    (2) High oil level causes too much oil around the high-speed rotating parts in the transmission, increases the rotating resistance, and changes into heat energy to raise the oil temperature.

     

    2.3 improper selection of working oil

     

    The viscosity index of oil is an important parameter of the oil, and the viscosity directly affects the working condition of the system. The viscosity is too high, the flow loss of oil is increased, the transfer efficiency is reduced, the oil temperature is increased, the viscosity is too low, the leakage is increased, the volume efficiency of the system will decrease, and the oil temperature will rise. At the same time, the density and viscosity of the working oil decrease with the increase of temperature, and the leakage is easy to occur, the lubrication performance and friction resistance will be increased. It is suggested that the special oil for dragons should be used.

     

    2.4 radiators have bad heat dissipation performance

     

    The radiator is the heat dissipation device of the working oil. The 50 series forklift torque converter and the transmission system are cooled by air cooling structure. The dust and other sundries in the radiator must be cleaned up at times. The blockage of radiator or tubing will hardly achieve heat dissipation.

     

    2.5 parts damage in the transmission

     

    Because of the serious friction caused by the damage of parts, the heat is changed to heat. Severe friction of variable speed pumps, torque converters, overriders, clutch plates and other components can cause varying degrees of oil temperature rise.

     

    2.6 continuous high load operation

     

    If the forklift runs for a long time and high load, the heat generated by the forklift is greater than its heat dissipation speed, then the temperature of the working oil is bound to exceed the limit. The temperature of the forklift will have a great damage to the moving parts, so it should be strictly forbidden for a long time overloading operation and should be paid more attention to when the temperature is high.

     

     

     

    32 tons 32t LNG heavy forklift



    3, troubleshooting and eliminating

     

    Because of the strong regularity of the fault, it usually appears after half an hour of continuous work, and can be eliminated one by one according to the above factors that lead to the rise of oil temperature:

     

    (1) because the continuous working time of the forklift is not long, it is possible to exclude the possibility of continuous high load operation resulting in the increase of oil temperature.

    (2) remove oil filter or oil pan check: no metal detritus was found. If there is a bright steel particle, it indicates that the bearing of the transmission pump is worn or damaged; if there are aluminum particles, the torque converter is damaged; if there are black or copper particles, it indicates that the clutch is worn. Removal of the oil pan magnetic filter screen inspection, no metal fragments, indicating that can eliminate the transmission, transmission gear box caused by damage to parts of the heating phenomenon.

     

    (3) when the fault occurs, touch the radiator by hand lightly, and feel the temperature difference, indicating that the radiator works normally.

     

    (4) check the oil quantity of the working oil in the transmission is normal, the oil brand name is selected according to the manufacturer's regulations 8# hydraulic transmission oil, after inquiry, no different brands of oil liquid mixing phenomenon is not found.

     

    (5) when the fault occurs, the variable speed oil pressure gauge is shown to be 1.1 MPa, within the normal range of 1.1 ~ 1.6MPa. The oil pressure measuring screw is unloaded and the pressure meter is installed on the side of the torque converter to show that the oil pressure of the torque converter fluctuates between 0.06 and 0.15MPa, indicating that the inlet pressure of the torque converter is obviously low, and the initial judgement of the pressure regulating valve of the torque converter has a problem, which leads to the low oil quantity entering the torque converter and the radiator. If the pressure regulating valve leakage is light, the system pressure can be increased to compensate for the leakage, but the check of the pressure regulating valve demolition found that the valve spool wear badly need to be replaced. After changing the pressure valve, and setting its pressure value of 0.50MPa, the test machine 2H temperature stable at 85 C, measuring the torque converter oil pressure display 0.45MPa, oil temperature and pressure value are in the normal range, troubleshooting.


    32 tons 32t LNG heavy forklift




     

    4, concluding remarks

     

    There are many reasons for the high temperature of the torque converter. Although the failure phenomenon is concentrated on the torque converter, it is not always the problem of the torque converter itself, because any problem in the whole system will affect the torque converter's work. In the case of specific judgment and analysis, the fault source should be found in the sequence of the first, the first, the first, and the difficult after the trouble, according to the possible cause of the failure.


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