Core tips: common faults and preventive measures of engine cooling system: (1) rust corrosion is caused by oxidation in the cooling system. The high temperature humidity will aggravate the oxidation reaction of the cooling system, and the rust will reduce the heat transfer efficiency of the cooling system, and will also aggravate the wear of the pump shaft and other parts.
1 common faults and their mechanism
(1) rust corrosion is caused by oxidation in the cooling system. The high temperature humidity will aggravate the oxidation reaction of the cooling system, and the rust will reduce the heat transfer efficiency of the cooling system, and will also aggravate the wear of the pump shaft and other parts.
(2) cavitation erosion is caused by high frequency vibration of cylinder liner. When the reciprocating movement of the piston goes through the top and back points, the piston will change the force direction of the cylinder wall, which will cause the high frequency vibration of the cylinder sleeve. The pressure of the cooling water also changes when the pressure of the cooling water is reduced to the saturated steam pressure or a certain critical pressure at that temperature, the gas dissolved in the water is separated in the form of small bubbles. When the cylinder sleeve vibrate to the cooling water, the bubbles that have been formed will be burst by the surge of pressure, and the tiny surface well of the cylinder sleeve is squeezed by a large impact pressure (up to hundreds of thousands of Mpa) to make its temperature 30 high. If the above process is carried out continuously, the metal on the tiny surface will be broken down from the surface, and the above function will be repeated, which will make the outer surface of the cylinder form four pits or deep holes.
(3) when the corrosion current flows through the coolant between different metals, it will cause electrical erosion due to the potential difference. Because the electromotive force of the electric conductor between the two metals between the two different metals causes the current to flow from where the electric potential is high to the lower electric potential in the lowest corrosion resistance metal L. When the current flowing through the coolant is caused by external power, there will also be electrical erosion.
(4) acid and alkali corrosion, in order to make the engine in the best working state, the pH value of the coolant must be kept between 8 and 11.3, which is weak alkaline. When the pH value is less than 8, the coolant will erode the black metal material Z when the pH is more than 11.3, and the coolant is too alkaline to corrode the aluminum, copper or nonferrous metal materials. When the pH value is below 6.5 or more than 11.5, the coolant affects the corrosion of the cooling system greatly.
(5) when the cooling system is stored in a certain amount of air, the air corrosion will cause cavitation in the water jacket, the radiator, the cylinder wall and the impeller of the pump. Therefore, when the cooling system is leaking and the high pressure gas leaked into or discharged by the air enters into the cooling system, the probability of cavitation will increase greatly.
(6) the pH value, temporary hardness and water temperature of the scaling water determine the formation and quantity of the scaling. The common fouling deposits in the cooling system include calcium carbonate, calcium sulfate, iron, copper and silica, and the effect of precipitates on the heat conduction of dry heat. Therefore, the formation of scaling and precipitation will reduce the efficiency of the cooling system, such as the thickness of only l.6 mm, and the sediment can reduce the heat conduction efficiency by 40% in many cases, such as the cylinder head and cylinder block, the piston and so on.
2 preventive measures for failure shall be made according to the mechanism of the above failures:
(1) supplement coolant additives used for corrosion prevention of cooling systems.
(2) the pH value of coolant should be strictly controlled between 8 and 11. 3.
(3) in order to restrain cavitation or slow down cavitation velocity, the clearance between piston and cylinder should be properly selected and the stiffness of cylinder liner should be increased. The outer surface of the cylinder liner is treated with aluminum plating, improving the temperature and pressure of cooling water, adding emulsified oil in the cooling water, reducing the amplitude of the cylinder liner, and avoiding the rough work of the diesel engine and so on.
(4) when the electrical system is designed, it must not apply the constant voltage to any part of the cooling system; when the machine appears in the operation, the coolant in the cooling system should be cleaned immediately after the cooling system is cleaned, and the coolant mixture well is re lived to determine the voltage power to prevent the continuous corrosion.
(5) the supplementary coolant additive used in the coolant mixture must contain a buffer in order to keep the pH value and neutralize the acidity produced by the gas leakage.
(6) to avoid the occurrence of bubbles, the sealing state of the cooling system should be checked regularly and foam inhibitor should be added to the coolant mixture. The quality of water is in accordance with the technical requirements of the engine manufacturer for cooling system.
