The failure of diesel engine in the use of construction machinery occurs from time to time, so I visited and investigated some construction machinery repair plants and construction units with a large number of construction machinery. The investigation found that the fault caused by the diesel engine in use was mainly caused by the improper use and maintenance of the diesel engine. Because some machine technical level is not high or the idea is not enough attention, in the use of construction machinery can not strictly implement the relevant regulations and operating procedures, and even use some wrong operation and maintenance methods, resulting in premature failure of diesel engines.
1, the new diesel engine or overhauled diesel engine is not run in
After the overhaul of the new car or diesel engine, the cylinder liner, piston, piston ring and bearing shell are replaced, and the load operation is not fully running-in, resulting in early wear of the parts, and some cylinder pulling and tile burning phenomenon. For example, the NT855 diesel engine installed on a TY220 bulldozer, after overhaul, did not run in according to the requirements of the direct load operation, and the phenomenon of burning tile appeared in less than 20h.
2. The diesel engine runs at high speed immediately after cold start
After the cold start of the diesel engine, due to the cold state, the oil viscosity is high, the flow resistance is also large, making the oil into the friction pair time lag, the parts of the diesel engine are not fully lubricated, resulting in poor lubrication of the gear and bearing of the diesel engine and damage, but also aggravate the wear of the cylinder and bearing. In particular, supercharged diesel will cause the shaft ablation of the turbocharger. To this end, the supercharged diesel engine should be idled for a while after starting, until the oil temperature rises, the fluidity improves, and the supercharger is fully lubricated before the speed can be increased, which is more important in the cold winter. For example, a T-330 bulldozer imported from Russia is powered by a B-400 diesel engine (V-8 cylinder with two superchargers, 300kw). When the bulldozer was unloaded from the carrier car, it was the winter season. The machine started the engine and drove to the site at high speed. The next day, it was found that the diesel engine could be idled, but the load could not be turned around. It turned out that the supercharger ablated the rotating shaft due to poor lubrication, and the intake gas in the cylinder was reduced, and the power of the diesel engine was greatly reduced.
3, the diesel engine suddenly stalled
When the supercharged diesel engine suddenly stops running at high speed, the oil pump immediately stops rotating, and the oil in the supercharger stops flowing. If the temperature of the exhaust manifold is very high at this time, its heat will be absorbed into the supercharger housing, the oil that stays there will be baked into carbon deposits, blocking the oil inlet, leading to the lack of oil in the shaft sleeve, accelerating the wear of the shaft and the shaft sleeve, and even the serious consequences of “biting”. Therefore, the supercharged diesel engine must first remove the load before stopping, so that it idles for a few minutes, and then extinguish after the diesel engine temperature drops.
4, the use of inferior diesel
When using unqualified diesel oil, the cetane number does not meet the standard, resulting in poor combustion of diesel engine, carbon accumulation, piston ring sintering caused cylinder pulling. At the same time, the inferior diesel fuel also accelerates the wear of the injection nozzle of the injection pump plunger, the oil outlet valve and the injector.
5, the wrong use of diesel engine oil
(1) Diesel engine misuses gasoline engine oil. Because the compression ratio of the diesel engine is more than 2 times that of the gasoline engine, the main components are affected by high pressure and high temperature more than the gasoline engine, so the materials of some parts of the two are different. For example, the gasoline engine main bearing bush and connecting rod bearing bush can be made of soft babbitt alloy with good corrosion resistance, and the diesel engine bearing bush must be made of high-performance materials such as copper lead alloy or tin aluminum alloy, but the corrosion resistance of these materials is poor, even if there are trace acidic substances in the engine, it will cause serious corrosion, so that the bearing bush appears spots, pits, and even the whole metal off. Therefore, in the refining process of diesel engine oil, it is necessary to add more anti-corrosion agents, so that a protective film can be generated on the surface of the bearing shell to reduce the corrosion of the bearing shell and improve its wear resistance. In addition, the sulfur content of diesel is higher than that of gasoline, this harmful substance in the combustion process will form sulfuric acid or sulfite, along with high temperature and high pressure waste gas into the oil pan, accelerate the oxidation of oil deterioration, so in the diesel engine oil refining process need to add some antioxidants, so that the oil is alkaline. If acidic gas enters, it can play a certain neutralization role, and does not cause the oil to oxidize too quickly.
(2) Oil is only added and not replaced. Many machines only pay attention to the amount of diesel engine oil and add it according to the standard, but do not pay attention to check the quality of the oil, ignoring the replacement of the deteriorated oil. Due to oil deterioration will lose the lubrication function, which leads to the diesel engine running parts always operate in a poor lubrication environment, accelerate its wear, and eventually produce some failures. Therefore, when checking the amount of oil, we must carefully check the quality of the oil, and if the oil deteriorates, we must replace the oil in time.
(3) Add more oil than less. Some machines are afraid of the lack of oil burning tile, think that more oil is better than less, often make the amount of oil filled exceeds the standard. In fact, too much oil will increase the crankshaft rotation resistance of the diesel engine, which not only increases the fuel consumption of the engine, but also reduces the output power of the diesel engine; Make a lot of oil into the combustion chamber to burn, resulting in blue smoke exhaust, oil consumption increased; The combustion chamber carbon accumulation increases, the diesel engine is easy to produce deflagellation phenomenon, increase the cylinder and piston wear. Therefore, diesel engine oil can not be too little, nor too much, the general oil level should be kept slightly lower than the upper limit of the dipstick scale is appropriate.
6. The engine is overloaded for a long time
Some machines one-sided pursuit of temporary economic benefits, so that the diesel engine for a long time overload operation, resulting in early wear of diesel engine parts. The test shows that when the diesel engine speed is unchanged and the load is increased by 2 times, the diesel engine wear is close to 2 times. If the diesel engine is overloaded for a long time, it will also cause the failure of the tile and the shaft.
7, the diesel engine for a long time idle operation
If the diesel engine is idled for a long time, its combustion will deteriorate, and then there will be some failures, such as overheating of the diesel engine, black smoke from the exhaust pipe, power reduction, wear of the machinery to reduce its life, causing cylinder or burning, crankshaft distortion and so on.
When the diesel engine idles for a long time, due to low speed and reduced fuel injection pressure, it will cause poor diesel atomization, incomplete combustion of mixture and carbon deposition. Carbon accumulation is easy to plug the injector hole, causing the diesel engine power decline and black smoke in the exhaust pipe. Too much carbon accumulation sometimes blocks the exhaust pipe muffler, turbocharger and other parts, so that the diesel engine can not work normally.
When the diesel engine is idle for a long time, the oil pressure will certainly be reduced, the oil circulation speed will be reduced, the cleaning capacity will be reduced, the sealing effect will be poor, the heat transfer capacity will be reduced, the amount of lubricating oil accepted by the splash lubrication parts will be reduced, the wear of the accelerated zero surface will be reduced, and the service life will be reduced. Such as: piston, piston ring and cylinder wall wear increases; The wear of the transmission parts of the valve mechanism is increased: the life of the main shaft and the connecting rod bearing shell is reduced.
8, clean the air filter or replace the filter element is not timely
The air filter is an important part of the diesel engine supply system, which can purify the air entering the gas pipe. If the air filter is not maintained in time, it will make the cylinder liner, piston ring, intake and exhaust valve and other parts wear early, reduce the engine power, and even shorten the service life of the diesel engine. The test shows that without air filter, cylinder wear increases by 8 times, piston ring wear increases by 9 times, and other parts wear is also intensified. The air filter maintenance is not timely or the maintenance quality is poor, and the filter effect will be significantly reduced. In order to save fuel, some machines do not install air filters, or when the filter is damaged, the connection hose is not replaced in time after aging or damage, which will lead to a large number of impurities in the air into the cylinder and aggravate the wear of the parts.
9, do not strengthen the precipitation and filtration of diesel, cleaning or replacing the diesel filter element is not timely
Due to the fuel in the storage and use of dust, moisture and other impurities mixed with the necessary substance is the stability of the fuel, while the fuel will oxidize and glue, will aggravate the wear of the cylinder, so that the engine is damaged in the early stage. In fact, the wear of precision coupling parts of diesel fuel supply system is mainly caused by hard abrasive particles contained in diesel. Therefore, strengthening the precipitation and filtration of diesel oil can greatly extend the service life of precision coupling parts. If there is no regular cleaning and replacement of the diesel filter element, there is no regular cleaning of the diesel tank, it will block the fuel supply system, resulting in insufficient oil supply, and it will also cause wear of the injection pump and the precision couple of the injector due to the unclean diesel.
10, in the engine maintenance and assembly careless and missing small parts
When repairing the engine, small parts may be negligently installed, and even some people think that it does not matter whether it is installed or not, which is very dangerous and harmful, the air door lock blade should be installed in pairs, if the leakage or installation will lead to the valve is out of control and damage the piston and other parts; The cotter pin, iron wire (lock piece) or spring pad on the connecting rod bolt and flywheel bolt are anti-loose devices, which may cause serious failure in use once they are missing; The piston pin lock ring is used to prevent the piston pin from moving, if the missing assembly will produce abnormal sound or damage the cylinder liner; The oil nozzle used to lubricate the gear in the engine timing gear chamber will cause serious oil leakage and make the diesel engine oil pressure too low. The loss of water tank cover, oil filler port cover, and oil tank cover will invade the cooling, lubrication, and fuel system due to wind sand and dust, which will aggravate the wear of each machine part.
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Post time: Mar-28-2025