Core Tip: Maintenance is an effective means to restore the technical performance of engineering machinery, eliminate faults and eliminate hidden troubles, and prolong the service life of the machine. At present, the domestic automobile maintenance industry has a considerable scale, and the construction machinery maintenance industry started relatively late, and there are still many technical problems in the maintenance.
Failure to pay attention to the model of the accessory, the substitution or misuse of the accessory is more common
When repairing construction machinery, the substitution or misuse of accessories is still common. Some accessories are feasible for emergency use, but long-term use is harmful and affects the safety and technical performance of the machine. Some maintenance personnel have little understanding of the mechanical structure and principle, and many spare parts models do not match, but they believe that as long as they can be installed, it is not considered whether the mechanical performance of the machine can be exerted. For example, the 4120F diesel engine should use a 350 watt generator, but use a 500 watt generator, which wastes power. The ZL50 loader uses the QD274 starter, but uses the QD50 starter. Due to insufficient power, the diesel engine is difficult to start; Unlike non-supercharged diesel engines, pistons, valves, rocker arms, etc. are not common, but mixed phenomena often occur, making diesel engines difficult to start, reducing power, and even causing serious damage to the machine. A 6135ZD turbocharged diesel engine, due to the misuse of the non-supercharged diesel engine piston, the diesel engine does not catch fire after assembly. After replacing the original piston (supercharged type), the diesel engine starts smoothly; different types of diesel engine high pressure fuel pipe, fuel injection The nozzle coupler and the plunger coupler are substituted, which causes the fuel injection quantity and the fuel supply advance angle to change; replace the qualified product with the defective product, replace the split pin with iron wire and iron nail, replace the cylindrical pin with steel bar and old bolt, etc., quality There is no guarantee that long-term use will never be allowed. Therefore, when repairing construction machinery, the original type of accessories should be used as much as possible, and other types of accessories should not be used instead, and it should not be misused.
Do not pay attention to the selection of bolts, the phenomenon of chaotic use of bolts is more prominent
When repairing construction machinery, the phenomenon of indiscriminate use of bolts is still prominent, because the performance and quality of bolts do not meet the technical requirements, resulting in frequent mechanical failures after maintenance. Special bolts used in construction machinery, such as drive shaft bolts, cylinder head bolts, connecting rod bolts, flywheel bolts, fuel injector fixing bolts, etc., are specially processed by special materials, which have high strength and strong shear resistance. Ensure that the connection is secure and reliable. In the actual maintenance work, some maintenance personnel found that when these bolts were damaged or missing, they could not find the standard bolts at the moment, and some of them were free to take other bolts instead, and some of them were replaced by their own. These bolts were poor due to poor materials or processing techniques. The late use of construction machinery leaves hidden troubles. The 6 bolts of the rear axle wheel reducer connected to the planetary carrier and the wheel reducer housing of the Type 74 type II excavator are subjected to large torque, and the six bolts are broken. Damage, some maintenance personnel use other bolts or self-processing substitutes, often broken due to insufficient bolt strength; some parts need to use "small pitch" "small buckle self-tightening" bolts, copper bolts, copper-plated bolts, but The use of ordinary bolts instead, resulting in loose bolts, difficult to disassemble, etc., such as diesel engine exhaust manifold fixing nuts are mostly made of copper, to prevent heat or long use time is not easy to disassemble, but in actual maintenance, most of them are used Ordinary nuts, it is very difficult to disassemble for a long time; some bolts will have defects such as stretching and deformation after use, and some technical requirements Therefore, when repairing the construction machinery, when the bolt is damaged or lost, it is necessary to replace the bolts that meet the requirements in time, and avoid using the bolts.
The bolt tightening method is more serious
There are many tightening torque requirements for fixing or connecting bolts in various parts of construction machinery, such as injector fixing bolts, cylinder head bolts, connecting rod bolts, flywheel bolts, etc. Some of them specify tightening torque, some specify tightening angle, and also specify tightening order.
Some maintenance personnel think that anyone who tightens the bolts will do it, it does not matter, do not tighten according to the specified torque and order (some do not understand the tightening torque and sequence requirements), do not use the torque (kg) wrench, or use the afterburner at will, Tightening by feeling, the tightening torque varies greatly. If the torque is insufficient, the bolt is prone to loosening, which will cause the cylinder liner to be damaged, the bearing bush to loosen, oil leakage, and air leakage. If the torque is too large, the bolt is easy to be stretched and deformed, or even broken, and sometimes the threaded hole is damaged, which affects the repair quality. One ZL50 loader, the torque converter slammed the hydraulic oil, and it was checked that the 24 bolts connecting the pump wheel and the cover wheel were not tightened in the specified order and torque. Therefore, when repairing construction machinery, be sure to tighten the bolts according to the specified torque and order to prevent mechanical failure due to excessive tightening torque, too small or improper sequence.
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Label: Common technical problems in engineering machinery maintenance (below)
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