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Special vehicle maintenance and repair notes

浏览:83 作者: 来源: 时间:2019-03-19 分类:Technical support

Special purpose vehicles and your car, also need maintenance and repair. The maintenance and repair of special purpose vehicle is to troubleshoot the malfunctioning vehicle through technical means, find out the cause of the failure, and take certain measures to make it troubleshoot and restore to a certain performance and safety standards.

Daily maintenance:

1, maintenance is usually in the vehicle before the failure of the operation.

2, maintenance to prevent, usually take the plan to implement the operation.

3, maintenance is usually to reduce parts wear speed, prevent failure, extend the service life of special vehicles.

Special vehicle maintenance and special vehicle maintenance are closely related. Repair in maintenance, maintenance in repair. In the process of vehicle maintenance may find a certain part or parts will be a failure or damage of the precursor, and can use the maintenance opportunity, to repair it. And in the process of repair, for some not damaged parts also want to carry out maintenance, this is a very natural thing.

Maintenance is an effective means to restore the performance of special vehicles and extend their service life. However, in the actual operation process, some users and maintenance personnel have many wrong practices, affecting the normal use of special vehicles.


1. Do not change the oil

Engine oil is essential in the use of diesel engines, mainly plays the role of lubrication, cooling, cleaning and so on. Therefore, many drivers will pay attention to check the oil quantity of lubricating oil and add it according to the standard, but neglect the inspection of the quality of lubricating oil and the replacement of the spoiled oil, resulting in some engine moving parts always run in a poor lubrication environment, thus accelerating the wear of each part. Under normal circumstances, the oil loss is not large, but it is easy to pollution, thus losing the protection of diesel engine. During the operation of diesel engine, a lot of dirt (soot, carbon and scale from incomplete combustion of fuel) will enter into the oil. For the new or overhaul of the machinery, after the test run impurities will be more, if only add do not change the rush to put into use, it is easy to cause burning tile, embrace shaft and other accidents. In addition, even if the oil is replaced, some drivers will not thoroughly clean the oil channel due to lack of maintenance experience or trouble saving, so that mechanical impurities still remain in the oil sump and oil path.


2, avoid the use of butter daub

(1) grease the cylinder gasket. Butter is commonly used in engineering machinery repair grease, can play a role in lubrication and sealing. As a result, when installing the cylinder gaskets, some mechanics apply a layer of butter to the gaskets, believing that this will increase the airtightness of the diesel engine. However, it affects the performance of diesel engine. Cylinder gasket is the most important seal between cylinder block and cylinder head of diesel engine. It can not only seal the high temperature and high pressure gas produced in cylinder, but also seal the cooling water and lubricating oil in cylinder head and cylinder block. If installed in the cylinder MATS and butter, when the cylinder head bolt is tightened, part of the butter will be squeezed into the cylinder in the channel and the oil duct, stay in the cylinder gasket between the butter in cylinder work, due to the effect of high temperature, part will shed cylinder combustion, others remain in the combination of the cylinder block and cylinder head, cylinder pad, cylinder head and the body plane between aperture, high temperature and high pressure gas from impact cylinder pad, easily damaged cylinder pad, cause air leakage. In addition, the butter for a long time in the state of high temperature will also produce carbon, causing premature aging deterioration of the cylinder pad. Do not apply butter when installing cylinder gaskets.


(2) grease the tire nuts. In order to tighten the nut easily and prevent corrosion, many repairmen grease the bolt and nut of the tire. This is actually a mistake. After tightening the tire nut, the thread has the feature of self-locking. This is because the screw Angle of the thread is smaller than the equivalent friction Angle between the threads. In a given bolted connection, the helix Angle is a certain value, while the equivalent friction Angle varies with the friction state between threads. Obviously, the equivalent friction Angle between threads decreases after oiling, and the self-locking performance of bolt joint becomes worse. Therefore, never grease or dribble grease on the bolts and nuts of the tires. Do so, can make nut loose instead, cause an accident even.


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3. Bogey cylinder liner and piston new products shall be installed without selection

When replacing the cylinder liner and piston, it is considered that the new cylinder liner and piston are standard parts with interchangeability. In fact, the size of the cylinder liner and the piston have a certain tolerance range. If the largest size of the cylinder sleeve with the smallest size of the piston, will make the fit clearance is too large, resulting in compression weakness, difficult to start. Therefore, it is necessary to check the size grouping code of the standard cylinder liner and piston when changing the assembly. The cylinder liner and piston used in the assembly must make the size grouping code of the standard piston and the size grouping code of the standard cylinder liner the same. Only in this way can a standard fit clearance be guaranteed between them. In addition, each cylinder with the same grouping code cylinder liner and piston at the same time, but also pay attention to the inspection of the cylinder plug gap before installation, in order to ensure that the assembly standard, before installation should also be a test, in order to prevent the installation of counterfeit defective products.


4. Do not check the plunger travel margin

In the ironic test of plunger type fuel injection pump, many maintenance personnel do not pay attention to check the plunger travel margin. The so-called plunger travel margin, refers to the plunger on the camshaft CAM top to the dead center, can continue to move upward. After adjusting the starting time of oil supply, the reason for checking the travel allowance is that the travel allowance of plunger is related to the wear of plunger and sleeve. After the wear of the plunger and sleeve, the plunger must move up for a period of time before the oil supply starts, thus delaying the start time of oil supply. After unscrewing out the adjusting bolt or replacing the thicker adjusting pad and gasket, the lowest position of the plunger moves up to reduce the travel margin of the plunger. Therefore, in the maintenance and debugging of the injection pump, should first check the travel margin, to determine whether the injection pump is still allowed to adjust. During inspection, the following methods should be adopted according to the different structures of the injection pump: a) rotate the camshaft, lift the plunger from top to dead center, remove the oil valve and seat, and measure with the depth vernier. B) after the plunger is pushed up to the top dead center, use a screwdriver to pry the spring seat of the plunger spring to make the plunger rise to the highest point. Then insert the thickness gauge between the lower plane of the plunger and the tappet adjusting bolt. The standard travel allowance of the plunger is about 1.5mm, and the ultimate travel allowance after wear should be no less than 0.5mm.


5. Cylinder clearance measurement shall not be allowed

When measuring cylinder clearance, the piston skirt cannot be measured in the direction perpendicular to the piston pin hole, but in other directions. Aluminum alloy piston structure is characterized by small on the large, for a cone, and the local section is oval, so along the circumference of the cylinder clearance is not equal. When measuring, it is stipulated that the clearance in the direction of the long axis of the ellipse shall prevail, that is, the clearance of the piston skirt perpendicular to the direction of the piston pin hole shall be measured. This measurement is more convenient and accurate, and in the reciprocating movement, the piston skirt perpendicular to the direction of the piston pin hole because of the lateral pressure and wear, so, when measuring the cylinder clearance, the piston skirt should be perpendicular to the direction of the piston pin hole measurement.


6. Avoid heating the piston with open fire

Because the piston and piston pin is interference fit, so when installing a piston pin, should first make the piston thermal expansion, at this time, some of the maintenance personnel will put the piston on the flame heating directly, so it is very wrong, because each part of the piston, uneven heat bilges cold shrink degree would be different, firing can make the piston balance, easy to cause deformation; The piston surface will be attached to the carbon ash, reducing the service life of the piston. If the piston is cooled naturally after reaching a certain temperature, its metallographic structure will be damaged and the wear resistance will be greatly reduced, and its service life will be significantly shortened. When installing the piston pin, the piston can be evenly heated in hot oil to make it expand slowly.


7. Avoid grinding the bearing bush with emery cloth

For some inexperienced repairmen, bearing bush is a difficult job, because scraping technology is difficult to master, so the bearing bush is not easy to meet the technical requirements, for this reason, someone in the replacement of bearing bush, in order to increase the contact area between the bearing bush and the crankshaft, with sand cloth grinding instead of scraping. This method is extremely undesirable in practical maintenance, because the abrasive particles on the emery cloth are hard, while the alloy of the bearing bush is soft. In this way, the sand particles can be easily embedded into the alloy during grinding. The diesel engine will accelerate the wear of the shaft neck and shorten the service life of the crankshaft.

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8. Do not screw the bolt too tightly

In the process of disassembly and assembly of construction machinery, many parts of the bolt are specified torque requirements, such as the transmission box, cylinder cover, tire, connecting rod and front bridge, etc., tightening torque in the manual have special provisions, must not be changed at will. However, many users mistakenly believe that it is safer to tighten the screw too tightly, which may cause the screw or bolt to break off, and may also cause failure due to thread slip.


9, avoid tire pressure is too high

The tire inflation pressure of wheeled construction machinery is an important factor to determine its service life and work efficiency. Too high or too low tire pressure will affect its service life, but also not conducive to safe driving, especially in the hot summer. The scientific inflation standard should be: the standard air pressure of the tire as a benchmark, with the change of temperature, slightly adjust the air pressure of the tire. For example: the summer should be 5%-7% lower than the winter, due to the high temperature in summer, gas heating, pressure increase, on the contrary, the winter must meet the standard pressure or slightly lower.


10, bogey tank pot suddenly add cold water

Engine overload, poor heat dissipation or lack of water in the tank will cause the water tank to boil, if you immediately add cold water, it will lead to cylinder head and cylinder burst. Therefore, once the water tank is found to be boiling in use, emergency measures should be taken to stop the operation, so that the diesel cooling water will cool down by itself.



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