What are the top ten taboos for winter mixer maintenance?

CIMC Concrete Mixer Truck

With the arrival of winter, the chill is getting more and more, the experienced mixer truck owners have begun to carry out the winter maintenance of the vehicle, but before the maintenance, these ten taboos should be kept in mind. Follow the mixer manufacturers together to learn more about the precautions for winter maintenance of the mixer truck!

1. The concrete mixer truck avoids the oil and only does not change.

Engine oil is essential in the use of diesel engines, mainly for lubrication, cooling, and cleaning. Therefore, many drivers will pay attention to check the oil quantity of the lubricating oil and add it according to the standard, but it ignores the inspection of the lubricating oil quality and the replacement of the already modified oil, which causes the moving parts of some engines to always be poorly lubricated. It operates in the environment to accelerate the wear of various parts. Under normal circumstances, the loss of oil is not large, but it is easy to pollute, thus losing the role of protecting the diesel engine. During the operation of the diesel engine, many pollutants (soot, coke and scale formed by incomplete combustion of the fuel) will enter the oil. For new or overhauled machines, there will be more impurities after the test run. If you only need to change it, you will be eager to put it into use. It is easy to cause accidents such as burning tiles and holding shafts. In addition, even if the engine oil is changed, some drivers will not completely clean the oil passage during the replacement due to lack of maintenance experience or trouble, so that mechanical impurities remain in the oil sump and the oil circuit.

2. The concrete mixer truck avoids the use of butter

(1) Apply butter to the cylinder head gasket. Butter is a grease commonly used in the repair of construction machinery to provide lubrication and sealing. Therefore, some repairmen apply a layer of butter to the cylinder mat when installing the cylinder head gasket, which is considered to increase the sealing performance of the diesel engine. As everyone knows, this will affect the performance of the diesel engine. The cylinder head gasket is the most important seal between the cylinder block and the cylinder head. It not only seals the high temperature and high pressure gas generated in the cylinder, but also seals the cooling water and lubricating oil in the cylinder head and cylinder. When installing the cylinder head gasket, pay special attention to its sealing quality. If butter is applied to the cylinder head during installation, when the cylinder head bolts are tightened, a part of the butter will be squeezed into the cylinder water channel and the oil passage. When the butter remaining between the cylinder heads is working in the cylinder, some will flow due to the high temperature. The cylinder is burned, and the other part remains on the joint surface of the cylinder block and the cylinder head, so that a gap is formed between the cylinder head gasket, the cylinder head and the plane of the body, and the high temperature and high pressure gas can easily impact the cylinder gasket from here, destroying the cylinder gasket and causing air leakage. . In addition, when the butter is exposed to high temperature for a long time, it will produce carbon deposits, causing the cylinder mat to deteriorate prematurely. Therefore, do not apply butter when installing the cylinder head gasket. If you can’t achieve the sealing effect, you can add a few more gaskets, so this will not happen and the effect will be better.

(2) Butt nuts are buttered. In order to easily tighten the nut and prevent rust, many repairers apply anti-rust oil to the bolts and nuts of the tire. In fact, this is a wrong approach. Because the tire nut is tightened, the thread has a self-locking feature. This is because the thread helix angle is less than the equivalent friction angle between the threads. In a given bolted joint, the helix angle is a certain value, and the equivalent friction angle varies with the friction state between the threads. Obviously, the equivalent friction angle between the threads after oiling is reduced, and the self-locking performance of the bolt connection is deteriorated. Therefore, never apply grease or drip on the bolts and nuts of the tire. Doing so will loosen the nut and even cause an accident.

3. The mixer car avoids the cylinder liner and the piston new product is installed without matching

When replacing the cylinder liner and the piston, it is considered that the new cylinder liner and the piston are standard parts, which are interchangeable and can be used when installed. In fact, the dimensions of the cylinder liner and the piston have a certain tolerance range. If the largest size cylinder liner is fitted with the smallest size piston, the matching clearance will be too large, resulting in compression weakness and difficulty in starting. Therefore, it is necessary to check the size group code of the standard cylinder liner and the piston when changing the package. The cylinder sleeve and the piston to be installed must make the standard grouping code of the standard piston the same as that of the standard cylinder sleeve. Only in this way can the two be guaranteed. Has a standard fit clearance. In addition, each cylinder is equipped with the same group code cylinder liner and piston. At the same time, it is necessary to pay attention to the pre-installation cylinder gap. In order to ensure the assembly standard, it should be tested before installation to prevent the counterfeit products. .

4. The concrete mixer truck should not check the plunger stroke margin

In the commissioning of the plunger fuel injection pump, many maintenance personnel do not pay attention to check the stroke allowance of the plunger. The stroke margin of the plunger refers to the amount of movement that can continue to move upward after the plunger is pushed from the cam top to the top dead center on the camshaft. After adjusting the start time of the oil supply, the reason for checking the stroke margin is because the stroke allowance of the plunger is related to the wear of the plunger and the sleeve. After the plunger and the sleeve are worn, the plunger has to be moved a little longer to start the oil supply, thereby delaying the fuel supply start time. When the adjustment bolt is unscrewed or replaced with a thicker adjustment pad or gasket, the lowest position of the plunger is moved up, so that the stroke allowance of the plunger is reduced. Therefore, when repairing and debugging the fuel injection pump, first check the stroke margin to determine whether the fuel injection pump is still allowed to adjust.

When inspecting, the following different methods should be used according to the different structure of the fuel injection pump:

a) Rotate the camshaft, after the plunger is pushed to the top dead center, remove the oil outlet valve and seat, and measure with a deep vernier.

b) After the plunger is topped to the top dead center, use a screwdriver to pry the spring seat of the plunger spring to raise the plunger to the highest point. Then use a gauge to insert the measurement between the lower plane of the plunger and the tappet adjustment bolt. The standard stroke allowance of the plunger is about 1.5mm, and the limit stroke allowance after wear should be no less than 0.5mm.

5. Concrete mixing transport car avoid cylinder gap measurement is not allowed

When measuring the cylinder clearance, it is not measured in the direction in which the piston skirt is perpendicular to the piston pin hole, but is measured in other directions. The structural characteristics of the aluminum alloy piston are large and small, a cone, and the partial section is elliptical, so the cylinder clearances in the circumferential direction are not equal. When measuring, it is stipulated that the gap in the direction of the long axis of the ellipse is taken, that is, the gap of the piston skirt perpendicular to the direction of the pin hole of the piston is measured. This measurement is convenient and accurate, and in the reciprocating motion, the direction of the piston skirt perpendicular to the pin hole of the piston is greatly worn by the lateral pressure. Therefore, when measuring the cylinder clearance, the piston skirt should be perpendicular to the piston. The direction of the pin hole is measured.

6. Avoid fire and open fire

Since the piston and the piston pin are in an interference fit, when the piston pin is installed, the piston should be heated and expanded first. At this time, some maintenance personnel will directly heat the piston on an open flame, which is very wrong because The thickness of the piston is uneven, and the degree of thermal expansion and contraction will be different. The heating of the open flame will cause the piston to be unevenly heated and easily cause deformation; the surface of the piston will also adhere to the charcoal to reduce the service life of the piston. If the piston is naturally cooled after reaching a certain temperature, the 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 uniformly heated in the hot oil to slowly expand, and it can not be directly heated by an open flame.

7. Concrete mixer truck should avoid sanding the bearing bush with abrasive cloth

For some inexperienced repairmen, the bearing bush is a difficult job. Because the scraping technology is difficult to master, the bearing bush is not easy to meet the technical requirements. For this reason, when the bearing is replaced, the bearing and the crankshaft are increased. The contact area is sanded with an abrasive cloth instead of the scraper. This method is extremely undesirable in actual maintenance because the abrasive grains on the abrasive cloth are hard and the bearing material is soft, so that the sand is easily embedded in the alloy during grinding, and the wear of the journal is accelerated when the diesel engine is working. The service life of the crankshaft.

8. Bogey bolts are too tight

In the process of disassembly and assembly of construction machinery, bolts in many parts have specified torque requirements, such as transmission box, cylinder head, tire, connecting rod and front axle. The tightening torque is specified in the manual. Feel free to change. However, many users mistakenly believe that it is safer to tighten, but tightening too tight can cause the screw or bolt to break, or it may cause a malfunction due to the thread or nut slip.

9. Avoid the tire pressure is too high

The tire inflation pressure of wheeled construction machinery is an important factor in determining its service life and work efficiency. Excessive or too low tire pressure can affect its service life, and it is also not conducive to safe driving, especially in the hot summer. The scientific inflation standard should be: based on the standard pressure of the tire, the tire pressure is slightly adjusted as the temperature changes. For example, summer should be 5%-7% lower than winter, because considering the high temperature in summer, the gas is heated and the pressure is increased. On the contrary, it must reach the standard pressure or slightly higher in winter.

10. Concrete mixing truck bogey water tank open cold water

If the engine is overloaded, the heat is not good, or the water tank is short of water, the water tank will be opened. If cold water is added immediately, the cylinder head and the cylinder will burst due to thermal expansion and contraction. Therefore, once the tank is found to be in use, emergency measures should be taken to stop the operation and the cooling water of the diesel engine should be cooled by itself.