Today, the construction machinery house Xiaobian to explain the 10 major taboos of construction machinery maintenance.

1. oil only add no change

Oil is essential in the use of diesel engines, mainly from lubrication, cooling, cleaning and other functions.

Therefore, many drivers will pay attention to check the oil amount of oil, and by standard addition, but ignored the lubricating oil quality inspection and had deteriorated oil change, leading to some engine moving parts are always in poor lubricating environment operation, thereby accelerating the parts abrasion.

Under normal conditions, the oil loss is not large, but it is easy to pollute, thereby losing the role of protecting the diesel engine. In the diesel engine operation process, many contaminants (incomplete combustion of fuel, soot and carbon deposition and fouling) will be entered into the oil.

For the new or overhauled machinery, after the trial operation, the impurities will be more, if only do not change, they are eager to put into use, it is easy to cause burning tile, axle and other accidents.

In addition, even if the replacement of oil, some drivers due to lack of maintenance experience or easy to save, but also in the replacement will not completely clean the oil duct, so that the mechanical impurities remain in the oil pan and oil circuit.

2. butter with chaos.

Grease the cylinder gasket. Butter is commonly used in construction machinery repair grease, which can play the role of lubrication and sealing.

As a result, some of the repairman will apply a layer of butter on the cylinder pad when installing the cylinder gasket, which is believed to increase the sealing performance of the diesel engine. However, this has affected the performance of the diesel engine.

Cylinder pad is a diesel engine cylinder block and cylinder head are among the most important of the seal, it can not only seal of high temperature and high pressure gas generated inside the cylinder, but also seal the cylinder cover and the cylinder cooling water and lubricating oil, so in the disassembly of cylinder pad, should pay particular attention to the quality of the seal.

If the installation on the cylinder pad butter, when the cylinder head bolt, a part of the butter will be squeezed into the cylinder and the oil path channel, in between the cylinder pad butter in cylinder working, as affected by high temperature, some people will flow in cylinder combustion, the other part is left in the cylinder and the combination of the cylinder head surface, so that a gap is generated between the cylinder head and cylinder pad, body plane, high temperature and high pressure gas easily from the impact of cylinder liner, cylinder gasket destroyed, resulting in leakage.

In addition, the butter will produce carbon deposition in high temperature for a long time, resulting in premature aging of cylinder gasket. So never grease when installing the cylinder gasket.

3. new cylinder and piston are installed without matching

When changing the cylinder sleeve and piston, it is considered that the new cylinder sleeve and piston are standard parts, and all of them are interchangeable, so they can be used when installed.

In fact, the dimensions of the cylinder sleeve and the piston have a tolerance range.

If the largest size of the cylinder sleeve with the smallest size of the piston, will make the gap is too large, resulting in compression weakness, start difficult.

Therefore, we must change size grouping code check standard of cylinder liner and piston, fitted with the cylinder liner and piston size grouping code must be standard piston size grouping code and standard cylinder, the only way to ensure that the clearance between the two is the standard.

In addition, the cylinder liner and piston cylinder is installed with the same grouping code at the same time, we must pay attention to dress before the test cylinder plug gap, in order to ensure the assembly standard, in front of the machine should also conduct a test, to prevent fake defective products.

4. cylinder clearance measurement is not allowed

When measuring the clearance of the cylinder, it can not be measured in the direction of the piston skirt perpendicular to the pin hole of the piston, while measuring in other directions.

The structure of aluminum alloy piston is small, big and big, which is a cone, and the skirt section is oval, so the cylinder gap along the circumference is not equal.

When measuring, the clearance of the ellipse long axis should be determined, that is to measure the clearance of piston skirt perpendicular to the direction of piston pin hole.

This measurement is more convenient and accurate, and in the reciprocating movement of the piston skirt, perpendicular to the direction of the piston pin hole by lateral pressure and greater wear and tear, so that the measuring cylinder clearance, should be measured at the piston skirt is perpendicular to the direction of the piston pin hole.

5. piston open flame heating

Because the piston and piston pin are interference fit, so when the piston pin is installed, the piston should be heated and inflated. At this time, some maintenance personnel will put the piston directly on the open flame heating.

This approach is very wrong, because different parts of a piston uneven thickness, thermal expansion and contraction rate will be different, open flame heating can make the piston uneven heating, easy to cause deformation; piston surface also attached ash, reduce the service life of the piston.

If the piston reaches a certain temperature and cools naturally, its metallographic structure will be damaged and wear resistance will be greatly reduced, and its service life will be shortened obviously.

When the piston pin is installed, the piston can be heated evenly in the hot oil to make it expand slowly, and the flame can not be heated directly by the open flame.

6. use emery cloth polishing pad

For some inexperienced repairman, scraping tile is a difficult job, because tile scraping technology is difficult to grasp, so the Bush is not easy to meet the technical requirements.

Therefore, some people in the replacement bearing, to enlarge the contact area of the bearing and shaft, use emery cloth grinding instead of scraping.

This method is not desirable in actual maintenance, because the abrasive emery cloth hard, and bearing alloy is soft, so the grinding sand is easy to be embedded in the alloy, the diesel engine will accelerate the shaft neck wear, shorten the service life of the crankshaft.

7. the bolts are screwed too tight

Engineering machinery in the process of disassembly, many parts of the bolts are specified torque requirements, such as transmission box, cylinder head, wheel hub, connecting rod and the front axle and other parts, tightening torque have special provisions in the instructions, must not arbitrarily change.

However, many users mistakenly think it is safer to tighten up, but too tight will cause screws or bolts to break, or it may be caused by thread slip.

8. tire pressure is too high

Tire inflation pressure of Wheeled Construction machinery is an important factor to determine its service life and work efficiency.

Tire pressure is too high or too low will affect its service life, but also is not conducive to safe driving, especially in the hot summer.

The standard of inflation should be based on the standard air pressure of the tire, and the tire pressure can be adjusted slightly with the change of the temperature.

For example, summer should be 5%-7% lower than winter, due to the high temperature in summer, the heating of the gas, the increase of the pressure, on the contrary, the winter must reach the standard air pressure or slightly lower.

9. do not check the piston stroke margin

The plunger type fuel pump 's trial, many maintenance personnel do not pay attention to check the piston travel allowance.

The so-called piston stroke margin, refers to the plunger by the camshaft on the top of the cam stop point, but also continue to move upward.

After adjusting the starting time of oil supply, it is necessary to check the stroke margin, because the piston stroke margin and plunger, sleeve wear related.

After the plunger and sleeve wear, the plunger should move upwards for a period of time to start the oil supply, so that the starting time of the oil supply is delayed. When the adjusting bolt is screwed out or replaced with a thicker cushion block and shim, the minimum position of the plunger is moved upwards, so that the stroke margin of the plunger is reduced.

Therefore, in the maintenance of fuel injection pump, should first check the margin of travel, to determine whether the fuel pump is allowed to adjust.

Inspection should be based on the different structure of the fuel injection pump using the following different methods:

A) turn the camshaft, then press the plunger to the stop point, remove the oil outlet valve and valve seat, and measure with the depth vernier ruler.

B) after the plunger is pushed to the top stop point, the spring seat of the plunger spring is pried with a screwdriver, so that the plunger rises to the highest point.

Then use the measuring feeler inserted between plane and tappet adjustment bolt plunger. The standard stroke margin of the plunger is about 1.5mm, and the limit stroke allowance after wear should be no less than 0.5mm.

10. water tank boiling sudden cold

Engine overload operation, bad heat or water tank of water will cause water tank boiling, if immediately add cold water, will lead to the cylinder head and the cylinder block cracking.

Therefore, the use of once found water tank boiling, should take emergency measures to stop the operation, the diesel engine cooling water to cool.