What are the precautions for using the engine of Komatsu excavator in cold weather?

Cold weather has a great adverse effect on the normal use of construction machinery engines, which will lead to difficulties in starting, increased fuel consumption during low-temperature driving, and poor lubrication will accelerate the wear and tear of engine parts. The following are some precautions for construction machinery users.

1, the problem of replacing antifreeze with hot water

In winter, especially in the northeast and northwest of China, the temperature is often below -20℃, so it is difficult to start the engine. Cold starting devices (such as quantitative ether injection device, flame preheating cold starting and electric heating cold starting) can effectively improve the low-temperature starting performance of the engine. One of the main reasons why it is difficult to start the engine at low temperature is that the viscosity of engine oil is high at low temperature, which increases the starting resistance and makes the engine fail to reach the required speed for starting. For this reason, some users use the method of filling hot water instead of antifreeze. Although the starting effect is good, it leaves hidden dangers and even damages the normal use of the engine. The main reasons are as follows:

(1) Using ordinary water as cooling liquid is easy to cause rust and scaling of cooling system components, and frequent water change is difficult to control.

(2) When the engine using ordinary water stops for more than 2 hours at a time, all the water in the cooling system must be discharged. The drainage part generally includes radiator, engine block and oil cooler. If there is water leakage, there is a danger of freezing and cracking the cooling system parts.

(3) When the temperature is lower than -20℃, the engine cooling system will be kept in the working state of small circulation (water only circulates in the engine block and does not exchange heat with the radiator) for a long time due to the action of the water temperature regulator, and the hot water in the radiator will gradually cool down or even freeze, so it is easier to freeze when it runs under light and light load continuously. Generally speaking, the icing phenomenon begins with the pipeline connecting the radiator oil pan and the engine water pump. Because this pipeline is at the lowest water level, it is least affected by the heat dissipation of the engine block. When the engine is switched to continuous heavy-load operation and the water temperature in the engine body rises to the opening point of the water temperature regulator, the cold water in the radiator cannot be replenished into the engine due to the freezing of the pipeline, and the water temperature in the engine body will rise rapidly until it boils. If the construction is not found in time at night, the cylinder may be strained, which may seriously lead to cracking of the cylinder head.

The author once experienced an example of using hot water to improve the serious damage of the engine caused by cold start. 199965438+During the construction of Gong Xuan SD7 bulldozer in a construction site in Inner Mongolia in February, due to the low temperature at night, the radiator downcomer froze, which led to the engine boiling and dry burning, but the driver's fatigue driving was not found in time, which eventually led to serious engine cylinder strain, burnt cylinder head seal and cracked exhaust pipe, resulting in heavy losses.

2. Influence of short-term frequent starting of the engine.

In cold weather, if the engine is started and stopped for many times, and the time of each start is not long enough to make the engine reach the normal working temperature, problems will occur. When the engine works at low temperature, the fuel and engine oil in the combustion chamber cannot be completely burned, and the unburned fuel will form carbon deposits on the valve stem, injector and other parts. Usually, when the engine is running at normal temperature, these carbon deposits will be gradually burned away, which will not cause problems. However, when the engine starts and stops at low temperature, its temperature never reaches normal temperature, and the carbon deposit on the valve stem will increase the sliding resistance of the valve, which will lead to the burning of the valve and the bending deformation of the valve tappet in serious cases.

For the engine with split nozzle, it is easier to form carbon deposit at the nozzle because the nozzle diameter is too small (generally 0.25-0.8mm). Carbon deposition in fuel nozzle will lead to poor fuel atomization, worse combustion and more difficult cold start.

Therefore, it is recommended to keep the engine running every time you start it until the temperature indicated by the water thermometer is not lower than 66℃.

In addition, if the engine continues to run until it is completely warmed up, other parts of the engine, such as bearings, pistons and piston rings, can also be in good working condition, thus prolonging the service life of the engine.

3. Causes and solutions of low engine working temperature.

When the engine water temperature is always below 7 1℃, there are generally two possibilities: one is that the thermometer shows abnormality, and the other is that the radiator coolant passes through the water temperature regulator when it is below 7 1℃. At this point, the following checks should be made:

(1) First, check whether the water thermometer and temperature sensor are working normally. The actual temperature can be measured by a thermometer or by the elimination method of replacing new parts.

(2) If the water thermometer and temperature sensor work normally, check whether the water temperature regulator is normal. You can remove the water temperature regulator, put it in a transparent container filled with water, heat the water, and measure the temperature change with a thermometer at the same time, and observe whether the water temperature regulator is turned on in advance when it fails to reach the specified starting temperature (generally around 78℃, the starting temperature of different engines is different). If the regulator is not working properly, it should be replaced in time.

If the water thermometer, temperature sensor and water temperature regulator are all working normally, a check valve should be installed on the breather pipe between the radiator and the cylinder head. The snorkel is used to remove air from the engine cooling system. A small amount of coolant can enter the cylinder head water channel through this pipe, which will affect the normal working temperature of the engine at very low temperature.