Main failure causes and preventive measures of diesel engine cylinder score

Main failure causes and preventive measures of diesel engine cylinder score

Cylinder score refers to the obvious longitudinal mechanical scratches and scratches in the inner wall of the cylinder in the range of motion of the piston ring. In severe cases, the dissolving wear occurs, which causes the engine to start difficult or self-extinguish. The root cause of the cylinder score is that it is difficult to form an oil film between the inner wall of the cylinder and the piston ring and the piston, thereby causing poor lubrication and even dry friction.

Causes the failure of the cylinder score

Problem from piston group

1. The piston ring clearance is too small. If the opening gap, the side clearance or the back clearance of the piston ring is too small, the piston ring is stuck by thermal expansion when the engine is working, and the cylinder wall is pressed tightly, or the piston ring is broken, and the groove is easily pulled out on the cylinder wall.

2. The piston pin is pulled out. Since the piston pin retaining spring is installed or detached, broken, and the piston pin is pulled out during the movement, it is easy to pull the inner wall of the cylinder, causing the cylinder to suffocate to the crankcase. 

3. The clearance of the piston cylinder is too small or too large. If the material of the piston is poor, the manufacturing dimensional error is too large, or the piston is deformed after the piston pin is assembled, the clearance between the piston and the cylinder is too small, and the piston is stuck after being thermally expanded, thereby pulling the cylinder wall. 

4. The piston ring is heavily carbonized. Excessive carbon deposits cause the piston ring to bond or bite into the ring groove, while carbon deposits are a hard abrasive that grinds into longitudinal grooves on the cylinder bore.

5. The piston is heavily biased. Due to the bending and torsion deformation of the connecting rod, the parallelism and coaxiality deviation of the connecting rod journal and the main journal piston pin seat are too large, causing the piston to be obviously biased to the cylinder, which will accelerate the wear of the piston ring, the piston and the cylinder, and damage the formation of the oil film.

Problem from cylinder liner

1. The circular tube and cylindricity tolerance of the cylinder liner exceeds the allowable range, so that the sealing performance between the piston and the cylinder liner is greatly reduced, the high temperature in the cylinder is smashed, and the oil film between the piston and the cylinder wall is broken, thereby causing prolapse.

2. The cylinder liner is deformed in China during the assembly process. For example, if the port surface of the cylinder liner is excessively overexposed, the cylinder liner will be deformed after the cylinder head is installed; the cylinder block water blocking ring is too thick, and the cylinder liner is deformed after being pressed into the body, which is easy to cause the cylinder to be pulled.

Problem from daily use

1. The air filter is not sealed, which makes the filtering effect worse. The dust, sand and other impurities in the air are sucked into the cylinder to form abrasive wear. The test shows that if a few grams of dust is sucked in every day, the wear of the cylinder liner will increase. More than 10 times.

2, poor running-in. After the new machine or the overhauled engine, there are many microscopic irregularities on the surface of the cylinder liner, the piston and the piston ring, and the lubricating oil film is difficult to form. If it is put into a heavy load operation immediately without running-in, it is likely to cause an accident such as a cylinder score. 

3, often low temperature start. When the engine is started at a low temperature, the viscosity of the lubricating oil is large. Poor fluidity makes it difficult to form an effective oil film on the inner wall of the cylinder. According to the research department's test, when the diesel engine is under load at a cooling water temperature of 30°C or less, the wear of the cylinder liner and other parts is 5 to 7 times that of the normal water temperature.

3. The engine is overheated. When the cooling system is not well maintained or is overloaded, the excessively high machine temperature not only reduces the mechanical strength of the part, but also prevents the formation of the lubricating oil film on the inner wall of the cylinder. After the piston and other parts are thermally expanded, they are easily stuck in the cylinder liner. The result is that the piston partially melts and the inner wall of the cylinder liner is pulled, forcing the engine to stall.

Precaution

1. For the new machine and the overhauled engine, it must first be run-in, that is, under the condition of maintaining good lubrication, according to the principle of low to high speed and load from small to large, carefully operate according to the running-in procedure, and then enter the formal The load is running.

2. According to the provisions of the instruction manual, correctly select the gap between the piston neck and the cylinder liner, the opening clearance and the edge clearance of the piston ring. In addition, in the repair, it is necessary to hold the piston off the cylinder and ensure the cylinder size accuracy.

3. Maintain the normal temperature of the cooling water from 70°C to 95°C to avoid overheating of the engine. Preheating measures should be taken before starting in winter.

4, use the engine in a reasonable operation, do not overload the operation, do not chaos the throttle, do not start with water shortage.

5. Strengthen the maintenance of the air filter to prevent dust from entering the cylinder. 

6. Maintain the lubrication system to prevent mechanical impurities and carbon deposits from mixing into the oil and aggravate the wear of the cylinder liner.

7. Check the oil level of the engine oil at the right time and add it when there is no oil. The cylinder head gasket is damaged, and the cylinder head gasket is generally damaged by air leakage and water leakage. This fault is also a malignant fault of the engine, and should be dealt with promptly when it occurs, so as to avoid causing greater damage to the engine.

Generators are prone to failures in long-term work. In addition, daily maintenance and repair measures must be taken. It is also one of the keys to prolonging the service life of generators.

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