Haixing Power explains the reasons and preventive measures for engine cylinder pulling

Engine cylinder pulling refers to obvious longitudinal mechanical scratches and scratches in the inner wall of the cylinder within the range of motion of the piston ring. In severe cases, melting wear occurs, causing the engine to start up or the engine to shut down on its own. Pulling the cylinder is a major accident in the engine.

According to the experience summary of Haixing Power technicians, the fundamental reason for the cylinder pulling of the generator set is that it is difficult to form an oil film between the inner wall of the cylinder and the piston ring and the piston, which causes poor lubrication and even dry friction. There are many specific reasons for this situation. There are roughly three aspects:

the reasons for the piston group

1. The piston ring gap is too small. If the opening gap, edge gap or back gap of the piston ring is too small, the piston ring is heat expansion and stuck when the engine is working, pressing tightly with the cylinder wall, or the piston ring is broken, it is easy to pull out the groove on the cylinder wall.

2. The piston pin burst out. Since the piston pin spring is not installed or falls off or breaks, the piston pin jumps out during movement, which can easily strain the inner wall of the cylinder, causing the cylinder to rush into the crankcase.

3. The cylinder clearance of the piston is too small or too large. If the piston is poor in material, the manufacturing size error is too large, or the piston deforms after assembling the piston pin, the fitting gap between the piston and the cylinder is too small, and the piston is stuck after expanding due to heat, which will intensify, and then strain the cylinder wall.

4. The piston ring has severe carbon accumulation. Excessive carbon deposit causes the piston ring to bond or bite into the ring groove. At the same time, carbon deposit is a hard abrasive that will be ground into longitudinal grooves on the cylinder wall.

5. The piston is severely tilted. Due to the bending and twisting deformation of the connecting rod, the parallelism and coaxiality of the connecting rod journal, main journal, and piston pin seat are too large, causing the piston to deviate significantly, which will accelerate the wear of the piston ring, piston and cylinder wall, and destroy the formation of the oil film.

Cylinder liner reasons

1. The roundness and cylindrical tolerance of the cylinder liner exceed the allowable range, which greatly reduces the sealing of the piston and the cylinder liner. The high-temperature gas in the cylinder flows down, destroying the oil film between the piston and the cylinder wall, and thus causing the cylinder to be pulled.

2. The cylinder liner is deformed during assembly. For example, if the upper end surface of the cylinder liner is too large, the cylinder liner will be pressed and deformed after installing the cylinder head; the cylinder liner water blocking ring is too thick, and the cylinder liner deformation will be caused after being pressed into the body, which can easily cause cylinder pulling.

Reasons for use

1. The air filter is not sealed, which makes the filtration effect worse, and impurities such as dust, sand and other impurities in the air are sucked into the cylinder, causing abrasive wear. Tests show that if a few grams of dust is sucked in every day, the wear of the cylinder liner will increase by more than 10 times.

2. Poor running-in. For new or overhauled engines, there are many microconcave and uneven surfaces on the cylinder liner, piston and piston ring, and it is difficult to form a lubricating oil film. If the operation is immediately put into high load without running-in, it is easy to cause accidents such as cylinder pulling.

3. Start at low temperatures frequently. When the engine starts at low temperature, the lubricant oil has a high viscosity and poor fluidity, making it difficult to form an oil film on the inner wall of the cylinder. According to the research department's test, when the diesel engine is operated at a load below 30℃, the wear amount of cylinder liners and other parts is 5 to 7 times that of normal water temperature.

4. The engine is overheated. When the cooling system is poorly maintained or overloaded, excessive machine temperature not only reduces the mechanical strength of the parts, but also prevents the lubricating oil film from the inner wall of the cylinder. After the piston and other parts are expanded by heat, they are prone to get stuck in the cylinder liner. The consequence is often that the piston partially melts, the inner wall of the cylinder liner is pulled and the engine is shut down.

In actual use, pulling the cylinder is often the result of several factors being jointly affected. For example, if the unrun-in engine cooler is started and it is easy to run at full load immediately after starting, a cylinder pull accident is easily caused.

The main measures to prevent cylinder pulling are:

1. For new engines and engines after overhaul, they must be run-in first, that is, under the conditions of maintaining good lubrication, they must operate carefully according to the running-in procedures according to the principle of speed from low to high and load from small to large, and then they can be put into formal load operation.

2. According to the instructions in the use instruction manual, correctly select the gap between the piston skirt and the cylinder liner, the opening gap of the piston ring and the edge gap. In addition, in repair, the piston cylinder is also required to control the dimensional accuracy of the cylinder liner.

3. Keep the normal temperature of the cooling water at 70℃~95℃ to avoid overheating of the engine. Preheating measures should be taken before the start of winter.

4. Use the engine reasonably, do not overload, do not slam the accelerator randomly, and do not start with water.

5. Strengthen the maintenance of air filters and strictly prevent dust from being sucked into the cylinder.

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

The engine is the core part of the diesel generator set, and regular maintenance must be done. At the same time, Haixing Power hopes that the majority of diesel generator set users will actively carry out standardized operation training. The correct operation is to directly protect the diesel generator set.