Common Tractor Cylinder Failures

The cylinder is one of the core components of the tractor engine, its wear degree determines whether the engine is to be overhauled. Cylinder common failures are the inner working surface of the wear, cylinder and cooling water contact with the outer surface of the cavity corrosion, and cylinder liner shoulder fracture and other failures. Therefore, we need to know the causes of tractor cylinder failure, and do a good job of prevention.

Causes of Working Surface Wear in the Cylinder

1. Cylinder liner material quality problem. Mainly is the hardness of the inner surface of the cylinder liner, material metallographic organization and chemical composition. And the material matching between cylinder liner and piston ring is also very important.
2. Lubrication problem. When the engine works, the piston does up and down reciprocating movement, when the piston movement to the upper stop and change direction, the piston movement speed drops to zero, due to the sudden change of speed, it is difficult to form an oil film, thus accelerating the wear between the piston and the cylinder wall. In addition, affected by the high temperature gas flushing during combustion, the lubrication condition of the upper part of the cylinder wall deteriorates and is in a semi-dry friction state, which increases the wear. Therefore, the quality of the lubricant is very high, if the lubricant deteriorates, it will intensify the wear of the cylinder.
3. Acidic generation of cylinder wall corrosion problems. Some information, when the temperature of the cylinder wall is lower than 80 ℃, water vapor is easy to condense from the combustion products, such as sulfuric acid is the fuel contains sulfur in the combustion and combustion products of the water vapor combined into. These acidic media accelerate the wear of the cylinder wall.
4. Intake system air filtering effect is poor, so that dust, impurities and even mechanical particles into the cylinder, so that the wear intensifies.
5. The crankshaft axial clearance is too large, or crankshaft bending deformation, or connecting rod bending, will accelerate the wear of the cylinder liner.

Measures to Prevent Early Cylinder Liner Wear

1. If you want to protect different cylinder head types and cylinder blocks should improve the wear resistance of the cylinder liner, to reasonably choose the cylinder liner material. China's research on cylinder liner material is more extensive, and has achieved certain results so that the cylinder liner wear resistance has been greatly improved. Such as high phosphorus cast iron cylinder liner, adding 0.3% to 0.8% of phosphorus in cast iron, so that it forms a higher hardness of phosphorus eutectic, thus improving the wear resistance of the liner. The surface treatment of the cylinder liner bore, there are chrome plating, nitriding, high frequency quenching, laser heat treatment, etc., these methods have good effect on improving the wear resistance of the cylinder liner.
2. The engine should work under the specified water temperature (80～90℃); when starting the engine, don't put the throttle to the maximum position, to be able to start the fire as the principle. Regular maintenance of the air filter: remove the dust collection tray and brush away the dust. Unclog the dust discharge port. Clear the dust of the air release dust pipe and central small pipe, pay attention not to stain with oil or water. Clean the upper and lower filters with diesel oil, blow dry them and then dip them slightly in oil and install them in the original place, not to be installed wrongly. It is strictly forbidden to enter the cylinder directly without filtering the air.
3. Keep the diesel engine main journals, connecting rod journals and piston pins parallel to the center line of the three, to prevent the piston from cylinder wear; crankshaft connecting rod should be corrected in time, and ensure that the crankshaft has a standard axial clearance.

Cavitation on the Outer Surface of the Cylinder

The outer surface of the cylinder cavity corrosion is caused by the dry and the outer surface of the cylinder in contact with the cooling water bubbles, bubbles in the external pressure collapse and rupture, resulting in shock waves, the damage to the cylinder wall. The cavitation on the outer surface of the cylinder is shown as a large area of pitting or honeycomb group. The right side of the cylinder liner (camshaft side) has more cavitation, and the electric starter diesel engine has more serious cavitation than the gasoline starter diesel engine.

Causes of Cylinder Liner Cavitation

Vibration is the main cause of cylinder liner cavitation. When the cylinder liner local strong vibration, part of the vibration energy through the solid-liquid phase interface, in the form of pressure waves spread to the outside of the cylinder liner cooling water, prompting the cooling water bubbles. Specific reasons are.

1. The clearance between the cylinder liner and the piston skirt, the clearance between the lower mounting band and the seat hole is relatively large, the larger the clearance the more likely to produce cavitation.
2. The water jacket is too narrow (on the camshaft side, the minimum clearance of the water jacket is only 1.55 mm).