Causes of discoloration of engineering machinery cylinders

During the use of construction machinery, the hydraulic cylinder will change color, thinking that the quality of the hydraulic cylinder has a problem, and it is often very anxious.In fact, the discoloration of the hydraulic cylinder is a very common phenomenon.

1. The discoloration of the hydraulic cylinder is not due to the discoloration of the cylinder itself. The cylinder becomes black, blue or purple. In fact, the surface of the cylinder is covered with a colored film, which is not a quality problem of the cylinder. Under normal circumstances, the cylinder will First it becomes blue, then the color deepens, becomes purple, and finally becomes black.

2. There are many reasons for the discoloration:

2.1. There is a high temperature phenomenon in the hydraulic system, and the piston rod is frequently in contact with the low temperature environment at high temperature during work (especially in the cold season) (the temperature drops instantly);

2.2. The special hydraulic oil for construction machinery of the brand is replaced during the maintenance cycle. This phenomenon generally occurs within a few days of changing the oil. The reason is that there is an extreme pressure anti-wear additive in the hydraulic oil. The quality and performance are different;

2.3. Due to uneven temperature control during the electroplating process of the piston rod, cracks appeared on the surface of the electroplating layer in the later work. The surface of the piston rod can be observed with a high magnification magnifying glass to see irregular small cracks.

2.4. The blue coloring is caused by the additives in the oil seal and hydraulic oil attaching to the cylinder rod at high temperature, and the blackening is caused by the lead-containing additives in the spray in the cup (ie wear-resistant sleeve) attaching to the cylinder rod at high temperatures. .

Generally, the hydraulic oil temperature is too high, and this phenomenon mostly occurs in the first half of the bucket cylinder that is used more. It is recommended to clean the dirt of the radiator part frequently to ensure the heat dissipation effect.

3. How to deal with the discoloration of the cylinder?

If there is a very small part of the blue in the cylinder, you can ignore it, and it will disappear automatically after a period of time;

If the discoloration is serious, you need to replace the oil seal and wear sleeve, and try to avoid the high temperature of the hydraulic oil, and it will return to normal after a while.

There are several reasons and treatment methods for the malfunction or malfunction of the hydraulic cylinder:

(1) The valve core is stuck or the valve hole is blocked. When the flow valve or directional valve spool is stuck or the valve hole is blocked, the hydraulic cylinder is prone to malfunction or malfunction. At this time, check the contamination of the oil; check whether dirt or colloidal deposits are stuck in the valve core or block the valve hole; check the wear of the valve body.

(2) The piston rod and the cylinder are stuck or the hydraulic cylinder is blocked. At this time, no matter how you manipulate it, the hydraulic cylinder does not move or moves slightly. At this time, check whether the piston and piston rod seals are too tight, whether dirt and colloidal deposits have entered: whether the axis line of the piston rod and the cylinder barrel is aligned, and whether the wearing parts and seals are invalid.

(3) The control pressure of the hydraulic system is too low. The throttling resistance in the control pipeline may be too large, the flow valve is improperly adjusted, the control pressure is inappropriate, and the pressure source is disturbed. At this time, check the control pressure source to ensure that the pressure is adjusted to the specified value of the system.

(4) Air enters the hydraulic system. Mainly because there are leaks in the system. At this time, check the liquid level of the hydraulic oil tank, the seals and pipe joints on the suction side of the hydraulic pump, and whether the oil suction strainer is too dirty. If so, hydraulic oil should be added, seals and pipe joints should be treated, and the coarse filter element should be cleaned or replaced.

(5) The initial movement of the hydraulic cylinder is slow. In the case of low temperature, the hydraulic oil has high viscosity and poor fluidity, which causes the hydraulic cylinder to move slowly. The improvement method is to replace the hydraulic oil with better viscosity and temperature performance. At low temperatures, it can be heated by a heater or the machine itself to increase the oil temperature at startup.