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What should do if the digging machine cylinder is discolored?

What should do if the digging machine cylinder is discolored?
Update Time:2019-01-28

What should  do if the digging machine cylinder is discolored?

The general process of discoloration of a hydraulic cylinder is like this: the cylinder first turns blue first, then the color gradually deepens, turns purple, and finally turns black. The discoloration of the cylinder is actually the surface of the oil covered with a layer of colored film, not a problem with the cylinder itself.

Reasons and methods for discoloration of hydraulic cylinders:

Reason 1: The temperature difference between the inside and outside of the hydraulic cylinder is too large

If the temperature of the hydraulic system is too high during the work of the excavator, and the temperature of the external connection is very low, especially in the winter, the temperature difference between the inside and the outside of the cylinder will be very large, and the piston rod works in this case. It is easy to cause discoloration of the cylinder.

Reason 2: Use non-dedicated hydraulic oil or poor quality hydraulic oil

Many users have insufficient experience or cheap maps. When excavating machine maintenance and replacing hydraulic oil, hydraulic oils not used by this brand of excavator are used, which can easily cause discoloration of the cylinder. Because there is an extreme pressure anti-wear additive in the hydraulic oil, the additives contained in different brands of hydraulic oil are different. If mixed, it will affect the cylinder.

Reason 3: Piston rods adhere to impurities

When the hydraulic cylinder is working, the piston rod is often in contact with the outside world, and it is easy to adhere to some impurities. As the impurities accumulate, the cylinder will also change color. Among them, the blue color may be caused by the oil seal and the additive in the hydraulic oil adhering to the cylinder rod at a high temperature. Blackening may be due to the fact that the lead additive contained in the spray coating in the wear sleeve adheres to the cylinder rod at a high temperature.

Reason 4: Poor electroplating process causes micro cracks on the surface of the piston rod

Another possibility is that there is a crack on the surface of the piston rod that is difficult for us to see with the naked eye. The reason for this crack is that the temperature of the piston rod is not uniform enough during the electroplating process. The cracks need to be seen with a high magnification magnifier. .


1. When the cylinder is found to be very fine and has a small area of ​​blue, it can be temporarily left untreated. Most of the time, the blue color will disappear by itself.

2. If the color change is serious, you need to replace the oil seal and wear sleeve. At the same time, you should avoid the high temperature of the hydraulic oil and return to normal after a period of time.

3. When discoloration occurs in the front half of the bucket cylinder, the radiator should be cleaned to ensure the heat dissipation of the hydraulic system.

4. If non-special hydraulic oil or inferior hydraulic oil is used to cause discoloration, it should be replaced immediately with the special hydraulic oil that is unified with the brand of the excavator.

5. If the color changes due to cracking, this is a cylinder quality problem, you need to negotiate with the manufacturer or agent, or replace the piston rod.