Among the failures of the hydraulic cylinder, the most problematic is that it is difficult to judge when the foreign matter enters the hydraulic cylinder. After foreign objects enter, if a seal with a lip is installed on the outer side of the sliding surface of the piston, the lip of the seal can scrape the foreign object during operation, which is beneficial to avoid scratches. However, the two ends of the piston equipped with the O-ring seal are sliding surfaces, and foreign matter is sandwiched between the sliding surfaces, which is easy to form scars.
There are several ways for foreign objects to enter the tank.
① Foreign matter entering the cylinder
a. Due to the careless opening of the oil port during storage, the condition of receiving foreign objects will occur at all times, which is absolutely not allowed. When storing, it is necessary to inject anti-rust oil or working oil and plug it well.
b. Foreign objects enter when the cylinder is installed. In the place where the installation operation is carried out, the conditions are not good, and foreign objects can enter unconsciously. Therefore, the surroundings of the installation site must be cleaned up, especially the place where the parts are placed must be cleaned so that there is no dirt.
c. There are "burrs" on the parts, or insufficient scrubbing. There are often burrs left during drilling in the oil port on the cylinder head or in the buffer device. Pay attention to it and install it after the sand is removed.
② Foreign matter generated during operation
a. Friction iron powder or iron filings formed due to the tension of the buffer plunger. The mating clearance of the buffer device is very small, and when the lateral load on the piston rod is large, it may cause sintering. These friction iron powders or metal fragments that have fallen off due to sintering will remain in the cylinder.
b. Scar on the inner surface of the cylinder wall. The sliding surface pressure of the piston is high, causing sintering, so the inner surface of the cylinder is squeezed and cracked, and the cracked metal falls off and remains in the cylinder, causing scars.
③ There are various cases of foreign matter entering from the pipeline.
a. Careless when cleaning. When the pipeline is cleaned after installation, it should not pass through the cylinder body, and a bypass pipeline must be installed in front of the oil port of the cylinder body. this point is very important. Otherwise, the foreign matter in the pipeline will enter the cylinder. Once it enters, it will be difficult to remove it, and instead it will become a foreign matter being transported into the cylinder. Furthermore, when cleaning, consider the method of removing foreign objects that have entered during the installation of the pipeline. In addition, for corrosion in the pipe, procedures such as pickling should be performed before the pipe is installed, and the rust must be completely removed.
b. Chips formed during pipe processing. After the pipe has been cut to length, there should be no residue left during the deburring operation at both ends. In addition, placing steel pipes near the site where the welding pipeline operation is performed is the cause of the mixing of welding foreign matter. For pipes placed near the welding operation site, the nozzles should be sealed. It must also be noted that the fitting material should be fully stocked on a dust-free workbench.
c. The sealing belt enters the cylinder. As a simple sealing material, PTFE plastic sealing tape is often used in installation and inspection. If the winding method of linear and tape sealing materials is incorrect, the sealing tape will be cut off and enter the cylinder. The linear belt seal will not have any effect on the winding of the sliding part, but it will cause the check valve of the cylinder to fail or cause the buffer control valve to not be adjusted to the end; for the circuit, it may cause the reversing valve, overflow Failure of valve and pressure reducing valve action.
The traditional repair method is to carry out outsourcing repair after disassembly of the damaged parts, or to carry out brush plating or overall scraping of the surface. The repair cycle of the hydraulic cylinder block is long and the repair cost is high.
