Prevention of Cavitation in Hydraulic Cylinders of Construction Machinery

Hydraulic cylinder cavitation damage is quite large, it will lead to the surface with black, or even support ring, ring charring phenomenon, resulting in the hydraulic cylinder to produce internal leakage. When the cavitation and other types of corrosion together, will be several times or even several times to accelerate the corrosion rate of the main parts of the hydraulic cylinder, which seriously affect the normal use of construction machinery. Therefore, the cavitation of the hydraulic cylinder for targeted prevention, is very necessary.

The main cause of cavitation

(1) the essence of cavitation analysis

Cavitation, mainly due to the hydraulic cylinder in the course of work in the piston and guide sleeve between the oil mixed with a certain amount of air. As the pressure gradually increases, the gas in the oil becomes air bubbles. When the pressure rises to a certain limit, the bubbles break under the action of high pressure, and the gas with high temperature and high pressure is quickly acted on To the surface of the part, resulting in cavitation of the hydraulic cylinder, resulting in corrosive damage to parts.

(2) the quality of hydraulic oil failure caused by cavitation

To ensure the quality of hydraulic oil is to prevent the occurrence of cavitation is an important factor. If the anti-foam oil is poor, it is easy to produce foam, leading to the occurrence of cavitation. Secondly, the oil pressure changes too fast, too high, will also directly lead to the formation of bubbles to accelerate the bubble burst rate. Tests have shown that the rate of cavitation increases when the frequency of the pressure change is high. Such as the hydraulic cylinder into the back port, etc., due to the relatively high frequency of pressure changes, the degree of cavitation is also relatively higher than other parts. In addition, oil overheating will increase the chance of cavitation.

(3) improper manufacture and maintenance lead to cavitation

As in the assembly or maintenance did not pay attention to the full exhaust system of the hydraulic system, resulting in the presence of gas in the system, under high temperature, high pressure can produce cavitation.

(4) coolant quality problems lead to cavitation

20162298558299.jpg

When the coolant contains corrosive media, such as various acid ions, oxidants, are prone to chemical, electrochemical corrosion, in their joint role, will also speed up the cavitation; if the cooling system is well maintained, can be To prevent the occurrence of cavitation. For example, the cooling system radiator pressure cover, if well maintained, you can make the radiator coolant pressure is always higher than the vapor pressure, thus preventing cavitation. Another example is the thermostat of the cooling system; a thermostat with good performance can keep the coolant in the proper temperature range and reduce the energy released when the bubble bursts.

Hydraulic cylinder hydraulic system is an important implementation of components for the implementation of reciprocating motion, widely used in construction machinery. Hydraulic cylinder piston rod is an important part of the hydraulic cylinder, which is usually made of 35,34 or seamless steel pipe made of solid rod or hollow rod, in order to improve the wear resistance of rust, the current domestic process is hard chrome plating Thickness: 0.02 to 0.05 mm) and polished to have a surface roughness Ra of 1.6 to 0.4 m. As chrome on the people, serious environmental pollution, a national environmental line item, and the coating is not uniform, high porosity, easy to skin, chrome costs are relatively high, can not meet the needs of the production, the use of appropriate economic plating instead of chrome Has been an important issue in the construction machinery industry. Electroless plating is the process of metal deposition by redox chemical reaction in the solution. It usually refers to the surface processing method in which metal ions in the solution are reduced to metal by the reducing agent under the action of the external current and deposited on the surface of the body to form the metal plating layer. Electroless Ni-P alloy amorphous coating, with excellent performance, can significantly improve the hard plating, wear resistance and corrosion resistance, can replace the hard chrome plating. Electroless plating is characterized by simple equipment, no electroplating power, for a variety of shapes of the workpiece can be made uniform thickness of the coating, the aging treatment temperature is low, small deformation.

Hydraulic cylinder is a hydraulic system of the implementation of the components, the work of the fault in addition to the hydraulic cylinder itself, but also with the entire system, so the work of cleaning the hydraulic cylinder when the problems should be carefully investigated the performance of defects, logical reasoning, Approach, from outside to inside carefully analyze the causes of illnesses, and then determine the cleaning methods, to prevent blindly large demolition unloading. In the hydraulic cylinder for many reasons, the equipment, use and protection is wrong is the reason for its problems, such problems are not discussed here. In this paper, only the typical work of a common fault - hydraulic cylinder to analyze the poor system.

Most of the poor performance of the hydraulic cylinder: the hydraulic cylinder can not move, the hydraulic cylinder action is not sensitive (with block representation) and the hydraulic cylinder creep and other phenomena.