In the maintenance of construction machinery hydraulic cylinder, you can often see the cylinder wall cylinder, piston or piston rod surface has some honeycomb-shaped cavities, which are caused by cavitation. Cavitation can cause the mating surfaces of the cylinder barrel and the piston rod to become rough, the hydraulic cylinder generates internal leakage, and the working speed decreases. When cavitation and other forms of corrosion together, will accelerate the corrosion rate of the main parts of hydraulic cylinders, thus seriously affecting the normal use of construction machinery.

1, the factors that affect cavitation In the hydraulic cylinder parts surface and the relative movement of hydraulic oil, dissolved in the hydraulic oil gas easily precipitated and the formation of bubbles. These bubbles flow to the high-pressure zone after the rupture, instantaneous high temperature and high pressure micro-jet and impact force repeatedly acting on the surface of the hydraulic cylinder parts, parts cavitation erosion. Hydraulic cylinder cavitation conditions and the hydraulic system structure, hydraulic cylinder parts materials, hydraulic oil quality, manufacturing and maintenance have a certain relationship.

(1) hydraulic system structure If the hydraulic system piping, control valves and other components of the passage is too narrow and too many elbows, hydraulic oil temperature will increase, the impact force increases, easy to produce bubbles in the hydraulic oil, resulting in Cylinder cavitation.

(2) Hydraulic cylinder parts material If the material used to manufacture hydraulic cylinder has better strength, toughness and corrosion resistance, its anti-cavitation ability is better; otherwise, cavitation will occur easily. In addition, the homogeneity of the material structure has a greater influence on the cavitation, the more uneven the material structure is, and the cavitation tends to occur where the strength is weak and where the corrosion resistance is low.

(3) hydraulic oil quality hydraulic oil quality is good or bad, is a hydraulic cylinder whether an important factor in cavitation. Hydraulic oil in the work inevitably with the valve, piping and other impact, if the anti-foam hydraulic oil is poor, it is easy to produce foam, resulting in cavitation and other parts of the hydraulic cylinder. If the hydraulic oil pressure changes too fast, too high, it will also promote the formation of bubbles, and accelerate the bubble burst rate. Such as hydraulic cylinder into the back to the oil Department, due to the relatively high frequency of pressure changes, the degree of cavitation is relatively higher than other parts.

(4) manufacturing and maintenance of hydraulic cylinder assembly or maintenance of the quality of their cavitation can not be underestimated. If the system is not adequately vented during assembly or service, gas will be trapped in the system and cavitation will occur at high temperatures and pressures.

2, the measure to prevent cavitation Although the impact of hydraulic cylinder cavitation is many factors, but as long as the necessary measures to take preventive measures, cavitation can be avoided. The measures are as follows:

(1) The selection of qualified hydraulic oil selection of good quality and brand suitable hydraulic oil, which can effectively prevent hydraulic oil bubbles in the work process. Selection of hydraulic oil should be in line with the relevant technical requirements under the premise, with reference to the choice of temperature in the region, and according to the dipstick standard filling.

In addition, keep the hydraulic system clean. Should always check the hydraulic oil, oil level and oil color, hydraulic oil found in the foam or become milky white, indicating that the hydraulic oil has been mixed with air, should carefully check the air source, and replacement of new oil. If you use high water-based hydraulic oil, high-mounted hydraulic oil tank should be configured to increase the pressure at the inlet of the hydraulic pump to effectively prevent cavitation in the hydraulic cylinder.

(2) Select the appropriate hydraulic oil Additives Select the appropriate hydraulic oil additives, which can effectively inhibit the hydraulic oil turbidity or hydration phenomenon, to prevent the foam, stabilize the hydraulic oil quality, hydraulic oil to maintain normal performance for a long time.

(3) to prevent the oil temperature is too high, reduce hydraulic shock reasonable configuration hydraulic oil cooling device, to prevent the hydraulic oil temperature is too high. If the phenomenon of oil temperature is too high at work, should find out the reasons and promptly ruled out to eliminate the conditions of bubbles in the hydraulic oil. In addition, hydraulic system work, avoid frequent increase engine throttle, should strive to control the smooth, to reduce the impact of hydraulic oil on the hydraulic components.

(4) Correct Assembly or Maintenance of Hydraulic Cylinders Assembling or repairing hydraulic cylinders such as cylinder blocks and piston rods should be performed in accordance with the lower limit of assembly tolerances, which can reduce cavitation. If the hydraulic cylinder parts have cavitation phenomenon, can only use metallographic sandpaper polishing method to remove cavitation pitting and surface fouling, can not be polished with ordinary fine sandpaper.

After the hydraulic cylinder is repaired, it should be operated under no load and steady condition for a period of time, so that the hydraulic oil can be fully circulated. If the hydraulic system is mixed with air, the manual exhaust can be done by slowly loosening the hydraulic cylinder inlet pipe or return pipe nut and tightening the nut when the air bubble is completely discharged.