There are two main types of leakage in the hydraulic system of engineering machinery, leakage at the fixed seal and leakage at the moving seal. Leakage at the fixed seal mainly includes the bottom of the cylinder and the joints of each pipe joint, etc., and leakage at the moving seal mainly includes the piston rod of the oil cylinder, Multi-way valve stems and other parts. Oil leakage can also be divided into external leakage and internal leakage. External leakage mainly refers to the leakage of hydraulic oil from the system into the environment. Internal leakage refers to the pressure difference between the high and low pressure sides. Due to reasons such as the existence and failure of seals, the hydraulic oil flows from the high-pressure side to the low-pressure side inside the system.

Reasons affecting leakage:

1) Design factors:

(1) The selection of seals The reliability of the hydraulic system depends to a large extent Regarding the design of hydraulic system seals and the selection of seals, due to the unreasonable selection of sealing structures in the design and the selection of seals that do not meet the standards, the compatibility type, load conditions, and ultimate pressure of the hydraulic oil and sealing materials were not taken into account in the design. , working speed, changes in ambient temperature, etc. These all directly or indirectly cause leakage of the hydraulic system to varying degrees. In addition, since the environment in which construction machinery is used contains dust and impurities, appropriate dust-proof seals must be selected in the design. , to prevent dust and other dirt from entering the system to damage the seal and contaminate the oil, thereby causing leakage.

(2) Other design reasons: The geometric accuracy and roughness of the moving surface are not comprehensive enough in the design, and the strength of the connection parts is not calibrated in the design. Nuclear, etc., which will cause leakage during the operation of the machinery.

2) Manufacturing and assembly factors

(1) Manufacturing factors: All hydraulic components and sealing parts have strict dimensional tolerances, surface treatment, surface finish and geometric tolerances, etc. Requirements. If the deviation is out of tolerance during the manufacturing process, for example: the piston radius of the cylinder, the depth or width of the sealing groove, the size of the hole for installing the sealing ring is out of tolerance, or it is out of round due to processing problems, there are burrs or depressions, chrome plating is peeling off, etc. , the seal will be deformed, scratched, crushed or not compacted, causing it to lose its sealing function. The part itself will have congenital leakage points, and leakage will occur after assembly or during use.

(2) Assembly factors: Brutal operation of hydraulic components should be avoided during assembly. Excessive force will cause deformation of the parts, especially using copper rods to hit the cylinder block, sealing flange, etc.; parts should be carefully inspected before assembly, and parts should be carefully inspected during assembly. Dip the parts in a little hydraulic oil and press them in gently. Use diesel when cleaning, especially rubber components such as sealing rings, dust rings, and О-rings. If you use gasoline, they will easily age and lose their original elasticity, thus losing their sealing function. .

3) Oil pollution and damage to parts

(1) Gas pollution. Under atmospheric pressure, about 10% of air can be dissolved in hydraulic oil. Under the high pressure of the hydraulic system, more air will be dissolved in the oil. Air or gas. Air forms bubbles in the oil. If the pressure of the hydraulic support changes rapidly between high and low pressure in a very short period of time during operation, the bubbles will generate high temperatures on the high-pressure side and burst on the low-pressure side. If When there are pits and damage on the surface of the components of the hydraulic system, the hydraulic oil will rush towards the surface of the components at high speed to accelerate the wear of the surface, causing leakage.

(2) Particle contamination Hydraulic cylinders are the main executive components of some engineering machinery hydraulic systems. Due to the work During the process, the piston rod is exposed and in direct contact with the environment. Although the guide sleeve is equipped with dust rings and seals, dust and dirt will inevitably be brought into the hydraulic system, accelerating scratches and damage to the seals, piston rod, etc. Wear, thereby causing leakage, and particle pollution is one of the fastest factors causing damage to hydraulic components.

(3) Water pollution Due to the influence of factors such as humid working environment, water may enter the hydraulic system, and the water will react with the hydraulic oil to form acid Substances and sludge reduce the lubrication performance of hydraulic oil and accelerate the wear of components. Water can also cause the stem of the control valve to stick, making it difficult to operate the control valve, scratching the seal, and causing leakage.

(4) Part damage is caused by oil resistance. Made of rubber and other materials, aging, cracking, damage, etc. due to long-term use will cause system leakage. If the parts are damaged by collision during work, the sealing elements will be scratched, causing leakage. What should I do? Main Leakage Prevention and Control Countermeasures The factors causing the leakage of the hydraulic system of construction machinery are the result of comprehensive influences from many aspects. With the existing technology and materials, it is difficult to fundamentally eliminate the leakage of the hydraulic system.

Only from the above influences Starting from the leakage factors of the hydraulic system, reasonable measures should be taken to reduce the leakage of the hydraulic system as much as possible. In the design and processing links, the important factors affecting leakage must be fully considered in the design and processing of the sealing groove. In addition, the selection of seals is also very important. If Failure to fully consider the influencing factors of leakage at the beginning will cause immeasurable losses in future production. Choose the correct assembly and repair methods and learn from past experience. For example, try to use special tools in the assembly of sealing rings, and Apply some grease on the sealing ring.

In terms of hydraulic oil pollution control, we must start from the source of pollution, strengthen the control of pollution sources, and take effective filtration measures and regular oil quality inspections. In order to effectively cut off external factors (Water, dust, particles, etc.) contamination of the hydraulic cylinder, some protective measures can be added. In short, the prevention and control of leakage must be comprehensive and comprehensive consideration can be achieved to be effective.