Created on:2021-09-04 14:30

Port equipment_ Leakage fault of hydraulic system of wharf equipment

Port equipment_ Leakage fault of hydraulic system of wharf equipment

The leakage of hydraulic system of wharf equipment is common, and there are two main types of leakage: leakage at fixed seal and leakage at moving seal. The leakage part at the fixed seal includes the hydraulic cylinder bottom and the connection of each pipe joint; The leakage at the moving seal mainly includes the hydraulic cylinder piston rod, multi-way valve stem and other parts.

(1) Design factors

The reliability of hydraulic system largely depends on the design of hydraulic system seal and the selection of seal. Due to the unreasonable sealing structure in the design, the selection of seals does not meet the specifications, and the compatibility between hydraulic oil and sealing materials is not considered in the design, which directly or indirectly causes the leakage of hydraulic system to varying degrees. In addition, the different properties of dust and impurities borne by the machine in different service environments are also important factors to be considered in the selection of seals in the design. Long term hydraulic shock and vibration will cause pipe joint looseness and leakage, which is also a common fault.

(2) Manufacturing factors

All hydraulic components and sealing components have strict requirements for dimensional tolerance, surface treatment, surface roughness and geometric tolerance. If the manufacturing process is out of tolerance, such as the diameter of the hydraulic cylinder piston, the depth or width of the sealing groove, the size of the hole with the sealing ring is out of tolerance or out of roundness caused by processing problems, the workpiece itself has burrs and pits, and the chromium plating layer falls off, the seal will be deformed, scratched, crushed or not pressed, and the sealing function will be lost.

(3) Assembly factors

During the assembly of hydraulic components, excessive force will deform the parts, especially knocking the hydraulic cylinder block and sealing flange with copper bar. Careless inspection of parts before assembly, failure to take lubrication measures during assembly, and unequal cleaning fluids during cleaning will cause system leakage.

(4) Wear and damage of dynamic seal

Dynamic seals are generally made of oil resistant rubber materials, which will age and crack after long-term use. Abrasives, dust and impurities in the oil will also accelerate the aging and damage of the seal, and the seal will be scratched by collision and damage during operation. These conditions are most likely to cause internal leakage.

(5) Environmental impact

As the main executive element of the hydraulic system, the hydraulic cylinder is exposed to the outside and in direct contact with the environment. Although the guide sleeve is equipped with dust rings and seals, it is inevitable to bring dust and dirt into the hydraulic system, accelerating the scratch and wear of seals and piston rods, resulting in leakage.

The humid working environment may cause water to enter the hydraulic system. The water will react with the hydraulic oil to form acidic substances and oil sludge, reduce the lubrication performance of the hydraulic oil, and also cause the valve rod of the control valve to stick, making it difficult to operate or scratch the seals, resulting in leakage. When the temperature rises by 10 ℃, the service life of the seal will be halved, and the optimal oil temperature is below 65 ℃, otherwise the seal will deteriorate prematurely. Under normal pressure, about 10% air can be dissolved in hydraulic oil. Under the high pressure of the hydraulic system, more air will be dissolved in the oil. Air forms bubbles in the oil. If the pressure changes rapidly between high and low in a very short time during the working process, the bubbles will produce high temperature on the high-pressure side and burst on the low-pressure side. At this time, if there are pits and damages on the surface of the hydraulic element, the hydraulic oil will rush to the element surface at high speed, accelerate the wear of the surface and cause leakage.

(6) Main prevention and control measures for leakage

① In the process of design and processing, the geometric accuracy of each element should be ensured and the seals should be selected correctly. In order to reduce impact and vibration, vibration damping support can be used. Accumulator shall be used as much as possible in the system, and pressure control valve shall be used appropriately to protect system components.

② Install the pipe joint, and use the oil return manifold block to replace each piping.

③ Select the correct assembly and repair method. Lubrication measures shall be taken during assembly, such as applying a little grease on the seal. During assembly, special tools shall be used as much as possible. Diesel oil shall be used when cleaning the seals of rubber materials. If gasoline is used, it is easy to aging and lose the original elasticity of rubber components.

④ If the hydraulic components are damaged during work, they shall be handled in time, especially the seals are most likely to be affected after the piston rod and cylinder barrel are damaged.

⑤ In terms of the working environment of the hydraulic system, we should start from the source of pollution, regularly test the oil quality, clean the filter device and oil tank, and cut off the pollution caused by external factors (water, dust, particles, etc.).

⑥ In order to prevent the oil temperature from being too high, a forced cooling device can be set.

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