1. Gap leakage
There are mainly two kinds of gap leakage in hydraulic system, the leakage at the fixed seal (static joint surface) and the leakage at the moving seal (dynamic joint surface). The leakage parts of the fixed seal mainly include the joint of the hydraulic cylinder head and the cylinder; The moving seal is mainly between the hydraulic cylinder piston and the inner wall of the cylinder, the piston rod and the guide sleeve of the cylinder head. The size of gap leakage is related to pressure difference, clearance and other factors.
2. Multi-pore leakage
Various cover plates in hydraulic components, due to the influence of surface roughness, it is impossible to completely contact between the two surfaces, in the micro-depression where the two surfaces do not contact, the formation of many cross section shapes, different sizes of the gap, the cross section size of the gap is related to the surface roughness. Multi-gap leakage, the liquid needs to flow through a number of curved voids, in the sealing performance test, after a certain pressure holding time, the leak can be revealed.
3. Adhesion leakage
There is a certain adhesion between the viscous liquid and the solid arm. After the two contact, a thin layer of liquid is adhered to the solid surface. If the film on the solid surface is thick, the oil film will be scraped off by the sealing ring due to mutual movement, resulting in adhesion leakage. The basic method to prevent adhesion leakage is to control the thickness of the liquid adhesion layer.
Fourth, power leakage
On the sealing surface of the rotating shaft, if there are traces of spiral processing, when the shaft rotates, the liquid flows along the groove of the spiral trace under the action of the rotating force of the rotating shaft. If the direction of the spiral trace is consistent with the rotation direction of the shaft, power leakage will occur due to the "pumping oil" effect of the spiral trace. The characteristic of dynamic leakage is that the higher the rotational speed of the shaft, the greater the leakage. To prevent power leakage, there should be no processing marks of "pumping oil" effect on the sealing surface of the rotating shaft and the lip edge of the sealing ring, or the use of the principle of power leakage, the use of the pump oil function of the spiral trace to pump the leak back and prevent the leak.
