1. machining accuracy of oil jar

Experiments show leaking volume of oil seal? and the wear value will shoot up if the surface roughness Ra is more than 0.8um when it is contact with oil seal,   it is suggested that work surface roughness Ra? should be 0.1~0.8um .
To ensure the performance? of the polyurethane seal or rubber-plastics seal, it should be avoid damage seal parts in assembly process.

    2. Cylinder
Material of construction：usually carbon steel;? aluminum alloy, bronze and stainless steel available in low-pressure systems and better friction occasions.?   
quality and roughness? of the inner surface：The inner surface normally should be? honing , polishing or rolling,? Ra 0.1~0.8um , and? can not have knife? grain .。
    3. Piston rod
Material of construction：usually carbon steel, chromium plated steel，aluminum alloy, bronze and stainless steel available in low-pressure systems and better friction occasions.?   
quality and roughness? of the surface：roughness should be Ra0.2~0.4um，after heat treatment the surface should be plated hard chromium. The? piston rod with hydraulic cylinder in engineering machinery may be scratched by gravel, surface hardness should be above HRC 60.。
    4.groove
structural form：can be divided into integrated groove and detached groove.

????????    which should be used depend on the section size of oil seal, structural requirement hydraulic cylinder? and dismantling convenience.
notice：
    a. Some? smaller diameter u-ring can not be installed in the integrated groove.
    b. Some large section and high hardness U-ring should not be installed in the integrated groove ?????because it is difficult to dismantle and easily damaged.
size：different oil seals have different design style of groove , it should be designed according to supplier's recommendation based on conditions used.
    Quality of Surface：Since the? size of groove installed and quality of the inner surface affect the seal performance, it should be processed according to the exact size recommend , Edge should be processed into inverse angle and deburred to prevent scratches, recommend Ra1.6,3.2um.。
    5. Local Structural Design
    inside and outside lip of oil seal is the most important part. pertain to the parts that potenial damage the lip of the oil seal during dismantling, we must take protective design, install with dedicated tools. For example，there should be buffer? stage? in thread end, and jacket should be setted in screw thread part; For enclosed entry(end),settling tank , shoulder, there must be inverse angle or slope mouth and be? deburred.

    6. wear ring slide fit gap f? and extrusion gap g of oil seal

wear ring slide fit gap fis related to the materia lof the selected weatr ring.
    extrusion gap is related to the material of oil seal,? structure, working pressure and material of the ring selected. The higher the working pressure, the smaller the extrusion gap g.
    the two gap? have great impact on the seal? performance, the smaller the better , manufacturers generally provide? recommended values. the recommend values should be strictly observed.