One, PU imports of O type of Ring Distortion damage
Many reasons cause the distortion, the most important one is that the gap between the piston, the piston rod and cylinder is not uniform, the eccentricity is too large, and the section diameter is not uniform. Because the seal ring by the friction is not uniform, some parts of the friction is small, some parts of the friction is too large, and therefore the occurrence of distortion. Under the usual conditions, the section size is small, easy to produce uneven friction, resulting in the phenomenon of distortion. Under the same conditions, in order to prevent the distortion, the movement of the O - ring is larger than the diameter of the fixed section. In addition, because the sealing groove has the phenomenon of the coaxial degree deviation, the sealing height is not equal and the section diameter is not uniform, the part of the compression is too large, the other part is too small or not compressed. When the groove is eccentric or coaxial deviation is greater than the amount of compression, the seal will completely fail. Another disadvantage is that the sealing groove of the coaxial degree of the seal ring along the circumferential compression. In addition, the hardness of the material, the diameter of lubricating oil film thickness uneven and sealing shaft surface roughness and other factors, led to the import of O ring part along the sliding surface of the workpiece, the other part is rolling, resulting in distortion. Movement makes it easy to damage the ring, which is an important reason for the damage and leakage of the sealing device. Therefore, it is an important factor to improve the machining precision and reduce the eccentricity of the sealing groove.  
When you install the sealing ring, you should ensure that you can't make it in a state of distortion. If the installation is distorted, the distortion of the damage will happen soon. In the work, the phenomenon of distortion will be cut off, resulting in a large number of oil spills, and cut off the O ring will be mixed to other parts of the hydraulic system, causing major accidents.
 
Two, manual installation of O ring, high wear-resistant O import PU type ring, imported O type of attention matters
1) attention to the use of no sharp edge of the operating tools;
2) as far as possible to use the auxiliary tools to install, and ensure the correct positioning;
3) to ensure that the O ring (O type rubber sealing ring) is not distorted, not excessive tension;
4) for the use of sealing strip bonded into the O - ring (O - type rubber sealing ring), not at the junction of tension.
 
Three, imported O type ring, pump with rubber O ring.
Because of its shape is very simple, so easy to manufacture, low cost, easy to use, easy to install, remove, more prominent advantage is that the O ring has a good sealing ability, the use of a wide range. The working pressure of the static seal can reach 100MPa, and the dynamic seal can also reach 30Mpa. Applicable temperature is -60 ~ 250 degrees C, can meet the requirements of the use of a variety of media. Therefore imported O type ring in the design of the pump has been more and more widely used.
The sealing ring is arranged in the groove and between the sealing surface, a certain amount of compression, the resulting rebound given sealed smooth surface and the bottom surface of the trench to the initial compressive stress, and thus plays a role in sealing. When the liquid pressure is sealed, the deformation of the O type of the inlet is also increased, so that the pressure on the sealing surface is also increased, and the function of the seal is also increased. This is the reason why imported products have good sealing ability.
Although the seal is reliable, but if you do not pay attention to the use of conditions, there will be leakage:
1) the groove size is very poor, especially the depth dimension is too large, the compression deformation is insufficient to affect the sealing ability. The compression deformation should be in 22% ~ 18%, when the section size is large, the relative deformation is small, and the relative deformation is larger when the section size is relatively small.
2) nominal size and the actual installation of too much difference, resulting in insufficient compression deformation and produce leakage.
3) at the time of installation, due to the sealing surface of the imported no smooth chamfered or rounded and will import the O ring scratch caused by leakage.
4) material does not apply to the sealing medium and erosion after failure.
5) the use of time is too long to deteriorate, decreased elasticity after failure, so in general will replace the equipment overhaul
4/ PU imported O type ring is generally installed on rectangular groove sealing circle in the outer circle or within (note that the design time gap is not too big). Usually used for static sealing and reciprocating seal, of course, can also be used for rotary motion seal, but limited to low-speed rotary seal.
Three, the correct use of O imports of PU type ring and other sealed products to note
1/ general oil seal bearing pressure ability is poor, the pressure is too large when the oil seal will be deformed. In this case, the pressure bearing ring or the enhanced pressure oil seal should be adopted;
2/ oil seal and shaft with eccentric can not be too large, otherwise the seal will become poor, especially in the shaft speed is particularly serious. If the eccentricity is too large, can use the "W" - shaped section of the oil seal;
3/ attention in the oil seal lip mouth should have a certain amount of lubricating oil, and to prevent dirt into the oil seal;
4/ due to the design and structure of the high speed shaft, should use the high speed shaft seal, using low speed low speed can not be used for oil seal oil seal; low speed high speed shaft, and vice versa;
The surface finish of 5/ shaft directly affects the service life of oil seal. Shaft finish high, oil seal service life is long;
6/ in the use of higher temperatures, the use of polypropylene ester or silicone, fluorine, silicone rubber. And should try to reduce the oil temperature in the tank. Cold resistant rubber should be used in the case of low temperature.