Several main factors of aging life shortage of silicone rubber O-rings

Leading to the function failure of silicone rubber O-rings is the most worrying phenomenon for many mechanical and electronic products and household appliances,

because the performance of a small sealing ring is likely to cause greater loss after aging In addition to the material and technology, the main reason for the performance

failure of silicone rubber products also has a certain impact on the use of products. In the use process of silicone rubber O-rings, it is often due to Force and some

objective reasons lead to performance failure, and there are also force distribution in the process of force, such as instant, side pressure, reverse pressure, etc. Let's

explain the details.

1. Interstitial bite

The phenomenon and cause of Y-rings gap bite is similar to that of O-rings, which occurs at the root. Similarly, the solution is to limit the sealing clearance

according to the working pressure and select the Y-ring material correctly. For the Y-ring with working pressure greater than 16MPa, a retaining ring or a special

sealing ring with a retaining ring embedded at the root shall be set. Retaining rings are usually made of rigid plastic materials, such as polytetrafluoroethylene,

polyamide, etc.

2. Reverse pressure damage

When the silicone rubber O-rings is used as the piston seal of double acting piston cylinder, it must be used in pairs to seal the high pressure fluid in both directions.

In this way, between the two back-to-back lip rings on the piston, or between the two lip rings between the piston rod and the guide sleeve of the hydraulic cylinder,

fluid will gradually infiltrate to form pressure storage. When the working pressure is removed or the pressure storage pressure is higher than the working pressure in

the compound movement, the special-shaped seal ring will be squeezed reversely from the root in the installation groove, and its lip tip will be squeezed into the gap

between the cylinder barrel and the piston, which will cause the reverse pressure damage.

The preventive measures for back pressure damage are as follows:

Open a small hole in the piston to release the pressure. When the working pressure is removed, trapped fluid can be led out through the small hole to release the stored pressure.

Set the support ring. The support ring acts between the two lips of the special-shaped silicone rubber ring for the piston, and resists the sealing ring from axial movement and

reverse extrusion. In addition, several evenly distributed oil guide holes are arranged in the groove to facilitate the pressure medium to act on the concave part of the Y-shaped

seal ring through the small holes, and to open the double lips of the Y-shaped seal ring; at the same time, back pressure is avoided to make the trapped oil drain smooth and

maintain the sealing posture of the Y-shaped ring. This measure has a better effect on preventing the damage of silicone rubber O-rings under reverse pressure.

3. Flip

If the external torque generated by friction force is greater than the torsional resistance of the seal ring itself, the seal ring will turn around or partially turn over and lose the sealing

ability. In order to prevent the seal from overturning, the hardness of the compound can be improved or the support ring can be used. The setting of support ring has a good effect

on preventing various dislocations of Y-shaped seal ring in the mounting groove. The Y-ring can also prevent overturning after it is inlaid with a retaining ring.

4. Root wear

Leakage will be caused when the root of sealing ring is worn seriously. The main reason of root wear is that the interference is too large, resulting in large friction and dry friction.

Therefore, it is necessary to pay attention to the relationship between the inner diameter of the sealing ring and the dimension of the hole shaft and groove.

The inner diameter D1 of the Y-ring used for the opposite shaft should be larger than the shaft diameter D2; the outer diameter D1 should be larger than the groove bottom diameter

D2; the inner diameter D3 of the Y-ring used for the opposite hole should be smaller than the groove inner diameter D4; the outer diameter D3 should be smaller than the cylinder

diameter D4. That is to say, the Y-ring and the bottom of the groove should be pressed tightly, and there is a certain gap between the Y-ring and the sealed sliding surface; the sealing

contact stress of the sliding surface is obtained by the working pressure of the sealed medium acting on the lip of the Y-ring.

The wear of the seal ring is also related to the roughness of the sliding surface, which accelerates the wear of the seal ring, and also related to the processing method. For example,

a polished shaft with the same roughness will wear the sealing ring much less than a polished shaft.

5. Abnormal sound

When the hydraulic cylinder works at high pressure and low speed, sometimes there is a sound of "Pi Li, PI Li". The reason is that when the Y-ring is sliding along the shaft or the

inner wall of the cylinder, the rubber and metal contact surface appears a temporary phenomenon of adhesion detachment adhesion detachment, which will reduce the service

life of the sealing device. The solution is to reduce the friction coefficient of rubber, keep the lubricating oil film on the sealing contact surface all the time, and pay attention to the

viscosity of working medium or lubricant not too low.

6. Dust damage

Mud, dust and sand will often cause abnormal wear of silicone rubber O-rings when they enter the hydraulic cylinder. Dust ring shall be set at the extension end of piston rod to

ensure the dust-proof effect, so as to prevent harmful impurities from entering the hydraulic cylinder.