The failure of products such as silicone rubber seals is one of the most feared phenomena in the mechanical and electronic industry. It is often possible to return to a serious result due to the lack of a sealing performance. Silicone rubber products are one of the more important reasons, causing it to fail. The main reason is caused by three factors such as materials and product production and function. For example, the materials and production processes of silicone products manufacturers have been controlled. So what are the main problems in the use of silicone rubber seals?
The common causes of failure of silicone seals are as follows:
1. Abnormal sound:
When the hydraulic cylinder is working under high pressure and low speed, sometimes the sound of "Piri, Pi Li" will occur. The reason is that when the Y-shaped sealing ring slides along the shaft or the inner wall of the cylinder, a short-term adhesion-disengagement-adhesion-disengagement phenomenon occurs between the rubber-metal contact surface, which lowers the life of the sealing device. The solution is to reduce the friction coefficient of the rubber so that the sealing contact surface always maintains the lubricating oil film; it should also be noted that the viscosity of the working medium or lubricant should not be too low.
2, root wear:
Leakage can occur when the root of the seal is severely worn. The main cause of root wear is that the interference is too large, resulting in large friction and dry friction. Therefore, attention must be paid to the relationship between the inner diameter of the seal ring and the hole axis and groove size.
3. Dust damage:
Intrusion of mud water, dust and sand into the hydraulic cylinder often causes abnormal wear of the silicone rubber seal. A dust seal should be placed at the outrigger end of the piston rod to ensure dustproof effect to prevent harmful impurities from entering the hydraulic cylinder.
4, rotation failure:
If the external torque generated by the frictional force during exercise is greater than the torsional resistance of the sealing ring itself, the sealing ring will be turned over or partially overturned, and the sealing ability will be lost. To prevent the seal from turning over, the rubber hardness can be increased or a support ring can be used. The provision of the support ring has a good effect on preventing various misalignments of the Y-shaped seal ring in the safety groove. The Y-ring seal can also suppress the flip after it is inlaid with the retaining ring.
5, gap bites:
The gap between the Y-ring seal and the cause is similar to that of the O-ring, which occurs at the root. Similarly, the solution is to limit the seal gap according to the working pressure and properly select the Y-ring material. For Y-shaped seals with a working pressure greater than 16 MPa, a retaining ring or a special sealing ring with a retaining ring at the root should be used. The retaining ring usually uses a relatively rigid plastic material such as polytetrafluoroethylene, polyamide, and the like.
6, reverse pressure damage
When the silicone rubber seal is used as a piston for a 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 hydraulic cylinder piston rod and the guide sleeve, fluid is gradually infiltrated to form a pressure accumulation. When the working pressure is removed or during the complex movement, the pressure is higher than the working pressure, the shaped sealing ring is reversely pressed from the root in the mounting groove, and the lip tip is squeezed into the gap between the cylinder and the piston. The inside is pinched and causes back pressure damage.
The preventive measures against back pressure damage are:
Open a small hole in the piston to release the pressure accumulation. When the working pressure is removed, the trapped fluid can be drawn through the small hole to release the accumulated pressure.
Set the support ring. The support ring acts between the lips of the shaped silicone ring of the piston, against the sealing ring so that it cannot be axially swayed and is not reverse extruded. In addition, the groove portion is provided with a plurality of oil guiding holes around the circle, so as to facilitate the pressure medium to act on the concave portion of the Y-shaped sealing ring through the small hole, and open the lips of the Y-shaped sealing ring; at the same time, avoiding back pressure, so as to avoid The trapped oil drains smoothly and keeps the Y-ring sealed. This measure is more effective in preventing back pressure damage of the silicone seal.