1. Sealing ring hardening and oxidation due to heat
① Reason: As the working temperature exceeds the normal use range, the elastomer hardens, and the plasticizer evaporates and oxidizes, resulting in small surface cracks perpendicular to the direction of the applied pressure on the seal ring, resulting in local dents or cracks. This failure mainly occurs on dynamic and static seals exposed to the air or in contact with other air pollutants.
② Solution: Use materials with good antioxidant properties and high-temperature resistance to reduce the operating temperature of the system oil.
2. The seal ring fails due to bulging, biting, and spiraling
① Reason: The main reasons for bulging and biting failure: the sealing gap is too large, the system pressure exceeds the sealing pressure strength or the back-up ring is not added, the sealing ring material does not meet the design hardness requirements, the processing size of the sealing ring sealing groove does not meet the standard requirements, the sealing ring is not selected properly (relative to the sealing groove size is too large), etc.
The main reasons for spiral failure: the concentricity of the parts being too low, the lubrication is not sufficient, the sealing ring material being too soft, when some parts of the sealing ring are sliding while the other part is rolling, causing distortion or cracks.
② Solution: Reduce the sealing gap, select the sealing ring of the right size, and ensure that the concentricity of the parts meets the design requirements; the sealing groove is strictly processed according to the standard, and an enhanced composite seal is used, such as a combination gasket, and the sealing ring material that meets the design requirements or a retaining ring is added to prevent the sealing ring from being squeezed out.
3. The sealing ring is damaged during installation
① Reason: This situation often occurs in dynamic and static seals. The main reason is that there are sharp edges on the sealing groove or the chamfered corners that do not meet the standards. No lubricant is applied during installation, so the sealing ring is cut by the sharp edge, twisted or stuck, and the surface has concave (or convex) marks, peeling, or peeling.
② Solution: Process the sealing groove according to the design requirements, and no sharp edges should be left. Apply lubricant on the groove and sealing ring during installation. When the sealing ring passes through the thread, put a metal sheet or belt on the thread to allow the sealing ring to be inserted smoothly.
