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Matters Needing Attention when Installing Hydraulic Cylinder Sealing Ring

2021-08-31

Matters needing attention when installing hydraulic cylinder sealing ring

1. Before installation, the surface quality of the seal should be checked, and there should be no flashes, burrs, cracks, and cut edges. For defects such as pores and looseness, the geometric size and accuracy of the seal must meet the standard requirements. The combined sealing ring for the hole is composed of an O-ring and a wear-resistant ring. Because the O-ring is more elastic, it is easier to install; while the wear-resistant ring is less elastic. If it is installed directly, the steps and grooves of the piston will easily scratch the sealing surface, which will affect the sealing effect. In order to ensure that the wear ring is not damaged during installation, certain installation measures should be taken.

2. The wear-resistant ring is mainly made of filled PTFE material, which has the characteristics of corrosion resistance and large thermal expansion coefficient. Therefore, it is soaked in oil at 100°C for 20 minutes before installation to make it gradually soft.

3. The expansion sleeve is made of 65 Mn steel with good elasticity after heat treatment, and processed into a uniform and symmetrical 8-petal structure. The head of the positioning sleeve has a 5º chamfer, which is used to guide the O-ring and wear ring into the groove at the end of the piston. It should be noted that when processing the small holes at the bottom of each petal, the indexing should be even. When milling each petal, the saw cut should be aligned with the center of the small hole to ensure that each petal of the expansion sleeve can expand evenly. At the same time, all parts should be chamfered to avoid damaging the sealing ring.

4. Another type of seal is a Y-shaped sealing ring made of polyurethane material, which is widely used in hydraulic cylinders because of its high hardness, high elasticity, oil resistance, wear resistance and low temperature resistance. Its inner and outer lips can be made into different height shapes according to the shaft or hole to play a role of sealing and self-protection. Y-shaped ring with unequal height, its short lip is in contact with the sealing surface, the sliding friction resistance is small, the wear resistance is good, and the life is long; the long lip and the non-relatively moving surface have a large amount of pre-compression, and it is not easy to move during work. Polyurethane Y-shaped ring has high hardness and large amount of pre-compression. During installation and replacement, the sealing ring is often squeezed, rolled, undercut and other damages, which will not provide the proper sealing effect or even fail. When assembling, use a screwdriver to press the sealing lip inward along the cylinder diameter; or tie the outer lip of the sealing ring tightly with a thin iron wire to make the outer diameter smaller than the inner diameter of the cylinder, and then send the sealing ring into the cylinder, and then pull out the thin iron wire . But these two installation methods are easy to scratch the sealing ring, leading to sealing failure and increasing maintenance time. In response to this situation, use a 0.1mm thick cold-rolled steel strip or copper sheet to cut it into a rectangle with a length equal to the circumference of the outer diameter of the Y-shaped ring, and then use it to wrap the sealing ring tightly, and then bit by bit. Send it into the cylinder barrel of the hydraulic cylinder, and then pull it out after the outer lip has all entered the cylinder barrel. The installation effect is better.

5. Each type of seal ring should have a set of corresponding tooling to ensure its assembly requirements. After installation, the sealing ring is not allowed to be wrinkled, twisted, scratched, or reversed. The threaded holes on the cylinder barrel of the hydraulic cylinder are often arranged after the welding process, so burrs will inevitably occur at the junction between the outlet of the threaded hole and the inner wall of the cylinder. In order to remove burrs, special tools must be designed and manufactured to process them to achieve the purpose of smooth transition.

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