There are a different types of hydraulic seals within the hydraulic cylinder. They have their own specific function. Some seals are used to cope with extreme pressure, while others are used to keep dirt out of the system. Each of these seals needs to be specially selected based on their functionality. Wrong seal selection during hydraulic cylinder repair may affect the cylinder life, lead to poor performance, increase operating costs. let us know about different types of seals being used in hydraulic cylinders to get better understanding about hydraulic seals.
Dynamic Seals vs Static Seals :
Hydraulic PU Seals have mainly two types. These are dynamic seals and static seals.
Dynamic seals are used between two parts that are in relative motion – such as the rod, piston and cylinder barrel. Piston seals, Rod seals, Wiper seals, Wear rings are dynamic seals. Due to the relative motion, dynamic seals must have more elastic strength, more abrasion resistance and are often designed to run on a film of hydraulic fluid.
Static seals are used between two parts that do not more. It creates a barrier between those static parts. That is why, static seals material may be less flexible and the material may be more heat and pressure resistant. Static seals are used in different locations in the Hydraulic cylinder depending on the design. Usually static seals are used between the piston and piston rod and between the head and cylinder bore tube.
Piston-rod seals :
Piston-rod seals are single acting U-symmetric seal. It is designed to have symmetrical lips in order to be used in both for rod and piston application. It has mechanically trimmed lips. Therefore, it creates excellent contact pressure in both dynamic and static one-way sealing.
Piston Seals :
Piston seals are located between the piston and the cylinder wall in a cylinder. It creates a pressure barrier and prevent fluid passing the piston. This pressure is required to control the cylinder motion or to maintain the position of the piston when at rest. Clearance between piston and cylinder wall is extremely tight. Piston seal has a vital role to maintain the relationship between these reciprocating components. Thus, correct seal size and material is critical to the performance of the cylinder.
Rod Seals :
Rod seals are ring of flexible elastomer (PU, Rubber) material. It is located between the reciprocating cylinder rod and the cylinder wall. Its function is to keep pressurized fluid contained within the cylinder. Therefore rod seal is very critical to the operation of the cylinder because it prevent fluid leakage from the cylinder to out side and maintain operating pressure required to move the actuator. Rod seals are also designed to maintain a thin film of fluid as the cylinder rod extends and retracts, which is very important to lubricate the rod, wiper seal and prevent rod corrosion.
Wiper Seals :
Wiper seals are located at the mouth of the cylinder barrel. This seal is usually visible when some one inspects a cylinder externally. The role of the wiper seal is to clear contaminants from the rod as the cylinder rod extends and retracts. The wiper seal also serves to retain the internal fluid lubrication film on the rod as it retracts.
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