Seals in Linear Actuators

Static Seals that have been grouped into static and dynamic applications. Static seals are fitted between two rigidly connected components. The seals between the piston rod and the piston, preventing external leakage past the joint where the tube is mounted onto the cap.

The requirement for seal in line actuator may vary depending upon the nature of hydraulic fluid. Some of the common types of seals are as follows:

Dynamic Seals prevent leakage between components which move adjacent to each other. Therefore, such seals are subject to wear, whereas static seals are wear free. The seals between the moving piston and the stationary actuator tube are generally dynamic seals. The seals which stop hydraulic fluid from escaping past the clearance gap between the moving piston rod and the end cap are also dynamic. The rod-wiper ring, which prevents contaminants from being drawn into the actuator when the rod retracts are also considered as a dynamic seal.

Another type of seals, the O-ring type seals are generally used as static seals. They may range from simple Chevron type compression packings to complex moulded cup or lip seals. Chevron seals are less suitable for smooth piston movement at low pressures and speed, but are an excellent seal for high system pressure and high stroking speeds.

Lip-ring seals provide good sealing even under stationary piston conditions. Lip-ring and glide-ring seals are used for applications where exceptionally low friction is required. For glide-ring seal applications, the piston is fitted with guide rings.