Working Principle of Step Seal

The step seal obtains initial preload from the O-ring. Medium pressure pushes the stepped PTFE slide ring tightly onto the piston rod, creating a self-energized single-acting seal with continuous wear compensation for high-pressure and low-friction reciprocating sealing. Its working process is described below:

• No-pressure / Low-pressure Condition (Static State & Low-pressure Startup)

During assembly, the O-ring is pre-compressed. Driven by rubber elasticity, it expands radially outward and pushes the stepped PTFE slide ring to closely fit the piston rod surface, establishing initial contact pressure to achieve low-pressure sealing and prevent medium leakage

• System Pressure Build-up (Core: Self-energizing Effect)

High-pressure hydraulic medium flows into the rear area of the stepped slide ring, and pressure acts on the back of the PTFE slide ring. The pressure presses the slide ring further against the piston rod. The higher the system pressure, the greater the contact pressure between the slide ring and rod surface, and the better the sealing performance. PTFE features an extremely low friction coefficient, enabling smooth reciprocating movement and resistance to stick-slip.

三、Dynamic Reciprocating Operation & Automatic Wear Compensatio

During reciprocating motion of the piston rod, the PTFE slide ring offers wear resistance and low friction. After slight wear occurs on the slide ring during long-term operation, the O-ring continuously expands outward to automatically compensate for the wear clearance and maintain sealing contact stress.

四、Additional Function of Stepped Profile

The unique stepped contour can scrape the residual thin oil film on the piston rod back into the high-pressure chamber. This keeps the friction surface well lubricated and limits leakage. The stepped structure also has better extrusion resistance than standard rectangular rings.