The rod seal is designed to ensure that pressurized fluid does not leak out of the system as the rod cycles back and forth out of the gland (dynamic pressure sealing).
The rod seal is the most critical seal on any type of fluid power equipment. A leaking rod seal not only reduces equipment performance, but also causes environmental issues. Our rod seals are available for both:
Single-acting Rod Seal :Single acting rod seal are capable of sealing dynamic pressure from one side (unidirectional).
Double-acting Rod Seal : Double acting rod seal are capable of sealing dynamic pressure from both sides (bidirectional)
We, at Sam Engineers give particular attention to selecting the best rod seal for your application. It is important to properly pair the rod seal and the wiper for the best sealing performance. If a less aggressive rod seal is paired with an aggressive wiper, the wiper can scrape off the microscopically thin film of oil that remains on the rod in microscopic surface imperfections during the return stroke, resulting in system leakage. The thickness of the oil film depends upon the surface finish, rod seal and surface speed of the rod.
Seal Design Considerations:
- Non-symmetrical Rod Seal Design
- Lip vs. Squeeze Type Seals
- Seal Lip Geometry
Non-symmetrical Rod Seal Design
Our rod seals are non-symmetrical lip or squeeze type rod seal designs in which the diameter of the seal is oversized (Fig.2), and are available for both bidirectional and unidirectional applications. This rod seal design creates a hoop pressure and ensures a high static sealing force over the entire surface of the outside diameter of the seal, providing significantly higher stability of the seal during operating cycles and eliminating rocking and pumping effects, thereby improving sealing performance. Instability of a seal can create leakage and seal damage.
- Non-symmetrical rod seals are seals where the shape of the outside diameter lip differs from the inside diameter (see Fig. 1).
- Non-symmetrical rod seals provided by AHPSeals are not centered in the gland and provide sealing contact (hoop pressure) with the gland across the entire surface of the outside seal diameter (Fig. 2).
- Non-symmetrical rod seals provide better sealing performance than symmetrical seals do.
Lip vs. Squeeze Type Seals
The basic design of a rod seal significantly affects the overall function of the seal, especially at low pressures. One of the most challenging applications is linear dynamic sealing at low pressure while providing low breakaway and running friction. AHP Seals provides a series of low-friction seals for these challenging applications.
- Lip seals: are without any energizing rubber elements; therefore, they provide a more flexible dynamic seal lip and are generally characterized by low friction, low wear and poor low-pressure sealing capabilities.
- Squeeze seals: typically incorporate an energizing rubber element and are generally characterized by high friction, high wear and good low-pressure sealing. To avoid a pressure trap between two seals and potential seal failure, do not use energizer-loaded seals for back-to-back bidirectional piston sealing applications.