Hydraulic & Fluid Seals

Contaminants can cause significant damage to the rod, cylinder wall, seals, valves and other components. One of the primary causes of premature seal and component failure in a fluid power system is contamination. It should be noted that rod seal failure is normally a swift result of wiper failure. Particular attention should be drawn to the selection of the wiper, and the following should be taken into consideration:

• Groove Geometry
• Lip Geometry
• Environment

Groove Geometry:

• Snap-in design (Fig.1)
  Generally the least expensive wiper, it is more costly to machine the groove; however, this style provides the best long term wiping performance.
• Press-in design (Fig.2)
  The wiper designed for press-in installation is typically more costly, while the machining of the gland is less costly.

(Fig.1) Snap-in design	(Fig.2) Press-in design

Lip Geometry:

When the rod extends past the rod seal, a thin film of oil remains on the rod trapped in microscopic surface imperfections. The thickness of the oil film depends upon the surface finish, rod seal and surface speed of the rod. During the return stroke, this thin film can be removed by an aggressive wiper lip, resulting in system leakage. It is important to properly pair the wiper and rod seal. If the wiper and the rod seal are not matched, leakage and premature failure can occur. An aggressive wiper lip requires an aggressive rod seal lip design or a redundant High-Performance Sealing System.

Further considerations are the lip geometry. We distinguish between:

• Single lip, straight wiper lip design (Fig.3) is the most aggressive. It offers the best scraping and dirt removal performance and is recommended for most sealing applications with high contamination.
• Single lip, beveled wiper lip or chamfered wiper lip (Fig.4) is less aggressive. The beveled lip allows the microscopically thin oil film on the rod to be retracted back into the system while providing adequate dirt exclusion in less contaminated environments.
• Single lip, rounded seal lip is the least aggressive sealing lip and is typically used in pneumatic applications to maintain a microscopically thin oil or grease film on the rod to keep the piston bearing and seal lubricated (Fig. 5).
• Double or redundant wiper lips (Fig.6) are one of the most effective ways to improve a system’s sealing performance. This wiper design must be paired with one of our Long-Life Rod Seals to provide for the driest long-life rod sealing available. It eliminates the release of built-up fluid pressure (pressure trap) between the wiper and the rod seal, also known as “burping,” by releasing built-up fluid pressure back past the rod seal into the system.

Wiper with single lip	Fig.3 straight wiper lip	Fig.4 beveled wiper lip	Fig.5 rounded wiper lip

Fig.6 Wiper A15 with double or redundant sealing lips

Environment:

In applications where the equipment is exposed to heavy dirt, mud and moisture, all-weather conditions or where the rod of the cylinder is vertical or upward orientated, it is possible for moisture or other contaminants to get past the wiper, leading to corrosion and damage of components and seals. For these applications, we offer High Contaminated Environment Wipers (Fig.7, Fig.8) with specific design features incorporating an accurate closure between the housing and the wiper outside diameter (OD) to keep contamination out on both the dynamic and static surface OD.

Fig.7 Wiper A15	Fig.8 Wiper W51
Examples of wipers for high contaminated environments.

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Other wiper designs available

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• American High Performance Seals designs and manufactures some of the most durable wipers complying with ISO 9000 quality standards.
• We utilize advanced materials engineered specifically to offer maximum durability and sealing performance.
• We provide a comprehensive range of wipers and material options to meet industry’s challenging fluids, temperatures, surface speeds.

Applications & Industries

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