Why would having a leaking seal be advantageous or desirable?

It may appear contradictory, but in instances where a rotating shaft needs to be sealed under pressure, utilizing a radial lip seal may be the appropriate solution.

Traditional non-pressurized radial lip seals operate by creating a sealing and lubricating oil film between the seal lip and the shaft surface. The mechanism for sealing relies on the seal actively pumping while being balanced by capillary suction forces on the air-side of the seal. The success of a radial lip seal in the long term is dependent on the presence of this thin lubricating film.

The two fundamental requirements of a radial lip seal present a challenge as they are often at odds with each other: the need for low leakage and low friction. Finding a balance is essential as applying more contact force can reduce leakage but also increase friction and wear. For non-pressurized lip seals, reputable manufacturers have typically achieved a satisfactory balance that meets customer expectations.

As the pressure requiring sealing intensifies, the force at the lip contact area also increases. This results in a decrease in the fluid film thickness and an increase in heat generated from friction. It is crucial to note that higher lip contact forces can potentially create mixed lubrication conditions beneath the seal lip, causing inconsistent lubrication. This may lead to alterations in the mechanical properties of the rubber in the contact region, attributed to additional vulcanization, physical and chemical aging, and oil absorption due to the rapid temperature elevation at the interface.

The engineering team at American High Performance Seals has determined that optimal service life can be achieved in pressurized conditions by strategically creating a controlled, small leak within the seal. This design ensures that the seal effectively handles fluid pressure while maintaining a thick lubricating film for full lubrication. By eliminating capillary suction forces, the seal's active pumping action will result in a minimal amount of fluid being pumped to the air side of the seal without any return flow.

In order to maintain a stable fluid film, the engineers at SNAK Seals have developed pressure-balanced seal designs. Unlike traditional seals that experience increased lip force with higher system pressure, resulting in high friction, heat, and wear, pressure-balanced designs have minimal changes in lip force and therefore preserve the fluid film.

It is advisable to install a secondary standard oil seal outside of the main pressure seal to address any minor fluid leakage that may occur past the pressure seal.

Are you in need of a unique seal design for your oil seals or high pressure seals? Look no further! China SNAK High Performance Seals has a team of experienced seal design engineers ready to assist with all of your high pressure oil seal requirements. Please reach out to us by phone or visit our Contact Us page to fill out a brief form detailing your specific seal needs promptly. Thank you for considering China High Performance Seals.