Different Types Of Bearing Seals

A contact seal, also known as a lip seal, is a rubber part (typically Buna-N and nitrile) bonded to a steel insert. This seal is designed to apply continuous pressure on a bearing’s inner ring, which is why it is aptly named a “contact” seal.

Pros: By providing direct contact with the inner ring, contact seals make it extremely difficult for contaminants like dust, dirt, and moisture to reach the inner parts of your bearing. Contact seals also do an excellent job of sealing lubricants inside your bearing.

Cons: The trade-off for premium sealing performance is that contact with the inner bearing produces both friction and heat. Added friction and heat can damage both the bearing and the seal and lead to premature part failure. Friction can also reduce the maximum speed of the bearing, so you’ll need to weigh your need for top-end sealing performance with the potential for wear and tear and loss of top speed.

Like contact seals, non-contact seals (typically Buna-N and nitrile rubber parts) are bonded to a steel insert. The main difference between the two is that non-contact seals are fixed to the outer ring and do not apply pressure to the inner ring of your bearing.

Pros: While non-contact bearings do not touch the inner ring, they feature a thin lip that rests adjacent to it. This design protects against contaminants and leakage, just not to the same degree as a contact seal.

Cons: However, the lack of contact with the inner bearing produces less friction, which can prevent overheating and other potential issues.

A labyrinth seal is a type of bearing isolator that combines elements of contact and non-contact seals in a single component. The idea of a labyrinth seal is to prevent leakage and contamination by creating a difficult path for both substances to follow. Labyrinth seals are composed of multiple pieces — one that remains stationary and another that rotates with the system. The two pieces interlock and create a thin, grooved path that is long and difficult for substances to escape or penetrate the bearing.

Pros: The complexity of a labyrinth seal allows it to provide excellent sealing capabilities. In addition, it can fend off contaminants and prevent leakage without contacting the inner ring. As such, labyrinth seals offer the sealing capabilities of a contact seal while limiting added friction like a non-contact seal.

Cons: Although labyrinth seals offer the best of both contact and non-contact seals, there are some potential downsides.

1. The complexity of the design may require more physical space than other seals, which can be difficult to manage depending on your application.
2. This same complexity can cause labyrinth seals to be more expensive than other sealing options. As such you’ll need to weigh the added benefits of these parts to determine if they make long-term sense for your situation.