Why is lip sealing essential?
A lip seal is simply a piece of rubber that holds lubrication in place to lubricate rotating components. However, this small piece of rubber plays a vital role in the functioning of the gearbox.
Almost all gearboxes on the market today use a contact lip seal. For some applications, users prefer a single lip seal, while other applications require a more robust solution. Lip seals in gearboxes perform two main functions: they maintain gearbox lubrication and prevent contaminants from entering (resulting in long-term damage).
Single lip seal
A simple single lip seal is the standard sealing option in many gear and drive applications. This seal configuration features a single inward-facing sealing lip to maintain lubrication within the gearbox.
The single lip performs double duty while also keeping contaminants out, a task it is not well suited for. Over time, dirt and debris will build up under the seal and eventually the seal will fail. Users often choose a single-lip sealing solution for simplicity in light-duty applications.
Single lip seal with dustproof lip
A single lip dust lip seal consists of two lips used together in a single seal. The outer rim is designed to keep out dirt, contaminants and debris, while the inner rim traps oil.
The single lip seal with dust lip is an improvement over the simple single lip design. The disadvantage of this configuration is that it prevents the lubricant from reaching the outer rim. Over time, contaminants and temperature will break down the outer rim, causing it to fail. With this failure, dirt and debris accumulate against the primary (inner) sealing lip. This very fine debris eventually builds up under the seal, creating an abrasive paste, like wet sandpaper. Slowly, friction works its way into the shaft, creating a leak and eventually causing the seal to fail.
Labyrinth sealing system
A labyrinth seal is an advancement in design from the standard single seal or single edge dust seal. They feature a series of small, narrow channels to provide very high levels of flow resistance. Labyrinth seals come in many variations, but all feature a series of small, narrow channels to reduce the amount of dirt and debris in contact with the sealing surface. There are also non-contact labyrinth seals, used in high-speed applications to avoid the heat generation that accompanies contact seals, but they are not a true seal and do not provide any static sealing capabilities.
Some variations of the labyrinth seal design include an integrated lip seal to seal statically and improve dynamic oil retention. Most gearbox labyrinth seals are equipped with a drain to prevent oil accumulation behind the seal, as their dynamic sealing performance is generally lower than that of standard lip seals.
