Labyrinth joints are bearing protectors that are installed in equipment as an alternative solution to shaft output seals.. Labyrinth seals can be mounted on process pumps, agitators, mixers, metering screws, hammer mills, impact mills, motors, gearboxes and fans, among other rotating machines.
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Functions of labyrinth seals
The labyrinth joint design consists of a stationary part (stator) and a rotating part (rotor) that are assembled together. The secret of labyrinth seals is that they perform three functions simultaneously:
- Hold the stator and rotor together.
- Prevent lubricant leakage of the bearing.
- Preventing the entry of contaminants such as dust, splashes from washing or projections of accidental fluids.
The rotor of the labyrinth seals has a O-ring with the dual purpose of making sealing gasket for the bearing lubricant and drive the rotor so that it turns in tight alignment with the shaft. On the other hand, the stator has one or two O-rings for attachment to the process equipment housing.
Labyrinth gasket materials
The materials available for the labyrinth joints are polytetrafluoroethylene (PTFE) o Teflon® (with FDA O-rings), bronze, stainless steel, aluminum and other materials to withstand the most extreme conditions. Labyrinth seals Teflon® Teflon have been developed for effective protection of the bearing from ingress of splashing or splashing of corrosive liquids such as acids and bases or water. For general protective services there are the labyrinth joints metallic with a degree of protection up to IP 66.
At very dusty environments such as grinding mills, cement, ceramics, tile or aggregate plants, it is recommended to have a labyrinth joint incorporating a particulate filter to retain incoming dust. Labyrinth seals have the great advantage that they work dry, i.e. without lubrication. Consequently, the mixture of dust and grease that slowly erodes the seal lip is avoided.
Sometimes the labyrinth seal bearing can be damaged by eddy current discharge, especially in electric motors. To combat this problem we have labyrinth joints with conductive elements that divert these currents. These labyrinth joints allow:
- Avoid discharge on the balls.
- Prevent the formation of stretch marks in the bearing raceways.
- Prevent lubricant leakage by acting as sealing gasket.
- Prevent the entry of pollutants.
Assembly of labyrinth seals
For the installation or assembly of the labyrinth seals, no specialized tooling is required since are usually installed by hand. In particular cases of difficult mounting conditions, a split mounting can be chosen, thus avoiding the opening of the machine by bolting the two halves of the labyrinth to the shaft.
It is also possible to replace the seals of the saddles or split bearing supports with labyrinth joints. For this purpose, the stator is specially machined to fit into the groove of the saddles, thus preventing the plug from being ejected due to excessive lubrication pressure.
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