Housing seals: felt, lip, labyrinth, taconite

The choice in one table

Circumferential speed is not rpm. It follows from shaft diameter and rotational speed — a ⌀90 mm shaft at 500 rpm gives about 2,4 m/s, so felt is fine. At 1500 rpm it is already 7 m/s and felt is out.

Above 100 °C felt is out — a temperature-resistant seal is required.

Felt — simple, but needs preparation

The felt seal is standard in SNI housings. It allows a circumferential speed of up to 4 m/s.

Before fitting, the felt strip must be soaked in warmed oil for several minutes — dry felt does not seal and wears through quickly. This is the step most often skipped during assembly.

Above 100 °C operating temperature the felt seal should be replaced with a temperature-resistant one.

Lip — twice as fast, but needs a polished shaft

The double lip seal is split and allows a circumferential speed of up to 8 m/s.

Two things during assembly: the gap between the two lips must be filled with grease, and the sliding surface on the shaft must be polished. A rough shaft will wear the lip out in weeks.

Labyrinth — non-contact, for high speeds

For high speeds and difficult conditions the manufacturer recommends a single or double labyrinth. The seal does not touch the shaft, so it does not wear and does not limit speed.

The supplied Perbunan cord goes between the labyrinth ring and the shaft — it makes the ring rotate with the shaft. Permissible misalignment between shaft and housing is 0,3°.

For continuous operation above 100 °C the cord must be of heat-resistant material. When regreasing the bearing, regrease the seal centre too where possible.

A double labyrinth can additionally be filled with grease through a nipple — extra sealing without changing the design.

A labyrinth is bought together with its Perbunan cord. Without it, it does not work.

Taconite — where dust gets everywhere

Taconite is the seal for the hardest conditions: aggregate, rock dust, cement. The manufacturer offers it in a standard and a special execution.

For genuinely extreme conditions the catalogue refers you to the manufacturer's technical department — and that is the honest answer, because such cases cannot be settled from a table.