Labyrinth seals for
idler rollers
Moulded polyamide seal sets for conveyor belt idler rollers. Four-piece sets for bearings 6204, 6205, 6206 and 6305, in PA6 and PA66. In continuous production since 2013.
Two jobs that pull against each other
The seal set closes the gap between the rotating roller shell and the stationary spindle. It has to retain grease on the inboard side and prevent the ingress of dust, grit and water on the outboard side — and add no drag doing either.
Most idler bearing failures are not wear. They are contamination. Fine dust that achieves ingress past the seal mixes with the grease into an abrasive paste that laps the raceway on every revolution. Water brings corrosion products that do the same. Coarser particles dent the raceway outright. In each case the bearing is not worn out; it is being destroyed by material that should never have reached it.
On a long conveyor with several hundred idlers, that is not one failure. It is a replacement programme.
Excluding contamination without touching anything
A labyrinth seal works by geometry rather than contact. The path between the rotating and stationary members is long and folded, and rotation flings incoming particles outward before they can travel inward. Nothing rubs. That gives four advantages over a contact lip seal:
A lip seal loses contact as it wears, and from that point permits the ingress it was fitted to prevent. A labyrinth has no contact to lose.
Lip friction is a real share of motor load once it is multiplied by several hundred rollers.
Heat is what breaks lubricant down. A non-contact seal generates none.
Lip sliding speed caps roller RPM. A labyrinth does not.
Four moulded pieces per roller end
The set assembles into the roller end in this order, working inward from the outside face:
| Order | Component | Function |
|---|---|---|
| 1 | Rain cap | Outermost closure. Sheds water and falling material before either reaches the labyrinth. Takes the direct strike from lump and stone. |
| — | Metal cap | Metal retaining cap. Not part of the seal set — shown only to place the plastic components correctly. |
| 2 | Fix seal | Stationary on the spindle. Forms the outer half of the labyrinth. |
| 3 | Rotary seal | Rotates with the shell. Forms the inner half of the labyrinth, and flings incoming particles outward. |
| — | Bearing | Not supplied by us. 6204, 6205, 6206 or 6305 to suit. |
| 4 | Back seal | Innermost. Provides the seating face that sets the bearing squarely in the shell, and closes the inboard side against grease loss. |
A set is four moulded pieces: rain cap, fix seal, rotary seal and back seal. The metal cap and the bearing are not included.
How the set assembles
Sized to the bearing
Seal sets are sized to the bearing fitted in the roller. The seal's outside diameter and spindle bore match the bearing's outside diameter and bore.
| Set | Bearing | Bore | OD | Width | Typical duty |
|---|---|---|---|---|---|
| 204 | 6204 | 20 mm | 47 mm | 14 mm | Return rollers, light-duty idlers |
| 205 | 6205 | 25 mm | 52 mm | 15 mm | General material handling |
| 206 | 6206 | 30 mm | 62 mm | 16 mm | Medium to heavy duty |
| 305 | 6305 | 25 mm | 62 mm | 17 mm | Heavy duty, long-centre conveyors, mining and bulk handling |
Roller shell diameter and spindle size vary between manufacturers. Send a roller drawing or a sample end assembly with your enquiry and we will confirm the correct set.
PA6 or PA66, specified per order
| Grade | Properties | Specify for |
|---|---|---|
| PA6 | High impact strength, good toughness, excellent wear resistance | General material handling, standard ambient duty, impact and stone-strike positions |
| PA66 | Higher stiffness, higher heat-deflection temperature, better dimensional stability | Hot conveyed material, higher roller speeds, heavy abrasive duty, sustained high ambient temperature |
Where the application is uncertain, PA6 is the safe default. PA66 is chosen when temperature or long-term dimensional stability governs.
Priced per set
A set is the four moulded pieces for one roller end — rain cap, fix seal, rotary seal and back seal. A complete roller takes two sets, one at each end.
Metal caps and bearings are not supplied.
What to send us
- Bearing size — 6204, 6205, 6206 or 6305
- Material grade — PA6 or PA66
- Quantity, in sets
- Roller manufacturer, or a drawing reference
A.B. Plastech · Modern Industrial Estate, Bahadurgarh, Haryana
+91 94160 55854 · info@abplastech.co.in