Seals
Seal families for heavy industry: what each type is for
Quick answer
Radial shaft seals, V-rings, metal face seals, cassette seals, housing seals, heavy-duty shaft seals, machined polyurethane seals and hydraulic seals, with where each one fits.
Three levels of supply
Seals come in three levels. Standard catalogue seals fit common shaft sizes and are quick to get. Customised catalogue seals use a standard design in a non-standard size, often without new tooling. Engineered seals are built for one application, such as a trunnion or a roller bearing in a vertical mill.
Seal families and where they fit
| Family | What it does | Typical places |
|---|---|---|
| Radial shaft seals | Lip seal on a rotating shaft, retains oil, keeps out dirt | Gearboxes, pump and conveyor drives |
| V-rings | Rubber rings that rotate with the shaft and throw off dirt; often used as an outer guard | Over the main seal on dusty drives |
| Wear sleeves | Thin hardened sleeve on the shaft, gives the lip a fresh running surface | Worn shafts, repair work |
| Housing seals for plummer blocks | Made to suit the housing and keep grease in and dust out | Fans, conveyors, crushers |
| Metal face seals | Two hard, lapped rings pressed together, with rubber rings as energisers | Wheel hubs, idlers, track rollers, mixers |
| Cassette seals | A complete seal and wear surface in one unit | Wheel ends and driveline parts |
| Heavy-duty shaft seals | Large rubber, fabric-reinforced or metal-reinforced seals, often split | Mills, large gearboxes, kiln drives |
| Machined polyurethane seals | Cut from stock in any diameter, can be welded on site | Large rotary and hydraulic jobs |
| Hydraulic seals | Rod, piston, wiper and guide parts | Cylinders on mobile and fixed machines |
| Track pin seals | Seal the pins in crawler tracks | Bulldozers, excavators, track vehicles |
Rules of thumb when choosing
- Choose the seal for the main duty first: oil retention, dust exclusion, pressure or heat
- For dusty drives add a V-ring or a labyrinth in front of the lip seal
- Check the shaft surface: hardness, finish and wear decide the seal life
- For large or hard-to-reach shafts check whether a split or weldable seal exists
- Keep the seal material compatible with the oil or hydraulic fluid
Link to failure analysis
When a seal fails, look at the pattern on the lip, the shaft and the grease. The seals failure-mode guide shows what each pattern means.
Takeaway. There is a seal family for each duty. Pick by duty, then by size and material, and check the shaft surface before you fit it.
Put it to work in the tool