Floating seal is a contact-type sealing device consisting of two hardened metal rings (typically alloyed cast iron) and two elastomeric O-rings that press them against each other, used primarily in heavy-duty mobile equipment — bulldozers, excavators, mining trucks — where rubber lip seals cannot withstand abrasive soil, mud, and impact loads.
Operating principle: one metal ring is fixed to the stationary housing, the other rotates with the shaft. Two O-rings seated behind each metal ring provide the axial force that holds the flat faces of both rings in contact — creating a metal-to-metal sealing interface. This interface is ground flat to Ra ≤ 0.4 µm and hardened to ≥ 58 HRC to resist wear.
A floating seal is not a conventional dust shield. It operates at low speeds (< 300 rpm) under heavy load, temperatures up to 150°C, and in soil and mud environments — conditions where lip seals or shaft seals wear out within a few hundred hours. NTN and NSK supply floating seals standardized for heavy equipment track roller assemblies. See all seal types compared at bearing seals and shields guide and browse deep groove ball bearings with 2RS seals for lighter-duty environments.
Construction and Technical Parameters
Floating seals are selected by the inner diameter (d) of the metal ring, matched to the housing pocket dimensions. Example: floating seal size 108 mm (d = 108 mm) installed in the track roller assembly of a D6 bulldozer, mating with spherical roller bearing 22218 EK (d = 90, D = 160, B = 40 mm, C = 228 kN).
Typical parameters for an industrial floating seal:
| Parameter | Typical Value |
|---|---|
| Metal ring material | Wear-resistant alloyed cast iron |
| Surface hardness | 58–62 HRC |
| Contact surface finish | Ra ≤ 0.4 µm |
| O-ring material | NBR (−30°C to 120°C) or FKM (to 200°C) |
| Maximum speed | 200–400 rpm (size-dependent) |
| Internal pressure | ≤ 0.1 MPa (internal oil lubrication) |
| Allowable eccentricity | ± 0.3–0.8 mm (size-dependent) |