Rotary shaft lip seals

Frequently asked questions — Rotary Shaft Seals

• How do I choose between an AS, BASL or BAUSL profile seal?

  The choice depends on the level of protection required against contaminants. The AS profile is a lip seal with a preload spring intended exclusively for inward lubricant retention. To also block dust, the BASL profile adds an outer lip without a spring. In heavily contaminated environments, the BAUSL or TC profile is recommended, as it incorporates a triple lip for enhanced sealing.
• Which material should be selected for a high-temperature application?

  NBR, the standard material, is limited to a range of -30 to +100 °C. For higher temperatures, FKM (Viton) is essential as it withstands +200 °C continuously and up to +230 °C peak. For the most severe conditions, including temperatures up to 250 °C and exposure to aggressive fluids, PTFE seals are recommended.
• What are the shaft requirements to guarantee sealing performance?

  The surface finish of the shaft seat is critical and must exhibit an Ra value between 0.2 and 0.8 µm after grinding, with no turning helix whatsoever. Hardness must reach a minimum of HRC 30, rising to HRC 45 for high-speed applications. If the seat is worn or poorly machined, a fitted Speedi-Sleeve wear sleeve can restore the surface without additional machining.
• What is the performance difference between NBR and FKM?

  NBR is suited to standard conditions with peripheral speeds limited to 14 m/s. FKM (Viton), on the other hand, offers superior resistance allowing peripheral speeds of up to 25 m/s. These capabilities make FKM an essential choice for combustion engines and gearboxes subjected to high thermal and mechanical stresses.
• When should a 100% rubber seal be selected?

  While the standard seal generally features a metal casing in zinc-plated steel or AISI 304 stainless steel to ensure rigidity, it can be overmoulded with elastomer or supplied in a 100% rubber variant. This unreinforced version is specifically suited to housings with machining defects or made from plastic materials, thereby facilitating insertion and sealing despite imperfections in the support.