Rotary Shaft Seals
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About rotary shaft seals
Rotary shaft seals keep oil and grease from leaking out along rotating shafts and stop dirt and moisture getting in. Gearboxes, pumps, transmissions, electric motors and bearing housings are the most common applications.
The basic difference from seals for linearly moving cylinders is that the sealing lip runs continuously in the same track on the shaft surface. The hardness, roughness and grinding direction of the shaft surface therefore directly determine seal life; the wrong surface finish will make even the best seal leak before long. Most profiles have a garter spring in the lip, which keeps the lip's radial force on the shaft constant even as the material ages.
Products in this category are offered in NBR and PTFE-based designs. NBR is used in standard applications with mineral oil and grease. PTFE-based solutions are chosen for high surface speeds, high temperatures, a risk of dry running or aggressive fluids.
Across the product tables in this category, operating limits reach up to 300 bar and span −30 °C to +105 °C; standard rotary shaft seals usually work at very low pressure, and the higher values belong to special profiles designed to withstand pressure.
Applications include reduction gearboxes, hydraulic and centrifugal pumps, electric motors, shaft bearings on agricultural machinery and mixers. In these applications seal life is governed by three factors: surface speed, temperature and oil level. If the oil level drops below the lip, the seal runs dry, and dry running quickly burns the lip. Fitting the lip the wrong way round is also a common mistake: the lip must always face the fluid being retained.
Selection requires the shaft diameter, housing diameter and seal width, together with rotational speed and fluid type. We supply and support from OSTİM, Ankara.
Frequently Asked Questions
How is a rotary shaft seal size specified?
By three dimensions: shaft diameter, housing (bore) diameter and seal width, usually written in that order. They may be printed on the old seal; if not, measuring with a calliper is enough.
I fitted a new seal but it still leaks — why?
The most common cause is the shaft surface. Because the lip always runs in the same track, it gradually wears a groove in the shaft; a new seal sitting in that groove keeps leaking. In this case use a shaft repair sleeve or move the seal to a different axial position.
What is the difference between spring-loaded and springless types?
The spring keeps the lip's radial force on the shaft constant and maintains sealing even as the elastomer relaxes over time. Spring-loaded types are generally used for sealing liquid oil; springless types are used only for retaining grease or keeping out dust.