The TC oil seal is one of the most commonly specified rotary shaft seal profiles in general industrial equipment. If you have replaced a seal on a gearbox, motor or pump, there is a fair chance it was a TC type. This article explains what the designation describes, how the seal works, and what to check when ordering and fitting a replacement.
What the TC designation describes
TC is a profile designation widely used in the trade for a rotary shaft seal with the following features:
- a rubber-covered outside diameter;
- a metal reinforcing insert;
- a spring-loaded primary sealing lip;
- an additional dust lip on the air side.
Profile designations are not uniform across the industry. Other designations, such as NSE, also appear in catalogues and on old seals, and the same letters do not always mean the same thing from one supplier to the next. Confirm any designation against a drawing or a sample before ordering.
How a TC seal works
Each feature has a specific function.
Primary sealing lip and spring
The primary lip faces the lubricant and runs on a thin film of it on the shaft surface. The garter spring behind the lip helps maintain the radial load on the shaft as the lip wears and as the rubber relaxes with time and temperature.
Dust lip
The dust lip faces the air side and helps keep dust, dirt and splashed moisture away from the primary lip. It is not spring-loaded and it is an excluder, not a second oil seal.
Rubber-covered outside diameter and metal insert
The metal insert gives the seal its rigidity and keeps it seated in the housing. The rubber covering provides the press fit and the static seal in the bore, and it is more forgiving of minor imperfections in the housing surface than a bare metal case.
Where TC seals are typically used
TC seals are used wherever oil or grease has to be retained on a rotating shaft and the surroundings are moderately dusty or damp: gearboxes, electric motors, pumps, axles and hubs, conveyor rollers and general machinery. They are standard lip seals, so they are not intended for significant pressure, and very heavy contamination may call for additional exclusion ahead of the seal. Whether a TC seal suits a particular speed, temperature or pressure depends on the compound, the seal design and the application, and should be confirmed against the supplier's data.
How to specify a replacement
A complete description avoids delays. Collect:
- Size: shaft diameter, housing bore diameter and width.
- Profile: the designation on the old seal or drawing, confirmed against a sample or a sketch of the cross-section.
- Material: NBR is the usual general-purpose choice for mineral oils and greases; FKM is commonly selected for hotter or chemically more demanding duties. See our comparison of NBR and FKM seals.
- Operating conditions: media, temperature, shaft speed and any pressure.
- Markings: any numbers or letters moulded on the seal face, noted exactly as they appear.
For the full selection process, see how to select a rotary shaft seal.
Installation points worth getting right
Many early leaks trace back to fitting rather than to the seal itself.
- Inspect the shaft. If the old lip has worn a groove, repair the shaft or arrange for the new lip to run on a fresh track.
- Check that the shaft end and the housing bore have lead-in chamfers and no burrs.
- Fit the seal with the spring-loaded lip facing the lubricant.
- Lightly lubricate the lip and the shaft before assembly. A small amount of grease between the sealing lip and the dust lip is common practice so the dust lip does not run dry.
- Cover keyways, splines and threads with a sleeve or tape so they cannot cut the lip.
- Press the seal in squarely with a tool that bears on the outer part of the seal face. Avoid striking the seal directly with a hammer.
Need help with a TC seal?
We supply TC and other oil seals in a range of sizes and materials. Send the shaft, housing and width dimensions, the media, temperature, pressure and speed, and a drawing or sample if you have one, to our sales engineers through the enquiry form, and they will help identify a suitable seal.
