Radial seals can be classified into contact seals and clearance seals. Contact seals are used for seals of rotating shafts that are split and piston rods that rotates. Sealing is achieved by springs which contain the segments. Contact seals are in constant contact with the counter surface and are easy to wear.
Clearance seals can be a single piece or segmental sealing rings and must be assembled after the clearance is calculated exactly.