V-rings are used as a shaft and bearing seal for example against dirt, dust, atomized water emulsion etc.
V-ring is usually directly threaded on the shaft, where it holds by its own adhesion. V-ring rotates with the shaft and axially seals against static surface perpendicular to the shaft. The sealing lip of V-ring is flexible and creates relatively small pressure, but enough to seal, against static surface. Such low pressure allows for many cases even function withoud liquid. By the centrifugal force with increasing speed, contact pressure decreases to about the speed of 15-20 meeters per second, where the friction decreases to zero.;
Types of O-rings:
- VA – standard profile
- VL – with a narrow cross section for tight installation spaces
- VS – with a strengthening reinforcement, ensuring a firmer fix of V-ring on the shaft
The most used materials of V-rings:
- NBR – for everyday use
- FPM (sometimes called FKM, or Viton) – more resistant to high temperatures and chemicals
Requirements for surface roughness and shaft tolerance are relatively free. It´s important to remember, that more strained V-ring on the shaft causes greater contact pressure of the lip because of the deformation of V-ring. Status of the sealing surface has great influence on the sealing function. The sealed medium and the speed of rotate determine what should be roughness of sealed surface. It is important to be straight, smooth without sharp edges. The mounting space must be relative free to achieve the full effect of media spin-off from the ring. It is also important to achieve the smallest possible gap between the shaft and the static counterpart to not recieve lip outside the sealing surface, when it is installed.