Shaft Seals

Mechanical Shaft Seals

The term Shaft Seals is used often and often misused. Technically anything that is sealing a shaft, be it an O-ring, a lip seal, braided packing, or a mechanical face seal can all be called a shaft seal. So let's discuss just how each of these is used. Let's start with the simplest first.

Lip seals often called radial lip seals or even "mechanical seals" (which is a bit confusing for reasons I will point out later), are probably the most common form of lip seal. On the positive side they are relatively inexpensive, and occupy minimal space. They do not however hold very high pressures. This form of lip seal is typical in automotive applications, sealing bearings on any type of equipment, and in some valves and pumps. However the pressure limitation keeps them out of many valves and pumps

O-Rings are often used to seal the shaft or stem in a valve and are very effective at it. The reason they can be used for this application is simply because the movement is minimal, and slow. Most valves be them gate, globe, or ball valves turn minimally (in the case of a quarter turn ball valve), and then it in the open or closed position for extended periods of time. This is the easiest way to seal a shaft.