O-ring Sealing Principles
O-rings are bi-directional seals, circular in shape and cross section. O-rings are generally
made of an elastomeric material, but may be made of other materials such as PTFE or
metal. An O-ring seals through the deformation of the seal material by installation and media pressure to close off the gap between mating components. Higher system pressures can cause deformation through the gap, known as extrusion, resulting in seal failure. Choosing a harder seal material or installing back-up rings to support the O-ring may alleviate this problem.
Method of operation
O-Rings are double-acting sealingelements. The inital squeeze,which acts in aradialora xial direction depending on the installation, gives the O-Ring its initial sealing capability.These forces are superimposed by the system pressure to create the total sealing force which increases as the systeme pressure increases (Figure 2).
Under pressure, the O-Ring behaves in asimilar way to a fluid with high surface tension. The pressure is transmitted uniformly to all directions.
EPDM (Ethylene-Propylene-Diene Monomer O-Ring):
EPDM O-ring in auto parts, hygiene supplies, medical equipment, marine equipment, petroleum equipment, telecommunications equipment, instrumentation, machinery and other industrial fields are widely used.
Use temperature range: -50 to 150 °C
Application
The O-Ring is used predominantly for static sealing applications:
- As aradial static seal, e.g. for bushings, covers, pipes, cylinders
- As an axial static seal, e.g. for flanges, plates, caps.
O-Rings in dynamic applications are recommended only for moderate service conditions.They are limited by the speed and the pressure against which they are to seal:
- Forlow duty sealing of reciprocatingpistons, rods, plungers, etc.
- For sealing of slowlypivoting,r otating or spiral movements on shafts, spindles,rotary transmission leadthroughs, etc.
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