What is an O-Ring?
An O-Ring is a torus or donut-shaped part of circular cross section made of an elastomeric (rubber) material. O-Rings function as low-cost, compact, reliable and forgiving sealing devices for liquids and gases. Because of the resilience of the elastomer, O-Rings absorb tolerance stack-up on the metal parts they seal.
How do O-Rings Seal?
An O-Ring blocks the gap between two closely spaced surfaces by its memory or tendency to return to original shape when deformed. Normally, the O-Ring is installed in a gland that consists of a rectangular groove and a facing surface. By design, the O-Ring is squeezed into the gland during installation and the resulting force provides sealing at low pressure. As pressure is increased, it is transmitted through the O-Ring to mating surfaces thus augmenting seal effectiveness.
All O-Ring applications can be classified into two basic types:
- Dynamic, where there is relative motion between the parts of the gland (a reciprocating rod or piston seal)
- Static, where the two parts of the gland do not move relative to each other (such as a pipe flange).
O-Ring design parameters:
The proper design for the application of an O-Ring seal falls naturally into two main areas, dimensions and material selection.
Dimensions of both the O-Ring and the gland in which it is installed depend on:
- The size and shape of the parts to be sealed
- The pressure to be contained
- The type of motion, if any
Material selection, that is, the choice of the specific The O-Ring Store LLC O-Ring compound, depends on:
- The fluids to be sealed
- The temperature of the application
- The pressure to be contained
- The type of motion, if any
- Material specifications, if any
Design steps The design of an O-Ring application falls logically into seven basic steps:
- Select the elastomer
- Select a standard size
- Determine the maximum gap
- Specify gland dimensions
- Check for installation
- Select the specific The O-Ring Store LLC compound
- Select the The O-Ring Store LLC part number