O Ring Design process

O-Ring seal design process begins with understanding the gland type in which the seal will be seated. It is recommended that O-Rings to be stretched 1 to 5% to ensure the O-Ring fits properly, with ideal stretch at 2%.

Seal Gland type, sealing application(fluid,solid & gas), pressures, operating temperatures, chemical interactions are considered to design O-Rings.Each and every factors involved with the design of O-Rings selection should be weighed with the elastomer capabilities and to be tested thoroughly whether the seal meets the application demand or not.

Design Process involves the following main things.

1. Preliminary Considerations

An O-Ring is a simple and versatile ring shaped packing or device. Circular cross section functions as a seal, in both static and dynamic applications, by being compressed between the mating surfaces comprising the walls of the gland in which it is installed. O-Ring can be made from variety of materials commonly moulded in one piece from an elastomeric material.

a) Function of O-Rings

  • Sealing/transmitting a fluid
  • Transmit/absorb energy
  • Provide structural support

b) Type of Environment

  • Wet/Dry Environment
  • Any water, chemicals, Oxygen, Ozone, Sunlight or Solvents
  • Continuous/Periodic pressure
  • Static/Dynamic stressing

c) Expected Product Life

  • Elongation/Tensile Strength
  • Resistance to Deformation
  • Compression sets
  • Resistance to embrittlement

d) Expected Properties

  • Compression Set resistance
  • Rebound resistance
  • Tear Strength
  • Ageing Resistance
  • Oil Immersion Resistance

2. Basic O-Ring Design

Between the two closely mated surfaces an O-Ring acts as a seal by blocking any potential leaching path, of a liquid or gas. An O-Ring is installed in a machined grooved gland in one of the two surfaces to be sealed. When the two surfaces are brought together the O-Ring cross section becomes deformed producing a tight seal, see image. Greater the squeeze greater the deformation. Since the O-Ring is made from elastomer material it will acts as a good seal.

An elastomer typically a highly viscous material having tendency to remember its original shape for a longtime allow it to be compressed and recompressed without loosing its original shape and therefore its sealing ability. Right elastomer is important for each intended application. Each elastomer has different thresholds for heat, cold water, gas etc., and different elastomers are having unique characteristics.

3. Types of Compression

O-Ring compression occurs in two possible ways i.e. Axial & Radial Compression.

Axial Compression is a compression occurs on both the top and bottom surfaces of O-Ring.

Radial Compression is a compression occurs on the inner and outer surfaces of O-Ring.