Designing the parts of an application where o-rings will be applied is broadly termed “o-ring groove design”. In order to seal properly, the o-ring has to deform in the application by being compressed and stretched in any number of ways. The design of the groove where the o-ring sits plays a major role in how the o-ring performs its sealing role.
EXTRUSION LIMITS & O-RING CLEARANCE GAPS
An o-ring is contained in a gland and forced to flow into the surface imperfections of the glands and any clearance gaps available to it.
An o-ring can perform sealing by means of squeeze under low pressure conditions. The extent of extrusion depends upon the hardness of o-ring, the pressure, and the size of the clearance gap.
STANDARD AS568B O-RING GROOVE DESIGN
The three main types of standard groove designs are Industrial Static, also called Radial, Industrial Reciprocating, also called Dynamic, and Face Seals also called Axial or Flange.
Radial and Dynamic seals require the presence of a diametrical clearance gap for installation. However, face seals have no clearance gap, but consist of a groove cut into one flange with a flat mating flange bolted together to give a surface to surface contact.
METRIC O-RING GROOVE DESIGN
Metric o-ring groove dimensions are listed for the most common metric cross-sections with and without backup rings. Included are Static, dynamic, and pneumatic applications.
DOVETAIL O-RING GROOVE DESIGN
Dovetail grooves are used to hold the O-ring in-place on a face seal groove during during assembly and maintenance of equipment. An undercut or dovetail groove has proven beneficial in many applications to keep the o-ring in place. However, this is an expensive groove to machine, and thus should be used only when absolutely necessary.