Gland Design

Special Considerations, Part 1

In many situations, it is very important to understand the anticipated response of an elastomer under a given compressive load. The compression/deflection curves for various elastomers are functions of the hardness (and bulk modulus) as well as the cross-sectional diameter.

High-pressure applications may present unique challenges to elastomeric seals. Elastomers are essentially high-viscosity liquids-and as such will flow under extreme pressure conditions. In applications where the clearance gap is larger than that recommended for a traditional o-ring seal, the user should consider backup rings. These flat or contoured rigid rings are inserted on the lowpressure side of the gland to prevent extrusion. Consideration of backup rings requires additional gland width to allow for elastomer expansion. In addition, chemical compatibility and ease of installation are other considerations when using backup rings.

Compression/Deflection Data for Elastomers

Irregular, noncircular glands may present challenges for seal design. The chart at the right illustrates the minimum recommended bend radius for irregular glands. Smaller, sharper radii may result in excessive stress and seal damage.

Next Topic Gland Design Special Considerations, Part 2