STATIC CRUSH SEALS

　　In crush seal applications, the O-ring is completely confined and pressure deformed (crushed) within a triangular gland made by machining a 45° angle on the male cover. Squeezed at an angle to the O-ring's axis, crush seals are used in such simple applications as the one depicted in Illustration 4.4.

　　Static Crush Seal Gland Dimensions

　　We recommended dimensions for static crush seal glands by ascending AS 568* numbers.

　　STATIC SEALS WITH DOVETAIL GLANDS

　　O-rings are sometimes employed in static or slow moving dynamic situations calling for specially machined "dovetail" glands. Because of the angles involved, controlling the tolerances in these glands may be difficult. The purpose of these glands is to securely hold the O-ring in place during machine operation and/or maintenance disassembly. A typical valve seat application is shown in Illustration 4.5.

　　In this application O-ring squeeze is primarily axial in direction (as valve operation exerts force on top and bottom seal surfaces). To avoid tearing or nicking, the use of O-ring lubrication is recommended while installing the O-ring into the dovetail gland. Because of the difficulty in creating the groove and tight tolerances required, this type of seal application should only be used when necessary.