Floating seal for fluid control devices

摘要

A floating secondary stem seal arrangement for fluid control devices which becomes operative only when fluid by-passes the primary stem seal. A secondary stem seal member is disposed outwardly along the stem from the primary seal in a secondary seal member receiving chamber. The cooperative configuration of the chamber, the secondary seal member and the stem is such that under normal operating conditions with no fluid by-passing the primary seal, the secondary seal will not perform any sealing function against the stem. Fluid by-passing the primary seal moves the secondary seal member within the secondary seal chamber axially of the stem and into a forced sealing position therewith. This selective operation of the secondary seal assures that it will be essentially free from wear during normal operating conditions and, therefore, effective for sealing purposes in the event of primary seal failure.