Glossary and index of fluid power principles and components U

The condition of a spool and body in a servo valve or other spool valve wherein the spool is displaced a specified amount (the underlap) to expose two adjacent cavities to each other.

To release flow (usually directly to the reservoir), to prevent pressure being imposed on the system or portion of the system.

A valve that is normally closed and opens from a separate fluid source on rising pressure that is balanced against a precision spring. Re-set point is normally fixed.

The passage ahead of a device, normally at the inlet of direction of flow.