Source: Ashcroft Inc.
With the Ashcroft® Isolation Ring, the instrument is in contact with the fill fluid, not directly with the process flow. Clogging or fouling is never a problem. The Iso-Ring has a flexible inner cylinder, behind which is the fill fluid. As process liquid flows through the pipe, it exerts pressure. The pressure exerted by the fill fluid is then monitored by the instrument-sensing element.