Pressure monitoring device isolator

Abstract

A pressure monitoring device isolator includes an annular member axially interposable in a pipeline for measuring the pressure of fluid in the pipeline. The annular member has an annular sensing fluid chamber, for a pressure sensing fluid, and an annular seal member separating the annular chamber from a central pipeline fluid passage. An opening in the outer periphery of the annular member is adapted to receive a pressure monitoring device. A sensing fluid passage extends radially inward from the pressure monitoring device opening. The sensing fluid passage is of substantially smaller volume than the sensing fluid chamber and the pressure monitoring device opening. A valve passage extends in from the periphery of the annular member to the annular sensing fluid chamber, meeting the sensing fluid passage at an acute angle. The valve passage has radially outer, middle and inner portions of progressively smaller cross sectional area. The inner portion joins the middle portion at an outward facing valve seat. The sensing fluid passage opens into the outer portion of the valve passage, thus communicating with the sensing fluid chamber via the valve passage. A valve member is threaded into the outer portion of the valve passage and is adapted to seat against the valve seat to interrupt the communication of the sensing fluid passage with the sensing fluid chamber.