Photoelastic leak detection methods

Claim 1

THE METHOD OF DETECTING FLUID FLOW THROUGH AN ORIFICE WITHIN A GIVEN AREA OF A WORKPIECE SUCH AS A PRESSURE VESSEL SUBJECTED TO DIFFERENTIAL PRESSURE, WHICH METHOD COMPRISES THE STEPS OF: PROVIDING A REFLECTING SURFACE SUBSTANTIALLY PARALLEL AND COEXTENSIVE WITH THE GIVEN AREA, ATTACHING A TESTPIECE OF PHOTOELASTIC MATERIAL ABOUT THE ENTIRE PERIMETER OF THE GIVEN AREA TO THE WORKPIECE BY MEANS PROVIDING A FLUID TIGHT ENCLOSURE OF SAID AREA, SAID FLUID FLOW THROUGH SAID ORIFICE BETWEEN SAID ENCLOSURE AND SAID VESSEL CREATING A PRESSURE SITE AT THE PHOTOELASTIC MATERIAL-WORKPIECE INTERFACE TO CAUSE SAID PHOTOELACTIC MATERIAL TO BULGE RELATIVE TO SAID GIVEN AREA OF THE WORKPIECE, PASSING POLARIZED LIGHT SUBSTANTIALLY NORMALLY INTO AND THROUGH THE TESTPIECE TO THE REFLECTING SURFACE, AND ANALYZING POLARIZED LIGHT DIRECTED THROUGH AND OUT OF THE TESTPIECE FROM THE REFLECTING SURFACE, WHEREBY DIRECTLY OBSERVABLE PHOTOELASTIC FRINGE PATTERNS ARE RELATED TO THE BULGE FORMATION DUE TO THE PRESENCE OF THE FLUID FLOW THROUGH ANY ORIFICE WITHIN THE GIVEN AREA OF THE WORKPIECE.