Reference gage for radiographic examination of tubing

Claim 1

A METHOD FOR NON-DESTRUCTIVELY INSPECTING THE INSIDE SURFACE OF A PORTION OF A BOILER TUBE ASSEMBLED IN AND FORMING PART OF A BOILER, TO DETECT DANGEROUSLY DEEP PITS IN THE TUBE WALL, AFTER THE BOILER HAS BEEN IN OPERATION FOR A TIME, WHERE THE INTERIOR OF THE TUBE IS INACCESSIBLE FOR DIRECT INSPECTION BY MEANS OF INSERTED INSPECTION DEVICES, AND WHERE MINERAL DEPOSITS ON SUCH INTERIOR SURFACE MAY FILL AND COVER SUCH PITS IN SUCH INTERIOR SURFACE, WHICH COMPRISES DISPOSING, AT ONE SIDE OF AND EXTERIOR TO SAID TUBE PORTION A SOURCE OF PENTRATING RAYS CAPABLE OF PENETRATING COMPLETELY THROUGH THE WALLS OF SAID TUBE PORTION AND DIRECTED TOWARD SAID TUBE PORTION TO PENETRATE THE SAME, DISPOSING A RECORDING FILM OF THE TYPE RESPONSIVE TO SUCH RAYS EXTERIORLY OF SAID TUBE PORTION IN A POSITION TO INTERCEPT THE RAYS FROM SUCH SOURCE WHICH PENETRATE SUCH TUBE PORTION, ALSO DISPOSING ADJACENT TO SAID TUBE PORTION AND BETWEEN SAID SOURCE AND SAID FILM IN THE PATH OF SOME OF SAID RAYS DIRECTLY FROM SAID SOURCE AND AT APPROXIMATELY THE SAME DISTANCE FROM SAID SOURCE AS SAID TUBE PORTION, A MEMBER OF THE SAME MATERIAL AS SAID TUBE PORTION AND HAVING IN THE PATH OF SUCH RAYS A THICKNESS GRADUATED IN PREDETERMINED THICKNESSES BETWEEN ABOUT 100 PERCENT AND 200 PERCENT OF THE THICKNESS OF THE WALL OF SAID TUBE PORTION, AND ACTIVATING SAID SOURCE TO RECORD IMAGES ON SAID FILM OF THE TUBE PORTION AND MEMBER CONCURRENTLY, WHEREBY UPON A COMPARISON OF THE RECORDINGS ON SAID FILM OF SAID TUBE PORTION AND MEMBER, OF THE IMAGES OF ANY RANDOM PITS IN THE WALL OF SAID TUBE PORTION AND THE IMAGES OF THE PORTIONS OF DIFFERENT THICKNESSES OF SAID MEMBER, ONE CAN ASCERTAIN THE PRESENCE OF DANGEROUSLY DEEP PITS IN THE WALL OF SAID TUBE PORTION.

Claim 2

A METHOD FOR NON-DESTRUCTIVELY INSPECTING THE INSIDE SURFACE OF A PORTION OF A BOILER TUBE ASSEMBLED IN AND FORMING PART OF A BOILER, TO DETECT DANGEROUSLY DEEP PITS IN THE TUBE WALL, AFTER THE BOILER HAS BEEN IN OPERATION FOR A TIME, WHERE THE INTERIOR OF THE TUBE IS INACCESSIBLE FOR DIRECT INSPECTION BY MEANS OF INSERTED INSPECTION DEVICES, AND WHERE MINERAL DEPOSITS ON SUCH INTERIOR SURFACE MAY FILL AND COVER SUCH PITS IN SUCH INTERIOR SURFACE, WHICH COMPRISES DISPOSING, AT ONE SIDE OF AND EXTERIOR TO SAID TUBE PORTION A SOURCE OF PENTRATING RAYS CAPABLE OF PENETRATING COMPLETELY THROUGH THE WALLS OF SAID TUBE PORTION AND DIRECTED TOWARD SAID TUBE PORTION TO PENETRATE THE SAME, DISPOSING A RECORDING FILM OF THE TYPE RESPONSIVE TO SUCH RAYS EXTERIORLY OF SAID TUBE PORTION IN A POSITION TO INTERCEPT THE RAYS FROM SUCH SOURCE WHICH PENETRATE SUCH TUBE PORTION, ALSO DISPOSING ADJACENT TO SAID TUBE PORTION AND BETWEEN SAID SOURCE AND SAID FILM IN THE PATH OF SOME OF SAID RAYS DIRECTLY FROM SAID SOURCE AND AT APPROXIMATELY THE SAME DISTANCE FROM SAID SOURCE AS SAID TUBE PORTION, A MEMBER OF THE SAME MATERIAL AS SAID TUBE PORTION AND HAVING IN THE PATH OF SUCH RAYS A THICKNESS GRADUATED IN PREDETERMINED THICKNESSES BETWEEN ABOUT 100 PERCENT AND 200 PERCENT OF THE THICKNESS OF THE WALL OF SAID TUBE PORTION, AND ACTIVATING SAID SOURCE TO RECORD IMAGES ON SAID FILM OF THE TUBE PORTION AND MEMBER CONCURRENTLY, WHEREBY UPON A COMPARISON OF THE RECORDINGS ON SAID FILM OF SAID TUBE PORTION AND MEMBER, OF THE IMAGES OF ANY RANDOM PITS IN THE WALL OF SAID TUBE PORTION AND THE IMAGES OF THE PORTIONS OF DIFFERENT THICKNESSES OF SAID MEMBER, ONE CAN ASCERTAIN THE PRESENCE OF DANGEROUSLY DEEP PITS IN THE WALL OF SAID TUBE PORTION.