Abstract: An improved scored reverse buckling rupture disk assembly is provided. The assembly includes a reverse buckling rupture disk having one or more scores on a surface thereof forming lines of weakness which define a blow-out portion connected by a hinge area in the rupture disk. An annular rupture disk support member is positioned adjacent the concave side of the rupture disk, and a supporting member for preventing the blow-out portion from fragmenting or tearing away from the rupture disk at the hinge thereof is disposed within the concave recess in the rupture disk.

Abstract: An ultra low pressure flow sensor consisting of a support gasket defining a flow way and having a thin, pliable membrane extending thereacross with right angle slits formed totally across the flow way portion. An electrical conductor strip is then bonded across each pair of opposing quadrants of the membrane in continuous connection to an electrical indicator circuit. The conductor strip across each pair of membranes is centrally notched to a preselected depth of cut thereby to adjust the flow pressure break strength.

Abstract: An improved replaceable carbon rupture disk element and element-holder assembly are provided. The carbon rupture disk element is comprised of a carbon disk having a pair of opposing bores extending thereinto whereby an integral blow-out portion having a particular rupture pressure is formed in the disk connected to an enlarged rim portion. A reinforcing ring is attached to the rim of the carbon disk having a height substantially equal to or greater than the height of the enlarged rim portion of the disk which prevents the rim portion from being subjected to compressive forces which change the rupture pressure of the blow-out portion.

Abstract: The invention renders fail safe a rupture disk assembly consisting of inlet head, outlet head, and rupture disk secured therebetween, whenever the assembly is installed upside down. A fail safe relief notch is formed in the inlet head disk seating surface to cause premature bursting of the rupture disk when the assembly is improperly installed.

Abstract: A distance measuring tool is provided for measuring the length of a drill pipe maintained under tension within a well. The tool includes a unitary instrumentation and instrument drive module which is sealed within an instrument housing and which may be removed and replaced as a single unit when malfunction occurs. The moving parts of the module are sealed in lubricating fluid, and a pressure equalization system is provided to equalize the pressure of the lubricating fluid relative to the external drilling mud pressure. The instrumentation and instrument drive module includes a mechanical distance counter and a drive mechanism which drives the counter only when the tool is descending into a drill pipe. The instrumentation within the tool is protected against impact by a shock absorbing nose assembly which includes both mechanical spring and hydraulic shock absorbing units.