Abstract: A safety interlock device is provided for preventing the opening of a vessel containing a pressurized fluid. In a typical application, the interlock device may be used in industrial applications to prevent the inadvertent unscrewing of a cap from the end of a large pressure vessel containing a hazardous gas. A pressure port end of the interlock body is adapted for threaded engagement with the vessel and is open to vessel pressure. A pressure-responsive locking piston movable within the body prohibits removal of a stem when vessel pressure exceeds a selected minimum pressure. A chain may be secured at each end to the stem and vessel cap, so that the cap cannot be unscrewed to open the container unless the stem is first removed. In one embodiment, the locking piston is prevented from manual override by the position of a second piston and a plurality of ball members locked in a groove.

Abstract: An oil reservoir gland stuffing box employed to extend the service life of the packing by providing an oil reservoir to maintain essential lubrication is provided with an attached container which will receive the overflow of the oil reservoir should the packing begin to leak excessively threatening thereby to create a pollution problem. A predetermined overflow actuates a weight sensitive micro-switch wired to shut off the pumping unit and/or send a warning signal to a remote control station. The control switch incorporates a manual re-set provision to prevent the pumping unit from restarting until the well has been serviced.