Abstract: A flow shut-off valve shuts off natural gas if there is a break in a gas line, for example, the line to a water heater toppled by an earthquake. The shut-off valve is fitted into a standard pipe nipple that is installed in a vertical position. The shut-off valve includes a plastic float having a tapered nose with a O-ring in a groove at the base of the nose, a flow-restricting orifice region, and guide fins at the lower end of the float to guide it along the bore of a plastic body having a bore and shoulders at either end to contain the float. The body includes an conical aperture at the upper end into which the float nose and the O-ring are inserted when a break occurs and the downstream pressure drops, forcing the float upward as the gas flow surges. No spring is used; the balance of gravity and gas=flow forces controls the operation of the shut-off valve. The body is spin-welded from two pieces and crimped into position in the nipple.

Abstract: A safety flow limitor of modular construction for use in gas supply lines for passing a combustible natural gas from a source to a consumer comprises a cylindrical shell defining an internal passageway in which resides an axially movable valve head member having an annular surface for mating with an annular valve-seat provided along the passageway. A coil spring having its downstream portion retained in the passageway and its upstream portion abutting the valve head member serves to bias the annular surface of the valve head member away from the annular valve-seat so as to maintain the passageway open. If there is a pressure drop downstream, then the upstream pressure acts against the force of the coil spring and moves the valve head member to a downstream position where its annular surface mates with the annular valve-seat.

Abstract: A method and apparatus of sealing and cutting an underground pipeline, such as a gas line or the like, at or near a point where it connects to a main utilizes an expandable plug which may be inserted in the line without the need to excavate to obtain access to the point of sealing. A thermally stabilized cross-linked preshrunk polyolefin plug is inserted into the line on a heater element. The plug may be inserted from a point where the line exits the earth. Once the plug is inserted on the end of the heater element, the heater element is heated causing the plug to expand fitting it tightly inside of the line at or near the main. The heater element may then be withdrawn, and the line may be cut adjacent the inserted plug.