Abstract: A cutting device which includes an external tube, an internal tube disposed within the external tube, and a number of steel rods or wires housed within the internal tube. A squib, with or without additional fuel, is disposed within the external tube and adjacent to one end of the internal tube. A plurality of vent holes are provided on the periphery of the external tube to allow the combustion gases to exhaust therethrough. The vent holes are located away from the squib but adjacent to the end of the internal tube. One of the open ends of the external tube is sealed with a plug.

Abstract: An RF-filter for an electric blasting cap comprises, in sequence from the cap's bridgewire, a first series-wired inductance plug (e.g., one or more ferrite beads), a shunt-wired resistance slug (e.g., conductive silicone rubber), two series-wired resistors (e.g., 27 ohm) in parallel geometry, and a second series-wired inductance plug adjacent the sealing plug on the cap. The filter elements are sheathed in a heat-resistant insulating and supporting sleeve, and an electrostatic flashover point is provided between the sealing plug and the inductance plug. The filter affords RF protection of 25 db between 1 and 4000 MHz, and withstands high current or voltage surges over a wide temperature range without permanent impairment.

Abstract: A liquid-disabled blasting cap, especially useful in oil well perforation assemblies, has a perforated cap shell and a porous tubular member, e.g., a ceramic, adjacent the perforations. An ignition charge is present in the bore of the porous tubular member and in the cap's ignition train. The porous tubular member allows disabling liquids to be transferred to the ignition train from outside the cap through the holes in the shell wall, while at the same time acting as a protective barrier element between the holes and the ignition and explosive charges. In oil well caps, a B/Fe.sub.2 O.sub.3 ignition powder is preferred because of its high-temperature stability.

Abstract: A mixture of about from 60 to 40 percent amorphous boron and about from 94 to 60 percent ferric oxide, useful as an ignition composition for electrically actuated blasting caps and squibs, has outstanding thermal stability, i.e., up to about 500.degree. C. making it especially suitable for use in blasting caps in oil wells that are deep and hot, e.g., in the liquid-disabled cap described in U.S. patent application Ser. No. 469,954. Bridgewire-sensitive compositions containing about from 10 to 20 percent boron are preferred. The compositions can be self-grained, or they may be grained preferably with a water-soluble polymeric binder.

Abstract: Disclosed is an improved underwater half-second pyrotechnic delay device ing an elongated tubular housing with a pair of holes for respectively threading suitable detonating cords through each end thereof. In operational burning series within said tubular housing are a plurality of lead sheathed protected explosives, a resilient pressure attenuating disc, a metallic capsule containing a calibrated delayed burning composition of 2/98B-Pb.sub.3 O.sub.4 having such geometrical configuration as to effect burning therealong for one-half second with considerable accuract, and another series of lead sheath protected explosives, a base charge, an explosive cord, and an end plug. An appropriate number of crimps are made along said tubular housing for holding the aforesaid elements in their proper places therein. Seals are employed at each end of said housing to make it watertight.