Pyronol Torch - A Non-Explosive Underwater Cutting Tool (1976)

ABSTRACT A unique, self-contained, underwater cutting torch containing an improved pyrotechnic material, Pyronol, has been developed for instantaneous cutting and perforation of heavy steel plate, chain, cable, or pipe in both surface and underwater environments. This simple, non-explosive, disposable tool has been used successfully to sever 2.0-inch diameter stranded steel cable at underwater depths down to 1200 feet in less than one second. Instantaneous perforation of 3.0-inch thick steel plate has been accomplished in open air surface tests, and similar steel plates up to 2.0-inch thickness have been penetrated at underwater depths in excess of 1200 feet. This tool offers great potential for offshore salvage and recovery operations as well as for emergency rescue and release operations. INTRODUCTION The energy crisis has created increased impetus for offshore resource explorations which in turn have dictated a need for improved tools, equipment, and technology. One specific area wherein improved tools and technology may play an important part in the future is that involving underwater recovery, clearance, and salvage operations. This paper describes a recent development that should be applicable in this particular area of offshore technology. It relates to a simple, non-explosive cutting device that has the capability for perforating or cutting heavy metal plate, cable, chain, or pipe in less than one second in underwater environments at various depths. This tool was developed at the White Oak Laboratory of the Naval Surface Weapons Center. It is unique in that it is a self-contained, non-explosive, disposable unit that can be placed in position by underwater remote controlled vehicles or by trained diving personnel and then initiated remotely to perform the instantaneous cutting operation. This self-contained torch makes use of an improved pyrotechnic fuel, Pyronol (1), which was developed in this Laboratory. This exothermic material consists of a powder mixture of nickel, aluminum, iron oxide, and a fluorocarbon (2) which can-be pelletized into any desired configuration and incorporated into specially designed cylindrical casings which contain appropriate nozzles and ignition systems(3). After initiation, Pyronol components react instantaneously and the resultant molten metals and oxides are ejected at high velocity through a specially designed nozzle and impinge on the target. The impact of the liquid jet against the target produces instantaneous cratering and perforation of the target material. Since the Pyronol reaction does not require external support of oxygen, this tool is equally effective in both surface and underwater environments. THEORY AND DEFINITION The magnitude of target damage and the efficiency of the Pyronol torch is largely dependent on the velocity of impact of the liquid jet against the target. Perforation implies a complete passage of the liquid jet through the target material. Both impact damage and perforation involves formation of a crater in the target. The maximum pressure generated during normal impact of a steady, incompressible jet against a rigid surface is given by the following equation:(Equation available in full paper)