SEALING OF PROPELLANT CONTAINERS BY ULTRASONIC WELDING

Abstract : It was demonstrated that it is practical to produce closures by ultrasonic welding which consistently approximate the strength of the parent material, and which are helium leak-tight when tested on a mass spectrometer at a leak sensitivity of 3.8 x 10 to the minus 10 power to 2.65 x 10 to the minus 10 power cc/sec, at STP conditions. The process is adaptable to production rates in excess of 1500 units per hour. an ultrasonic ring-welder of 2-kilowatts capacity is suitable for the production of container assemblies of the shape and size required by this contract. There appears little danger of ignition of propellants, such as type M-5 or M-9, due to the heat or vibratory energy developed during the ultrasonic welding process. This was demonstrated with propellant placed at the weld interface. Quality control during production can be limited to visual inspection of the assemblies, and to a water-submersion leak-test of control samples. Moreover, welding can readily accomplished under helium gas pressure and would permit 100% inspection of all assemblies manufactured by passing all pieces through a helium sensor. (Author)