AN IMPROVED VACUM PNEUMATIC SYSTEM FOR FILLING LARGE DRY CHEMICAL FIRE EXTINGUISHERS.
NAVAL RESEARCH LAB WASHINGTON D C
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An improved vacuum pneumatic conveying system has been developed for filling dry chemical fire extinguishers of 150 lb and larger capacity. It features more rapid filling and eliminates the lifting and dumping of cans, with its attendant dust nuisance. The main components are a 1-12-horsepower industrial type vacuum cleaner and an especially designed separator cap which fits on the fill-cap threads and serves to separate the powder from the conveying air stream. Three different separator caps have been designed for three large extinguisher types presently used at military activities. Design variations are necessary in order to achieve the proper balance between powder-transfer rate to the extinguisher and carryover of powder to the vacuum cleaner, which varies according to the differing geometries of the extinguisher shells. A powder-transfer rate of 0.40 pound per second was maintained during the fill cycle, and the amount of carryover reclaimed in the vacuum-cleaner bag was 2.0 percent or less. In using this system, the powder is drawn directly from the shipping cans on the ground, elevated, and placed into the extinguisher with little effort. The lack of dusting during the operation makes it possible to charge these extinguishers indoors. Author