GB866620A - Improvements in and relating to explosives - Google Patents

Abstract

866,620. Blasting devices and explosive compositions therefor. UNION CARBIDE CORPORATION. Jan. 9, 1959 [Jan. 13, 1958], No. 867/59. Classes 9(1), 9(2) and 68(1). A blasting device comprises a water-impervious flexible plastic tube 21 containing ammonium nitrate coated with a waterproofing agent and enclosed by an outer plastic tube 22, which is weighted at the bottom. The explosive is fed into the tube after the tube has been lowered into a borehole. To facilitate charging of the casing the tubing assembly is provided with an inner tube 20 which is used to inflate the tube 21. The composite tube, made from material such as polyethylene, polyethylene terephthalate, or polyvinylidene chloride, may be made up in uniform lengths or wound on a reel for shipment. To use the tubing, 1 - 2 ft. of the outer tube 22 is turned back to expose the tube 21, the exposed length of tubes 20 and 21 being then cut off near the fold. Notches 26 are made near the end of tube 20 before heat-sealing the cut ends of tubes 20, 21 together. The outer tube 22 is then straightened and a seal 28 is made below the seal 27 to form a pocket 29 in which ballast 32 or a soluble material is placed before the pocket is closed by a cord 33. Preferably a cord 34 is placed around the seal 28 and its ends 35 used to lower the tubes into a borehole after the tubing has been folded along its length and secured by bands of paper, or tape or by adhesive. Excess water is removed from the borehole or if the hole is dry a limited quantity of water may be introduced to obviate air pockets. The upper edges of tubes 21, 22 are drawn together around a plug 37 and clamped by a ring 38, which may have support legs 39. The inner tube 20 extends through a hole 41 in the plug, a relief valve 44 is fitted into a hole 45 and a charging funnel 42 is placed in a hole 43. Compressed gas forced into the tube 20 escapes through the notches 26 and inflates the tubes 21, 22 until they are fully expanded. The explosive 47 is then fed in through funnel 42, primer cartridges 48, which may be provided with fuzes 49 engaging notches in the plug 37, being introduced at intervals during the charging process. The inner tube 20 may be pulled out and the upper part of the tubes 21, 22 tied off as in Fig. 9 before the borehole is stemmed. The ammonium nitrate is coated with a liquid hydro-carbon in which a metallic soap is dissolved. In an example, an aluminium soap of 2-hexoic acid compound was dissolved in kerosene in the proportions of 7¢ parts by weight of soap to 100 parts kerosene, 1 gallon of the solution being added to about 80 1bs. of ammonium nitrate. Instead of aluminium soap, colloidal carbon blacks, colloidal silicas and mineral waxes may be used as gelling agents. The pocket 29 may be punctured to allow water to seep between the ballast granules or, if a water-soluble ballast such as a metal salt is used, to dissolve the salt, so that the explosive sinks to the bottom of the borehole.