Abstract: A weld inspection process and an associated system for the determination and assessment of weld seams by first producing a flawless weld seam on a test specimen, making a point by point inspection of the test specimen using a pair of alternately pulsed X-ray or gamma ray sources, while generating signals which may be simultaneously displayed and stored, to form a permanent record of the test specimen weld seam, on a target plate. A point by point comparison of is made of a new, similar weld and the recorded image is instantaneously compared with the previously recorded, stored image of the flawless test weld. In the event of identical images, that point of the weld is deemed flawless, while a lack of identity indicates a flaw, in which event, the defective position is marked for subsequent repair, removal or total rejection.

Abstract: An apparatus for breaking coal or other mineral matter from a bed thereof which comprises a string filling a bore hole which can rise steeply in this bed. The string consists of alternating breaking units and connecting pipes each braking unit having a differential piston displaced solely by the action of air pressure so that breaking slots are unblocked to discharge compressed air built up in the string. The pistons are provided with check valves to permit filling of the string.

Abstract: Forming a hole between lower and upper parallel galleries formed in a mine by boring upwardly from the lower gallery a bore hole having a first length equal to a fraction of the distance between the lower and upper galleries, then casing the bore hole by thrusting upwardly at least one pipe section having a diameter sufficient to be gripped by the shrinkage of the bore hole into the bore hole.