Abstract: In order to provide safety in a borehole communicating in particular with a cavity washed out from rock salt and containing gas under pressure, the prior art provides devices suffering from the drawback of reducing the flow sections through the tubes in the borehole. The present invention minimizes this section reduction by means of a hollow cylindrical sleeve closed inside by a plug and including ducts formed in its wall in such a manner as to cross over the flows of fluid taking place respectively in a central tube of the borehole and in the annular space between the central tube and a peripheral tube. In one embodiment of the present invention, the sleeve is sandwiched between portions of the central tube and of the peripheral tube, with safety valves advantageously being mounted on the portions of central tube above and below the sleeve.

Abstract: The disclosure relates to a method and a device for butt-welding rotational cylindrical metallic rods without filler metal and without forming a rim or deformation in the welded area. The method consists of bringing the two ends coaxially to be welded into contact proximity without compression and applying welding power while simultaneously rotating the two rods in relation to the welding heat source around their common rotational axis to an extent of more than one complete revolution.