Abstract: The invention refers to the mixing of gas or gases with air, in a controllable ratio, by means of a mixing apparatus wherein the entrance air is forced in a complete developed rotation stream, by which a strong suction pressure is created in the center, so that gas can be sucked in ratio independent of the total volume per second. The mixing ratio of gas and air is controlled through an adjustable angle of the air entrance nozzles. The rotating airstream is accelerated in the radial entrance plane and via a logarithmic curved profile, the airstream is guided in the axial outlet direction of the mixing apparatus. The rotating airstream develops a center-core stream, where inside it a maximal under-pressure is created. By this underpressure, the main gasstream can be sucked and mixed with the airstream via the whirl grates, which are fixed in the outletsection just in front of the mixture outlet valve.

Abstract: Method of laying pipelines on land, in which straight pipe pieces are aligned to each other above the trench route and are welded together, and the thus formed pipeline in welded condition is bent to an extent and in a direction defined by the trench route and subsequently is lowered down in a trench.

Abstract: An apparatus for excavating a trench underneath a pipeline installed at the sea bottom, which apparatus is provided with rotating excavators, means for guiding the excavator relative to the pipeline, as well as means for advancing the excavator along the pipeline, whereby the excavators comprise at least two bucket wheels, 15, 16, 15', 16', disposed side-by-side on either side of the pipeline 9 parallel to the direction of advancement P, the main planes of said buckets enclosing an acute angle with each other and intersecting each other underneath the pipeline 9, which bucket wheels are disposed in said main planes, and being adjustable in height.