Abstract: The bottom wall of a combustion chamber for fluid-bed combustion is formed as a membrane wall consisting of parallel tubes and fins welded between adjacent tubes, preferably in the common plane containing the tube axes. To the upper side of the tubes there are welded sheet metal strips perforated by relatively closely spaced orifices. In operation fluidizing and combustion air is injected into the combustion chamber from a plenum chamber located below the membrane wall through apertures, preferably elongate slits, in the fins of the membrane wall and the orifices in the overlying strips. A coolant flows through the tubes of the membrane wall whereby the bottom wall can be kept at a temperature which is so low and so uniform that warping of the wall will not occur even if the injection of air ceases.

Abstract: An apparatus for multi-bead welding of two rotating workpieces with a welding seam, which is deep relative to the maximum radius of the workpieces, includes a flat filler wire holder which can be inserted into the gap between the workpieces and which is periodically pivoted forth and back about an axis which at the beginning of the welding operation is located within the gap. The holder may be angled and comprise a first limb extending generally perpendicular to the axis of rotation of the workpieces and which holds the filler wire, and a second limb extending out of the gap in the direction of the pivot axis. A pipe for supplying welding powder or protective gas may be mounted on the holder parallel to the second limb thereof. At its inner end the pipe may carry a sensor which controls the outward movement of the holder during the welding operation.

Abstract: An apparatus for multi-bead welding of two rotating workpieces comprises a flat filler wire holder which can be introduced into the gap between the workpieces and which is periodically pivoted forth and back at substantially constant angular velocity between the two sides of the gap. The pivoting is effected by a motor which is started when a cam rotating in synchronism with the workpieces actuates a stationary signal generator. The cam is provided on a cam disc which is driven through a friction coupling and which, on each revolution, is arrested by a pawl during a period determined by an adjustable timer. The timer is started when the cam actuates a stationary signal generator mounted shortly in advance of the pawl, and after the expiry of the period of the timer the pawl is retracted so that the rotation of the cam disc can continue. The pawl is again advanced to operative position when the cam actuates the first mentioned signal generator.