Abstract: A tube bundle reactor carries out endothermic or exothermic gas phase reactions. The tube bundle of reactor tubes are filled with catalyst, and have their ends fastened tightly in tube sheets (3, 4). A fluid heat carrier (10) flows around the tubes during operation. A shell (5) encloses the tube bundle. A gas inlet head (6) spans one of the tube sheets, and a gas outlet head (7) spans the other tube sheet. The reactor tubes are in fluid communication with the gas inlet and outlet heads (6, 7), and further include at least one stage thermometer (9) installed in a thermometer tube (2) disposed in the tube bundle. The at least one stage thermometer (9) is axially movable inside the thermometer tube (2), and the tube bundle reactor (1) includes a mechanical positioning means (8) to effect the axial movement of the stage thermometer (9). Moreover, a method is proposed for measuring a temperature profile in tube bundle reactors of the kind specified.

Abstract: In a tube bundle reactor for carrying out endothermic or exothermic gas phase reactions, comprising a tube bundle of reactor tubes filled with catalyst, having their ends fastened tightly in tube sheets (3, 4), a fluid heat carrier (10) flowing around the tubes during operation, a shell (5) enclosing the tube bundle, a gas inlet head (6) spanning one of the tube sheets, a gas outlet head (7) spanning the other tube sheet, the reactor tubes being in fluid communication with the gas inlet and outlet heads (6, 7), further comprising at least one stage thermometer (9) installed in a thermometer tube (2) disposed in the tube bundle, the at least one stage thermometer (9) is axially movable inside the thermometer tube (2), and the tube bundle reactor (1) comprises a mechanical positioning means (8) to effect the axial movement of the stage thermometer (9). Moreover, a method is proposed for measuring a temperature profile in tube bundle reactors of the kind specified.

Abstract: An automatic arc welding machine of the type which operates with rod electrodes. The electrodes (46), which are held in a welding head (28), are moved automatically with respect to the workpiece. The electrodes are moved longitudinally away from the workpiece in accordance with the arc voltage such that a certain arc length is sustained. After use they are automatically replaced with new electrodes. For this purpose there is provided an arc striking control by means of which the particular electrode (46) is placed on the workpiece with the current limited to a value below the selected welding current; the electrode is then raised from the workpiece by an amount corresponding to the predetermined arc length while the welding current is released, before the longitudinal movement of the electrode in accordance with the arc voltage begins. A precisely timed and accurately placed ignition is achieved in this manner, even if the location of the weld is covered with scale or slag.