Siemens Aktiengesellschaft

Alexander Hummeler

Siegfried Forner

Erich Katscher

Peter Krausser

Harald Hegenberger

Gunter Rabe

A tube plug for closing a defective heat exchanger tube includes a hollow conical portion having a closed free end and a hollow cylindrical portion merging fluidly with the hollow conical portion without a step. The hollow cylindrical portion has an outer surface with an outside diameter being smaller than the inside diameter of the heat exchanger tube to be closed. The outer surface of the hollow cylindrical portion has a roughened region to be expanded into sealing contact with the inner surface of the heat exchanger tube. The roughened region has a peak-to-valley height of substantially between 0.05 and 0.2 mm. A device is disposed in the hollow cylindrical portion and/or the hollow conical portion for positioning and locking a pulling tool. A method for loosening a tube plug firmly retained in a heat exchanger tube by melting the surface of the wall of the tube plug along a predetermined path with a welding tool, and a method for closing a defective heat exchanger tube by inserting a tube plug and expanding a cold-formed roughened region of the cylindrical portion from inside and forcing the roughened region into locking contact with the inner surface of the heat exchanger tube, are also provided.

Tube plug for closing a defective heat exchanger tube, method for

A twist-proof mechanical connecting assembly includes first and second components. The first component has a recess formed therein with a groove in the form of at least one pocket. A connecting element in the form of a bolt penetrates the first component and is secured to the second component for interconnecting the components. The bolt has a polygonal head including a safety cup embedded in the recess. At least part of the safety cup is outwardly bent into the at least one pocket for locking the safety cup to the first component and securing the connecting element against loosening.

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Rottenbach, Germany

Alexander Hummeler