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Bäretswil, Switzerland

Lusch C.,Karlsruhe Institute of Technology | Borsch M.,WEKA AG | Heidt C.,Karlsruhe Institute of Technology | Magginetti N.,WEKA AG | And 3 more authors.
IOP Conference Series: Materials Science and Engineering | Year: 2015

Joints between copper and stainless steel are commonly applied in cryogenic systems. A relatively new and increasingly important method to combine these materials is electron-beam (EB) welding. Typically, welds in cryogenic applications need to withstand a temperature range from 300K down to 4 K, and pressures of several MPa. However, few data are available for classifying EB welds between OFHC copper and 316L stainless steel. A broad test program was conducted in order to qualify this kind of weld. The experiments started with the measurement of the hardness in the weld area. To verify the leak-tightness of the joints, integral helium leak tests at operating pressures of 16MPa were carried out at room and at liquid nitrogen temperature. The tests were followed by destructive tensile tests at room temperature, at liquid nitrogen and at liquid helium temperatures, yielding information on the yield strength and the ultimate tensile strength of the welds at these temperatures. Moreover, nondestructive tensile tests up to the yield strength, i.e. the range in which the weld can be stressed during operation, were performed. Also, the behavior of the weld upon temperature uctuations between room- and liquid nitrogen temperature was tested. The results of the qualification indicate that EB welded joints between OFHC copper and 316L stainless steel are reliable and present an interesting alternative to other technologies such as vacuum brazing or friction welding.


Boersch M.,WEKA AG | Holdener F.,WEKA AG | Iten E.,WEKA AG | Oertig D.,WEKA AG
Refrigeration Science and Technology | Year: 2012

Engineering components in cryo-technological plants have to meet demanding requirements derived from functional needs or prescribed in relating standards. For cryogenic components such as cryogenic valves and couplings some of the most important characteristics are defined in tightness requirements and pressure stability. However the performance is needed at service under cryogenic conditions, specific time-tested procedures are established since long time and carried out under ambient temperature level. Whereas for pressure tests it can be followed to the international standards and regulations, the preconditions for definition, testing and interpretation of acceptable leakage rates are based on limits of detectibility of the methods and lastly the experiences in the field. Corresponding specifications and test procedures for test objects to their encircling vacuum insulation, their ambient and their function related pipe connections has been established.


Wesche R.,Ecole Polytechnique Federale de Lausanne | Borsch M.,WEKA AG | Bruzzone P.,Ecole Polytechnique Federale de Lausanne | Holdener F.,WEKA AG | And 6 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2012

High temperature superconductor current leads have been demonstrated to provide cryogenic savings compared to conventional copper leads. The applicability of HTS current leads to industrial fabrication is now a possibility. CRPP and WEKA AG are collaborating in the development of current leads for currents in the range of 3 kA to 30 kA, which are suitable for industrial fabrication. The design of these leads is such that the architecture and construction can be easily scaled to the required current level. The main components of these current leads are an HTS module, a copper heat exchanger, and cold and warm end connections. Two 10 kA prototype current leads, mainly distinguished by different designs of the copper heat exchanger, will be constructed. They will be tested at CRPP to verify the manufacturing processes and the overall design. © 2011 IEEE.

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