Stud Tensioning Technology

Efficient automatic opening and closing

For more than 40 years Siempelkamp has successfully provided stud tensioning technology all around the world with: hydraulic stud tensioners (MST), single stud tensioners or small tensioners for opening and closing reactor pressure vessels or other primary circuit components.

Concepts with a high degree of automation – e.g. stud tensioners for all reactor types – are provided by us with the same ease of operation as plant service solutions which are exactly tailored to our customers' needs. We have established our position in the market thanks to many years of experience and an uninterrupted service chain. This extends from concept development and construction, production and delivery right through to commissioning of the nuclear power plant. In addition to the new construction of MST, we carry out the modernization of stud tensioners on our customers' premises worldwide. If the customer wishes, we provide continuous support within the scope of service contracts. This even includes the operation of the machines during inspections.

Our product range covering the whole field of opening and closing primary circuit components is rounded off by appliances and specialist tools which supplement the use of stud tensioners and tensioning systems such as:

  • Stud turning devices, available both as single and multiple turning devices
  • Thread cleaning units for the pressure vessel studs (bolts) and/or blind holes
  • Transportation facilities
  • Test stands

The most modern and technically advanced concepts, products that have been proven in practice and a worldwide 24-hour service enable our customers to increase the profitability of their facilities, reduce the exposure of their personnel to radioactivity and minimise the risk of primary circuit components failing.


Siempelkamp NIS Ingenieurgesellschaft mbH
Hüttenallee 80
44534 Lünen
Phone: +49 (0) 2306 / 3732-0
Fax: +49 (0 )2306 / 3732-100

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