Tensioning multi-part backup rollers using STG 3000-3K and SSV
In August 2008, SCHAAF received an order from an Italian smithy company to supply all the equipment needed to tension two multi-part backup rollers, of previously unseen dimensions, which were developed and patent-registered by SMS Siemag.
The order consisted of an STG 3000-3K hydraulic unit for jointing tapered shafts and hubs by means of compressed oil, and an SSV to provide axial pretension and to generate the axial force required for jointing.
In this case the weight of the tools alone was 26.5 tonnes. The challenge in this project was the process for jointing the individual components: Jointing two shaft journals simultaneously into a single base unit had not been done before and required complex procedures when it came to controlling the jointing parameters.
However, there are benefits if you get it right:
Reducing the size of individual components: In future, even very large end products will not need to be manufactured as a single piece. Instead, several smaller components will be form-fitted to each other.
Material optimisation: Breaking down the whole into several individual components allows the best materials to be combined to suit the load. Examples include heavy-duty shaft journals, wear-resistant surfaces, and high-strength, pretensioned tie bars.
The time saved in supplying the product is immense because the smaller, individual components are very much easier to manufacture. The number of suppliers of small components is much greater, and this helps lower costs.
These points lead to completely new solutions in a variety of industrial sectors involved in the manufacture of very large components, same as in the SMS Siemag design of the multi-part backup rollers.
The several researches and inserting the know-how of SCHAAF GmbH & Co. KG made it possible in this case to accomplish the project successfully and on time. The hub was first expanded radially using oil pressure and then the shaft journals were inserted in the hub in an axial direction simultaneously but from opposite sides, using the screw clamping device. The entire jointing process was monitored and recorded by the measuring unit in the hydraulic controller. The parts were jointed using an axial pretensioning force of 40,000 kN over a total elongation of some 300 mm, but it took only 6 hours and was accomplished in collaboration with SCHAAF employees. The result was a fully jointed backup roller with an overall weight of more than 200 tonnes.