Ruukki and its former associated companies have been collaborating with VTT Expert Services and the VTT organisations preceding it in various forms for at least 25 years. Ruukki has also been manufacturing sandwich panels for more than 25 years. Ruukki has had VTT Expert Services accompanying it all this time.
Ruukki's panels are used in façades, partition walls and ceilings, and also as roof panels. The most typical applications include their use in industrial and commercial buildings, sports halls, warehouses and power plants. The panels are also suitable for food industry construction and demanding cleanroom purposes. Sandwich panels are prefabricated elements that consist of an inner insulation core between two colour-coated steel sheet layers. The insulating core can be mineral wool or some other structural insulant.
For Ruukki, the safety of all products is of utmost importance, so it was clear from the very beginning that each new product would be thoroughly tested. There is a harmonised product standard for self-supporting sandwich elements, and a CE marking must be acquired for any products falling in to this category. Sandwich elements are also used as load-bearing structures, and this is one of the reasons why Finland has drawn up a national application standard for them. Ruukki wanted to complement the CE marking with a VTT certificate that takes into account the requirements for load-bearing capacity set by the national application standard. The VTT certificate reports such data as partial safety factors and load curves or tables that the manufacturer is unable to report in their declaration of performance. In addition, as regards strength properties, the certificate entails third party supervision, which a CE marking does not currently require.
Testing helps product development as well
Sandwich panels have been tested according to need in the very beginning and in various ways over the years, for example, when new products have been developed. Testing methods and relevant practices have changed in certain respects over the last 25 years, but so have the requirements and regulations. The manufacturer is able to conduct some of the testing on their own if they have access to proper methods, equipment and competence, but in some cases it is advisable or compulsory to commission the testing services from an external provider.
The versatile testing of sandwich panels covers such issues as mechanical properties, burning behaviour, thermal insulation and tightness properties, sound insulation and long-term durability. These construction solutions are extremely energy efficient, helping the users of the buildings save energy.
The application process for a VTT certificate involves more than just testing
The certification process with all its phases was rather laborious and time-consuming, but also educational and useful. The starting point for and purpose of the process was to develop a certificate with content that, for its part of the process, provides a specific answer to the requirements concerning the presentation of strength properties in accordance with practical needs and third-party supervision applied in Finland.