Long-term effects of repetitive axial loads on district heating pipes

We know the effect of temperature and that mechanically loaded district heating pipes degrade significantly faster than unloaded ones. In this project, we intend to investigate in detail the long-term effects of cyclic mechanical loads on the rate of degradation and to develop a new model for calculating life expectancy that considers the combined effects of high temperature and repetitive axial loads.

Relationships between different stress levels and the rate of degradation will be investigated in laboratory experiments. The impact of the number of cycles will also be addressed. The effects of mechanical stress will be evaluated from field tests as well. An important part will be collaboration and the exchange of experience regarding ageing and lifetime predictions with experts both in Sweden and internationally.

The project leads to knowledge that gives the owners of the district heating networks the opportunity to operate and maintain their networks in a more optimal way. Society at large has an interest in increasing the sustainability of district heating networks from an environmental perspective. Reduced costs for maintenance and heat losses as well as reduced reinvestments are also beneficial for society and especially the owners. The knowledge is also useful for companies that develop and manufacture sustainable materials and producers of district heating pipes. There is a need for reliable methods to verify the long-term properties of the products.

In summary, the project contributes to increased sustainability of distribution systems for district heating, increased competitiveness of the Swedish energy sector whose knowledge and service create business in and outside of Sweden, contributes to the development of district heating systems for future operation and useful knowledge in standardization bodies regarding district heating.