Reserves in axial shear strength of district heating pipes

Cost reduction for the installation of district heating pipes can be achieved through improved engineering strategies activating reserves of the system. This paper investigates experimentally the axial shear strength of the insulation of pre-insulated bonded district heating pipes. The standard design assumes a perfect bond. Conversely, the experimental investigation showed a shear displacement and reproducible conditions for small shear strain. Thus, a relative displacement of the service pipe within the pipe system seems to be possible without harming the bond. This relative displacement will relax the medium pipe from the highest axial stresses, representing a hidden reserve in the pre-insulated bonded pipe system. Using this reserve in static calculation may allow more economic pipe solutions.