Non-destructive methods for assessment of district heating pipes

Paper in proceeding, 2018

Many energy companies are facing renewal of their district heating network. However, there are no methods to determine the thermal performance of an existing pre-insulated district heating pipe during its operation. The insulation performance of the pipes decreases gradually during time due to degradation of polyurethane (PUR) foam. The aim of our project is to find non-destructive methods for assessing the lifetime and the status of both old existing pipes and new pipes. All present methods demand some kind of excavation and interference in the system in order to assess the thermal status of the pipes, the methods determine the status of the excavated part and not the status of the system. In existing pipes, copper wires are used for detection of moisture/water intrusion into the insulation part of the pipes. The copper wires is possible to use with other measuring or evaluation techniques in order to assess thermal properties. One of the tested methods, which is based on the electrical resistance in the copper wire has been named TCR-method (thermal coefficient of resistance). It may be used for new pipes but also for old pipes if it is combined with a cooling method. Laboratory tests has been performed both for the cooling method and TCR-method in order to develop the methods for further test in field.