Quality inspection of PBP-System components, inspection of pre-insulated bonded pipe joints (Final report on the project) (Booklet 1/2024)

As part of a recurring test of PBP systems, the AGFW (The Energy Efficiency Association for Heating, Cooling and CHP) has this time subjected connections for pre-insulated bonded pipes (joint systems) to various tests in accordance with EN 489-1:2019 [12] with the aim of demonstrating the standard conformity of these systems. The project was carried out at HCU (HafenCity University of Hamburg) under the “Technical Infrastructure Management” professorship and was supported and accompanied by the BFW (Federal Association of District Heating Lines e.V.) and the system manufacturers and installers.

As part of the commissioned investigations, shrink and welding joints were examined, on which soil stress tests were carried out with subsequent determination of resistance to penetration of water, as well as standardized tests to determine the foam properties, including the determination of cell size, foam density, compressive strength, and water absorption.

While there was no criticism of the foam quality at any point, there was an outlier in the soil stress tests in the form of a leak in a joint system after the earth pressure load. The resulting questions regarding clarification of the cause were consistently investigated through various additional investigations. In particular, the functionality of the system in question was checked and proven again in a repeat test at the FFI (District Heating Research Institute in Hannover e.V.). The discussion about the soil stress test conditions according to EN 489 triggered by the incident will continue and should also be incorporated into European standardization.

Overall, it was therefore primarily possible to determine that the tested systems meet the set requirements and that the tested systems represent a high level of quality. Based on the available studies, a decline in the quality of pre-insulated bonded pipe connections in district heating pipeline construction cannot generally be conceded.