Dr. Villalobos-Jara, Felipe

The development of a monitored district heating piping system has allowed the study of axial displacement variations in a buried pipeline. This piping system includes four instrumented sections of piping within an in use district heating network. There are also different conditions under testing such as thickness of expansion cushions, temperature ranges and bedding soil types. The pipe axial displacements were on-line monitored by means of extensometers in six positions along each of the four sections of the pipeline. Measured maximum pipe axial displacements were 24 and 25 mm in the corners of the 41 m long monitored pipelines, while estimated values were 23 mm using current recommendation procedures and 27 mm using calibrated commercial computer programs. One temperature unloading-reloading caused displacements to not return to the same values as before, but around 3 mm smaller. Therefore, several unloading-reloading temperature cycles may affect the pipe deformation behaviour in the short and long term. © 2021 Published with permission by the ICE under the CC-BY 4.0 license

The need for understanding the performance of district heating pipeline systems has led to the development of a monitoring program. This program includes the design of the connection of an instrumented section of piping within an in-use district heating network. The design complies with the current European district heating recommendations and standards. Monitoring consists of the measurement of earth pressures against the pipes, axial pipe displacements, and temperature of the fluid and soil around the pipes. There are different conditions being tested such as thickness of insulation materials, temperature ranges, and bedding soil type. In particular, there is interest in testing the corner positions. Details of the piping and instrumentation arrangements as well as soil geotechnical characteristics are presented. It was found that when the fluid temperature increased from ambient conditions up to 90°C, pipes were moving all along their length. Moreover, after a fluid temperature drop from 90°C to 20°C over 20 days and subsequent increase to 90°C again, pipe axial displacements did not return to the same values as before