Segregation of influences on flexible pipe connectors (REPA) force under field operation condition for parabolic trough collector plants

Flexible pipe connectors (REPAs) for parabolic trough collectors have been subject to numerous investigations and technical improvement at different test rigs worldwide. Still, REPAs remain a critical key component, that need further improvement to meet the life time expectations from power plants, especially at the comparably hot collector outlet locations. This paper analyzes the influence of the REPA setup in terms of pressure, temperature and the adjacent tubing (bottom connection) on the load cell readings at two REPAs. The investigations are performed using two flex hose assemblies, each composed of a corrugated hose and a swivel joint in combination with two different bottom connections. A set of five scenarios is investigated in order to conclude the most promising REPA testing setup with minimum mechanical loads on the load cell at the swivel joint from the bottom connection. This is not only relevant for testing ball joint assemblies and flex hose assemblies but gives a clear hint on how to integrate flex hose assemblies in power plant applications. It is found that the temperature has a comparably dominant influence in one of the bottom connections and thus impedes a load comparison of the two REPAs under testing. System pressure significantly increases the readings of the load cells, due to the fact that when pressurized, the flexible hoses introduce higher reaction forces especially when performing rotation cycle. Based on these findings the test rig at PSA will be adapted to execute tests of ball joint assemblies and flex hose assemblies in the near future.