The premature failures of a valve head bolt, buried pipe, and inhome heat exchanger from a local geothermal water system have motivated a forensic approach to finding the mechanisms of these failures. These issues can potentially harm water distribution and damage homes, a concern leading to a collaboration between the overseeing district board and a senior project team from Boise State University’s Materials Science and Engineering program. Failure analyses consisted of visual inspection, scanning electron microscopy (SEM), xray fluorescence spectroscopy (XRF), xray diffraction (XRD), electrochemical testing, and inductivelycoupled plasma mass spectrometry (ICPMS). SEM coupled with energydispersive spectroscopy (EDS) were used for basic chemical analysis. XRD of corrosion products correlated with EDS data to determine molecular species. Visual inspection and SEM of the bolt and pipe failure sites and crosssections developed information on failure propagation and possible chemical influences. Failure site isolation for the heat exchanger indicated that the pipes failed near braze sites, with the braze materials having been identified by XRF. ICPMS analysis of the geothermal water aided our electrochemical testing of the corrosion behaviors likely contributing to failure. Suggested alterations to material selection and treatment might prevent similar component failures moving forward.
Herren, Benjamin; Lester, Kelci; Miner, Robert; and Warren, Patrick, "Failure Analysis of Geothermal Water System Components" (2016). 2016 Undergraduate Research and Scholarship Conference. Paper 32.