Document Type

Student Presentation

Presentation Date

4-18-2016

Faculty Sponsor

Harold Ackler

Abstract

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.

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