14 – Failure-Mode Analysis

Publisher Summary All of the analysis techniques discussed to till this chapter have been methods to determine whether potential problem exists within the machine-train or its associated systems. Failure-mode analysis is the next step required to specifically pinpoint the failure mode and identify which machine-train component is degrading after the determination of the existence of a potential problem within the machine-train or its associated systems. Although failure-mode analysis identifies the number and symptoms of machine-train problems, it does not always identify the true root-cause of problems. Visual inspection, additional testing, or other techniques such as operating dynamics analysis must verify root-cause. Failure-mode analysis is based on the assumption that certain failure modes are common to all machine-trains and all applications. It also assumes that the vibration patterns for each of these failure modes, when adjusted for process-system dynamics, are absolute and identifiable. Two types of information are required to perform failure-mode analysis: machine-train vibration signatures, both FFTs and time traces; and practical knowledge of machine dynamics and failure modes. Several failure-mode charts are available that describe the symptoms or abnormal vibration profiles that indicate the existence of potential problems.