Cryogenic Pumps Monitoring, Diagnostics and Expert Systems Using Motor Current Signature Analyses and Vibration Analyses

Abstract

The paper discusses the Cryogenic Pumps Condition Monitoring and Machinery Diagnostics Systems, including the automated Expert Diagnostics Systems. The Cryogenic Pump construction differs by design, failure modes and criticality and no single solution will suit all designs. Therefore, two approaches are discussed: Motor Current Signature Analyses and Vibration Analyses. The paper further shows the real case studies, diagnostics and findings on Cryogenic Pumps using both analyses. The article addresses common failure types and proposes applicable solutions. The Cryogenic Pumps mechanical and electrical malfunctions are discussed, their reflection on the dynamic current spectrum using improved Motor Current Signature Analysis (MCSA), aka. Model-Based Voltage and Current (MBVI) Analyses and vibration spectrum using Vibration Analyses (VA). The article contrasts the similarities vs. differences and advantages vs. disadvantages of both methods and may be of value for field engineers to understand the pros. and cons. of each technology. The paper outlines the Expert Diagnostics System based on MBVI, able to distinguish automatically among different malfunctions. The Expert System uses the power spectral density of the difference between the expected current obtained from the model and the actual current. These differences include only abnormalities generated by the motor anomaly. Therefore, they are immune to the noise or harmonics present in the supply voltages. The presented results, using both approaches: Model-Based Voltage and Current Analyses and Vibration Analyses, prove the potential of both techniques and the advantages of their combined use for reaching a maximum reliable Condition Monitoring and Diagnostics of Cryogenic Pumps.