ISO 13373-9:2017

Overview

ISO 13373-9:2017 - "Condition monitoring and diagnostics of machines - Vibration condition monitoring - Part 9: Diagnostic techniques for electric motors" provides a practical, step‑by‑step vibration‑based approach for diagnosing faults in electric motors. It covers four motor types: squirrel‑cage induction, wound‑rotor induction, salient‑pole, and DC motors, and is mostly applicable to motors with power above 15 kW. The standard focuses on vibration diagnostics only; use of non‑vibration quantities (voltage, current) is outside its scope.

Key topics and requirements

• Scope and applicability
  • Targeted diagnostic procedures for the four main motor types; can sometimes be adapted to other electrical machines (e.g., generators) with caution.
  • Primarily for motors >15 kW.
• Measurement guidance
  • Vibration transducer selection: non‑contacting probes (inductive, capacitive, eddy‑current) for rotating shafts and seismic transducers (accelerometers, velocity sensors) for non‑rotating parts.
  • Importance of appropriate signal conditioning and measurement system selection (see ISO 13373‑1 and ISO 13373‑2).
  • Operational parameters to record: rotational speed, load, mounting, orientation, temperatures.
• Diagnostic methodology
  • Initial analysis per ISO 13373‑3 to assess severity, safety, and need for shutdown.
  • Motor‑specific analysis using flowcharts, process tables and fault tables to identify likely root causes.
  • Techniques described: spectral analysis, time waveform analysis, phase analysis, operational deflection shape (ODS), and visual inspection.
  • Special considerations: high spectral resolution required to detect rotor bar and slip‑frequency related faults; grounding and electrical field effects before measurement.
• Supporting annexes
  • Annex A: normative fault table and systematic approach.
  • Annex B: methodology for vibration diagnosis.
  • Annex C: illustrative case studies and examples.

Practical applications

• Routine and forensic vibration diagnostics of industrial motors driving pumps, fans, compressors, conveyors, etc.
• Root‑cause analysis of high or erratic vibration to decide corrective actions or maintenance priority.
• Integrating vibration diagnostics into condition monitoring programs and predictive maintenance strategies.

Who should use it

• Condition monitoring practitioners, vibration analysts, reliability engineers, maintenance technicians, and consultants involved in motor diagnostics and predictive maintenance.

Related standards

• ISO 13373‑1, ISO 13373‑2, ISO 13373‑3 (vibration measurement and analysis methods)
• ISO 20958 (definitions for induction motor types)
• ISO 7919, ISO 10816, ISO 20816 (vibration severity and acceptance criteria)
• ISO 13372, ISO 2041 (vocabulary)

Keywords: ISO 13373-9:2017, vibration condition monitoring, electric motor diagnostics, rotor bar faults, slip frequency, vibration measurements, condition monitoring standard.