Overview
ISO 22096:2007 - Condition monitoring and diagnostics of machines - Acoustic emission - defines the general principles for applying acoustic emission (AE) to machine condition monitoring and diagnostics. The standard is applicable to all machinery and associated components and covers structure-borne measurements only. It describes AE phenomena, instrumentation, installation, data acquisition and basic analysis approaches used to detect early mechanical and structural deterioration.
Key topics and requirements
- Scope and principle: AE are transient elastic waves generated by rapid release of energy (e.g., crack growth, friction, leakage). Typical detected frequencies lie roughly between 20 kHz and 1 MHz.
- AE system components: sensors/transducers, pre-amplifiers, filters and data acquisition systems; systems may be permanent, semi‑permanent or portable.
- Sensor installation and coupling: correct mounting, clean contact surface, appropriate couplant (oil, grease, adhesives, paste, wax) or dry contact, use of magnets/clamps or adhesives; waveguides can be used to improve transmission or protect sensors from temperature.
- Calibration and characterization: sensor selection considers size, sensitivity and frequency response; reference checks such as the Hsu‑Nielsen (pencil lead break) may be used to simulate AE events.
- Interference and limitations: identify and mitigate electronic, airborne, mechanical and process background noise. Recognized limitations include susceptibility to attenuation, sensitivity to high operational background noise, and challenges in correlating AE signatures to exact fault mechanisms.
- Data acquisition and baselines: acquire data under known operating conditions; establish baselines for stable machine states and for different operational modes; trending is emphasized over absolute values.
- Data analysis criteria: increasing AE activity over time, magnitude during steady state, emergence of new signal features, and instrument-specific methods to relate AE trends to machine condition.
Practical applications
ISO 22096 supports AE use for a wide range of equipment where a transmission path exists. Typical applications include:
- Bearings (early defect detection and contamination)
- Pumps, compressors and gearboxes
- Electric motors and generators
- Steam and gas turbines
- Slow‑speed rotating machines (