Condition Monitoring & Analysis Techniques

Vibration, Thermography, Ultrasound, and Analysis

• Vibration, thermography, ultrasound, and analysis are key points in CAT III.
• They give a guide to topics required as per ISO 18436-2.
• These points are an excellent study resource.

Condition Monitoring Programs

• CAT III analysts are responsible for setting up and managing condition monitoring (CM) programs.
• ISO and other standards guide these programs.
• Maintenance strategies depend on criticality, P-F intervals, and failure modes.
• Strategies include run-to-failure, preventive, and condition-based.
• Performing proactive tasks and precise maintenance are key for reliability.
• Managing a CM program involves defining standards, test frequency, setting up and managing databases, refining alarms, writing reports, follow-up, review, and educating others.

Ultrasound

• Instruments convert high frequencies to audible sounds.
• Primarily used for listening for faults.
• Amplitude readings and waveforms can be captured.
• Can be used in contact and airborne applications.
• Useful in high noise environments.
• Applications include detecting bearing and lubrication problems, steam, air, and gas leaks, faulty steam traps, and electrical faults.
• Can be used while greasing bearings.

Thermography

• Thermography (infrared imaging) detects temperature changes inexpensively.
• Cameras have varying capabilities, matching the right camera to the application is important.
• Principles like transmission, absorption, reflection, and emission should be understood to avoid costly errors.
• Test conditions (wind, sunlight, ambient temperature, angle) affect readings.
• Applications include detecting electric motor and mechanical wear, steam trap malfunction, and other process issues.

Oil Analysis

• Oil analysis checks oil chemistry, condition, and contamination for wear.
• Checks for particles up to 8-10 microns in size.
• Analysis can be done by oil labs or on-site instruments.

Wear Particle Analysis

• Utilizes microscopes to view microscopic particles on prepared slides.
• Used to determine the nature and severity of wear, and wear on components like lubricating oil and hydraulic fluid.
• Essential for critical gearboxes.
• Standard oil analysis limits particle detection to 8-10 microns.

Signal Processing

• Introduction: Covers the basic steps in signal processing, including high pass, low pass, and band pass filters, and their characteristics. Includes concepts like phase accuracy.
• Dynamic Range: The ratio of the largest to smallest signal.
• Aliasing: A phenomenon to avoid in signal processing; it occurs in signals that have frequencies above half of the sampling rate, leading to inaccurate results.
• Sampling Rate: Relationship between sample time (T) and the line of resolution, Understanding of Nyquist criterion.
• Windowing: Use of Windows in Signal Processing. Trade-offs in frequency and accuracy.
• Averaging: Techniques for reducing noise using averaging methods. Discusses various overlapping methods.
• Triggering, TSA, autocorrelation, order tracking: Advanced signal processing techniques, for timing issues.
• Time Waveform Analysis: Time settings, relationship between Time and Frequency waveforms, relevant measurement units.

Phase Analysis

• Representing Phase: Relates phase changes to displacement and acceleration. Understands importance of relative phase in various contexts.
• Measuring Phase: Methods for measuring phase using external references (tachometer, keyphasor, or strobe light). Differentiates relative & absolute phases.
• Fault Diagnosis: Using bubble diagrams, diagnosing common machine operation issues.

System Dynamics

• Single Degree of Freedom (SDOF): The definition and application.
• Damping: Types of damping (viscous, frictional, hysteresis) and the effect on system. Relationships between mass, stiffness and natural frequency. Magnitude, phase and damping concepts.
• Multi-degree of freedom (MDOF): Systems and their properties. Natural Frequency, resonances, detection and tests for resonance, the graph displays and data collection settings. Cross-Channel Measurements (Cross-channel phase, transmissibility, Frequency Response Function).

Balancing Rotating Machinery

• General Considerations: Safety, preparation, equipment, etc.
• Vectors and Polar Plots: Understanding vectors, magnitudes, phases.
• Single-Plane Balancing: Procedure, trial weights, weight placement, units, and phase lag.
• Two-Plane Balancing: Concepts of static and couple unbalance, methodology for performing the process.

Additional Topics

• High frequency techniques: Early detection of bearing wear or detection of bearing wear in low speed bearings.

• Rolling Element Bearing Analysis: High-frequency techniques, measuring high-frequencies, sensor mounting and proximity with bearings, demodulation, interpreting the data and techniques to detect bearing wear.

• Journal Bearing Analysis: Different bearing designs, considerations for stability, vibration, damping as well as installation, calibration and sensitivity. Proximity probes use and considerations.