Vibration Diagnostics: From Theory to Practice

Introduction to Vibration Diagnostics

Vibration diagnostics is a modern non-destructive testing method based on analyzing vibrations produced by machines and mechanisms during operation. It enables the early detection of defects and malfunctions, preventing accidents, reducing repair costs, and extending equipment lifespan.

Key Concepts and Terminology

Vibration: Mechanical oscillation of a body or system relative to its equilibrium position.

Vibration Amplitude: The maximum deviation from the equilibrium position.

Vibration Frequency: The number of oscillations per unit of time.

Vibration Spectrum: The distribution of vibration amplitudes across different frequencies.

Vibrosignature: A characteristic vibration spectrum corresponding to a specific type of defect.

History and Development of Vibration Diagnostics

Vibration diagnostics began to develop in the mid-20th century with the advent of the first vibration meters and spectrum analyzers. With advances in electronics and computing, the capabilities of vibration diagnostics have significantly expanded. Today, it is one of the primary non-destructive testing methods used across various industries.

Fundamentals of Vibration Analysis

The Nature of Vibrations

Vibrations arise from various forces, such as the imbalance of rotating parts, impacts, friction, aerodynamic, and hydrodynamic forces. Each type of malfunction has its characteristic vibrosignature, which allows it to be identified through vibration spectrum analysis.

Types of Vibrations and Their Characteristics

Vibrations can be classified according to different criteria:

By Direction: Vertical, horizontal, axial.

By Frequency: Low-frequency, mid-frequency, high-frequency.

By Amplitude Variation: Constant, variable, impulsive.

Methods of Measuring Vibrations

Different types of sensors are used to measure vibrations:

Accelerometers: Measure vibration acceleration.

Velocity Sensors: Measure vibration speed.

Displacement Sensors: Measure vibration amplitude.

The choice of sensor type depends on the specific task and characteristics of the measured vibration.

Equipment Installation and Configuration Techniques

Proper installation and configuration of vibration sensors are crucial for obtaining reliable measurement results. Sensors should be mounted on rigid structural elements as close as possible to the vibration source. Ensuring secure sensor attachment and protection from external influences is also important.

Spectral Analysis of Vibrations

Basics of Spectral Analysis

Spectral analysis decomposes a complex vibration signal into simple harmonic components, each with its own frequency and amplitude. This allows identifying characteristic signs of various defects and malfunctions.

Frequency Spectra and Their Interpretation

The frequency spectrum of a vibration signal is a graph showing the amplitude of vibration as a function of frequency. Spectrum analysis helps identify dominant vibration frequencies and link them to potential sources. For example, an elevated vibration level at the rotor's rotational frequency (1x) may indicate imbalance, while increased vibration at multiples of the rotational frequency (2x, 3x, etc.) may suggest bearing or gear defects.

Diagnosing Malfunctions Through Vibrations

Vibrosignatures of Various Malfunctions

Each malfunction has its characteristic vibrosignature, which manifests in specific frequency ranges and has a distinct shape. For instance, rolling bearing defects usually show increased vibration at high frequencies, while rotor imbalance is reflected at the rotational frequency.

Techniques for Identifying and Analyzing Malfunctions

Various techniques are used to identify and analyze malfunctions, such as:

Comparing vibration spectra with reference models.

Analyzing trends in vibration changes over time.

Using expert systems and databases of vibrosignatures.

Vibration diagnostics software enables various types of vibration signal analysis, including spectral analysis, envelope analysis, impact pulse analysis, and more. It may also include vibrosignature databases for automatic fault diagnosis and tools for rotor balancing.

Balanset-1A, beyond its primary function as a portable balancing device, also serves as a powerful vibration diagnostic tool through its "Vibrometer" and "Graphs" modes. These modes offer extensive capabilities for in-depth analysis of vibration signals, aiding in the detection of potential equipment issues.

Vibrometer Mode

In this mode, Balanset-1A functions as a traditional vibrometer, providing real-time data on various vibration parameters. It displays overall vibration levels, vibration components at the rotational frequency (1x), and the phase angle. The inclusion of a tachometer allows precise measurement of rotational speed (RPM), further enhancing diagnostic capabilities. The "Measurement Log" feature conveniently saves this data for later analysis and trend tracking.

Graphs Mode

The "Graphs" mode takes vibration analysis to the next level by offering visual representations of vibration data. It provides four different types of graphs:

Overall Graphs: These provide a visual overview of the overall vibration level, helping quickly identify any abnormal increases in vibration.

1x Graphs: These focus on the vibration component at the rotational frequency (1x), often indicating balancing issues. Analyzing these graphs helps identify the source of imbalance and plan corrective actions.

Harmonic Graphs: These display the presence and impact of harmonic frequencies, which are multiples of the fundamental frequency. Significant harmonics may indicate specific mechanical problems, such as misalignment or bearing defects.

Spectral Graphs: These provide a detailed breakdown of the vibration signal across a wide frequency range. By examining the spectrum, specific frequencies associated with various machine faults can be identified, allowing for targeted maintenance and repairs.

Combining these graph types offers a comprehensive view of the machine's vibration behavior, facilitating effective diagnosis and fault resolution. The ability to visualize vibration data in various forms helps understand the underlying causes of vibration and enables proactive maintenance strategies to prevent equipment failures and downtime.

Practical Aspects of Vibration Diagnostics

Organizing and Conducting Vibration Diagnostic Surveys

To effectively conduct vibration diagnostics, it is essential to develop a survey program that includes:

Selecting monitoring objects.

Identifying vibration measurement points.

Determining the measurement frequency.

Establishing measurement procedures.

Analyzing results and compiling reports.

Report Preparation and Recommendations

Based on the results of vibration diagnostics, a report is generated, containing information on the equipment's condition, identified defects, and malfunctions, as well as recommendations for their elimination. The report should be clear and informative so that management can make informed decisions about repairs or equipment replacement.

Vibration diagnostics is an effective tool for maintaining equipment in working condition, preventing accidents, and reducing repair and maintenance costs. Proper application of vibration diagnostics significantly increases the lifespan of machines and mechanisms, enhancing their reliability and efficiency.