Vibration Diagnostics: Interpreting the Language of Machines

Devices

Portable balancer & Vibration analyzer Balanset-1A

€1,975.00 + VAT (if applicable)

Parts

Vibration sensor

€90.00 + VAT (if applicable)

Parts

Optical Sensor (Laser Tachometer)

€124.00 + VAT (if applicable)

Devices

Balanset-4

€6,803.00 + VAT (if applicable)

Parts

Magnetic Stand Insize-60-kgf

€46.00 + VAT (if applicable)

Parts

Reflective tape

€10.00 + VAT (if applicable)

Devices

Dynamic balancer “Balanset-1A” OEM

€1,735.00 + VAT (if applicable)

Vibration Diagnostics is an advanced form of condition monitoring in which vibration data is not merely collected but deeply analysed and interpreted to determine the health of a machine and pinpoint the root cause of specific faults. It is the process of translating raw vibration signals into actionable maintenance information. Where simple monitoring asks “is anything wrong?”, diagnostics asks the harder and more valuable question: “what exactly is wrong, how bad is it, and why did it happen?”

1. Definition: What is Vibration Diagnostics?

While vibration monitoring may track overall levels and raise an alarm when a threshold is crossed, diagnostics focuses on the “why.” It seeks to answer questions like: Is this vibration caused by unbalance or misalignment? Is that bearing failing? Is there a problem with the gears, the coupling, or the foundation? Diagnostics therefore sits one level deeper than detection: it is the interpretive layer that turns a “high vibration” reading into a named defect on a named component.

That distinction matters because every fault demands a different corrective action. Confusing unbalance with misalignment, or a bearing defect with looseness, wastes labour and can leave the real problem untouched — so accurate diagnosis is the difference between a lasting repair and a repeat failure.

2. The Diagnostic Process

A typical vibration diagnostics process follows a structured, repeatable sequence:

1. Data Acquisition: collecting high-quality data with sensors such as accelerometers and a data analyzer. This means selecting the right sensor, mounting it correctly — per ISO 5348 — and choosing appropriate settings (Fmax, resolution, averaging). Poor mounting or the wrong Fmax can hide the very fault you are hunting.
2. Signal Processing: converting the raw time waveform into a more useful form, most commonly a frequency spectrum via the FFT (Fast Fourier Transform). Phase analysis and enveloping add further views.
3. Spectral Analysis: the core of diagnostics. The analyst examines the spectrum for patterns, because different faults generate energy at predictable frequencies. For example:
   • Unbalance: high amplitude at 1× the rotor’s running speed, mostly radial.
   • Misalignment: high amplitude at 1× and especially 2× running speed, often with strong axial vibration.
   • Bearing Defects: non-synchronous, high-frequency peaks at the specific bearing fault frequencies (BPFO, BPFI, BSF, FTF).
   • Gear Defects: peaks at the gear mesh frequency and its sidebands.
4. Fault Confirmation: using multiple data types to corroborate a diagnosis — examining time-waveform shape for impacting that betrays a bearing fault, or using phase to separate unbalance from a bent shaft. A single peak rarely proves a fault; a complete, consistent signature does.
5. Reporting and Recommendation: clearly communicating the findings — the identified fault, its severity, and a recommended course of action — to maintenance personnel.

3. Key Tools and Techniques

Vibration diagnostics relies on a toolkit of complementary analytical methods, each exposing something the others miss:

• Spectrum Analysis (FFT): the primary tool for identifying which frequencies are present in a signal.
• Time Waveform Analysis: useful for observing signal shape, impacts, and modulating events that can be missed in the FFT.
• Phase Analysis: a crucial tool for confirming unbalance, misalignment, and looseness, and the essential reference for balancing.
• Envelope Analysis (Demodulation): a technique for detecting the very low-energy, repetitive impacts associated with early-stage bearing and gear defects.
• Order Analysis: used for variable-speed machines, relating vibration to multiples (orders) of running speed rather than to fixed frequencies.
• Operating Deflection Shape (ODS): an animation showing how a machine or structure actually moves at a given frequency, valuable for diagnosing resonance and structural weakness.

4. Diagnostics in the Field — Confirm, then Correct

Much diagnostic work happens on running plant, not in a lab. A maintenance engineer arrives with a portable instrument, mounts an accelerometer on each bearing, captures spectra and phase, and forms a diagnosis on site. When the verdict is unbalance, the same visit can resolve it: a two-channel analyzer and field balancer such as the Balanset-1A measures the 1× amplitude and phase, computes the influence coefficients, and guides single- or two-plane correction in the machine’s own bearings — diagnosis and cure in one stop. Severity is then judged against an accepted standard such as the modern ISO 20816 series (the successor to ISO 10816), which sorts vibration into acceptance zones by machine type and mounting.

5. The Goal: From Reactive to Proactive

The ultimate goal of vibration diagnostics is to support a proactive maintenance strategy. By identifying the root causes of failure — misalignment, resonance, improper lubrication, structural looseness — organisations can move beyond simply fixing broken machines and begin to eliminate the conditions that cause them to fail in the first place. This underpins a mature condition-based maintenance programme, delivering significantly improved reliability, longer asset life, and lower total cost.

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