Choose signal views from the physical behaviour and time scale that must remain visible. For a rolling-element-bearing pump, overall velocity can serve the broad change question, while acceleration or bearing-condition processing exposes higher-frequency behaviour and a spectrum separates components. For a slow-speed fan, a waveform may preserve impacts or modulation compressed by an overall value.

A critical asset does not need every available vibration view. It needs a signal set that answers the next maintenance question with enough context to be interpreted responsibly. Critical asset vibration signals should therefore be selected by decision purpose: screening a change, locating frequency content, understanding time behaviour, comparing relative motion, or relating the reading to speed and process state.

That sequence keeps the measurement plan focused. Rotating machinery fault indicators can reveal a change worth investigating, but a single signal rarely identifies the cause on its own. The asset’s operating modes, failure exposure and available reviewer capability determine what should be collected next.

Start with the question, not the display

The same machine can produce several useful vibration views, each with a different job. An overall value can make a route trend easier to screen. A spectrum separates vibration energy by frequency, while a time waveform shows how amplitude develops through time. Fluke’s vibration-analysis guide identifies the waveform and frequency spectrum as core analysis views. Phase adds a relative timing relationship to another signal or speed reference.

The important distinction is between selection and diagnosis. A rise in overall vibration may justify a closer look, a repeat collection or further analysis. It does not prove misalignment, imbalance, bearing damage or another fault. Frequency content, waveform shape and phase become useful only when the machine configuration, speed, load and collection quality support the question being asked.

Give each signal a defined job

Build the collection plan around the decision that follows the result. The following map is useful for a critical pump, fan, compressor, gearbox, motor or turbine auxiliary, provided the asset-specific plan defines the details.

  • Overall trend: use a broad level to screen comparable readings for change. It helps identify where attention may be needed, especially when the same point and operating condition can be repeated.
  • Frequency spectrum: use frequency content when the next question is whether a change is concentrated around particular running, rotational or other frequency relationships. It narrows the analytical question; it is not a self-contained fault verdict.
  • Time waveform: use time behaviour when impact, modulation, transient behaviour or non-steady vibration needs closer examination. Compare the waveform with the machine state that existed during collection.
  • Phase and speed reference: use these when the review depends on relative motion, timing or a rotational reference. The interpretation must follow the machine arrangement and the competence available.
  • Process and operating context: preserve speed, load, flow, pressure, control state and time since start-up where they affect comparability. These inputs often explain why two otherwise similar vibration readings differ.

The set may be small. A stable, low-complexity asset may need a routine trend and defined exception route, while a high-consequence or variable-duty machine may need more context. Criticality changes the consequence of missing a developing condition; it does not make every signal mandatory.

For an asset whose next question is only whether a change is repeatable at a stated duty, the condition-monitoring category does not turn that screen into a requirement for spectrum, waveform or continuous collection. Add those views only when the remaining question needs frequency content, time behaviour or behaviour between route visits. Collecting every available display can make review slower if no one has defined how each result will be used.

For example, a pump that changes duty with process demand may need a stated operating window before its route trend is compared, whereas a fixed-speed standby machine may place more value on a repeatable point and consistent mounting. The right distinction comes from the machine and the decision, not from a universal signal menu.

Separate the signal view from the collection mode

Portable and continuous collection answer different timing needs. A portable route is useful when teams need condition and process context at the machine, then compare readings at planned intervals. The VIBXPERT II portable analyser collects vibration, bearing-condition, inspection and process data with on-site analysis functions.

Continuous observation can be appropriate when the question is how behaviour changes between route visits or across operating states. Online condition monitoring options are a separate equipment route for that need. Their presence does not make online monitoring necessary for every critical asset, and a continuous trend still needs the correct operating context.

Before choosing either mode, define the machine train, measurement locations, operating states to compare, expected review interval, person who will review exceptions and the evidence needed if the result changes. This prevents a more frequent data stream from becoming a less useful one.

Apply the signal map to two machines

For a constant-speed pump route, overall vibration is efficient for comparable screening. If the overall value changes, a spectrum helps show which frequency bands account for the difference, phase can support relative-motion questions across coupled components, and the time waveform can reveal impacting or modulation that the single overall number conceals.

For a variable-speed fan, a single overall value collected at different speeds is a weak comparison. Retain speed with every observation. A spectrum related to running speed can separate orders that move with speed from fixed-frequency content, while a waveform is useful where the behaviour is intermittent during run-up or load change. The collection plan should specify the operating state before it specifies the display.

Good escalation notes retain the asset, point, direction, acquisition condition, trend comparison and the exact question needing review. They should also name limits such as an unavailable speed reference, a changed process condition or an uncertain mounting arrangement. That lets the reviewer distinguish a machine change from a comparison problem.

Signal selection should remain consistent in the route record. If an overall value, spectrum or waveform is collected for a particular purpose, record that purpose with the measurement point and operating state. A later reviewer can then see whether a missing signal was outside the original plan or was expected but not captured. This is especially important on critical assets, where a compact summary can otherwise hide a gap in the evidence needed for the next review.

When the need is for measurement and analysis support, the vibration-analysis service scope includes CAT II vibration analysis using VIBXPERT II with varied measurements and portable or permanent monitoring modes. The useful handover is the defined evidence gap, not a request for a predetermined diagnosis.

Give every signal one machine question

The final signal map should start with the asset, operating state and failure-related question. A route measurement, permanently observed channel and process reference may complement one another, but each needs a declared purpose and comparison basis.

Every vibration signal needs one machine question and a declared operating state. CAT II analysis using VIBXPERT II, in the selected portable or permanent mode, may be booked through Aquip; submit the defined asset service request. A channel lacking both labels remains unassigned data rather than a condition-monitoring conclusion.

Close the map by writing one question beside each vibration signal and one operating state beside that question. Signals without both labels remain unassigned data, not a monitoring conclusion.