AXILINEIndustrial vibration diagnostics
Vibration has risen and the cause isn't clear? You balanced it, but the vibration came back? Then what you need first is diagnostics, not another round of balancing. We come to site, measure vibration at every bearing housing, and analyse the spectrum (vibration broken down by frequency) and the phase (tying the oscillation to the shaft's rotation). Then we deliver a finding: which causes are most likely, what to check first, and how urgent it is.
When you need diagnostics, not balancing straight away
Balancing corrects one cause of vibration: rotor unbalance. It only reduces the running-speed component, the vibration at the rotation frequency. If the machine is shaking for a different reason, balancing won't help, and you'll have spent money on the visit anyway. So in unclear cases, the right order is: find the cause first, then fix it.
You need diagnostics instead of balancing when at least one of these signs is present:
- The cause of vibration isn't clear: the unit was running fine, then vibration rose for no obvious reason.
- It looks like there's more than one fault: vibration behaves differently at different operating modes or at different bearings.
- A repair didn't hold: vibration came back within days or weeks of balancing or replacing parts.
- Vibration appeared after some intervention: a motor rewind, bearing replacement, or moving the unit onto a new foundation.
- Vibration depends on load, temperature or pressure, not just on speed.
If the case is obvious, diagnostics as a separate service isn't needed. The instrument shows the spectrum and the ratio between overall vibration (the total level across all frequencies) and the running-speed component before balancing anyway, that's part of the standard procedure.
What we do on site
- 01
Readings at every bearing, in three directions
We fit accelerometers on every bearing housing of the unit and measure vibration in the horizontal, vertical and axial directions. The distribution of vibration across bearings and directions already narrows down the likely causes: unbalance, shaft misalignment and looseness each produce a different picture.
- 02
Spectrum and time waveform
We take an FFT spectrum and a time waveform at every point. We look at which frequencies dominate: the running-speed 1x, the second harmonic 2x (twice running speed), series of harmonics, bearing defect frequencies, blade-pass and mains-related frequencies. We go through how to read these patterns in detail in our article on the vibration spectrum.
- 03
Phase and order analysis
The laser phase sensor, referenced to a marker on the shaft, ties the vibration to the rotation. Phase relationships between bearings and order analysis referenced to running speed tell unbalance apart from misalignment and resonance, which look identical on amplitude alone.
- 04
Cross-checking against history and mode
We establish what's changed: repairs, part replacements, operating modes, when the vibration rose. If past readings or reports exist, we compare against them. We check how vibration behaves as speed and load change, and during run-up and coast-down (free deceleration by inertia).
- 05
Ranking the hypotheses
We bring everything together into a list of probable causes, from best supported to least. For each one, we state which signs point to it and how to check or fix it. You get a full picture with priorities, not a single guess.
What faults we find
Rotor unbalance
The 1x running-speed component dominates, and vibration rises with speed. The most common diagnosis, and the most convenient one: corrected by balancing right on site, without removal.
Shaft misalignment
Characterised by an elevated 2x, axial vibration and typical phase relationships between the bearings on either side of the coupling. We have a separate article on telling it apart from unbalance.
Looseness and soft foot
Bolts not fully tightened, cracks in the frame, mounting feet that don't sit flush on the base. Shows up in the spectrum as series of harmonics; vibration changes when fastenings are tightened.
Bearing defects
Peaks at the characteristic defect frequencies of the races, rolling elements and cage, not multiples of running speed, plus changes in the high-frequency region of the spectrum.
Resonance
The running speed coincides with the structure's natural frequency. A narrow amplitude peak and a fast phase shift as speed changes. Balancing in resonance is unstable; the frequencies need separating first.
Rubbing and thermal bowing
The rotor touches stationary parts or bows as it warms up. Vibration changes with running time and temperature, and the 1x picture is unstable.
Electrical causes
Defects in windings and rotor bars, an uneven air gap. Sign: components tied to the mains frequency, and vibration that disappears when power is cut, checked on coast-down.
Hydraulic causes
Cavitation, a pump operating outside its working range, blade-pass frequencies in pumps and fans. Vibration depends on flow rate and pressure, not just on speed.
Sources: ISO 13373-3:2015 · ISO 13373-5:2020
What you get
The result of diagnostics isn't a table of numbers, it's an answer: what's wrong with the machine and what to do next. In the finding you'll find:
- A ranked list of causes: which is most likely and what signs confirm it.
- What to check first, and by whom: some things your own mechanic can check in an hour, others need a shutdown and disassembly.
- An urgency assessment: keep running and monitor, plan a repair, or stop now.
- Measured vibration levels by bearing and direction, compared against the assessment zones of the applicable part of ISO 20816.
- A recommendation for the next step: balancing, shaft alignment, fastenings, bearings, or further investigation.
If the diagnosis is unbalance, we can balance the rotor in the same visit: the instruments and weights are already on site. Balancing is billed separately, by package, depending on the rotor's size.
Sources: ISO 20816-1:2016
One-off diagnostics or a periodic route
A one-off visit answers the question "what's wrong with this machine right now". It's the right format when a problem already exists and needs solving.
A periodic route solves a different problem: catching degradation before failure. We record the baseline vibration level of each unit while it's in sound condition, set alarm setpoints (warning and alarm threshold levels), and repeat measurements on a schedule at the same points. What triggers an alarm isn't an absolute figure, it's a rise relative to that machine's own baseline. More on this approach in our article on vibration monitoring, routes and setpoints.
| One-off diagnostics | Periodic route | |
|---|---|---|
| Task | Find the cause of a problem that's already there | Catch degradation before failure |
| When | Vibration has risen, a repair didn't hold, the cause is unclear | Continuously, on a measurement schedule |
| Basis for conclusions | Spectrum, phase, behaviour across modes | Trend relative to the baseline level and setpoints |
| Result | A finding with causes and an action plan | Early warnings and repair planning |
Sources: ISO 20816-1:2016
What vibration diagnostics doesn't give you
Let's say plainly where the method's limits are, so you don't expect the impossible.
It can't predict an exact remaining service life. Vibration diagnostics shows that a defect exists and is developing, and lets you rank the urgency. But it can't name a date for bearing failure: how a defect develops depends on load, lubrication and conditions, all of which change. Even the calculated bearing life under ISO 281 is a probabilistic figure, not the service life of a specific unit.
A single reading is weaker than a series. Without history we see the condition, but not the trend. Some conclusions from a one-off reading remain reasoned hypotheses, to be confirmed by checks or a repeat measurement.
Faults with no vibration signature aren't visible this way. Seal wear, corrosion, the condition of winding insulation, these need other inspection methods, and we'll say plainly if your case isn't a vibration one.
Sources: ISO 281:2007 · ISO 13373-3:2015
What we measure with, and who measures
Diagnostics is carried out by engineers who design and manufacture Balanset instruments themselves and use them for on-site balancing themselves. That means the person on your site sees not just numbers on a screen, but the physics behind them.
We measure with the two-channel Balanset-1A system: two accelerometers, a laser phase sensor referenced to a marker on the shaft, simultaneous acquisition on both channels. The software gives an FFT spectrum, a time waveform, overall vibration and the 1x running-speed component with amplitude and phase, and saves the data for comparison between visits. We also supply the same instrument as a product: if you want to run your own measurements, see the Balanset-1A page.
Sources: Balanset-1A manufacturer specification · Balanset-1A operation manual
Cost and travel terms
The minimum invoice per visit is 500 EUR, the minimum time on site is 4 hours. The first 20 km of travel are included, beyond that 0.60 EUR/km round trip. Payment: 50% upfront. All prices are + VAT (charged at the applicable rate).
If diagnostics shows unbalance and you decide to balance right away, the work is priced by package depending on the rotor's size: S, 550 EUR, M, 750 EUR per unit including diagnostics, L (75-300 kW or 0.5-2 t), 1000 EUR, XL (over 2 t or high speed), from 1500 EUR per unit including diagnostics. A written report is included in diagnostics.
Based in Vila Nova de Gaia (Porto), we travel across Portugal.
Sources: ISO 21940-11:2016
How to order diagnostics
Send us on WhatsApp or by email: a photo or video of the unit, its power and speed, a description of the problem (when the vibration appeared, what's changed, what's already been tried), and, if you have them, any past readings or reports. That's enough for us to assess the job and propose a visit date.
Phone and WhatsApp: +351 931 831 229. Email: axilinegeral@gmail.com. Instagram: @axiline.pt. Address: Rua das Colectividades 76 R/C ET, 4430-625 Vila Nova de Gaia.
Frequently asked questions
Can the cause of vibration be identified from a video or a phone-app measurement?
No. Video and phone apps only show that "it shakes a lot". A diagnosis needs the spectrum, the phase referenced to a marker on the shaft, and readings at every bearing in three directions. But video is useful at the enquiry stage: we can use it to assess the unit and prepare for the visit.
Do I need to stop the equipment for diagnostics?
The main measurements are taken on the running machine in its normal mode. But being able to start and stop it is useful: how vibration behaves during run-up and coast-down helps tell resonance and electrical causes apart from mechanical ones. We'll agree this with your process in advance.
If the cause is unbalance, will you balance it in the same visit?
Yes, usually that's possible: the instruments are already on site, the sensors are fitted. You'll need access to the rotor for fitting weights, and the ability to run the machine. Balancing is billed by package depending on the rotor's size; fitting work done by your own staff is included.
Can you tell me how much longer the bearing will last?
No, and don't trust anyone who promises an exact date. Vibration diagnostics shows that a defect exists and is developing, and lets you assess the urgency: monitor, plan a replacement, or stop. An exact remaining service life can't be predicted from vibration.
How does one-off diagnostics differ from vibration monitoring?
One-off diagnostics looks for the cause of a problem that's already there. Vibration monitoring means periodic measurements on a route, with a baseline level and setpoints, to catch degradation early through a rise in vibration relative to that machine's own norm. For critical units, it makes sense to move to periodic measurements after diagnostics.
Related content
Vibration analysis: measuring and assessing equipment condition
Here's what vibration analysis looks like with us: we measure vibration velocity at the bearing housings of the running machine in mm/s RMS (root mean square, the standard way of averaging oscillation) over the 10-1000 Hz band. We separately record the 1x running-speed component, vibration exactly at the rotation frequency, with its phase, plus the spectrum, time waveform, speed and operating mode. We compare the result against zones A-D of the applicable part of ISO 20816 and issue a report with a finding: operate, monitor, or fix the cause. Balancing and other corrections aren't part of this service and are carried out separately, based on the measurement results.
How to find the cause of equipment vibration: a methodology, not a list of causes
The cause is found not from a single spectrum (the breakdown of vibration by frequency) but from the whole set of signs together: context (what changed and when it started), how reliable the reading is, the ratio of vibration across all bearing supports in three directions, how the frequencies relate to running speed, the shape of the time waveform, repeatability, and phase — the angle showing at what point in the turn the vibration reaches its peak. You gather this data first, then formulate a single hypothesis, and test it with one controlled action. The diagnosis is not made by the instrument — it comes from the combination of the signs, the machine's behaviour, and a confirming check.
On-site pump balancing: impellers, rotors, and shafts of pump units
Yes, we balance pump rotors on site, in their own bearing supports, with no dismantling and no sending the impeller to a machine shop. Three conditions apply. First: most of the vibration has to come from the 1x running-speed component — vibration at the rotor's rotational frequency, the main sign of imbalance. Second: at least one correction plane has to be accessible, meaning a spot where a weight can be fitted — usually the coupling bolts or the impeller nut. Third: the pump has to be able to hold a stable mode with a constant flow rate. If the level is being driven by cavitation, operation away from the best-efficiency point, shaft misalignment, or worn wear rings, we'll show that with a measurement and say plainly: weights won't help.
Describe your equipment and the problem
We'll answer your questions, clarify the details, and let you know what's needed for an estimate and a visit.