Balancing and vibration diagnostics services: where to start in your case

For some, the machine started shaking after the wheel was cleaned, and it's obvious weights are needed. For others, vibration has risen for no clear reason, and balancing there might change nothing at all. This is a fork-in-the-road page: it shows which service fits your situation, what happens on site, and what it costs. Based in Vila Nova de Gaia, near Porto, we travel across Portugal.

Updated 27 August 2026 · by AXILINE · Vila Nova de Gaia

Your situation and the first step

Half of all enquiries start with "we need balancing" and end with tightening bolts, replacing a bearing, or a shaft alignment. The other half is the opposite: people spend months replacing components when fitting two weights would have been enough. So the first question isn't "how much does balancing cost", it's "what's actually going on with your machine".

Find your row in the table below. If none of them fit, send us a couple of lines and a photo of the machine on WhatsApp: an engineer will tell you where to start.

Diagnostics and balancing often happen in a single visit. We come out, measure, and if the picture is clear, we balance right there. You don't pay separately for "diagnostics before balancing": the initial reading is part of the job.

Five lines of work

Formally these are separate services; in practice they all rest on the same set of instruments and the same measurement method. The difference is in how each one ends: with weights on the rotor, a finding on the cause, a report, or an instrument in your own hands.

We have separate pages by machine type: fans and induced-draft fans, pumps and impellers, electric motor rotors, crushers and hammer mills, mulchers and farm equipment, cardan shafts, pulleys and couplings, machine-tool spindles, centrifuges and separators, blowers, cooling-tower fans. If you have a specific type of equipment, start with its page in the equipment section.

Balancing or diagnostics: how not to order the wrong thing

The difference is simple, and it's worth understanding before you call. Balancing only reduces the running-speed component of vibration, the part that occurs exactly once per revolution. It leaves everything else untouched.

If overall vibration at the bearing is nine millimetres per second and the running-speed component is only two, weights will remove those two millimetres, and the other seven will stay. The machine will shake almost as much as before, and you'll conclude that balancing doesn't work. In fact it did work, the problem just wasn't unbalance.

That's why we always start with measurement, even when the client is sure of the diagnosis. The first half hour on site answers the question of whether weights are even worth fitting. If they're not, we say so straight away, not after three trial runs.

• A peak dominates at running speed and the phase repeats from run to run: that's unbalance, balancing is the right call
• A noticeable second harmonic (a peak at twice running speed) plus axial vibration: more often misalignment, shaft alignment first, then balancing
• Many harmonics, a raised noise floor, an unstable phase: loose fastenings, soft foot, cracks
• High-frequency peaks that aren't multiples of running speed: looks like bearings, weights won't help
• A sharp rise in amplitude over a narrow speed range plus a phase reversal: resonance, balancing in it is pointless

Our site guides cover this in more depth: how unbalance differs from misalignment, how to read a spectrum, what the three different meanings of "tolerance" are, and when balancing simply won't help.

How a typical visit runs

1. 01

   Enquiry and initial assessment

   You send photos and a short description. We reply with which package fits your rotor size, roughly how long the job will take, and what to prepare. If the description shows the job isn't ours, we say so before any visit.

2. 02

   Agreeing the visit

   We agree a date, a shutdown window for the equipment, site access, and who on your side is responsible for start-up and lockout. Payment is 50% upfront, the rest after the work.

3. 03

   Mechanical inspection on the stopped machine

   Housing and foot fastenings, how the impeller sits on the shaft, the condition of the blades or knives, how clean the rotor is, the belt drive, clearances, signs of rubbing, the condition of the frame and foundation. Takes fifteen to thirty minutes and often settles the question without any balancing at all.

4. 04

   Initial reading and decision

   We fit sensors on the bearing housings, a marker and the laser phase sensor on the shaft, and run the machine at its working condition. We compare overall vibration with the running-speed component, check the spectrum and the repeatability of the phase. This is where the decision is made: balance, or look for another cause.

5. 05

   Trial runs

   We fit a trial weight of known mass at a known radius, run the machine, and check the response. One correction plane means one trial run, two planes means two. The instrument itself checks whether the amplitude and phase changed enough for the calculation to be reliable.

6. 06

   Fitting the correction weights

   The software outputs a mass and an angle for each plane, or, when working in fixed-position mode, straight away a blade or hole number. We attach weights with a bolt, a rivet or by welding, or remove metal by drilling. Your own team can fit the weights, in which case that work is included in the price. If we fit them, that's a separate option.

7. 07

   Check reading and trim

   We run the machine and measure again. If we didn't reach tolerance on the first pass, the software calculates additional weights to add to the ones already fitted. One trim pass is usually enough.

8. 08

   Report and recommendations

   We show you the figures before and after right on site. As a separate option, we write up a report with the measurement points, mode, speed, values and a polar plot. We also tell you separately what we noticed about the machine beyond unbalance, and what to watch next.

Minimum time on site is 4 hours. That's what a proper cycle takes: inspection, readings, trial runs and checking. Promises of "we'll balance it in an hour" usually mean someone is going to skip the inspection or the check reading.

What we don't do, and when we'll honestly send you elsewhere

A short list of what we turn down saves time on both sides. We don't take on any of the following, and we don't try to do it "roughly".

• We don't balance a rotor that's been removed from the machine and is sitting on its own. That work belongs on a balancing machine in a workshop, and we'll say so plainly
• We don't balance flexible rotors, ones that visibly bend at running speed and require modal balancing at several speeds. On-site work is designed for rotors that behave as rigid at their running speed
• We don't carry out major repairs: bearing replacement, housing and shaft repair, or reworking and restoring blades. We'll tell you exactly what needs replacing, but your own team or a repair contractor does the replacing
• We don't offer shaft alignment as a standalone service. We detect and show misalignment in the readings, but the alignment work itself stays with your own team or a specialist contractor
• We don't balance a machine that can't reach a stable running speed or can't be restarted the required number of times
• We don't fit weights where there's no physical access to the correction plane, and we don't cut into housings to create access
• We don't guarantee a specific vibration figure before we've measured the machine. Until the initial reading is done, any such promise is fiction
• We don't continue work if we see a crack, play in a fit, or a wrecked bearing. Balancing in that condition is dangerous and pointless

If, after the inspection and the initial reading, we tell you balancing won't help, you still get a result: measurements, a spectrum, and a finding on what's actually going on. That's work too, and it's billed, but it costs less than repairing at random.

Sources: ISO 21940-12:2016 · ISO 13373-3:2015

Requirements for the equipment and the site

On-site balancing doesn't always work. The conditions are checkable, and it's better to go through them in advance than to find out when we arrive.

• The machine reaches a stable running speed and holds it. Speed that varies from run to run ruins the calculation
• Repeated starts and stops are possible: at least three, usually four or five
• There's access to both bearing housings for fitting sensors, with a clean flat spot for a magnet or stud
• There's access to the correction planes: an inspection hatch, a removable cover, an opening in the casing, an exposed blade
• There's room on the shaft for a reflective marker, and a clear line of sight for the laser phase sensor
• The rotor is clean. A layer of caked dirt just two or three millimetres thick on one sector generates unbalance on its own, and there's no point balancing on top of it
• Fastenings are tight, the impeller sits on the shaft with no play, and there are no cracks or a worn-out hub
• There's power for a laptop near the operator's working position
• Someone on your side is designated responsible for start-up and lockout of the equipment
• The method of attaching weights has been agreed: welding isn't allowed everywhere, in explosion-hazard and paint areas only bolted attachment is used

If you're unsure about any point, send photos of the rotor, the bearing housings and the access points. We'll take a look and tell you whether it's realistic on site or cheaper to remove the rotor and take it to a workshop.

What it costs

The price depends on the rotor's size, not on the industry and not on how urgently you need it. All prices are + VAT (charged at the applicable rate).

• Second correction plane: plus 150 EUR
• Higher precision, grade G2.5: plus 175 EUR
• Higher precision, grade G1.0: plus 350 EUR
• Written report: included in the vibration diagnostics
• Travel: the first 20 km are included, beyond that 0.60 EUR per kilometre, round trip
• Fitting and welding work done by AXILINE: without welding plus 150 EUR per rotor, with welding plus 400 EUR per rotor. Done by the client's own team, included in the price
• Minimum invoice per visit is 500 EUR, minimum time on site is 4 hours
• Payment: 50% upfront

The pricing page has a calculator: pick the package, the number of planes, the precision grade and the distance, and see the total straight away. Choose the precision grade that your type of machine actually needs, not "the highest one": G6.3 is enough for most industrial fans and pumps, and G1.0 is money spent on precision that the machine's own bearings won't reproduce anyway.

Sources: ISO 21940-11:2016 · ISO 20816-1:2016

What to send for an assessment

To give you a real answer, not "from 450 euros, we'll come and take a look", we need a bit of information. Usually that's five minutes of your time and three photos.

• The type of machine and what it does: fan, pump, crusher, mulcher, electric motor, spindle
• Drive power in kW and the approximate rotor mass, even just the order of magnitude
• Running speed and how it's set: direct drive, through a belt, through a frequency converter
• Photos of the rotor and the impeller, photos of the bearing housings, photos of the access point to the correction plane
• What's happening and since when: humming, bearings running hot, it got worse after a repair, bolts keep loosening
• Whether you have any vibration readings, and what they are, even just values in mm/s and the points
• The site address or nearest town: this determines the travel cost
• Whether you need a written report, and whether the machine's manufacturer specifies a precision grade
• Who on site can do welding or drilling, if attaching the weights requires it

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. WhatsApp is fastest: send a photo and a couple of lines, and an engineer will answer, not a salesperson.

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Frequently asked questions