AXILINEArticles on balancing and vibration
Articles on balancing and vibration
Written by the people who do the work on site: how to measure, how to read the numbers, when balancing fixes it and when the problem is something else.
In short: Written by the people who do the work on site: how to measure, how to read the numbers, when balancing fixes it and when the problem is something else.
Where to start
If the machine has just started vibrating, start with the causes and with measurement. If you already know it is unbalance, look at the tolerances and the number of planes. If you are buying the instrument, read the Balanset-1A and training pages.
All pages in this section
How to reduce equipment vibration: a sequence that saves money
A step-by-step route from ‘the machine is shaking’ to normal: checking the reading, 1x versus overall, fasteners, resonance, balancing. What to do yourself, and when to call an engineer.Overall vibration, the 1x running-speed component, and phase: what balancing actually fixes
Breaking down the three readings on a vibration instrument's screen: overall vibration in mm/s RMS, the 1x running-speed component, and phase. When balancing will help, and when it won't.Three tolerances in balancing: what “within norm” actually means
Three different tolerances get mixed up constantly: the target 1x in the software, overall vibration under ISO 20816 (zones A-D), and residual imbalance in grades G under ISO 21940-11.Balancing in one or two planes: how to choose the number of correction planes
How to choose the number of correction planes: the L/D rule, couple imbalance, between-bearing and overhung rotors. When one plane isn't enough, and what to do on site.Trial (calibration) weight: why it's needed and how to choose it
The trial (calibration) weight in rotor balancing: why it's needed, how to choose the mass and radius, the 30/30 rule, mounting, safety, and common mistakes.Correction weight angle: zero point, direction, and fixed positions
Where to measure the correction weight's angle from, which direction to count, and why a mirrored error doubles the vibration. Fixed positions and drilling.Equipment resonance: signs, how to check, and what to do
How to tell resonance apart from imbalance: a narrow amplitude peak, a 180° swing in the 1x phase, a bump test. Why balancing in resonance is pointless, and what to do instead.How to read a vibration spectrum: 1x, 2x and harmonics
Reading an FFT spectrum: when 1x dominates and balancing is the answer, when 2x points to shaft misalignment, and what harmonics, sidebands and Δf resolution actually mean.Why balancing does not help: 7 cases where vibration stays
Balancing only removes the 1x running-speed component. We go through 7 cases where the vibration stays: resonance, oil whirl, pulley problems, looseness, wear.Balancing machine retrofit: old mechanics, new measurement system
How to modernise an old balancing machine: the Balanset-1A OEM measurement core, sensors, laser tachometer, software, G-grade tolerances and reports.Rotor unbalance: what it is and why it is dangerous
Rotor unbalance: what it is, its types, where it comes from and why it is dangerous. Centrifugal force grows as the square of speed, and bearing life falls even faster than the load.How to tell whether you need balancing: a decision checklist
A decision checklist: which signs mean balancing will help, and which mean it will not. An observation table, a 20-minute self-check, and the cases where it is mandatory regardless.How to find the cause of equipment vibration: a methodology, not a list of causes
A methodology for finding the cause of vibration: context, measurement reliability, three directions at every support, frequency multiples, the time waveform, alarm setpoints and trend.How to tell unbalance from shaft misalignment: signs, phase and the right order of work
Unbalance or shaft misalignment: signs in the spectrum, direction, phase, behaviour during warm-up. Why balancing a misaligned machine does harm, and the right order to work in.How to Balance a Fan: The On-Site Procedure
How to balance a fan or induced-draft fan on site: pre-job checks, sensors on the bearing housings, trial weight, mounting the weights, verification run.How to Measure Vibration Correctly: Point, Mounting, Condition
Where to mount the sensor, how to fix it in place, what to measure in mm/s RMS and what in g, why you need a tachometer marker, and what conditions to record so the reading can be trusted.Vibration Limits per ISO 20816: Zones A, B, C, D and How to Use Them
Zones A, B, C, D per ISO 20816 (formerly ISO 10816): mm/s RMS in the 10–1000 Hz band, a table by machine classes I–IV, rigid and flexible supports, setpoints, and trending.How to Choose a Balance Quality Grade: G6.3, G2.5, and Everything Else
Grade G per ISO 21940-11 sets residual unbalance in g·mm. We break down how G16, G6.3, G2.5, and G1 differ, how to calculate the tolerance, and why you shouldn't ask for tighter than you need.Bearing Diagnostics from Vibration: Signs, Stages, and What to Do
How vibration reveals the condition of rolling bearings: the four defect stages, BPFO and BPFI frequencies, the envelope, crest factor, and how to tell it apart from looseness and lubrication issues.Building Your Own Balancing Machine: Supports, Bed, Drive, and Measurement System
How to build a balancing machine or rig on your own: supports, bed, drive, sensors, commissioning, and accuracy verification on a reference rotor.The Influence Coefficient Method: How the Instrument Calculates the Correction Weight
How the instrument calculates the correction weight: 1x vibration as a vector, the influence coefficient, a worked numerical example, the 2×2 matrix for two planes, and the method's limits.On-site balancing or shop balancing on a machine: how to choose without overpaying in downtime
On-site balancing or shop balancing on a machine: a comparison by downtime, cost, accuracy, risk and paperwork. When to remove the rotor, and when that's unnecessary.How long on-site balancing takes, and how many runs it needs
How many runs balancing in one and two planes needs, what actually eats up time on site, and how long field work takes by machine type.Trim balancing and saved influence coefficients: how to skip repeated trial runs
Trim balancing: how to add a weight without a new trial run, and when to reuse saved influence coefficients. A look at the conditions and common mistakes.Preparing equipment for on-site balancing: a customer checklist
A checklist before on-site balancing: condition, rotor cleanliness, access, a window for the runs, power, safety, machine data. What to prepare and why.Vibration came back after balancing: why, and what to check
Vibration came back weeks after balancing: build-up on the impeller, blade erosion, a weight that came loose, a bearing, loosened fasteners. How to tell the causes apart.Vibration measurement settings: Fmax, number of lines, window and averaging
How to choose Fmax, the number of lines, record length, averaging and windowing so a defect actually shows up in the spectrum. Settings for balancing versus settings for diagnostics.Vibration monitoring: route, baseline level, alarm thresholds and trend
How to build working vibration monitoring for a plant section: choosing machines for the route, points and directions, baseline level, three alarm levels, frequency and trend.ISO 18436-2: Vibration Analyst Categories I, II, III and IV
Categories I, II, III and IV under ISO 18436-2: what each one covers, how the 18436-1/2/3 series fits together, how to choose a training provider, and who to bring onto your site.How to Choose a Balancing Instrument: Vibrometer, Analyzer or Balancer
Vibrometer, vibration analyzer or balancer: how the instrument classes differ, which specifications matter when choosing, and when it's cheaper to book a site visit instead.Static and Dynamic Balancing: The Difference in Practice
Static and dynamic balancing: the difference in practice. One plane versus two, what's left in a long rotor, and why knife-edges don't replace phase measurement.Overhung and Between-Bearings Rotors: How the Support Layout Changes Balancing
How an overhung rotor differs from a between-bearings one when balancing: where to put the sensors and correction planes, where cross-coupling comes from, and three-support shafts.Residual Unbalance in Practice: g·mm, g·mm/kg and Microns
Residual unbalance in g·mm: how to get the allowable mass at a radius from grade G and speed, how to split the tolerance between planes, and what to write in the report.Vibration Measurement Units: mm/s, g, µm, and What RMS Means
Vibration displacement in µm, vibration velocity in mm/s, vibration acceleration in g: where each quantity works, how RMS differs from peak, and why 1.41 lies on impacts.Acceptance Testing After Repair: Vibration, Baseline and the Report
What to measure when accepting a machine after repair: points and directions, regime and load, baseline level, the ISO 20816 criterion, an acceptance report template, and typical disputes.Shaft Misalignment: Types, Signs, and How to Check It
Shaft misalignment: parallel, angular, combined. Vibration signs, soft foot, checking with dial indicators and laser, tolerances and work sequence.Loose Mounting and Soft Foot: the Cheapest Find on the Site
Mechanical looseness and soft foot: types, signs in the spectrum and phase, checking with a dial indicator, a walk-down checklist, and why balancing won't hold.Hydraulic Causes of Pump Vibration: Cavitation, Vane-Pass Frequency, and Operating Point
Cavitation, recirculation, vane-pass frequency, and piping pulsation in a pump: how to tell hydraulics apart from imbalance, and why balancing won't help here.Electrical Causes of Motor Vibration: How to Separate Them from Mechanics
How to tell a motor's electrical vibration from mechanical: 100 Hz, sidebands, the coast-down test, current, and heat. Why balancing won't help here.Belt Drive Vibration: Pulley, Tension, and What Gets in the Way of Balancing
Belt frequency and its harmonics, pulley runout, tension, misalignment: how a belt drive produces vibration, why it's mistaken for imbalance, and the order to fix it in.Rotor Rubbing and Thermal Bow: Why Balancing Won't Converge
Vibration rising and phase drifting as the machine warms up? We break down rotor rubbing and thermal bow: signs, tests, and what to do before in-situ rotor balancing.Bearing Life, Vibration, and Load: What Balancing Actually Gets You
How imbalance loads bearings, why calculated life per ISO 281 depends so sharply on load, and how to honestly assess the benefit of balancing on your own machine.Balancing report: what it should contain and how to check it
What a balancing report should contain: RPM, measurement points, 1x amplitude and phase before and after, trial runs, correction, acceptance criterion. An acceptance checklist and red flags.Safety during on-site balancing: start-up, lockout, weights, and the throw zone
Safety during on-site balancing: who's responsible for start-up, lockout/tagout, weight mounting, the throw zone, PPE, emergency stop, and a pre-start checklist.Mounting correction weights: welding, bolting, riveting, and removing metal by drilling
How to mount a correction weight so it doesn't come loose: a full weld instead of a tack, a bolt with thread-locking, a magnet only as a temporary fix, and how to calculate drilling and radius.Vibration sensors in practice: types, sensitivity, mounting
Piezo accelerometer, velocity sensor, non-contact proximity probe: why integration is needed, how to enter sensitivity, and how mounting sets the measurement bandwidth.The phase sensor and reflective marker: how the instrument measures phase
How the laser phase sensor gives you RPM and a reference point, where to place the reflective marker, how to aim the sensor, and how to check the pulse count before the first run.Savings from balancing without removal: how to calculate the full cost and avoid overpaying in downtime
On-site balancing or removing the rotor: how to calculate the full cost of downtime, disassembly, transport, and shaft alignment, and work out which is actually cheaper for you.What vibration costs a plant: how to calculate the cost and build the case for the work
How to calculate the cost of elevated vibration: downtime, emergency repairs, bearings, scrap, energy. A calculation table with blank fields, and what to bring to management.How to build vibration monitoring and balancing into your maintenance program
How to build vibration monitoring and balancing into your maintenance system: three maintenance approaches, machine selection, measurement intervals, thresholds, documentation, and staff training.How to verify a balancing result: a verification measurement that can't be disputed
What to compare after balancing: overall vibration and 1x at the same points and under the same operating regime. Signs of an honest result, an acceptance checklist, and the report.How to choose a balancing and vibration diagnostics contractor: questions, red flags, contract
What questions to ask a balancing and vibration diagnostics contractor, which answers count as red flags, and what to pin down in the contract and the acceptance report.Critical speed and flexible rotors: why a correction made at one speed doesn't work at another
Rotor critical speed: how it differs from support resonance, when a rotor becomes flexible, and why a correction made at one speed doesn't work at another.Multi-bearing rotor balancing: a long shaft on three or more bearings
Rotors on three or more bearings: why the influence coefficient matrix grows, why you need to measure every bearing, how many runs it takes, and when a shop balancing machine is the better choice.How to balance an electric motor rotor: the on-site procedure
On-site electric motor rotor balancing: what to check before starting, how to separate electrical causes from mechanical ones, where the correction planes are, and the step-by-step run sequence.Balancing and vibration glossary: 57 terms an engineer actually uses
57 balancing and vibration terms, each defined in one sentence with practical context: unbalance, G grades, ISO 20816 zones, phase, BPFO, resonance.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.