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Vibration analysis: route survey, online monitoring or a one-off diagnosis, and how to read the report

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In short

Vibration analysis measures vibration at the bearings of rotating machines to find unbalance, misalignment, looseness and bearing wear before failure. It is bought as a route survey, online monitoring or a one-off diagnosis. A useful report grades each reading against a named ISO part and edition, shows the change since the last survey, names the fault and ranks the actions.

What does vibration analysis do?

Vibration analysis measures how the bearings, housings and shafts of rotating machines vibrate and reads the pattern to find developing faults; an instrument manufacturer's guide names unbalance, looseness, misalignment and bearing degradation as the four factors behind many common machinery failures.[10]

Two ISO standards describe the method: ISO 13373-1:2002 covers measuring and collecting machine vibration (transducers, measurement points, operating conditions, continuous and periodic monitoring), and ISO 13373-2:2016 covers processing, analysing and presenting the data in the time domain and the frequency domain.[5][6]

In practice, an analyst looks at two things: the overall level, graded against a severity standard such as ISO 20816-3, and the spectrum, which separates each source of vibration by frequency, so a peak at shaft speed points to a different fault from a peak at a bearing or gear-mesh frequency.[13][2]

In South Africa, an electrical engineering company quoted in an Engineering News feature of March 2026 says power interruptions and fluctuations add stress on motors and pumps and raise the risk of failure during restarts and load changes. The same company calls bearing failure, often from poor lubrication, contamination or misalignment, probably the most common cause of motor and rotating-equipment failure in process industries.[11]

Route survey, online monitoring or a one-off diagnosis: which should you buy?

Choose by how critical the machine is and whether you need a reading at set intervals, all the time or once. ISO 13373-1 gives guidance for both continuous and periodic measurement and ISO 20816-3 applies its evaluation criteria to both; the table shows how each option is bought in practice.[5][2][10][13][14]

Route survey, online monitoring or a one-off diagnosis: which should you buy?
OptionHow the data are collectedFitsWhat the quote coversWatch for
Route surveyA technician walks a fixed route with a portable collector and measures each point at a set intervalMany machines of moderate criticality; a first survey that sets baselinesMachines and points per visit, visit interval, travel, analysis and reportEach reading is a snapshot of that moment; nothing is recorded between visits
Online monitoringSensors fixed to the machine collect data throughout operation and send them to software, often wirelesslyCritical machinesSensors, installation, software subscription and who reviews the alarmsSoftware raises the alarm: ask who diagnoses it and how the finding reaches you
One-off diagnosisAn analyst tests one machine after a complaint, a repair or an installation, often adding phase and bump testsA machine with an existing fault or a persistent problem; an acceptance reading after an overhaul or alignmentCall-out, tests, report and any correction such as balancing or alignmentOne visit shows no trend: ask for a repeat reading after the repair

Sources:[10][5][2][13][14]

Which standard sets vibration limits for machines?

The ISO 20816 series sets how machine vibration is measured and evaluated, and two of its parts were reissued on 28 October 2026: ISO 20816-1:2026, the general guidelines, and ISO 20816-3:2026, for coupled industrial machines running between 120 and 30 000 r/min.[1][2]

ISO 20816-3:2026 replaced ISO 20816-3:2022, which had itself replaced ISO 10816-3:2009 and ISO 7919-3:2009; the 2022 edition covered machines with a power rating above 15 kW, while the 2026 edition's title drops the power rating and its abstract states no 15 kW limit.[2][3]

ISO 20816-3:2026 covers, among others, steam turbines and generators of up to 40 MW, rotary compressors, gas turbines of up to 3 MW, electric motors with a flexible coupling, rolls and mills, conveyors, and fans above 300 kW or not flexibly supported.[2]

Rotodynamic pumps have their own part: the 2022 edition of ISO 20816-3 excluded them and referred them to ISO 10816-7:2009, which ISO still lists as published (marked to be revised) and which covers industrial rotodynamic pumps with a nominal power above 1 kW.[3][4]

ISO 20816-3's criteria apply to "in-situ broad-band vibration measurements taken on the shafts, bearings, bearing pedestals or housings of machines close to bearings under steady-state operating conditions", for acceptance tests and operational monitoring, and for continuous and non-continuous monitoring alike.[2]

ISO 20816-3 is not a diagnosis: it applies to machines with gears or rolling bearings "but does not address the diagnostic evaluation of the condition of those gears or bearings", and only to "the vibration produced by the machine set itself and not for vibration that is transmitted to the machine set from external sources".[2]

ISO 20816-1:2026 presents its evaluation criteria "in terms of both vibration magnitude and change in vibration" and gives guidance on setting operating limits, so a report should show how a reading has moved as well as where it sits.[1]

What should a vibration analysis report contain?

In practice, a useful vibration report lets you act without phoning the analyst: for each machine it says what was measured, how it compares, what the fault is and what to do. Check for these items:[1][10]

  • the machine list with each machine's running speed, power, drive and bearing type, because the evaluation criteria and the fault frequencies depend on them;[2][13]
  • each measurement point and direction (horizontal, vertical, axial) and the unit used: velocity in mm/s, acceleration or displacement;[13][10]
  • the speed and load at the time of the reading, since ISO 20816-3 grades readings taken under steady-state operating conditions;[2]
  • the grade against a named part and edition (ISO 20816-3:2026, for example), the alarm or operating limit used, and the change since the baseline or last survey;[1][2]
  • for every machine flagged, the spectrum or waveform and the fault named, such as unbalance, misalignment, looseness or a bearing defect, with its severity;[6][10]
  • a ranked action list: what to do, how urgent, and whether the machine can run to the next planned stop;[10]
  • the date of the next reading, and the analyst's name, ISO 18436-2 category and certificate number.[5][7]

Who is qualified to do vibration analysis?

ISO 18436-2:2014 sets the training, experience and examination requirements for people doing vibration condition monitoring and diagnostics in four categories, and a certificate or declaration of conformity issued in accordance with ISO 18436-1 "provides recognition and evidence" that the person can perform vibration measurements and analysis.[7]

A third edition, ISO/FDIS 18436-2, retitled to cover training and certification of personnel, was registered for formal approval on 8 October 2026 and will replace the 2014 edition.[8]

In South Africa, one training provider runs the four categories as courses leading to certification by a board accredited to ISO/IEC 17024 and ISO 18436, so the course and the certificate come from different organisations.[12]

That provider's course descriptions show the gap between levels: Category I teaches detecting bearing faults and unbalance with portable analysers; Category II teaches deciding how the data collector is set up, analysing a range of fault conditions, setting alarm limits manually and with statistics, and balancing and alignment; Category III is intended for analysts with at least two years' vibration analysis experience and Category II certification.[13][14][15]

One certifying body in the United States, accredited by ANAB to ISO/IEC 17024 for a four-category programme whose body of knowledge is compliant with ISO 18436-2, publishes a list of its certified analysts: ask for the certificate number and check it with the body that issued it.[16]

What should a vibration analysis quote itemise?

In practice, a route survey quote should itemise the number of machines and measurement points, the visit interval, travel to site, and the analysis and report; an online monitoring quote should itemise the sensors, their installation, and the software and analysis subscription.[10][5]

A one-off diagnosis adds tests such as phase analysis and bump tests, and often a correction such as balancing or alignment; ask for each correction as a separate item, carried out and charged only once you approve it.[14]

To compare quotes, send each supplier the same machine list, points and visit interval, and ask for the price per machine per visit, travel and the report as separate lines.[5][10]

What should happen after a vibration report?

Each finding should become a work order: in practice the maintenance team plans the ranked actions (balance, align, tighten, replace a bearing) into the next stop, and maintenance software can raise the work order when a reading crosses its alarm.[10][14]

After the repair, ask for a new reading graded against the same standard: ISO 20816-3 covers acceptance tests as well as operational monitoring, and the new reading becomes the baseline for the next survey.[2]

What to put in your request

  1. The service: a route survey at a stated visit interval, online monitoring of named machines, or a one-off diagnosis of one named machine and its symptom.[10][5]
  2. The machine list: tag, machine type, running speed in r/min, power in kW, coupling or belt drive, and bearing type where known.[2][13]
  3. The report to grade against ISO 20816-3:2026 for coupled industrial machines and ISO 10816-7:2009 for rotodynamic pumps, not the withdrawn ISO 10816-3.[2][4][3]
  4. Past reports and baselines, attached; the report to show the change since the last survey as well as the level.[1]
  5. When each machine runs at its normal speed and load, and which machines run only intermittently.[2]
  6. Safe access to each bearing housing while the machine runs, and the site's guard, permit, escort and induction requirements.[2][9]
  7. The report to show spectra for flagged machines, the fault named, a ranked action list and the date of the next reading.[6][10]
  8. The analyst's ISO 18436-2 category, certificate number and issuing body; Category II or higher where the analyst sets up the collector and analyses a range of faults.[7][14]
  9. For online monitoring: the number of sensors, who owns them, the subscription term and who reviews the alarms.[10]
  10. Prices per machine or point per visit, travel and the report on separate lines, with balancing and alignment as separate items.[14][10]

Questions buyers ask

Is vibration analysis required by law in South Africa?

The text of the Occupational Health and Safety Act 85 of 1993, as published in Government Gazette 14918, does not mention vibration analysis. Section 8(2)(a) requires the employer to provide and maintain "systems of work, plant and machinery that, as far as is reasonably practicable, are safe and without risks to health", and section 8(2)(d) to establish the hazards attached to plant and machinery and the precautions to take.[9]

How do you become a vibration analyst in South Africa?

Through the four ISO 18436-2 categories, each with its own training, experience and examination, and a certificate from an accredited certification body. One South African provider runs the courses in Johannesburg and KwaZulu-Natal and says its Category III course is intended for analysts with at least two years' vibration analysis experience and Category II certification.[7][12][13][15]

Does a vibration survey check gears and bearings?

Not by its severity grade alone. ISO 20816-3 applies to machines with gears and rolling bearings but does not address the diagnostic evaluation of their condition. For that, the analyst reads the spectrum, the waveform and envelope (demodulation) readings, the methods ISO 13373-2 and the Category II syllabus cover.[2][6][14]

Describe the job.

Post a request and the suppliers who do this work can respond.

Post a request

Sources

  1. International Organization for Standardization (ISO), ISO 20816-1:2026 Mechanical vibration: measurement and evaluation of machine vibration, Part 1: General guidelines (edition 2, catalogue entry and abstract), October 2026.
  2. International Organization for Standardization (ISO), ISO 20816-3:2026 Mechanical vibration: measurement and evaluation of machine vibration, Part 3: Industrial machines with operating speeds between 120 r/min and 30 000 r/min (edition 2, catalogue entry and abstract), October 2026.
  3. International Organization for Standardization (ISO), ISO 20816-3:2022, Part 3: Industrial machinery with a power rating above 15 kW and operating speeds between 120 r/min and 30 000 r/min (withdrawn; catalogue entry, abstract and life cycle), October 2022.
  4. International Organization for Standardization (ISO), ISO 10816-7:2009 Mechanical vibration: evaluation of machine vibration by measurements on non-rotating parts, Part 7: Rotodynamic pumps for industrial applications, including measurements on rotating shafts (catalogue entry and abstract), February 2009.
  5. International Organization for Standardization (ISO), ISO 13373-1:2002 Condition monitoring and diagnostics of machines: vibration condition monitoring, Part 1: General procedures (catalogue entry and abstract), February 2002.
  6. International Organization for Standardization (ISO), ISO 13373-2:2016 Condition monitoring and diagnostics of machines: vibration condition monitoring, Part 2: Processing, analysis and presentation of vibration data (catalogue entry and abstract), January 2016.
  7. International Organization for Standardization (ISO), ISO 18436-2:2014 Condition monitoring and diagnostics of machines: requirements for qualification and assessment of personnel, Part 2: Vibration condition monitoring and diagnostics (catalogue entry and abstract), May 2014.
  8. International Organization for Standardization (ISO), ISO/FDIS 18436-2, requirements for training and certification of personnel, Part 2: Vibration condition monitoring and diagnostics (edition 3, under development; life cycle), October 2026.
  9. Government Gazette 14918, Occupational Health and Safety Act 85 of 1993, 2 July 1993.
  10. Fluke Corporation, What Is Vibration Analysis? A Complete Guide, March 2026.
  11. Engineering News (Creamer Media), Predictive maintenance improves plant reliability, 13 March 2026.
  12. Yellotec, Mobius Institute: certification and course list (ISO Category I to IV vibration analyst), 2026.
  13. Yellotec, ISO Category I Vibration Analyst: Basic (course page and outline), July 2026.
  14. Yellotec, ISO Category II Vibration Analyst: Intermediate (course page and outline), July 2026.
  15. Yellotec, ISO Category III Vibration Analyst: Advanced (course page), December 2025.
  16. Vibration Institute, Vibration Analyst Certification, November 2025.