ISO 10816 vs ISO 20816: What Changed and Which One Applies to Your Machine

If you searched for ISO 10816 and landed on something about ISO 20816, you have found the answer to your question, and it is worth about ninety seconds of explanation.

ISO 10816 has been superseded. It was not corrected, withdrawn in disgrace, or found to be wrong. It was merged with a second standard into a single unified series, ISO 20816, part by part, over several years. Most of the numbers you remember from it survived that merge intact.

But the two standards are not interchangeable in every respect, the part numbering does not map one-to-one in every case, and there are still situations where citing 10816 is the correct thing to do. This article sorts out which is which, and covers the question most people are actually asking when they search for the old number: what the A, B, C and D zones mean, and where "newly commissioned" fits.

For the boundary values themselves and how to apply them, see our detailed guide to ISO 20816 vibration limits.

Why There Were Two Standards, and Now One

For decades, machine vibration evaluation lived in two parallel documents describing the same physical machine.

ISO 10816 covered vibration measured on non-rotating parts: the bearing housings, pedestals and casings where you attach an accelerometer or a velocity transducer. This is the measurement most plants take, because it requires no permanent instrumentation inside the machine.

ISO 7919 covered vibration measured on the rotating shaft itself, using proximity probes that watch the shaft move within its bearing clearance. This is the measurement used on large machines with fluid-film bearings, where what matters is whether the shaft is staying where it should inside the bearing.

Having two standards for one machine created obvious friction. A turbine generator with both housing accelerometers and shaft proximity probes was evaluated against two documents with different structures, different criteria and separate revision cycles.

The ISO 20816 series merges them. Each part of 20816 covers a machine class and contains both the housing vibration criteria and the shaft vibration criteria for that class, typically in separate annexes of the same document. One machine, one standard, both measurements.

How the Parts Map Across

This is where the practical confusion lives, because the mapping is mostly clean and not entirely.

ISO 20816-1:2016 is the general framework and it replaced ISO 10816-1:1995. It sets out measurement principles, evaluation criteria and definitions. It contains no boundary numbers for specific machine types. Anybody quoting limits "from 20816-1" or "from 10816-1" for a specific machine is improvising.

ISO 20816-2 covers land-based gas turbines, steam turbines and generators above 40 MW with fluid-film bearings at 1,500, 1,800, 3,000 or 3,600 r/min. This is the utility power station document.

ISO 20816-3:2022 covers general industrial machinery and replaced ISO 10816-3:2009 along with its shaft-vibration counterpart. This is the part most industrial plants need, and it carries a scope change worth knowing about: 10816-3 applied to machines with nominal speeds between 120 and 15,000 r/min, while 20816-3 extends the upper limit to 30,000 r/min. High-speed machinery that fell outside the old part now has a home.

ISO 20816-4 covers gas turbines above 3 MW with fluid-film bearings, corresponding to ISO 10816-4:2009.

The mapping trap worth flagging: pumps moved before the merge, not during it. The 2009 edition of ISO 10816-3 removed pumps from its scope, and they were dealt with in ISO 10816-7 instead. If you are evaluating a pump against a pre-2009 chart derived from 10816-3, you are using a document that no longer claimed to cover it even before 20816 existed.

Two standards describing one machine became one standard describing one machine. Each part of ISO 20816 carries both measurements, typically in separate annexes. Sources: ISO 20816-1:2016; ISO 20816-3:2022.

The Zones: A, B, C and D

This is the part most engineers actually want, and the zone structure survived the transition unchanged. It works the same way in both standards.

Zone A is where the vibration of newly commissioned machines normally falls. This is the answer to the question people are usually asking: Zone A is not a target to be achieved, it is a description of what a machine typically reads when it is new and correctly installed. A machine reading in Zone A is in as good a condition as machines of its type generally get.

Zone B covers machines normally considered acceptable for unrestricted long-term operation. This is where a great many healthy machines live for their whole service life, and there is nothing wrong with being in Zone B. Plants that treat Zone B as a problem to be fixed are chasing a target the standard never set.

Zone C covers machines normally considered unsatisfactory for long-term continuous operation. The machine may generally be run for a limited period in this condition until a suitable opportunity for remedial action arises. Zone C is not an emergency; it is a booking for the next outage.

Zone D covers vibration of sufficient severity to cause damage to the machine. This is the zone that justifies acting now rather than at the next convenient point.

The zones are separated by boundary values that differ by machine group, by size, and by whether the machine is mounted on a rigid or a flexible support. That last distinction shifts the boundaries substantially, and getting it wrong is the most common misapplication of either standard. The support classification is determined by comparing the machine and support system's natural frequency against running speed, and it should be established by calculation or by a bump test rather than by looking at whether the foundation appears solid.

The Two Criteria, and Why Criterion II Matters More

Both standards evaluate machines against two criteria, and most plants only use the first.

Criterion I is the magnitude of the vibration, assessed against the zone boundaries. This is the criterion everybody knows, and it is the one printed on the wall chart.

Criterion II is the change in magnitude from an established baseline. A significant change warrants investigation even when the absolute value stays inside an acceptable zone. A machine that has doubled its vibration level while remaining in Zone B has changed in a way that means something, and the zone table cannot see it.

Criterion II is the more useful of the two in day-to-day practice, because it is sensitive to the machine's own history rather than to fleet averages. It is also the criterion that requires the plant to have done something in advance: establish a baseline under repeatable conditions and keep measuring the same way. Our article on how to read vibration readings covers what "the same way" has to mean for the comparison to be valid.

What Actually Changed in the Numbers

For most industrial machines measured on bearing housings in velocity terms, the familiar zone boundary values carried across the transition. An engineer holding a velocity severity chart derived from ISO 10816-3 is holding numbers that are, for the housing measurement, still broadly the numbers in ISO 20816-3.

What that old chart is missing is everything the merge added and everything the chart never contained in the first place: the shaft vibration criteria that came in from ISO 7919, displacement limits for slower machines, guidance on transient and non-steady operation, the extended speed range, and the conditions attached to each measurement.

This is the honest summary of the transition for a practising engineer. The numbers you know are mostly still right. The document you are quoting is out of date, and the parts of it you never read are the parts that changed.

The A to D zone structure, unchanged across the transition from ISO 10816 to ISO 20816. Zone A is a description of new-machine condition, not a target. Sources: ISO 20816-1:2016; ISO 20816-3:2022.

Which One Should You Cite?

The answer depends on what the citation is for.

For new contracts, specifications and acceptance criteria, cite ISO 20816 and the specific part. It is the current standard, it is what a supplier's engineering department will expect, and citing a superseded document invites an argument at the worst possible moment.

For existing contracts that reference ISO 10816, the referenced document stands unless the parties agree to update it. A contract citing ISO 10816-3:2009 is a contract about ISO 10816-3:2009, and unilaterally applying different criteria because a newer standard exists is not a strong position. If the difference matters, agree the change formally.

For internal procedures and wall charts, update to ISO 20816 and take the opportunity to add the parts that were missing: the support classification method, the change criterion, and the measurement conditions.

For historical records, keep the original citation. A 2015 inspection report evaluated against ISO 10816-3 should continue to say so. Retrospectively relabelling old assessments destroys the audit trail without improving anything.

Practical Misapplications That Outlive the Standard

Quoting a limit without naming the part. The series is deliberately split by machine type and the limits genuinely differ between parts. A limit "from ISO 10816" is not a limit.

Ignoring the support classification. Rigid and flexible support boundaries differ enough that misclassifying a machine moves it a whole zone. This error is extremely common and it is trivially avoidable.

Applying an industrial machinery part to a large turbine generator. A 20 MW industrial steam turbine and a 100 MW utility unit belong to different parts with different criteria.

Using a pre-2009 chart on a pump. Pumps left the scope of 10816-3 in 2009.

Treating the tables as acceptance specifications. Both standards state explicitly that the boundary values are guidelines rather than acceptance criteria, and that they are not intended to be used as the sole basis for acceptance testing. Suppliers know this. Plants that build acceptance regimes on the zone table alone tend to discover it during a commissioning dispute.

Forgetting Criterion II entirely. The most valuable half of the standard, routinely ignored.

How the parts map across, and the scope change worth knowing about. Pumps left the scope of 10816-3 in 2009, before the merge. Sources: ISO 10816-1:1995; ISO 10816-3:2009; ISO 10816-4:2009; ISO 20816-1:2016; ISO 20816-3:2022.

Frequently Asked Questions

Is ISO 10816 still valid? It has been superseded part by part by ISO 20816 and the relevant parts are withdrawn. It remains the correct reference for existing contracts and historical records that cite it, but new work should reference ISO 20816.

What does Zone A mean in ISO 10816-3? Zone A describes where the vibration of newly commissioned machines normally falls. It is a description of typical new-machine condition rather than a target or an acceptance threshold. A machine in Zone B is entirely acceptable for unrestricted long-term operation.

Did the vibration limits change between ISO 10816 and ISO 20816? For housing velocity measurements on general industrial machinery, the familiar boundary values largely carried across. What the merge added was the shaft vibration criteria from ISO 7919, wider speed coverage, and clearer treatment of measurement conditions.

Which part of ISO 20816 applies to my machine? Part 2 for land-based gas and steam turbines and generators above 40 MW with fluid-film bearings at synchronous speeds. Part 3 for general industrial machinery above 15 kW between 120 and 30,000 r/min. Part 4 for gas turbines above 3 MW with fluid-film bearings. Part 1 is the framework and contains no machine-specific limits.

Can I keep using my old ISO 10816 wall chart? The velocity numbers on it are probably still broadly correct for housing measurements, which is why nobody notices it is out of date. It is missing the shaft criteria, the extended speed range, the measurement conditions and the change criterion, so treat it as a rough severity scale rather than as the standard.

The Number on the Chart Was Never the Hard Part

The transition from ISO 10816 to ISO 20816 is a smaller event than the renumbering suggests. Two standards describing one machine became one standard describing one machine, the velocity numbers most people rely on came through largely intact, and the parts that changed are mostly the parts that were being ignored anyway.

That is the useful lesson in it. The plants that get into trouble with vibration standards are almost never the ones citing the wrong edition. They are the ones that classified the support wrongly, never established a baseline, or treated a severity guideline as a pass or fail line. Across four decades of rotating equipment work, from turbine overhauls in Nigeria to root cause investigations at White Nile Sugar in Sudan, the standard has rarely been the thing that was wrong.

Need a defensible answer on whether a reading is acceptable? Talk to our engineering team. We will classify the machine against the correct part and support condition, measure it under the right conditions, and give you an assessment you can put in front of a supplier.