ISO 10816 vibration severity zones: the complete guide

Abnormal vibration is often the first sign that rotating machinery is degrading — weeks or even months before failure. The challenge is interpreting the reading. That is exactly what the ISO 10816 standard does: it translates a vibration velocity into a clear verdict, graded into four severity zones, from A (new machine) to D (risk of failure).

What is the ISO 10816 standard?

ISO 10816 (now extended by the ISO 20816 series) governs the evaluation of mechanical vibration on rotating machinery — motors, pumps, fans, compressors, conveyors — from measurements taken on the non-rotating parts (bearings, housings).

Its value: it doesn't just give a number. It compares that number to standardized thresholds by machine type, then classifies it into a severity zone. The same 4.5 mm/s can be "good" on a large machine on a flexible foundation and "unacceptable" on a small motor.

The 4 severity zones (A, B, C, D)

Zone	Condition	Interpretation	Action
A	New / excellent	Vibration typical of a machine just commissioned	None — baseline
B	Acceptable	Unrestricted long-term operation	Normal monitoring
C	Unsatisfactory	Operation tolerated for a limited time	Plan an intervention
D	Unacceptable	Severity high enough to damage the machine	Stop / immediate action

In practice, you aim to keep machines in zone A or B. Moving into zone C is a warning; zone D calls for a fast decision.

Machine classes: why one threshold doesn't fit all

Zone thresholds depend on the machine class, defined by its power/size and the rigidity of its support (rigid or flexible foundation):

• Class I — small machines (motors up to ~15 kW).
• Class II — medium machines (~15 to 75 kW).
• Class III — large machines on a rigid foundation.
• Class IV — large machines on a flexible foundation.

The larger the machine and the softer its support, the higher the tolerated thresholds. A raw reading without the class is meaningless.

How is severity measured?

The reference indicator is the RMS vibration velocity, in mm/s, measured over a broad range (typically 10–1000 Hz). Best practices:

• Measure on the bearings, in three axes (horizontal, vertical, axial).
• Use consistent measurement points from one inspection to the next.
• Track the trend over time: a progression toward C or D tells you more than a single value.

What to do by zone

• Zone A/B → periodic monitoring; log the reading as a trend point.
• Zone C → diagnose the cause (imbalance, misalignment, looseness, bearing) and plan the fix.
• Zone D → treat as priority; consider stopping the machine depending on criticality.

From manual readings to digital inspection

Traditionally, the technician wrote readings on paper, then recalculated class and zone back at the office — slow and error-prone. ROVIK is a tablet vibration-inspection software that applies ISO 10816 natively: the technician enters readings (up to 18 per inspection) and the app automatically computes the severity zone (A to D) based on the machine class — in the field, even with no Internet connection. Each inspection produces a signed PDF report, and trend tracking is automatic.

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FAQ

What is the difference between ISO 10816 and ISO 20816?

ISO 20816 consolidates and updates the former ISO 10816 and ISO 7919. The principles (zones A to D, machine classes, RMS velocity) stay the same; the term "ISO 10816" is still widely used.

Which indicator does ISO 10816 use?

The RMS vibration velocity in mm/s, measured over a broad frequency band, on the bearings.

At which zone should you intervene?

Zone C signals an unsatisfactory condition: plan an intervention. Zone D is unacceptable and requires prompt action.

Can ISO 10816 inspections be done offline?

Yes. With a field-built app like ROVIK, readings, zone calculation and reports happen offline, then sync when connectivity returns.