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Vibration Severity Checker - ISO 10816 / 20816 Zone Classification for Rotating Equipment

Classify machine vibration levels against ISO 10816 & ISO 20816 standards for pumps, motors, fans, compressors & turbines

Check vibration severity for rotating machinery against ISO 10816 classification zones. Enter vibration velocity (in/sec peak or mm/s RMS) and select machine group to get an instant severity rating from Zone A (new machine condition) through Zone D (damage occurring). Covers ISO 10816-3 for industrial machines 15 kW to 300+ kW on rigid and flexible foundations, ISO 10816-7 for rotodynamic pumps, and general industrial guidelines. Includes alarm and trip setpoints, trending guidance, and diagnostic frequency references.

Pro Tip: Overall vibration level tells you severity, but frequency analysis tells you the cause. A machine at 0.3 in/s peak could have imbalance (1× RPM), misalignment (2× RPM), bearing defects (BPFO/BPFI), or looseness (sub-harmonics). Always pair severity checks with spectrum analysis. If overall vibration doubles, you have already lost 75% of remaining bearing life - do not wait for the next scheduled outage to investigate.

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Vibration Severity Checker
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How It Works

  1. Select Machine Group

    Choose the ISO 10816 machine classification: Group 1 (small machines up to 15 kW), Group 2 (medium machines 15-75 kW rigid foundation), Group 3 (large machines 75-300 kW on rigid foundation), or Group 4 (large machines on flexible/spring foundations). Different groups have different severity thresholds.

  2. Enter Vibration Reading

    Input the overall vibration velocity value from your analyzer or portable meter. The calculator accepts readings in inches per second peak (in/s pk), inches per second RMS, or millimeters per second RMS. Conversions between units are handled automatically.

  3. Review Severity Classification

    See the ISO 10816 zone classification: Zone A (new/reconditioned, baseline), Zone B (acceptable for long-term operation), Zone C (short-term acceptable, investigate), or Zone D (damage occurring, immediate action). Each zone includes specific velocity ranges for your machine group.

  4. Set Alarm and Trip Points

    The calculator recommends alarm setpoints at the B/C zone boundary and trip setpoints at the C/D zone boundary. These values can be programmed directly into continuous monitoring systems or used as route-based data collector alert levels.

Built For

  • Vibration analysts performing route-based data collection on plant rotating equipment
  • Maintenance planners using severity trends to schedule predictive maintenance outages
  • Millwrights verifying acceptable vibration after motor, pump, or fan installations
  • Reliability engineers setting alarm and trip points for continuous online monitoring systems
  • Plant operators performing daily walk-around vibration checks with handheld meters
  • Commissioning technicians accepting new rotating equipment against contractual vibration limits

Features & Capabilities

ISO 10816 / 20816 Zone Classification

Classifies vibration into Zones A through D per ISO 10816-3 and its successor ISO 20816-3 for industrial machines. Includes both rigid and flexible foundation categories with correct threshold values for each machine group and power range. Both standards are widely referenced in industry.

Multi-Unit Input

Accepts vibration velocity in in/s peak, in/s RMS, or mm/s RMS and converts automatically. Also displays displacement (mils peak-to-peak) and acceleration (g peak) equivalents at a user-specified frequency for cross-referencing different measurement standards.

Alarm and Trip Recommendations

Provides recommended alarm (Zone B/C boundary) and trip (Zone C/D boundary) setpoints for the selected machine group. Values are formatted for direct entry into monitoring system configuration.

Trending Guidance

Displays rate-of-change warnings when vibration readings approach zone boundaries. Includes guidance on measurement intervals: monthly for Zone A/B machines, weekly for Zone C machines, and continuous monitoring recommended for Zone D equipment.

Diagnostic Frequency Reference

Quick-reference table of common vibration fault frequencies: 1× RPM (imbalance), 2× RPM (misalignment), bearing defect frequencies (BPFO, BPFI, BSF, FTF), gear mesh, and vane/blade pass frequencies to guide follow-up analysis.

Comparison

ISO Zone Group 1 (mm/s) Group 2 (mm/s) Group 3 (mm/s) Group 4 (mm/s) Condition
Zone A 0 - 0.71 0 - 1.12 0 - 1.8 0 - 2.8 New machine baseline
Zone B 0.71 - 1.8 1.12 - 2.8 1.8 - 4.5 2.8 - 7.1 Acceptable long-term
Zone C 1.8 - 4.5 2.8 - 7.1 4.5 - 11.2 7.1 - 18 Investigate / short-term
Zone D > 4.5 > 7.1 > 11.2 > 18 Damage occurring

Assumptions

  • Vibration measurements are taken at the bearing housing in the direction of highest amplitude.
  • Machine is operating at steady-state conditions (not during startup, shutdown, or transients).
  • Measurement instrument is calibrated and has adequate frequency range for the machine speed.
  • ISO machine group classification is correctly selected for the equipment type and mounting.
  • Velocity readings are broadband RMS values measured in the 10-1000 Hz frequency range.

Limitations

  • Does not perform spectral analysis or identify specific fault frequencies (bearing, gear mesh, imbalance).
  • Zone thresholds are general guidelines and may not apply to all machine configurations.
  • Low-speed machines (below 120 RPM) may require displacement-based criteria instead of velocity.
  • Does not account for structural resonance, foundation flexibility, or piping strain effects.
  • Cannot replace trained vibration analyst interpretation for root cause diagnosis.

References

  • ISO 10816-3 — Mechanical Vibration, Evaluation of Machine Vibration by Measurements on Non-Rotating Parts.
  • ISO 20816-1 — Mechanical Vibration, Measurement and Evaluation of Machine Vibration (general guidelines).
  • ISO 2954 — Mechanical Vibration of Rotating and Reciprocating Machinery, Requirements for Instruments.
  • Vibration Institute Category I-IV analyst training body of knowledge.

Frequently Asked Questions

ISO 10816 is the international standard for evaluating machine vibration by measurements on non-rotating parts (bearing housings, structural supports). It classifies vibration severity into four zones based on the broadband vibration velocity, typically measured in mm/s RMS or in/s peak. The standard covers various machine types from small electric motors to large turbomachinery. Most industrial plants use ISO 10816 severity zones to set alarm and trip points for their vibration monitoring programs.
Displacement (mils or micrometers) measures how far the surface moves and is most useful for low-frequency vibration below 600 CPM. Velocity (in/s or mm/s) measures how fast the surface moves and is the standard measurement for general machinery vibration between 600 and 60,000 CPM because it correlates well with vibration severity across a broad frequency range. Acceleration (g) measures force and is best for high-frequency vibration above 60,000 CPM, particularly bearing defects and gear mesh.
For a typical 50 HP (37 kW) industrial motor on a rigid foundation (ISO 10816 Group 2), acceptable long-term vibration in Zone B is up to 2.8 mm/s RMS (approximately 0.16 in/s peak). Vibration above 7.1 mm/s RMS (0.40 in/s peak) enters Zone D where bearing damage is actively occurring. New motors from reputable manufacturers typically run below 1.0 mm/s RMS when properly installed and aligned.
Industry best practice is monthly readings for most process-critical rotating equipment. Equipment showing stable Zone A/B vibration can be extended to bi-monthly or quarterly. Any machine in Zone C should be monitored weekly or bi-weekly to track the rate of change. Zone D equipment needs continuous online monitoring or daily manual checks until corrective action is taken. NEMA MG-1 and API 610/541 provide additional guidance for specific equipment types.
Vibration at 1× running speed is predominantly caused by mass imbalance - uneven weight distribution around the axis of rotation. Other 1× causes include bent shafts, eccentric rotors, and thermal bowing. Imbalance produces a sinusoidal vibration at exactly 1× RPM with relatively stable amplitude. If the 1× amplitude changes with temperature, suspect thermal bow. If it changes with load, suspect eccentricity. Field balancing typically reduces 1× vibration by 70-90% in a single correction.
Strong vibration at 2× running speed is the classic signature of shaft misalignment, both angular and offset. Misalignment forces the shaft coupling to flex twice per revolution, producing a dominant 2× component. Other causes of 2× vibration include cracked shafts, stiffness asymmetry, and looseness. When the 2× amplitude exceeds 50% of the 1× amplitude, misalignment is the primary suspect. Verify with coupling alignment measurements using dial indicators or laser alignment tools.
For a sinusoidal vibration signal: mm/s RMS = in/s peak × 25.4 ÷ 1.414 = in/s peak × 17.96. So 0.3 in/s peak equals approximately 5.4 mm/s RMS. Real machine vibration is not purely sinusoidal, so this conversion is approximate. For broadband vibration with multiple frequency components, the actual RMS-to-peak ratio can range from 1.4 to 4.0 or higher. When in doubt, set your analyzer to measure directly in the unit your severity standard uses.
ISO 20816 is the updated replacement for ISO 10816, consolidating and revising the machine vibration evaluation standards. The severity zone concept remains the same (Zones A through D), but ISO 20816 incorporates shaft vibration measurements (previously under ISO 7919) alongside bearing housing vibration. For most industrial maintenance programs, the severity thresholds in ISO 20816-3 are similar to ISO 10816-3. The transition is gradual and both standards are still widely referenced in industry.
Disclaimer: This tool provides vibration severity classification based on ISO 10816 and ISO 20816 guidelines. Actual acceptable vibration levels depend on machine type, bearing design, foundation, and operating conditions. Vibration analysis requires trained personnel for accurate diagnosis. ToolGrit does not provide predictive maintenance or reliability engineering services and is not responsible for equipment damage or failure.

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