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Vibration Analysis Calculator

ISO 10816, API 617 & API 618 Compliance

Vibration Analysis Calculator
Evaluate machinery vibration severity per ISO 10816 and API standards. Enter measured vibration data to determine severity zone, compliance status, allowable limits, balance quality grade, and recommended corrective actions for compressors, pumps, motors, turbines, and fans.

Machine Configuration

RPM
HP

Vibration Measurement

in/s pk

ISO 10816 uses bearing housing velocity (mm/s RMS). API 617/684 uses shaft displacement (mils pk-pk).

Optional Parameters

lbs
lbs

Required for ISO 1940 balance grade calculation

Bearing Geometry (optional)

Enter bearing parameters for defect frequency calculation. Leave blank to skip.

-
in
in
degrees

Vibration Severity Assessment

ISO 10816 Zones:
Zone A: Good (newly commissioned)
Zone B: Satisfactory (long-term OK)
Zone C: Unsatisfactory (restricted)
Zone D: Unacceptable (damage risk)
Machine Classes:
Class I: Small (<15 kW)
Class II: Medium (15-75 kW)
Class III: Large rigid (>75 kW)
Class IV: Large flexible foundation
Common Vibration Sources:
Unbalance (1x RPM), misalignment (2x RPM), looseness (fractional harmonics), bearing defects (BPFO/BPFI), gear mesh, vane pass frequency, electrical (2x line frequency).

Learn the Theory

Vibration diagnostics, ISO/API standards, balancing methods, and bearing analysis fundamentals

Read Engineering Guide →

Key Formulas

v = π × f × d / 1000
v = Velocity (in/s peak)
f = Frequency (Hz) = RPM / 60
d = Displacement (mils pk-pk)
a = 2πf × v / 386.4 (g's)
Amax = √(12000/N) mils (API 617)

Standards & References

  • ISO 10816-1:1995
    Mechanical vibration — Evaluation of machine vibration by measurements on non-rotating parts
  • ISO 7919
    Mechanical vibration of non-reciprocating machines — shaft vibration
  • API 618 (6th Ed.)
    Reciprocating Compressors — 0.5 in/s pk bearing housing limit
  • API 617 (8th Ed.)
    Centrifugal Compressors — Shaft vibration limits
  • API 684
    Rotordynamics tutorial — critical speed and unbalance response
  • ISO 1940-1:2003
    Balance quality requirements of rotating rigid bodies

Engineering Notes

  • Velocity: Best overall indicator for general machinery (10-1000 Hz range)
  • Displacement: Best for low-speed machines (<600 RPM) and shaft vibration
  • Acceleration: Best for high-frequency defects (bearings, gears >1000 Hz)
  • Trending: A 50% increase from baseline warrants investigation
  • Critical speed: Avoid operating within ±20% of any critical speed per API
  • API 618: Reciprocating machines have inherent vibration from gas forces; limits are higher than rotating equipment

Quick Reference — ISO 10816 Limits

  • Class I (<15 kW): Good < 0.71 mm/s, Alarm > 1.8
  • Class II (15-75 kW): Good < 1.12 mm/s, Alarm > 2.8
  • Class III (>75 kW rigid): Good < 1.8 mm/s, Alarm > 4.5
  • Class IV (large flex): Good < 2.8 mm/s, Alarm > 7.1
  • Values are velocity in mm/s RMS

Frequently Asked Questions

What is ISO 10816 vibration severity?

ISO 10816 classifies machinery vibration into four zones (A through D) based on broadband velocity measured on bearing housings. Zone A is 'Good' (newly commissioned), Zone B is 'Satisfactory' (long-term operation acceptable), Zone C is 'Unsatisfactory' (restricted operation), and Zone D is 'Unacceptable' (damage may occur). The zone boundaries depend on the machine class (I through IV) determined by power rating and foundation type.

What are the API vibration limits for compressors?

API 617 (centrifugal compressors) limits shaft vibration to A_max = sqrt(12000/N) mils peak-to-peak, with a trip value of 1.5 times the alert level. API 618 (reciprocating compressors) limits bearing housing vibration to 0.5 in/s peak unfiltered. Both standards require the machine vendor to specify exact acceptance criteria based on the specific design.

How do you convert between displacement, velocity, and acceleration?

For sinusoidal vibration at frequency f (Hz): Velocity (in/s peak) = pi * f * Displacement (mils pk-pk) / 1000. Acceleration (g peak) = pi * f * Velocity (in/s peak) / (386.4 / (2*pi*f)). These conversions assume simple harmonic motion and are exact for single-frequency vibration. For broadband signals, the relationships are approximate.

What is ISO 1940 balance quality?

ISO 1940 defines balance quality grades (G values) representing the permissible residual unbalance for different rotor types. G2.5 is specified for compressors and turbines, G6.3 for pumps, fans, and general machinery, and G16 for agricultural equipment. The allowable residual unbalance in oz-in is calculated as G * W * 6.015 / N, where W is rotor weight in pounds and N is operating speed in RPM.

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