Mod 7 - Vibration Analysis

Module from the Rotating Equipment Training Curriculum curriculum.

VIBRATION ANALYSIS · Learning Objectives · 1. Apply ISO 10816 vibration severity criteria 2. Interpret frequency spectra to identify fault patterns 3. Calculate bearing defect frequencies (BPFO, BPFI, BSF, FTF) 4. Establish vibration baselines and trending programs · ISO 10816 Vibration Severity — Velocity (in/sec peak)

Machine Class	Zone A (Good)	Zone B (Acceptable)	Zone C (Alert)	Zone D (Danger)	Measurement	Notes
Class I: Small (<15 kW)	<0.03	0.03-0.07	0.07-0.18	>0.18	Housing velocity	Small pumps, fans, motors
Class II: Medium (15-75 kW)	<0.07	0.07-0.18	0.18-0.45	>0.45	Housing velocity	Medium pumps, motors
Class III: Large (>75 kW, rigid)	<0.11	0.11-0.28	0.28-0.71	>0.71	Housing velocity	Large pumps, compressors, motors
Class IV: Large (>75 kW, flexible)	<0.18	0.18-0.45	0.45-1.12	>1.12	Housing velocity	Turbines, large compressors on flex mounts
Common Vibration Fault Frequencies
Fault Pattern	Frequency	Direction	Severity Indicator	Corrective Action	Measurement Point
Unbalance (mass)	1× RPM (dominant)	Radial (horizontal + vertical)	Amplitude proportional to unbalance	Field balancing (single or two-plane)	Bearing housing, both directions
Misalignment (angular)	1× and 2× RPM, high axial	Axial dominant, 2× often > 1×	Axial vibration > 50% of radial	Laser realignment per API 686	Bearing housing, axial direction
Misalignment (offset)	2× RPM dominant	Radial, 180° phase across coupling	2× amplitude high	Laser realignment, check for soft foot	Bearing housing, radial H+V
Mechanical Looseness	1×, 2×, 3× (harmonics + sub-harmonics)	All directions, chaotic	Multiple harmonics, half-harmonics (0.5×)	Tighten foundation bolts, shim/grout baseplate	Foundation bolts, near loose joints
Rolling Element Bearing Defect	BPFO, BPFI, BSF, FTF (calculated)	Radial, high frequency	Envelope/demodulation peaks at defect frequency	Replace bearing, investigate root cause	Bearing housing, accelerometer (high-freq)
Oil Whirl (fluid instability)	0.42-0.48× RPM (sub-synchronous)	Radial, forward precession	Unstable orbit, sub-synchronous peak	Upgrade to tilting-pad bearings, increase bearing load	Proximity probes (shaft relative)
Vane/Blade Pass	Z × RPM (Z = number of vanes)	Radial and axial	Normal at low amplitude; high if BEP far off	Operate closer to BEP, trim impeller if far off design	Bearing housing, near volute/diffuser
Source: ISO 10816, Vibration_Analysis_Quick_Reference_v1.xlsx, FOS Chief Files — Compressor & Pump folder

Source: Rotating_Equipment_Training_Curriculum_v1.xlsx · Sheet: Mod 7 - Vibration Analysis

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