By Greg Buscarello
Overview
The book begins by explaining the importance of balancing and the challenges involved. It then introduces foundational concepts such as measuring imbalance, types of imbalance, and vector plotting.
This book provides a practical understanding of field balancing of rigid rotors. Designed as a textbook for training, it combines theory with straightforward language, practical procedures, and useful techniques. No prior experience is required, though it remains valuable for experienced practitioners.
A key issue in field balancing is that vibration may not be caused solely by imbalance. The text addresses how to distinguish imbalance from other vibration sources and introduces resonance as a major complicating factor.
Pre-balance checks and proper setup are emphasized to prevent failure during the balancing process. The book then walks through single-plane balancing, including graphical correction methods, sensitivity vectors, one-shot balancing, and the four-run no-phase method.
It also explores real-world complications—common issues that prevent successful balancing—and how to avoid them.
Balancing tolerances are examined, including discrepancies between shop and field results due to assembly errors.
The book concludes with dual-plane balancing, the static-couple method, flexible rotor balancing, and strategies for achieving long-term reliability through precision balancing.
Table of Contents
1. Introduction
- Why balancing is so important
- Causes of imbalance
- Field balancing vs. shop balancing
- When to do balancing
- Why precision balancing is not usually done
- Best practices
- Why field balancing can be difficult
- About this course
- A brief history of balancing
2. Balancing Concepts
- “Imbalance” and “Unbalance”
- Center of gravity vs. geometric center
- Units of measure
- Vectors
- Static imbalance
- Couple imbalance
- Dynamic imbalance
- “Quasi-static” (false couple)
- Phase measurement
- Strobe light
- Optical transducer
- Two-channel instruments
- Balancing without instruments
- Knife edges
- Static balancer
- Measuring static imbalance of large rotors
- High spot marking
- Plotting vectors
- Splitting and combining weights
3. Determining Imbalance through Vibration Analysis
- Machine history
- Frequency
- Misalignment
- Eccentricity
- Bent shaft
- Looseness
- Defective rotor bars
- Combined faults
- Amplitude
- Phase
- Vectors
- Resonance
- Beats and modulation
4. Resonance and Balancing
- Understanding resonance
- Resonance in spectra
- Phase behavior near resonance
- Identifying resonance via phase change
- Determining resonant ranges vs. RPM
- Tunable instruments and strobe use
- FFT-based resonance detection
- Transducer precautions
- Vibration shaker applications
- Structural vs. source vibration
- Resonance vs. critical speed
- Rigid vs. flexible rotors
5. Pre-Balance Checks and Setup
- Can the machine be balanced?
- Safety
- Machine preparation
- Tools and equipment
- Job setup
6. Single Plane Balancing
- Procedure
- Trial weight response
- Graphical calculations
- Sensitivity vectors
- One-shot balancing
- Four-run no-phase method
7. What Goes Wrong
- Insufficient analysis
- Changing conditions
- Incorrect orientation
- Unstable measurements
- Slow beat issues
- Resonance
- Looseness
- Angle inaccuracies
- Changing radii
- Arc effectiveness
- Incorrect trial weights
- Correction weight errors
- Non-symmetrical rotors
- Foreign material
- Resonance complications
8. Balance Tolerances
- ISO standards
- API standards
- Field balancing tolerances
- Supplier tolerance negotiation
9. Imbalance from Assembly Errors
- Poorly balanced parts
- Incorrect key length
- Set screw issues
- Improper fits
- Cocked rotors
- Burrs
- Bent shafts
- Looseness
- Coupling issues
- Bolt problems
- Lubrication inconsistencies
- Belt-driven systems
- Taper lock and QD hubs
10. Dual Plane Balancing
- When to use dual-plane balancing
- Procedure
- Graphical vs. software methods
11. Static-Couple Method
- Narrow and overhung rotors
- Separating static and couple imbalance
- Application procedure
- Alternative methods
- Applying tolerances
12. Balancing Flexible Rotors
- Multi-plane balancing
- Papermill roll balancing
- Preventing whip
- Key considerations
- Procedures
- Driving rolls in-machine
- Removing whip
- First and second critical speed corrections
13. Strategies for Best Reliability
- Supplier tolerance negotiation
- Audits and inspections
- When suppliers cannot meet precision standards