Field Dynamic Balancing Using Portable Instruments

Field Dynamic Balancing Using Portable Instruments
Authored by:
Mr. Gene Ford
Technical Associates of Charlotte, P.c.
Specialists in Predictive Maintenance, Machinery Diagnostics, and Vibration Reduction
By: James E. Berry, P.e., Mechanical Engineer
Technical Associates of Charlotte
Charlotte
Specialists in Predictive Maintenance, Machinery Diagnostics, and Vibration Reduction
Technical Associates Field Dynamic Balancing
2001 Technical Associates of Charlotte, P.c.
Section Subject Page
1. Introduction to Dynamic Balancing 1-1
2. Types of Unbalance 2-1
A. Static Unbalance . 2-2
B. Couple Unbalance 2-3
C. Quasi-static Unbalance 2-4
D. Dynamic Unbalance . 2-5
3. Types of Balance Problems 3-1
A. Rigid Vs Flexible Rotors 3-1
B. Critical Speeds 3-4
4. How to Ensure the Dominant Problem is Unbalance . . 4-1
A. Review of Typical Spectra and Phase Behaviors for Common
Machinery Problems . 4-1
1. Mass Unbalance . 4-1
2. Eccentric Rotor 4-1
3. Bent Shaft . 4-3
4. Misalignment 4-3
5. Resonance 4-3
6. Mechanical Looseness/weakness . 4-4
B. Summary of Phase Relationships for Various Machinery 4-4
1. Force (or Static) Unbalance . 4-4
2. Couple Unbalance 4-4
3. Dynamic Unbalance . 4-4
4. Angular Misalignment . 4-6
5. Parallel Misalignment . 4-6
6. Bent Shaft . 4-6
7. Resonance 4-6
8. Rotor Rub 4-6
9. Mechanical Looseness/weakness Due to Base/frame
Problems or Loose Hold Down Bolts . 4-6
10. Mechanical Looseness Due to a Cracked Frame 4-6
C. Summary of Normal Unbalance Symptoms 4-6
1. Special Characteristics . 4-6
2. Centrifugal Force Due to Unbalance . 4-6
3. Unbalance Force Directivity 4-7
4. Radial/axial Vibration Comparison 4-7
5. Overhung Rotor Unbalance Directivity 4-7
6. Steadiness & Repeatability of Phase Due to Unbalance . 4-8
7. Resonant Amplitude Magnification . 4-8
8. Phase Behavior for Dominant Static,couple & Dynamic Unbalance . 4-8
Table of Contents and Seminar Agenda
Field Dynamic Balancing 2001 Techncial Associates of Charlotte, P.c.
Techncial Associates Field Dynamic Balancing
Section Subject Page
5. Causes of Unbalance 5-1
A. Assembly Errors . 5-1
B. Casting Blow Holes . 5-1
C. Fabrication Tolerance Problems 5-1
D. Key Length Problems 5-1
E. Rotational Distortion 5-3
F. Deposit Buildup or Erosion 5-3
G. Unsymmetrical Design 5-3
6. Why Dynamic Balancing is Important 6-1
7. Units of Expressing Unbalance 7-1
8. Vectors . 8-1
9. Dynamic Field Balancing Techniques . 9-
A. Recommended Trial Weight Size 9-
B. How a Strobe-lit Mark on a Rotor Moves When a Trial Weight is Added 9-
C. Single-plane Balancing Using a Strobe Light and a Swept-filter Analyzer 9-
D. Single-plane Method of Balancing 9-
E. Balancing in One Run . 9-
F. Two-plane Balancing Techniques 9-
G. Cross-effects . 9-
H. Single-plane Method for Two-plane Balancing 9-
I. Vector Calculations for Two-plane Balancing 9-
J. Rotor Balancing by Static Couple Derivation 9-
K. Single-plane Balancing With Remote Phase and a Data Collector . 9-
L. Taking Phase Readings With a Data Collector . 9-
M. Single-plane Balancing Using a Data Collector . 9-
N. Two-plane Balancing Using a Data Collector 9-
O. Overhung Rotors . 9-
P. Multi-plane Balancing 9-
Q. Splitting Balance Correction Weights 9-
R. Combining Balance Correction Weights Using Vectors 9-
S. Effect of Angular Measurement Errors of Potential Unbalance Reduction . 9-
1. Effect of Phase Angle Measurement Errors by Instruments 9-
2. Effect of Angular Measurement Errors When Attaching
Balance Correction Weights 9-
Table of Contents and Seminar Agenda
Field Dynamic Balancingtechncial Associates Field Dynamic Balancing
2001 Techncial Associates of Charlotte, P.c.
Section Subject Page
10. Balancing Machines – Soft-bearing Vs Hard-bearing Machines . 10-
A. Soft-bearing Machine . 10-
B. Hard-bearing Machine 10-
11. Recommended Vibration and Balance Tolerances 11-
A. Vibration Tolerances . 11-
1. Recommended Overall Vibration Specifications 11-
2. Synopsis of Spectral Alarm Band Specifications . 11-
B. Balance Tolerances on Allowable Residual Unbalance . 11-
1. Iso 1940 Balance Quality Grades 11-
A. Application of Tolerances to Single-plane Problems 11-
B. Application of Tolerances to Two-plane Problems 11-
C. Application of Tolerances to Special Rotor Geometries 11-
C. How to Determine Residual Unbalance Remaining in a Rotor After
Balancing 11-
D. Comparison of Iso 1940 With Api and Navy Balance Specifications 11-
Appendix a Balancing Terminology
Appendix B Weight Removal Charts
Appendix C Conversion Chart for Converting Inches of Flat Stock # 1020 Steel to
Ounces of Weight
Appendix D Three-point Method of Balancing
Table of Contents and Seminar Agenda
Field Dynamic Balancing
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