GB/T 9239.12-2021 in English
VALIDMechanical vibration—Rotor balancing—Part 12: Procedures and tolerances for rotors with flexible behaviour
- Issued on:2021-08-20
- Implemented on:2022-03-01
- File Format:PDF
- Delivery:Via email within 5 business days
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$476.00
《GB/T 9239.12-2021机械振动 转子平衡 第12部分：具有挠性特性的转子的平衡方法与允差》由TC53（全国机械振动、冲击与状态监测标准化技术委员会）归口，主管部门为国家标准化管理委员会。
Introduction
Analysis of the core content of the standard
Scope of application: This standard is applicable to flexible rotors such as steam turbines and generator rotors whose operating speed is close to or exceeds the critical speed, and specifies a full set of methods from low-speed three-plane balancing to multi-speed modal balancing.
Technical evolution: Compared with the 2009 version, the flexible dynamics description (Chapter 4.2) and modal imbalance assessment method (Chapter 9.2.3) are newly added, and redundant appendices F and H are deleted.
Technical evolution: Compared with the 2009 version, the flexible dynamics description (Chapter 4.2) and modal imbalance assessment method (Chapter 9.2.3) are newly added, and redundant appendices F and H are deleted.
Comparison of key balancing methods
| Method type | Applicable scenarios | Number of correction planes | Typical rotor |
|---|---|---|---|
| Low-speed double-plane balancing (B) | The initial imbalance is concentrated on two lateral planes | 2 | Rigid shaft segment assembly |
| Multi-speed balancing (G) | Operating speed spans multiple critical speeds | n+2 (n is the critical speed order) | Multi-stage centrifugal compressor rotor |
| Operating speed balancing (H) | High damping or fast passing through critical speed | 2 | Motor with damping winding |
Vibration limit calculation model
Allowable vibration formula: Y = X·K0·K1·K2
- X: Allowable total vibration on site (refer to ISO7919)
- K0: Fundamental frequency ratio (0.7~1.0)
- K1: Support condition conversion factor (see Table C.1)
- K2: Measuring point position correction coefficient
Example: When calculating the bearing vibration limit of a 300kW motor (Class II), K1 is taken as 1.6~5.0 (axis relative measurement)
Implementation suggestions
New rotor balancing process:
- Determine the rotor rigidity/flexibility properties according to Appendix E
- Select the balancing method recommended in Table 1 (such as the combination of methods G+H)
- Use the three-plane balancing method in Appendix B to optimize low-speed correction
- Verify the equivalent vibration mode unbalance according to Clause 8.3.4
Note for on-site installation: The coupling runout (Appendix A.3) may cause false vibration and must be corrected to ≤50μm before balancing.
Sample only — not a preview of GB/T 9239.12-2021
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