What is ISO 21940‑1-Rotor balancing of machines about?  
ISO 21940‑1 is the first part of a series of documents is applicable to mechanical vibration for rotor balancing.
ISO 21940‑1 provides a general background to balancing technology, as used in the ISO 21940 series, and directs the reader to the appropriate parts of the series that include vocabulary, balancing procedures and tolerances, balancing machines, and machine design for balancing.
Who is ISO 21940‑1- Rotor balancing of machines for? 
ISO 21940‑1 on mechanical vibration is useful for:
- Manufacturers of rotating machines
- Manufacturers of balancing machines
- Product designers
- Mechanical engineers
Why should you use ISO 21940‑1- Rotor balancing of machines?
Balancing is a procedure by which the mass distribution of a rotor (or part of a rotor or module) is measured and adjusted to ensure that unbalance tolerances are met. Many factors can cause rotor unbalance, e.g. non-homogenous material, manufacture, assembly, wear during operation, debris or an operational event.
Vibration caused by rotor unbalance is one of the most critical issues in the design and maintenance of rotating machines. It gives rise to dynamic forces which adversely affect both machine and human health and well-being.
The purpose of ISO 21940‑1 is to give guidance on the usage of the other parts of the ISO 21940 series. Balancing is explained in a general manner, using the specific terms and definitions, to help you select the appropriate balancing approach for your application.
With ISO 21940‑1-compliant balancing procedures and tolerances, you can minimize rotor imbalance and resulting vibrations, ultimately enhancing energy usage, efficiency and service-life of rotating machines.
What’s changed since the last update?
BS ISO 21940‑1:2019 supersedes BS ISO 19499:2007, which is withdrawn. Some significant changes between BS ISO 21940‑1:2019 and BS ISO 19499:2007 are:
- Reference made to all International Standards in the ISO 21940 series
- Deletion of former Table 2 "Guidelines for balancing procedures"
- Deletion of former Annex C "How to determine rotor flexibility based on an estimation from its geometric design
