ISO 21940 Mechanical Vibration - Rotor Balancing

The ISO 21940 set of standards, published by the International Organization for Standardization (ISO), provides a general background in balancing technology and includes criteria for balancing procedures and tolerances, balancing machines and machine design for balancing.

Vibration caused by the imbalance of the rotor is one of the most critical issues in the design and maintenance of rotating machines. This situation causes the emergence of dynamic forces that negatively affect both the machine and human health and well-being.

The ISO 21940 set of standards consists of the following parts:

• ISO 21940-1 Part 1: Introduction (this standard provides a general background on balancing technology and directs the reader to the appropriate sections of the series which include the glossary, balancing procedures and tolerances, balancing machines and machine design for balancing).
• ISO 21940-2 Part 2: Terms and definitions (this standard defines terms related to balancing).
• ISO 21940-11 Part 11: Balancing tolerances specification and verification (this standard specifies procedures and unbalance tolerances for balancing rotors with rigid behavior).
• ISO 21940-12 Part 12: Procedures and tolerances for flexible behavior rotors (this standard presents typical configurations of flexible behavior rotors according to their characteristics and balancing requirements, defines balancing procedures, specifies methods for evaluating final equilibrium state, and establishes guidelines for balance quality criteria) .
• ISO 21940-13 Part 13: Criteria and safety measures for in-situ balancing of medium and large rotors (this standard specifies the procedures to be adopted when balancing medium and large rotors in the field mounted in their own bearings).
• ISO 21940-14 Part 14: Procedures for evaluating balance errors (this standard specifies balance acceptance criteria for residual unbalance, both directly after balancing and for subsequent checking of balance quality by the user).
• ISO 21940-21 Part 21: Description and evaluation of balancing machines (this standard specifies requirements for evaluating, by certain tests, the performance of machines to balance rotating components).
• ISO 21940-23 Part 23: Enclosures and other protective measures for the measuring station of balancing machines (this standard specifies the requirements for guards and other protective measures used to minimize the mechanical hazards produced by the rotor in the imbalance measuring station of centrifugal balancing machines).
• ISO 21940-31 Part 31: Susceptibility and susceptibility of machinery to unbalance (this standard specifies methods for determining the susceptibility of machinery vibration to unbalance and provides evaluation guidelines as a function of the proximity of the respective resonance rotation speeds to the operating speed).
• ISO 21940-32 Part 32: Shaft and coupling wrench arrangement (this standard describes a rule for balancing shafts and assemblies of a keyed rotor assembly).

Mechanical vibration is a measurement of the periodic oscillation process with respect to an equilibrium point. Vibrations are oscillations in mechanical dynamic systems. In mechanical engineering, the term vibration is generally used for systems that can oscillate freely without applied forces. Sometimes these vibrations cause minor or serious performance or safety issues in engineered systems. For example, when an airplane wing vibrates excessively, passengers on the airplane become uncomfortable, especially when the vibration frequencies correspond to the natural frequencies of the human body and organs.

Mechanical vibration analyzes use mathematical tools to model and predict potential vibration problems and solutions that are often not obvious in pre-engineering designs.

Rotor balancing is an analysis method that compares the vibration profile with the rotation of a mechanical element to determine the inconsistent weight distribution around the diameter while calculating the amount and position of the weight required to maintain the imbalance condition.

Our organization also provides mechanical vibration and rotor balancing testing services within the scope of ISO 21940 standard, with its trained and expert staff and advanced technological equipment, among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors.