ISO 21940-1:2019

Overview

ISO 21940-1:2019 - "Mechanical vibration - Rotor balancing - Part 1: Introduction" provides a concise, authoritative introduction to rotor balancing technology and to the wider ISO 21940 series. It explains core concepts (for example the unbalance vector expressed as U = m·r and common units such as g·mm or kg·m), describes how unbalance generates once‑per‑revolution vibration, and directs users to the specific parts of the series that cover vocabulary, procedures, tolerances, balancing machines and machine design.

Key Topics

• Fundamentals of balancing: definition of balancing, sources of rotor unbalance (manufacture, assembly, wear, debris), and basic representations of unbalance.
• Unbalance representation: vector representation, units and practical interpretation of eccentricity and correction mass.
• Rotor behaviour: distinction between rotors with rigid and flexible behaviour; effects of shaft and component elasticity and settling behavior.
• Measurement and correction: measurement approaches (bearing motion, shaft motion, force gauges) and use of correction masses in one or multiple correction planes.
• Selection guidance: factors influencing choice of balancing procedure and balancing machine, including speed, support conditions and initial unbalance.
• Unbalance tolerances and vibration limits: overview of permissible residual unbalance concepts and factors that affect tolerances.
• Standards mapping: pointers to related ISO 21940 parts for vocabulary, procedures and machine requirements.

Applications

ISO 21940-1 is an essential reference for anyone involved in controlling rotor vibration and ensuring machine reliability. Typical applications and benefits:

• Manufacturers: setting production balancing practices and specifying acceptance criteria for new rotors.
• Maintenance & rotating equipment engineers: choosing appropriate balancing methods (shop vs in‑situ) after repair, retrofit or during vibration troubleshooting.
• Condition monitoring & reliability teams: understanding how unbalance contributes to vibration signatures and how balancing reduces dynamic forces.
• Balancing machine designers & test labs: selecting machine characteristics and protective measures in line with ISO series guidance.
• Machine designers: assessing machine susceptibility to unbalance and design features that facilitate balancing.

Related Standards

ISO 21940-1 references and directs users to the ISO 21940 family, including:

• ISO 21940-2 (vocabulary), ISO 2041 (vibration vocabulary)
• ISO 21940-11 / -12 (procedures & tolerances for rigid and flexible rotors)
• ISO 21940-13 (in‑situ balancing criteria)
• ISO 21940-14 (balancing error procedures)
• ISO 21940-21 / -23 (balancing machine description and safety measures)
• ISO 21940-31 / -32 (machine susceptibility and shaft conventions)

Use ISO 21940-1 as a practical starting point to navigate the full series for rotor balancing, mechanical vibration control, and implementation of industry‑level balancing practices.