ISO 21940-11-2016 PDF

Full title and description

Mechanical vibration — Rotor balancing — Part 11: Procedures and tolerances for rotors with rigid behaviour. This International Standard specifies procedures and unbalance tolerances for the balancing of rotors that behave as rigid bodies during operation, giving rules for permissible residual unbalance, required correction planes and allocation of tolerances, and guidance on accounting for balancing-process errors.

Abstract

ISO 21940-11:2016 establishes the magnitude of permissible residual unbalance, the necessary number of correction planes, how permissible residual unbalance is allocated to tolerance planes, and how to take account of balancing-process errors. It is limited to rotors with rigid behaviour; flexible-rotor procedures are covered in other parts of the ISO 21940 series.

General information

• Status: Published (International Standard, confirmed on review).
• Publication date: November 2016 (ISO edition 1, published 9 November 2016).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 21.120.40 (Balancing and balancing machines).
• Edition / version: Edition 1 (2016); consolidated with Amendment 1 (2022) in some national adoptions/republishings.
• Number of pages: 28 (original ISO publication).

Key bibliographic and lifecycle details above are taken from the ISO record for ISO 21940-11:2016; an amendment (ISO 21940-11:2016/Amd 1:2022) was published and some national bodies have issued consolidated adoptions that incorporate that amendment.

Scope

This part of ISO 21940 specifies methods for determining and specifying permissible residual unbalance on rotors that behave as rigid bodies at balancing speed. It gives requirements for selecting the number of correction planes, assigning permissible unbalance to tolerance planes, and evaluating and accounting for errors introduced by the balancing process. It does not cover rotors that exhibit flexible (shaft‑elastic) behaviour; those are addressed in ISO 21940‑12.

Key topics and requirements

• Definition and specification of permissible residual unbalance (unbalance tolerances) for rigid rotors.
• Rules for selecting the necessary number of correction planes (single‑plane vs two‑plane, etc.).
• Allocation of permissible residual unbalance to tolerance planes and to individual components.
• Procedures to measure, reduce and verify residual unbalance using balancing machines and test runs.
• Methods to assess and account for errors arising from the balancing process (references to procedures for assessing balance errors are found elsewhere in the series).
• Cross‑references to related parts of the ISO 21940 series (vocabulary, flexible‑rotor procedures, assessment of balance errors, and balancing‑machine description/evaluation).

Typical use and users

Engineers and technicians in rotating‑equipment design, manufacturing and maintenance; vibration analysts; balancing‑machine manufacturers and test laboratories; OEMs specifying unbalance tolerances for shafts, rotors, impellers, fans, motor/generator rotors, turbines and other rotating machinery; quality and acceptance teams defining production and repair acceptance criteria. The standard is used both as a normative specification for tolerance requirements and as practical guidance for balancing operations on rigid rotors.

Related standards

ISO 21940 is a multi‑part series. Relevant related documents include ISO 21940‑12 (procedures for rotors with flexible behaviour), ISO 21940‑14 (procedures for assessing balance errors), ISO 21940‑21 (description and evaluation of balancing machines), ISO 21940‑2 (vocabulary) and guidance/fundamentals such as ISO 19499. National adoptions and consolidated publications (for example some DIN adoptions) may combine the base edition with later amendments.

Keywords

rotor balancing, mechanical vibration, unbalance tolerance, correction planes, rigid rotor, balancing procedures, balance errors, balancing machines, ISO 21940

FAQ

Q: What is this standard?

A: ISO 21940-11:2016 is the International Standard that defines procedures and tolerance rules for balancing rotors that behave as rigid bodies at operating (balancing) speed, including permissible residual unbalance and the number and allocation of correction planes.

Q: What does it cover?

A: It covers the specification of permissible residual unbalance, the required number of correction planes, assignment of unbalance to tolerance planes, and how to account for errors during the balancing process. It explicitly excludes rotors with flexible (shaft‑elastic) behaviour, which are covered by ISO 21940‑12.

Q: Who typically uses it?

A: Mechanical/vibration engineers, balancing‑service providers, OEM designers, quality and test laboratories, and balancing‑machine manufacturers—anyone who specifies, performs or certifies rotor balancing for rigid rotors.

Q: Is it current or superseded?

A: The original ISO 21940-11 was published in 2016 (edition 1); an Amendment 1 was published in 2022. The ISO record shows the 2016 edition as published and subsequently amended; some national bodies have issued consolidated adoptions (for example consolidated DIN publications in 2023 that combine the 2016 text with the 2022 amendment). Users should check the issuing body or national standards reseller for the most up‑to‑date consolidated text for normative use.

Q: Is it part of a series?

A: Yes — ISO 21940 is a multi‑part series covering rotor balancing (introduction, vocabulary, rigid‑rotor procedures, flexible‑rotor procedures, assessment of balance errors, balancing machine descriptions/evaluation, etc.). ISO 21940‑11 is the part that addresses rigid‑behaviour rotors.

Q: What are the key keywords?

A: rotors, balancing, mechanical vibration, unbalance tolerance, correction planes, rigid rotor, balancing machine, ISO 21940.