ISO 21940-32:2012 PDF

Mechanical vibration — Rotor balancing — Part 32: Shaft and fitment key convention

First page of standard ISO 21940-32:2012

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Title (English):

ISO 21940-32:2012

Mechanical vibration — Rotor balancing — Part 32: Shaft and fitment key convention

Document status:: Active
Format:: Electronic (PDF)
Number of pages:: 16
Publication date:: March 16, 2012
Edition:: ISO IS 21940 edition 1 version 1
ICS:: 21.120.40

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Description (English):

ISO 21940-32:2012 specifies one convention for balancing the individual components (shaft and fitments) of a keyed rotor assembly. This provides compatibility of all balanced components so that when they have been assembled the overall balance tolerance and/or vibration limit for the rotor assembly is met. ISO 21940-32:2012 specifies that half-keys be used when balancing the individual components of a keyed rotor assembly. It also specifies a marking of the components balanced in accordance with the key convention used. ISO 21940-32:2012 applies to rotors balanced in a balancing machine, in their own bearings or in situ. The key convention can also be applied when measuring the residual unbalance and/or vibration of rotors with keyways, but to which fitments have not yet been assembled. In addition to applying to keys of constant rectangular or square cross-section mounted parallel to the shaft centreline, ISO 21940-32:2012 also applies to keys mounted on tapered shaft surfaces, to woodruff, gibhead, dowel and other special keys. The principle of the half-key convention is applied as is appropriate to the particular shape and location of the special key.

Technical details

Technical committee: ISO/TC 108/SC 2 - Measurement and evaluation of mechanical vibration and shock as applied to machines, vehicles and structures
SKU: ISO 21940-32:2012

Abstract

Overview

ISO 21940-32:2012 - "Mechanical vibration - Rotor balancing - Part 32: Shaft and fitment key convention" specifies a standardized half-key convention for balancing keyed rotor assemblies. The standard ensures compatibility when shafts and fitments (e.g., gears, pulleys, couplings) are balanced separately by different suppliers so that, after assembly, the rotor meets its overall balance tolerance and vibration limits. It applies to balancing in a balancing machine, in bearings, or in situ, and covers common key types (rectangular/square), tapered keys, woodruff, gibhead, dowel and other special keys.

Key topics and technical requirements

Half-key convention mandated: use a half-key in the shaft keyway during shaft balancing; use a complementary half-key when balancing the fitment on a mandrel (or follow the mandrel-specific methods in Annex A).
Mandrel/fitment rules (Annex A): procedures vary if the balancing mandrel has no keyway, one keyway, or two opposite keyways - preferred mandrel designs are those inherently balanced.
Two-opposite-keyways: if shaft/fitment have two equal keyways 180° apart, balancing without keys is permissible.
Axial CG alignment: the centre of gravity of the half-key must align axially with the full key in the final assembly.
Material and holding of half-keys: half-keys used for balancing should have the same density as the final key (typically steel) and be held using means that introduce negligible unbalance (e.g., fibreglass tape).
Marking requirements: permanently mark shaft and fitment adjacent to the keyway with H to indicate the half-key convention was used. If another convention is used for compatibility with existing parts, mark with F (full-key) or N (no-key).
Implementation: manufacturers and processors are encouraged (and expected) to adopt the half-key convention and mark components accordingly. Annexes provide specifications, practical guidance for making half-keys, and comparison of conventions.

Practical applications and users

Who uses ISO 21940-32:

Rotor and rotating-equipment manufacturers (pumps, motors, gearboxes)
Balancing service providers and repair shops
OEMs and component suppliers (keys, shafts, couplings)
Maintenance and vibration-analysis engineers performing in-situ balancing

Benefits:

Ensures cross-supplier compatibility of separately balanced components
Reduces residual unbalance and vibration in assembled rotors
Prevents internal bending moments introduced by inconsistent key conventions

Related standards

ISO 21940 series (Parts 1, 2, 11–14, 21, 23, 31) - broader rotor balancing guidance and vocabulary
Normative reference: ISO 1925 (Balancing - Vocabulary)
Note: Some standards such as IEC 60034-14 reference or prescribe the half-key convention for rotating machines

Keywords: ISO 21940-32, rotor balancing, half-key convention, shaft and fitment key convention, keyways, residual unbalance, mechanical vibration.

Related standards

Standards mentioned in the description

Abstract

Overview

Key topics and technical requirements

Half-key convention mandated: use a half-key in the shaft keyway during shaft balancing; use a complementary half-key when balancing the fitment on a mandrel (or follow the mandrel-specific methods in Annex A).
Mandrel/fitment rules (Annex A): procedures vary if the balancing mandrel has no keyway, one keyway, or two opposite keyways - preferred mandrel designs are those inherently balanced.
Two-opposite-keyways: if shaft/fitment have two equal keyways 180° apart, balancing without keys is permissible.
Axial CG alignment: the centre of gravity of the half-key must align axially with the full key in the final assembly.
Material and holding of half-keys: half-keys used for balancing should have the same density as the final key (typically steel) and be held using means that introduce negligible unbalance (e.g., fibreglass tape).
Marking requirements: permanently mark shaft and fitment adjacent to the keyway with H to indicate the half-key convention was used. If another convention is used for compatibility with existing parts, mark with F (full-key) or N (no-key).
Implementation: manufacturers and processors are encouraged (and expected) to adopt the half-key convention and mark components accordingly. Annexes provide specifications, practical guidance for making half-keys, and comparison of conventions.

Practical applications and users

Who uses ISO 21940-32:

Rotor and rotating-equipment manufacturers (pumps, motors, gearboxes)
Balancing service providers and repair shops
OEMs and component suppliers (keys, shafts, couplings)
Maintenance and vibration-analysis engineers performing in-situ balancing

Benefits:

Ensures cross-supplier compatibility of separately balanced components
Reduces residual unbalance and vibration in assembled rotors
Prevents internal bending moments introduced by inconsistent key conventions

Related standards

ISO 21940 series (Parts 1, 2, 11–14, 21, 23, 31) - broader rotor balancing guidance and vocabulary
Normative reference: ISO 1925 (Balancing - Vocabulary)
Note: Some standards such as IEC 60034-14 reference or prescribe the half-key convention for rotating machines

Keywords: ISO 21940-32, rotor balancing, half-key convention, shaft and fitment key convention, keyways, residual unbalance, mechanical vibration.

ISO 21940-32:2012 PDF

Technical details

Abstract

Overview

Key topics and technical requirements

Practical applications and users

Related standards

Related standards

Abstract

Overview

Key topics and technical requirements

Practical applications and users

Related standards

Related standards

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