Translate | ISO 21940-11 G2.5, G6.3, RPM and g·mm Residual Unbalance — Preserve Rotor Balancing Reports Across Languages

How do you translate an ISO 21940-11 rotor balancing report when it lists “G2.5,” “G6.3,” “1,500 rpm,” “permissible residual unbalance” and values expressed in g·mm? A technician may immediately recognise those notations, but a translated maintenance report can become unsafe or commercially misleading if the reader mistakes a balance quality grade for a vibration measurement, loses the operating speed or changes the plane allocation. The translation must preserve the relationship between rotor mass, speed, permissible unbalance and actual balance evidence.

This article answers the specific search for how to translate ISO 21940-11:2016, G2.5 and G6.3 rotor balance grades, residual unbalance, static and dynamic balancing records, rpm, g·mm and correction-plane measurements across languages. It is intended for turbine and pump teams, motor repair workshops, fan and compressor suppliers, inspection staff, engineering students and professional translators. The purpose is not to calculate a new balancing tolerance from memory. It is to show exactly what a certificate means, what it does not establish and which figures, units, conditions and acceptance terms need to survive translation.

The published ISO 21940-11:2016, amended in 2022, addresses balancing rotors with rigid behaviour, permissible residual unbalance, correction-plane requirements, allocation and balancing errors. Its scope differs from the standards and procedures for rotors with flexible behaviour. We will examine real document structures, worked interpretation problems and a multilingual audit workflow. The examples are educational; use the applicable issued standard, machine specification, approved engineering procedure and trained balancing specialist for an actual safety or acceptance decision.

The 50-second translation answer

A balance grade G relates permissible specific residual unbalance to angular speed. A rotor may have a target such as G2.5 or G6.3, but the actual permissible residual unbalance depends on rotor mass, speed and the appropriate balancing arrangement. Values in g·mm express an unbalance moment-like mass-radius product, not a vibration velocity. Translate grade, rotor identity, operating speed, balance plane, allowable result, actual result and acceptance basis as linked fields. A certificate for a rigid rotor does not guarantee that an assembled machine has acceptable vibration in every installation.

Nineteen essential readings before translating a balance certificate

1. A balance report is not a general machine-health certificate

Balancing addresses uneven mass distribution relative to the intended axis of rotation. It does not by itself prove that a machine has correct alignment, sound bearings, adequate structural stiffness or safe operation under every load. A translating engineer must separate a balance tolerance from operating vibration measurements. A product can meet a rotor balancing criterion and still vibrate because of installation, resonance, looseness or another fault. Do not translate “balanced to G2.5” as “all vibration eliminated.”

To check this part of a translation, trace the target statement back through the certificate’s data fields and any drawing of the rotor. Ask whether the reader can identify the variable, unit, rotor configuration, relevant operating speed and the authority behind the conclusion. A statement about measurement should not become a statement about mechanical health. If the source does not state a result, the target document should preserve that boundary rather than filling it with plausible engineering language.

2. Know the reference and edition

ISO 21940-11:2016 describes balancing procedures and tolerances for rotors with rigid behaviour. ISO lists a 2022 amendment, and the 2016 document remains the published reference as of October 2026. A source certificate must retain its actual cited edition or amendment status. Do not replace a historical ISO 1940-1 citation with ISO 21940-11 silently, even though the latter superseded the former. Historical evidence remains historical evidence. Check the contractual basis and the report’s issue date.

3. Rigid and flexible are different balancing problems

The standard in this article concerns rotors that behave rigidly for the relevant balancing problem. Flexible rotors can exhibit bending modes and require a different framework, such as the separate ISO 21940-12 subject area. A target-language rendering that calls all rotating shafts “rigid rotors” can hide a major applicability limit. Preserve the technical phrase and consult the machinery engineer if the rotor’s behaviour is disputed. Material strength or stiffness alone does not settle which method is applicable.

4. What quality grade G means

Balance quality grades such as G2.5 and G6.3 relate an allowed specific residual unbalance to angular speed. The number is not a direct reading of a vibration sensor and not itself a count of grams. It is a criterion used within a balancing calculation and acceptance framework. Preserve capitalization, decimal value and grade symbol. A reader should be able to distinguish a grade selected for a machine class from the measured state of a particular specimen. G2.5 is not a universal guarantee of greater real-world reliability than every machine labelled G6.3.

5. Rotational speed belongs in the interpretation

Rotational speed is commonly expressed as rpm, revolutions per minute. The relevant balancing tolerance depends on angular speed, so reporting a grade without the service speed and rotor mass can leave the actual permissible unbalance undecidable. Keep the actual operating and balancing speeds separate. If the certificate uses 1,500 rpm and a translated quotation says 3,000 rpm, the numbers are not interchangeable. A reading that discards speed makes the grade look more self-contained than it is.

6. Specific unbalance and residual unbalance

Specific residual unbalance relates residual unbalance to rotor mass and can be expressed as an eccentricity-equivalent quantity. Residual unbalance is commonly represented in units such as g·mm and depends on the mass-radius product. These are not equivalent labels. A translation that changes µm of permissible eccentricity into g·mm without the rotor mass changes the variable. Record the symbol, physical dimension and calculation status with each value, especially where a bilingual table has narrow columns.

7. The arithmetic behind the labels

For an idealized explanatory relation, angular speed ω equals 2π times rpm divided by 60. A balance quality grade G can be related to permissible specific residual unbalance through e = G/ω with consistent dimensions. For example G2.5 at 1,500 rpm gives an illustrative specific value of about 15.9 µm; multiplying appropriately by rotor mass yields a total residual unbalance allowance. Actual tolerances and plane allocation must follow the applicable issued standard and machine requirements. Do not publish an independent engineering acceptance calculation as though it were the lab’s signed conclusion.

8. Do not mix g·mm with g

A correction mass can be measured in grams while the unbalance quantity is represented in gram millimetres. If 2 grams is added at a radius of 50 millimetres, the simple mass-radius product is 100 g·mm. Calling 100 g·mm a “100-gram correction weight” is a hundredfold conceptual error about the object being applied. Preserve the multiplication dot or an unambiguous phrase such as gram-millimetre. Check whether the report’s angular position and reference radius are essential to the correction instruction.

9. Planes and allocation matter

Some rotors can be corrected in one plane; others require two or more relevant correction planes. An acceptance tolerance can be allocated to planes under defined conditions. A report may show separate values for drive end and non-drive end, or plane 1 and plane 2. Do not sum plane allowances casually or declare each plane acceptable from a total allowance without the controlling rule. Keep plane identification with measurements, correction locations and acceptance decision.

10. Static versus couple unbalance

A translating technician may encounter static unbalance, couple unbalance and dynamic unbalance. Each refers to different aspects of mass distribution and correction needs. They should not become one generic word meaning “imbalance.” A rotor can be acceptable in a static check yet require additional correction of couple effects. When source terminology is inconsistent, record the uncertainty for an engineer rather than choosing an attractive equivalent. Diagrams and phase observations can help determine which concept is actually intended.

11. Residual after balancing is the result to preserve

Reports often present an initial unbalance, trial correction, final residual and permitted value. The difference between “before” and “after” is the central story of the intervention. If the translation shows only the initial figure or swaps two columns, it may reverse the apparent result. Keep step order and explicitly identify final residuals, each relevant plane and accepted tolerance. Do not label an intermediate trial run as the final accepted state.

12. Phase angle is not decorative

Balancing machines may provide an angle measured relative to a tachometer reference mark or other reference convention. The reference direction, point of view and angular zero must be preserved. A nominal 30° correction at one reference cannot be moved to 210° because a translator thinks the angle is an orientation adjective. The same numerical angle may need interpretation under clockwise or counterclockwise conventions. Keep the position definition with the phase value and refer ambiguity to the balancing specialist.

13. Correction weight is a location as well as a mass

A report might instruct adding a small mass at a specified radius and angular position in plane A. Translating only the number of grams discards where that mass must act. Removing material at another location is not automatically equivalent to adding it. The language should preserve action, mass, radius, angle, plane and whether the correction is proposed or completed. Practical alteration of rotating equipment demands competent safety controls, not an instruction reconstructed by a translator.

14. Measurement and machine uncertainty

Balancing results depend on the setup, fixture, measurement repeatability and errors in the process. The ISO 21940-11 public scope explicitly acknowledges balancing errors. A translated certificate should keep the instrument or machine ID, calibration where supplied, fixture arrangement and declared uncertainty. A blank calibration field does not permit a fabricated claim of calibration. Do not call a rounded value exact; a measured residual close to tolerance deserves a careful review of the specified decision rule.

15. Service speed versus balance machine speed

A rotor may be balanced at one rotation speed while the grade tolerance references a service condition. A translation that merges these numbers can change interpretation of tolerance and test results. Identify which field means test or balancing speed and which means nominal or maximum service speed. If the source is ambiguous, ask the lab. Do not use an installation’s variable-frequency-drive setting to reconstruct a certification condition without authorization.

16. Report revision and traceability

The certificate may identify rotor serial number, impeller model, work order, balancing machine, operator, date and revision. These are essential when many physically similar rotors are repaired. Translate labels but protect alphanumeric identifiers. If a rotor is reworked or a weight removed after final balancing, a previous certificate may no longer describe the current condition. The target document must not imply a new test took place merely because it was translated after the mechanical work.

17. Vibration severity is another subject

An on-machine vibration report can use mm/s RMS vibration velocity, displacement, acceleration or frequency spectral measures. Those measurements must not be silently equated with balance grade G values, even where G has the dimensional appearance of a speed. The grade concerns permissible unbalance at a referenced rotational speed, not the measured casing vibration. If a report mixes balancing and operation tests, give each data section its own definitions and acceptance context.

18. Language used in acceptance

Terms such as within tolerance, balanced, corrected, verified, conditionally accepted and preliminary are not synonyms. One may describe a numerical comparison while another is the lab’s authorized release status. Translate the measured result separately from the final verdict. If a certificate records a target grade but has no signed final measurement, do not declare that the target was achieved. Engineers and authorized inspectors must make the actual acceptance decision.

19. Prepare an auditable termbase

Create approved target-language equivalents for balance quality grade, residual unbalance, permissible residual unbalance, specific unbalance, correction plane, phase angle, reference mark, correction radius, test speed and final residual. Keep abbreviations and units consistent across all bilingual forms. A glossary should also warn against tempting false equivalents such as vibration versus unbalance or grams versus gram-millimetres. Terminology can make a technical document clearer, but every conclusion still needs its source measurement.

Twenty-six worked examples of balancing translation errors

Worked case 1: G grade without mass

Imagine an engineer receives this source fragment in a maintenance record: Balance grade G2.5; rotor mass not shown. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that no complete residual unbalance allowance can be inferred from the grade alone. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to keep the specified grade and request mass and speed before calculating. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

A return audit asks the bilingual reviewer to identify the rotor, speed, plane, numeric value, unit and action from the target version alone. The reviewer then checks the report or drawing and decides whether the target permits exactly the same interpretation. If a local engineer cannot reproduce the original conclusion, the translation is not complete. Mark unresolved fields for the issuer rather than turning a qualified reading into a confident instruction.

Worked case 2: G6.3 mistaken for vibration

Imagine an engineer receives this source fragment in a maintenance record: G6.3 translated as 6.3 mm/s casing vibration. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that the grade is treated as a direct instrument reading. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to use balance quality grade as the technical label. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 3: Wrong speed

Imagine an engineer receives this source fragment in a maintenance record: Report says 1,500 rpm; summary says 3,000 rpm. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that changing speed changes the interpretation of permissible specific unbalance. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to copy the governing reference speed exactly. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 4: g·mm becomes grams

Imagine an engineer receives this source fragment in a maintenance record: Final residual 180 g·mm presented as 180 g correction mass. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that a mass-radius product was reduced to mass. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to preserve g·mm and distinguish correction weight. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 5: Total versus plane allowance

Imagine an engineer receives this source fragment in a maintenance record: Total permissible residual 300 g·mm; plane results separately reported. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that a total allocation is incorrectly applied to each plane. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to retain actual plane allocation and the governing acceptance basis. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 6: Drive-end label swapped

Imagine an engineer receives this source fragment in a maintenance record: Plane A = drive end; plane B = non-drive end. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that a bilingual diagram reverses physical correction locations. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to reconcile plane labels, photographs and shaft orientation. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 7: Correction angle loses zero

Imagine an engineer receives this source fragment in a maintenance record: Correction at 45° relative to keyway. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that the reference feature disappears from the instruction. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to keep zero reference and angular direction. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 8: Before and after columns

Imagine an engineer receives this source fragment in a maintenance record: Before 820 g·mm; after 90 g·mm. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that a spreadsheet reorder reverses the apparent improvement. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to preserve before/after labels and final result. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 9: Proposed weight becomes installed

Imagine an engineer receives this source fragment in a maintenance record: Add 5 g at 60 mm radius. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that a plan is presented as completed work. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to maintain proposal versus recorded action. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 10: Removed versus added mass

Imagine an engineer receives this source fragment in a maintenance record: Remove 1.5 g at plane 2. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that a translated imperative says to add the mass. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to keep direction of correction; never improvise shop operations. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 11: Rigid versus flexible rotor

Imagine an engineer receives this source fragment in a maintenance record: Rotor classified as rigid for balancing. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that the translation generalizes to high-speed flexible-rotor methods. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to retain the classification and its scope. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 12: Historical standard number

Imagine an engineer receives this source fragment in a maintenance record: ISO 1940-1 in a historical record. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that automatic modernization rewrites the issued reference. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to keep source code and add any current citation separately. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 13: Untested speed range

Imagine an engineer receives this source fragment in a maintenance record: Tested at 900 rpm; rated to 3,600 rpm. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that a translator assumes testing occurred at maximum speed. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to separate test speed from rated or service speed. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 14: Tachometer phase convention

Imagine an engineer receives this source fragment in a maintenance record: 0° at reflective mark; clockwise positive. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that the angle is copied without the reference direction. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to preserve position reference and sign convention. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 15: Conditional pass

Imagine an engineer receives this source fragment in a maintenance record: Within balance tolerance after recheck. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that the conditional qualification is dropped. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to retain recheck status and named authority. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 16: Vibration severity mixed in

Imagine an engineer receives this source fragment in a maintenance record: Vibration measured 3.2 mm/s RMS. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that a separate machine vibration value is called residual unbalance. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to keep the vibration metric and test method distinct. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 17: Uncertainty near limit

Imagine an engineer receives this source fragment in a maintenance record: Residual 298 g·mm; allowance 300 g·mm. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that a translator announces unconditional safety from a narrow difference. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to preserve exact numbers and leave acceptance decision to reviewer. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 18: Different rotors

Imagine an engineer receives this source fragment in a maintenance record: Two impellers share the same model code. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that serial numbers are removed as repetitive. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to preserve specimen identity and traceability. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 19: Sample not signed

Imagine an engineer receives this source fragment in a maintenance record: Workshop provisional run sheet. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that a preliminary observation becomes a certified final report. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to maintain report status and signature information. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 20: Correction radius truncated

Imagine an engineer receives this source fragment in a maintenance record: Mass 4 g at radius 75 mm. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that only grams remain, removing the lever arm of correction. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to keep radius and angular position in the same action. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 21: Plane numbers in translation

Imagine an engineer receives this source fragment in a maintenance record: Plane I and II. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that roman numerals are OCR-converted to 1 and 11. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to check plane mapping against source drawing. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 22: Nominal versus maximum speed

Imagine an engineer receives this source fragment in a maintenance record: Nominal 1,450 rpm; maximum 1,800 rpm. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that a grade calculation uses an unlabelled speed. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to keep both speed descriptions and governing design choice. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 23: Machine health overclaim

Imagine an engineer receives this source fragment in a maintenance record: Balanced to G2.5, therefore bearings are good. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that the result is treated as a complete condition assessment. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to state only the balance result and separate bearing evidence. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 24: Assembly changed after balance

Imagine an engineer receives this source fragment in a maintenance record: Impeller balanced before final coupling installed. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that a certificate is presented as covering a later assembly. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to preserve the measured configuration and subsequent change. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 25: Missing correction plane

Imagine an engineer receives this source fragment in a maintenance record: Final residual 120 g·mm with no plane. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that the value cannot be assigned to a location. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to request the plane or document total-result meaning. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

Worked case 26: Mass unit migration

Imagine an engineer receives this source fragment in a maintenance record: Rotor mass 48 kg becomes 48 g. The fragment might be a certificate field, handwritten correction log or summary for an overseas supplier. Its hazard is that a unit error catastrophically changes calculated allowances. The reader may not have the balancing machine report open and may act on the translated sentence as though it captured the whole measurement. For rotating machinery, an apparently minor change in a unit or location can alter the practical conclusion.

The safer approach is to verify rotor mass and units before comparison. Keep the source’s original measured variables and configuration near the explanatory wording. If the record does not prove the stage of work or the acceptance result, state that limitation. A translator should never supply a correction mass, angular position or approval that was absent in the issued source. This is especially important when a shop drawing, spreadsheet and service certificate disagree.

A practical end-to-end review workflow

First, preserve the authoritative record: certificate number, rotor serial, work order, test date, specified grade, ISO reference, revisions and signatories. Distinguish a test summary from a work instruction. A historical report should not be silently rewritten to conform to a later equipment configuration.

Second, extract all measurements and symbols before language editing. Lock rpm, kg, g·mm, µm, phase angles, plane labels, reference radius and before/after sequence. A bilingual phrase can change sentence order, but cannot alter the technical values on which a mechanical decision is based.

Third, make the termbase specific to the job. Include permitted specific unbalance, total residual, allocated plane tolerance, correction radius, mass addition and removal, rigid behaviour and balance quality grade. Label false equivalents explicitly. Use a specialist reviewer when a source term could refer to a different balancing mode.

Fourth, rebuild the final document and inspect it as a machine-service document, not a generic essay. A correction location can be obscured by a page break or disconnected caption. Verify that the translated drawing, picture key, numeric result and acceptance statement point to the same physical plane and the same rotor.

Fifth, establish a narrow claim: the issued report says what was measured and how it was judged under the applicable procedure. It does not independently certify bearing condition, installed vibration or universal safety. Escalate consequential ambiguity to the qualified balancing specialist and document the answer.

Frequently asked questions

1. What is G2.5?

It is a balance quality grade used with rotor speed and other information to determine a permissible residual unbalance criterion under the applicable framework. For language review, locate the definition in the cited report or procedure and check which fact the original document actually supports. Do not treat a related term as a synonym just because it is used nearby. A precise explanation is one a reader can test against the rotor identity, method, numeric data and designated acceptance criteria.

2. Is G6.3 the same as 6.3 mm/s machine vibration?

No. The balance grade is not a direct casing-vibration measurement, even if the dimension of the underlying quality relationship can invite confusion. For language review, locate the definition in the cited report or procedure and check which fact the original document actually supports. Do not treat a related term as a synonym just because it is used nearby. A precise explanation is one a reader can test against the rotor identity, method, numeric data and designated acceptance criteria.

3. Can I interpret a grade without knowing rpm?

You can identify the grade label, but the quantitative permissible specific unbalance depends on angular speed. For language review, locate the definition in the cited report or procedure and check which fact the original document actually supports. Do not treat a related term as a synonym just because it is used nearby. A precise explanation is one a reader can test against the rotor identity, method, numeric data and designated acceptance criteria.

4. What does g·mm mean?

Gram-millimetre is a mass-radius product often used to express unbalance. It is not simply the mass of a correction weight. For language review, locate the definition in the cited report or procedure and check which fact the original document actually supports. Do not treat a related term as a synonym just because it is used nearby. A precise explanation is one a reader can test against the rotor identity, method, numeric data and designated acceptance criteria.

5. How does rotor mass matter?

Actual residual unbalance allowance depends on the specific permissible unbalance and rotor mass under the applicable procedure. For language review, locate the definition in the cited report or procedure and check which fact the original document actually supports. Do not treat a related term as a synonym just because it is used nearby. A precise explanation is one a reader can test against the rotor identity, method, numeric data and designated acceptance criteria.

6. What does residual mean?

It refers to unbalance remaining after a balancing stage, often distinguished from initial or trial results. For language review, locate the definition in the cited report or procedure and check which fact the original document actually supports. Do not treat a related term as a synonym just because it is used nearby. A precise explanation is one a reader can test against the rotor identity, method, numeric data and designated acceptance criteria.

7. Is a single-plane result enough for every rotor?

No. Required correction planes depend on rotor behaviour and the procedure. Preserve the issued plane allocation. For language review, locate the definition in the cited report or procedure and check which fact the original document actually supports. Do not treat a related term as a synonym just because it is used nearby. A precise explanation is one a reader can test against the rotor identity, method, numeric data and designated acceptance criteria.

8. Can I change an ISO 1940-1 citation to ISO 21940-11?

Not inside a historic certificate. Keep the original citation and explain the successor reference separately if required. For language review, locate the definition in the cited report or procedure and check which fact the original document actually supports. Do not treat a related term as a synonym just because it is used nearby. A precise explanation is one a reader can test against the rotor identity, method, numeric data and designated acceptance criteria.

9. Does balanced mean vibration-free?

No. Installed vibration can arise from alignment, looseness, resonance, bearings and other factors. For language review, locate the definition in the cited report or procedure and check which fact the original document actually supports. Do not treat a related term as a synonym just because it is used nearby. A precise explanation is one a reader can test against the rotor identity, method, numeric data and designated acceptance criteria.

10. Can balancing be performed at a different speed?

The report may distinguish balancing-machine speed from service speed. Translate them as separate variables and defer procedure acceptance to specialists. For language review, locate the definition in the cited report or procedure and check which fact the original document actually supports. Do not treat a related term as a synonym just because it is used nearby. A precise explanation is one a reader can test against the rotor identity, method, numeric data and designated acceptance criteria.

11. Why is the angular reference important?

Correction angle is meaningless for practical work without knowing the reference direction and zero location. For language review, locate the definition in the cited report or procedure and check which fact the original document actually supports. Do not treat a related term as a synonym just because it is used nearby. A precise explanation is one a reader can test against the rotor identity, method, numeric data and designated acceptance criteria.

12. Is residual unbalance the same as correction mass?

No. Correction mass at a specified radius contributes to an unbalance quantity; the two numerical values are not interchangeable. For language review, locate the definition in the cited report or procedure and check which fact the original document actually supports. Do not treat a related term as a synonym just because it is used nearby. A precise explanation is one a reader can test against the rotor identity, method, numeric data and designated acceptance criteria.

13. What if a report lacks a plane label?

Retain what the source actually says and ask whether the value is total or allocated to a plane. For language review, locate the definition in the cited report or procedure and check which fact the original document actually supports. Do not treat a related term as a synonym just because it is used nearby. A precise explanation is one a reader can test against the rotor identity, method, numeric data and designated acceptance criteria.

14. Who can accept a balance report?

Acceptance belongs to the authorized engineer, quality system or contract under the relevant standard and machine requirements, not to the translator. For language review, locate the definition in the cited report or procedure and check which fact the original document actually supports. Do not treat a related term as a synonym just because it is used nearby. A precise explanation is one a reader can test against the rotor identity, method, numeric data and designated acceptance criteria.

15. Can a translated service report be used as the sole work instruction?

Only if authorized and verified for that operational purpose. Translation alone does not establish safe engineering instructions. For language review, locate the definition in the cited report or procedure and check which fact the original document actually supports. Do not treat a related term as a synonym just because it is used nearby. A precise explanation is one a reader can test against the rotor identity, method, numeric data and designated acceptance criteria.

Primary references and connected learning

The official standard catalogue is ISO 21940-11:2016, with 2022 amendment. The published scope covers rigid-rotor balancing tolerances, correction planes, their allocation and balancing errors. Refer to the full controlling document and any relevant machine-specific specification for normative procedures; the examples in this educational guide are not replacement acceptance calculations.

For the general system of cross-language meaning preservation, return to Master Art of Translation. Learn technical vocabulary through the protected Vocabulary Learning Hub, and explore sentence-level English precision via How English Works. This article solves only the narrower problem of translating rotor balance evidence and does not create a competing hub.