Technical insight
Rotor Balance Correction: Approve the Locations Before Work Begins
Before authorizing rotor balancing, ask who may approve physical corrections and where those corrections are permitted. Separate a measured unbalance result from permission to change the component. The purchase package should identify the approved correction definition and the response to an out-of-scope proposal.
By Geetai Precision
- Published
- Updated
Separate measurement from alteration authority
The public scope of ISO 21940-11:2016 includes the necessary number of correction planes for rotors with rigid behaviour. It excludes balancing of rotors with flexible behaviour. [1]
Schenck describes drilling-based correction for its Distec system and material addition or removal in its ESB/ESC/ESD product descriptions. These are examples of different equipment approaches, not a recommendation for a particular rotor. [2]
The purchasing question is not which of those methods sounds convenient. Ask the design authority to define the permitted intervention for the actual component. A supplier measurement can inform a proposed correction, but do not treat the measurement itself as authorization to remove material or attach anything.
Create a correction-permission sheet
Use the following as an editorial checklist accompanying the released drawing. It is not a substitute for engineering analysis or the applicable balancing standard.
| Decision | Required clarification | If unresolved |
|---|---|---|
| Permitted location | Identify the approved region on controlled geometry | Pause the proposed alteration |
| Excluded features | Identify features that must remain untouched | Refer unclear boundaries to the design authority |
| Method | Specify the approved type of intervention | Request disposition of any alternative |
| Extent | Use the engineering-defined limits and acceptance conditions | Do not infer permission from spare-looking material |
| Record | Link correction and subsequent checks to the part | Request a traceable record before acceptance |
Ask the supplier to acknowledge the permission sheet as part of the quoted scope. If it cannot work within the approved definition, request a technical exception rather than a general promise to balance the part. Keep changes to the permission sheet under the same revision discipline as the drawing.
Specify a stop-and-review response
Consider a hypothetical proposal to correct outside a designated region. The useful response is an exception package identifying the proposed location, reason, affected drawing requirement and requested decision. The design owner should decide whether a revised definition is acceptable. Purchasing can then confirm any effect on scope and records. Silence or a commercial purchase order should not be treated as technical approval.
Include the required response when an approved correction is insufficient. Ask who receives the exception and whether work stops pending disposition. Do not pre-authorize an unlimited sequence of changes merely because the order requests a final balance report. This is approval workflow guidance, not a balancing algorithm.
Agree the post-correction handoff
Request records showing the component identity, the authorized correction reference, what was changed and the agreed checks performed afterward. Ask the technical reviewer which dimensional, surface-condition or other requirements need reassessment. Do not assume that the balancing record also closes unrelated drawing requirements.
Confirm the component configuration represented by the final record and whether any later assembly or modification requires another review. This article addresses alteration permission; the separate bare-component versus assembled-unit question still needs its own agreed scope. Keep equipment operating approval distinct from the manufacturing handoff.
Prepare the supplier discussion
Send the released drawing, proposed correction-permission sheet and requested report contents for a project-specific discussion. State which technical decisions are already approved and which remain open. If no correction definition exists, request clarification from the design authority before placing an unrestricted alteration order.
Inspection scope and documentation are defined during quotation according to drawing requirements and application needs.
The sources provide background on correction planes and example methods. The permission sheet and escalation process are editorial recommendations, not evidence that a specific method is suitable for the supplied rotor.
Related review paths
More from Blog
References
- ISO 21940-11:2016 — public scope — ISO. Accessed 2026-09-28T01:17:33.963Z.
- Product Finder — Distec and ESB/ESC/ESD descriptions — Schenck RoTec. Accessed 2026-09-28T01:17:33.963Z.