Can a motor rewound by a general workshop still be used in a hazardous area?
Abstract
Only if the rewind was done to IEC 60079-19: competent responsible person, original winding data, prescribed tests, records and repair marking. A rewind that cannot show the temperature class, the Ex e tE time or the flamepaths are intact must not go back into the zone.
Only if the workshop did the work to IEC 60079-19 and can prove it: a competent responsible person, the original winding data (or a verified copy winding), the prescribed tests, a repair report and the repair marking. A motor rewound by a workshop that worked as for an ordinary industrial motor cannot show that its temperature class, its Ex e safe stall time (tE) or its flameproof joints are still as certified, so it must not go back into the hazardous area until a competent Ex service facility has assessed and, where possible, restored it.
Short answer
- What matters is not the name on the door but whether the facility meets IEC 60079-19 (Equipment repair, overhaul and reclamation, edition 5.0, 2025). A user's own workshop or an independent repairer can qualify; a "general" workshop working without it does not.
- The user has to check that the repairer can demonstrate compliance with the standard before sending the motor.
- The rewind must reproduce the original winding: the 2025 edition does not allow the type of winding to change, and the rating must not be raised without reference to the manufacturer.
- Ex e motors are the most sensitive: the public 2006 text required the original manufacturer to rewind unless the repairer could meet the whole equipment standard, and allowed copy winding only with the tE time verified.
- Ex d motors: the winding still sets the temperature class, and dismantling exposes the flamepaths, which must be inspected and measured against their limits.
- Without a valid repair record and marking, treat the motor as unverified: use it only outside hazardous areas, have it assessed, or replace it.
Why an ordinary rewind can make an Ex motor unsafe
An Ex motor's certificate rests on its design data. The temperature class (T-class) and, for increased safety, the tE time depend on the winding: wire size, turns, connection, insulation and varnish system, and the losses in the core. A workshop that "improves" the winding, changes the number of turns, uses a different winding type or damages the lamination insulation while burning out the old coils can raise the hottest surface temperature without any visible sign.
The public 2006 text of IEC 60079-19 makes the same point: burning out old windings with heat can degrade the insulation between the core laminations, and the higher core loss can upset the Ex e parameters (tE) or push the motor past its temperature class, so damaged or skimmed stator cores need a flux test for hot spots. It also warned that a better insulation class is not a reason to raise the rating, and that rewinding for another voltage or speed needs reference to the manufacturer.
For flameproof motors, the protection is in the enclosure joints. Every rewind means taking end shields and bearing covers off. Damaged spigots, scored shaft gaps, wrong bolts or paint on the joint faces turn a sound motor into one that may transmit an internal explosion.
What IEC 60079-19 requires from the repairer
| Requirement | What it means for a rewind |
|---|---|
| Responsible person and competent operatives | Someone with Ex knowledge accepts responsibility for the agreed repair status |
| Quality management system (Annex D in 2025) | Documented procedures, calibrated instruments, traceable records |
| Original data first | Schedule drawings or manufacturer's winding data; a copy winding only where allowed and verified |
| Same winding type, no rating increase without the manufacturer | Keeps the losses and temperatures inside the certified limits |
| Tests after rewinding | Resistance, insulation and high-voltage tests and running tests as the standard lists, plus industrial machine standards (IEC 60034 series) |
| Flamepath checks (Ex d) | Gaps and widths measured and compared with drawings or the standard's tolerances |
| User report and marking | Job record to the user; repair plate with the R symbol next to the original nameplate |
The 2025 edition also makes repair to the Schedule Drawings the first option: repair to the standard alone is not allowed when those drawings are available. The IECEx Certified Service Facility scheme certifies repairers against these requirements; such facilities may repair equipment of any manufacturer provided they have the necessary documentation.
What the law says about the repaired motor
In the EU, the ATEX Guidelines (6th edition, 2026) treat a product restored after a defect, without new features or modification, as not placed on the market again, so Directive 2014/34/EU does not apply to it; national workplace rules may still require an assessment. A substantial modification, one that affects a safety characteristic such as temperature or the integrity of a type of protection, brings the product back under the directive, with conformity assessment and new marking. A rewind with different winding data can fall into that category.
Under the workplace rules (1999/92/EC and its national versions) the employer must keep equipment in hazardous areas safe, so a motor of unknown repair status stays out of the zone.
Practical case: the motor is already back
A maintenance team finds a rewound Ex e pump motor with no repair plate and an invoice that says only "rewound, varnished, tested". Options, in order:
- Ask the workshop for the winding data used, the tests and the measurements. If they match the original data, a competent Ex service facility may be able to evaluate the motor with its own checks and tests and agree a repair status with you.
- Otherwise send the motor to a competent Ex facility. A rewind to the original data, with tE verified where needed, may restore it.
- If neither is possible, use the motor only in a non-hazardous area or scrap it, and replace it with certified equipment.
Common mistakes
- Choosing the repairer on price and lead time only. Ask for evidence of IEC 60079-19 competence first.
- Upgrading insulation and the rating together. A higher output from the same frame changes the thermal basis of the certificate.
- Forgetting the flamepaths. A perfect winding in an Ex d motor with damaged joints is still unsafe.
- No paperwork. Without a user report the next inspector cannot tell what was done.
Related on excodex
- Repair, overhaul and modification of Ex equipment (IEC 60079-19)
- Ex d or Ex e? Choosing between flameproof and increased safety for motors and junction boxes
- What does the 'R' marking on repaired Ex equipment mean?
- Is corrosion on a flameproof flamepath a reason to take equipment out of service?
- Standards space IEC 60079-19
Standards and further reading
- IEC 60079-19:2025 (edition 5.0), equipment repair, overhaul and reclamation; publisher preview with contents and list of changes (winding type, Schedule Drawings first): https://cdn.standards.iteh.ai/samples/iec/iec-60079-19-2025/d4ff902a79f94903879f5438a8e513c9/iec-60079-19-2025.pdf
- IS/IEC 60079-19:2006, public text of an earlier edition with the Ex d and Ex e winding clauses (superseded; check the current edition): https://law.resource.org/pub/in/bis/S05/is.iec.60079.19.2006.pdf
- IECEx Certified Service Facility scheme, overview: https://www.iecex.com/certified-service-facility-scheme/overview/
- European Commission, ATEX 2014/34/EU Guidelines, 6th edition (2026), section on used, repaired or modified products: https://webgate.ec.europa.eu/circabc-ewpp/d/d/workspace/SpacesStore/496c6b44-4224-468b-abee-cdb5617f3f90/download
- IEC 60034-23:2019, rotating electrical machines, repair, overhaul and reclamation: https://webstore.iec.ch/publication/33241
This article is general technical information prepared by the excodex editorial team. It does not replace the applicable standards, the equipment certificates and instructions, national regulations or the assessment of a competent person.