Proper storage of electric motors is not “putting it in the corner of a warehouse”, but a regulated procedure: humidity control, protection of bearings from false brinelling, anti-corrosion treatment, periodic checks of insulation resistance. Violations during the storage stage lead to hidden defects that appear only under load, and in 30% of cases - to failure of the new engine in the first 200 hours of operation. Below, engineers from the Elektromotors service center in Tashkent discuss the rules for short-term and long-term storage in accordance with GOST 15150-69 and the recommendations of leading manufacturers.
Short-term and long-term storage: what's the difference
The separation is fundamental, because the entire set of protective measures depends on the period.
- Short-term storage - up to 6 months. Allowed in original packaging, in a closed heated or ventilated room without strong temperature changes. Basic conservation is sufficient.
- Mid-term - from 6 to 24 months. Requires periodic rotation of the shaft, insulation monitoring, and replacement of silica gel cartridges.
- Long-term - over 2 years. Complete preservation regulations including disassembling bearing units, replacing grease, sealing seals and registration with quarterly inspection.
For engines from a warehouse in Tashkent, where the difference between summer and winter temperatures reaches 60 °C, we recommend immediately applying the medium-term storage regulations - even if start-up is planned in 3 months.
Storage environment requirements
The environment determines how quickly the insulation degrades and whether corrosion appears on the shaft and bearings.
| Parameter | Norm | Maximum permissible |
|---|---|---|
| Air temperature | +5…+35 °C | −20…+45 °C |
| Relative humidity | no more than 65% | no more than 80% (short-term) |
| Temperature difference per day | up to 5 °C | up to 15 °C |
| Vibration from external sources | absent | no more than 0.5 mm/s |
| Content of aggressive gases (SO₂, NH₃) | absent | trace |
Motors should not be placed on a concrete floor without pallets - condensation from below is inevitable. The minimum gap from the floor is 150 mm, from the walls - 300 mm. It is strictly forbidden to store near battery rooms (sulfuric acid vapors) or galvanizing areas.
Protection of bearings during storage
The most common hidden malfunction after long-term storage is false brinelling, imprints of rolling elements on the tracks due to microvibration when the shaft is stationary. Signs will appear only after 50–100 hours of operation as increasing noise and vibration, requiring bearing replacement.
- Rotate the shaft 5-10 revolutionsevery 30 days, stopping in a new position - not the same one.
- For motors above 75 kW, additionally load the bearing through a clutch simulator so that the contact area moves.
- Before long-term storage, replenish the bearing with fresh lubricant (Mobil Polyrex EM, SKF LGHP 2 - this displaces moisture and seals the unit).
- Install transport stoppers on the shaft for large machines - they remove the axial load from the bearings when the warehouse floor vibrates.
- Once every six months, measure the vibration during a short-term start-up - an increase in the level signals the need for disassembly.
Anti-corrosion protection and insulation control
Exposed metal surfaces - the end of the shaft, keyway, paws, flanges - are treated with conservation lubricant K-17 or Tectyl 506. The internal cavities of the stator are protected by installing silica gel cartridges (250–500 g for an engine with a power of up to 100 kW) with a humidity indicator. Replacement of cartridges - every 6 months or when color changes.
The insulation resistance of the winding is measured with a 500 or 1000 V megger:
- when received at the warehouse - fixed as a base value;
- further - every 3 months;
- the value must be not lower than 1 MOhm for each kV of rated voltage + 1 MOhm (for a 0.4 kV motor - not lower than 1.4 MOhm at +20 °C);
- if it falls below the norm, the engine is dried using the thermal method or sent for diagnostics.
For engines in unheated warehouses, anti-condensation heaters are effective (if built-in) - they are connected to 220 V through a thermostat at humidity above 70%.
Periodic checks: regulations
Each stored engine must have an accounting card with inspection marks.
- Monthly: external inspection, turning the shaft, checking the integrity of the packaging and silica gel.
- Once a quarter: measuring the insulation resistance, checking the mounting bolts, inspecting the terminal box for condensation.
- Every six months: replacing silica gel, replenishing preservative lubricant, short-term start-up without load for 5-10 minutes (for medium-term storage and longer).
- Once a year:full inspection - partial disassembly of bearing shields, checking lubrication condition, checking clearances.
It is convenient to combine these procedures with the maintenance of a fleet of existing machines, especially if the enterprise in Tashkent uses a park of asynchronous motors of different sizes.
Preparation for commissioning
You cannot start the engine “from the shelf” - this is a typical reason for warranty failures.
- Remove the preservation grease from the shaft and flanges with white spirit.
- Remove the transport stoppers.
- Measure the insulation resistance - if the readings are below normal, dry at +80...+90 °C for 8–12 hours.
- Check the ease of rotation of the shaft manually - without scoring, distortions and extraneous noise.
- Replace the grease in the bearings with standard working grease (if preservation was used) - especially for engines with a shelf life of more than 12 months.
- Perform a test run without loadfor 30 minutes, monitoring current, bearing temperature and vibration.
- If there is vibration above 2.8 mm/s, rotor balancing will be required.
Storage limits
Manufacturers of IEC asynchronous motors set the following maximum periods subject to compliance with all regulations:
- in original packaging without opening - 12 months;
- with medium-term storage regulations - 24 months;
- with full conservation and quarterly inspection - up to 60 months;
- over 5 years - mandatory complete disassembly, replacement of bearings, checking the winding using high-voltage testing methods.
According to our experience in Tashkent, engines that have been lying in a warehouse for more than 3 years without routine maintenance, in 60% of cases require either rewinding the stator or replacement of bearings before putting them into operation.
Do you need help with preserving or putting a backup engine into operation? Elektromotors engineers will develop storage regulations for your warehouse, conduct periodic checks and prepare the machine for start-up. Contact us via contact page - a specialist will visit Tashkent on the same day.