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Air gap inspection

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The service provides a visual inspection of the stator core, rotor core and winding without the need to remove the rotor.

ABB’s in-situ visual inspection service uses a robotic crawler – ABB Air Gap Inspector – to examine the stator core, rotor core and winding of large motors and generators. The inspections make it possible to check for faults without the need to remove the rotor.

The robotic crawler moves in the air gap between the stator and rotor, traversing the stator core laminations using modular, magnetic tracks. It can be used in all motors and generators with air gaps of 10 mm and upwards. Unlike conventional inspection devices, which are restricted to turbo/hydro generators with very large air gaps, ABB Air Gap Inspector can be used on all large synchronous motors and generators with air gaps of 10 mm or more.

Benefits of air gap inspection

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  • Visual inspection of the air gap without removal of the rotor
  • Avoiding the need to remove the rotor means significant savings in time and costs as well as reduced risk
  • Extent and quality of inspections are greatly enhanced compared to conventional methods
  • Optimizes maintenance planning and increases availability of motors and generators by reducing the number of outage days where rotor removal is required
  • All data are recorded for later, in-depth assessment and expert evaluation when necessary

Enhancing preventive maintenance

ABB Air Gap Inspector can be used during planned outages without removing the rotor, and in cases where removal of the rotor is not possible. The inspections enhance preventive maintenance work, including ABB preventive maintenance level L3 and ABB AbilityTM LEAP (ABB Life Expectancy Analysis Program).

In-situ visual inspections can be used for:

  • Internal inspections during minor outages
  • Inspections in combination with ABB preventive maintenance level L3 and, to some extent, L4 (in special cases when rotor removal is not possible)
  • Gathering additional information to support ABB AbilityTM LEAP

Downloads and links

Leaflet
Air gap inspection service
Leaflet
Diesel to gas engine conversation

Recommendations for continuous generator availability
Aricle in MantWorld
Predictive maintenance grows in sophistication with new robotic inspection crawler
Web page
Synchronous motors service solutions
E-book
Data and Advisory services

ABB Air Gap Inspector questions and answers

Why should the crawler be used for inspection?

  • Reduced inspection cost.
  • In-situ inspection technologies enable motor or generator testing and inspection with the rotor in place.
  • Early problem detection.
  • Less risk of collateral damage from disassembly/reassembly.
  • Inspection time reduced by more than 33% compared to inspection with the rotor removed.
  • More time between rotor pulls.
  • Periodic monitoring of known conditions.

What kind of motors or generators can the crawler inspect?

  • Due to the low profile of the ABB Air Gap Inspector, it can be used to inspect synchronous motors as well as synchronous generators, turbo generators and hydro generators.
  • The low height of the crawler allows it to operate in any motor or generator with an air gap of 10 mm or more.
  • The crawler is designed to move over the stator teeth by means of magnetic attraction. It can therefore be used both when the rotor is in place and when it is removed.
  • The crawler’s drive module moves on ferric material, however, normally only the teeth are made from this. Therefore, the tracks on the drive module have to be aligned with the stator teeth. Since the dimensions of the teeth and the ratio of the tooth width to the wedge width vary across different motors/generators, the tracks have to be adjustable to match the tooth configuration for the motor/generator being serviced.
  • The crawler is highly configurable so that it can be adjusted to fit in a wide variety of stator designs. This makes the crawler unique as it can be adjusted so that it always stays aligned with the stator teeth.
    1. Height constraint: air gap 10 mm or greater.
    2. Diameter constraint: any diameter. Links to adjust the crawler will be available for standard motor/generator sizes as part of the kit. For specific motors/generators, links can be developed when the inspection order is booked to ensure alignment with the stator teeth.
    3. Access for the crawler: end shields, gas baffles, upper shields at both sides of the motor/generator, upper and lower shields, sometimes rotor fan blades. The requirements depend on the design of the motor/generator in question – sometimes just the outer doors and coolers are sufficient, sometimes more parts have to be disassembled.

 

What are the deliverables at the end of the inspection? How will the results be delivered?

  • ABB will deliver a report of the visual inspection as well as a compact disc of the motor/generator inspection with problem areas clearly marked.
  • ABB will give a verdict on the state of the motor/generator based on the visual inspection results.
  • ABB can also provide an action plan for the next recommended maintenance actions using the visual inspection results.

What preparations need to be made to perform a visual inspection with ABB Air Gap Inspector?

  • Inspections with ABB Air Gap Inspector can be carried out during a planned outage.
  • Some minimal disassembly of the end shields, gas baffles, upper shields at both sides of the motor/generator, upper and lower shields, sometimes rotor fan blades. The requirements depend on the design of the motor/generator in question – sometimes just the outer doors and coolers are sufficient, sometimes more parts need to be disassembled.
  • ABB Air Gap Inspector has been tested to work in environments up to about 40 °C.
  • The crawler kit includes a power outlet and appropriate converter for the different voltage/frequency levels in different countries.

How much time does it take to carry out an inspection?

  • The inspection time is directly dependent on the type of motor/generator, and also on the number of stator slots.
  • Experience shows that an inspection takes around 8 hours for an industrial synchronous motor/generator with about 100 slots.

What are the limitations to using the crawler? Where can the crawler not be used?

  • Air gaps smaller than 10 mm. Motors and generators with no end shields and pedestal fans that are difficult to remove.

Does the crawler have CE certification?

Yes, the crawler has CE certification. 

Can customers rent the crawler to carry out the service?

  • It is NOT possible to rent the crawler. The service is provided by ABB Motion Services.

Can the crawler be used to inspect Ex motors?

    • Currently we do not have certification to operate the Air Gap Inspector in hazardous areas. Nonetheless, Ex motors can be inspected, if located in safe areas (motor temporary removed from hazardous areas, or environment temporary secured to carry out the needed service).

    Related offering

    ABB Ability™ LEAP for HV motors and generators​
    Predictive maintenance
    Preventive maintenance


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