Air gap inspection provides a visual inspection of the stator core, rotor core and winding without the need to remove the rotor. The inspections make it possible to check for faults without the need to remove the rotor. Have a look at the most frequently asked questions and answers.

There are different reasons: 

 

• 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.

Due to its low profile, the ABB Air gap inspector can be used to inspect synchronous motors,  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 and generators, the tracks have to be adjustable to match the tooth configuration for the motor or 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 to ensure it always stays aligned with the stator teeth.

 

1. Height constraint: air gap of 10 mm or greater.

2. Diameter constraint: any diameter. Links to adjust the crawler will be available for standard motor and generator sizes as part of the kit. For specific motors and 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 or generator, upper and lower shields, sometimes rotor fan blades. The requirements depend on the design of the motor or generator in question – sometimes just the outer doors and coolers are sufficient, while at other times more parts have to be disassembled.

ABB will deliver a report of the visual inspection as well as a compact disc of the motor or generator inspection with problem areas clearly marked. 

ABB will also provide a verdict on the state of the motor or generator based on the visual inspection results and can also provide an action plan for the next recommended maintenance actions using the visual inspection those results.

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 on both sides of the motor or generator, upper and lower shields, and sometimes rotor fan blades. The requirements depend on the design of the motor or generator in question – sometimes just the outer doors and coolers are sufficient, while at other times more parts need to be disassembled.

The 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 and frequency levels  in various countries.

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

Air gaps smaller than 10 mm. 

Motors and generators with no end shields and pedestal fans that are difficult to remove.

Yes, the crawler has CE certification. 

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

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 temporarily removed from hazardous areas, or environment temporarily secured to carry out the needed service).