Robotic Inspections

Keystone has developed a robotic inspection system that would allow our engineers and technicians to perform a generator inspection without having to first remove the rotor. Robotic inspections can help reduce the time and cost of the generator inspections. If you are interested, please contact us for more information and availability.

Generator/Field In-SITU Inspection

At a moments notice, Keystone’s staff of experienced generator specialists and technicians can mobilize to a site with state of the art equipment to affect a broad array of stator services. Whether the need is to test, inspect, evaluate the stator, re-stack core laminations, completely rewind and upgrade the stator coil support structure. Keystone provides customers with cost effective solutions to any stator problem that might be encountered.

Keystone’s new Generator Robotic Inspection Vehicle (GRIV) was developed to give customers a state of the art, precise, and affordable device to perform in-situ turbine generator inspection and testing. The GRIV has the capability to perform visual inspections of the field and stator components. GRIVs testing capabilities include core lamination integrity (ELCID) and wedge tightness assessment. GRIV was designed to fit in very small air gaps. The customer can be provided with time and location stamped video and still images.

Electromagnetic Core Imperfection Detection (ELCID)

Electrical integrity of the turbo-generator core is a key indicator of serviceability. Shorting or low resistances in the interlaminar insulation may result in abnormal currents, localized heating and iron damage, requiring maintenance that can extend from coil repair to full rewind.


Example of ELCID slot traces

Early detection of incipient problems in interlaminar integrity is essential. However, various conventional inspections have each fallen short of this goal in terms of: subsurface evaluation accuracy, objectivity, repeatability and/or personnel safety.
The EL CID technique has been recognized since the 1970’s as the leading method of detecting insulation breakdown between the stator core laminations in generators and large motors.

Digital processing – phase and quadrature data gathered simultaneously provides a permanent record of the generator’s core condition that can be evaluated and compared at subsequent maintenance outages.

Wedge Tightness Detection

Illustration of GRIV wedge tightness detection robot in air gap

Loose stator slot wedges could result in excessive vibration of the stator coils in large generators, which would accelerate the deterioration of the groundwall insulation and even eventually lead to catastrophic failure of large generators.

The tightness of each stator wedge is measured electronically and compared to all other wedges in the winding, the wedges of another winding or an absolute external reference.


A permanent record is established and available for comparison at future maintenance outages. Removes the subjectivity inherent with the current methods used for evaluating stator wedge tightness (wedge tapping).


  • decrease cost
  • decrease downtime
  • decrease risk of damage from removal of generator field
  • a permanent report/record to compare and track the stator condition over time.



Past Robotic Inspections

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Robotic Inspection