Mitsubishi Electric Generator Robotic Inspections“GenSPIDER ”®

Generator Smart & Precise Inspection Accomplishedby Generator Dedicated Expert RobotG e n S P I D E R®

Mitsubishi Electric Generator Robotic Inspections

Contents

1. Introduction

2

2. GenSPIDER® Features3

� Compact3

� Quantitative Approach to Wedge Tapping3

� Outage Duration Reduction

4

� Two Inspectors

4

3. Beneﬁts

5

4. Robotic Inspection Capabilities

5� Visual Inspection5

� Stator Wedge Tapping6

� EL-CID

6

6. Summary

8

5. Robotic Inspection Equipment

7

List of Figures8

List of Tables

81

G e n S P I D E R®

Mitsubishi Electric Generator Robotic Inspections

1. Introduction

Power plant availability is a key focus in the industry worldwide and continuous generator operation is more

likely when a comprehensive maintenance program is implemented by the owner. However, Mitsubishi Electricrecognizes the customer needs to maintain a high level of availability while minimizing maintenance costs.

Therefore, the GenSPIDER® was developed in order to offer an alternative to frequent, costly major generator
inspections while still providing intelligence as to the condition of the generator. Conventional generator

inspections are costly and require a long outage duration, in part because the rotor must be removed. Electricpower producers have been looking to shorten these inspections as well as improve inspection accuracy toextend the availability of their generators. Mitsubishi Electric Corporation developed a dedicated robot

capable of inspecting a turbine generator by passing through the narrow gap between the rotor and stator (airgap), eliminating the need to remove the rotor. Hence, more thorough inspections can be completed withinshort duration outage. Further, thanks to its high accuracy, interior inspections can be carried out lessfrequently and help operators avoid stocking parts they do not yet actually need. As a result, Mitsubishi

Electric’s new robot will help reduce total inspection costs and time, improving both the reliability andavailability of turbine generators.

Mitsubishi Electric’s new robot, GenSPIDER® (Generator Smart & Precise Inspection Accomplished bygenerator Dedicated Expert Robot) crawls along the stator core and performs a visual inspection utilizing abuilt in high definition camera. Stator wedge tapping and EL-CID (Electromagnetic Core ImperfectionDetection) tests are also options that can be performed by the robot. GenSPIDER® can be applied to a wide

capacity range of Mitsubishi Electric and Non-Mitsubishi Electric generators. Robotic inspection will lead toreliable maintenance planning and the minimizing of forced outage risk.

2G e n S P I D E R®

Mitsubishi Electric Generator Robotic Inspections

2. GenSPIDER® Features

GenSPIDER® was developed by Mitsubishi Electric with the following features in order to respond to customers’ maintenance demands.

[1] Compact

GenSPIDER® is designed to travel in the air gap to performof inspecting most Mitsubishi Electric mid- and large-sizedmechanism comprising a crawler belt and flat plate, GenSPIDER®

robots cannot be applied to some of Mitsubishi Electric’s

accurate inspections. Thanks to a proprietary traveling

generators and Non-Mitsubishi Electric generators. Conventional

has the advantage of a thin 19.9-millimeter profile. It is capable

generators due to the air gap size.

[2] Quantitative Approach to Wedge Tapping
GenSPIDER® can accurately ascertain wedge tightness across astator wedge looseness.

uses original vibration analysis technology to accurately detect“tight” and “loose”, however does not have sufficient capability

full range: very tight - moderate - very loose. The tapping test

By comparison, the conventional robot is able to fully evaluate

five levels of stator wedge tightness. As a result, GenSPIDER® isto distinguish “moderate”.

able to evaluate stator wedge looseness, as equivalent to an

A classification comparison of stator wedge tapping between

inspection carried out by hand, and to detect early stages ofActual tightness

GenSPIDER® and the conventional robot is shown in Figure 1.

Tight

Loose

Conventional robot
GenSPIDER®
Index :Very tightTight

ModerateFigure 1. Classification of Stator Wedge Tapping

3

Loose

Very looseG e n S P I D E R®

Mitsubishi Electric Generator Robotic Inspections[3] Outage Duration Reduction

After a generator enters a periodic inspection, it is very important

Simplified inspection covers similar generator inspection items tocan be returned to service as fast as possible. GenSPIDER® canaddition, a generator rotor does not need to be pulled out for anthat customers quickly assess the generator condition so the unit

the Major inspection, as opposed to the Simplified inspection. In

provide a solution to reduce the outage duration.

inspection by GenSPIDER®. Therefore, the robotic inspection can

Table 1 lists each inspection part and the items of typicalbe completed within the time period of a minor inspection. As thegenerator-related inspections compared with “ADVANCED”

result, outage duration is shortened and customers can restart

simplified inspections carried out by GenSPIDER®. The Advanced
Inspection Part

Inspection Item

Stator End Winding

VI

Stator Winding in the Slot

Trapping for Wedges

operation of the generator earlier than with other inspections.

Simpliﬁed

Advanced Simpliﬁed by GenSPIDER® Package

Major✔

✔

✔

✔

✔

✔

✔

✔

✔

✔

✔

✔

✔

✔

✔

✔

✔

✽✽

✔

VIET

✔

VI

Stator Core

Inspection Category

EL-CIDIR for Through Bolt✔

VI

NDT for Wedges

Rotor Shaft

NDT for Retaining Ring

Rotor Winding

Center Bore Leak Test✔

VI

Rotor pulling out

VI : Visual Inspection✔

ET

Not required

IR : Insulation Resistance Test

1 weekET : Electrical TestNDT : Non-Destructive Test✔

✔

✔

Outage duration✔

✔

RequiredNot required
1 week✽ : Will be released in near future

1.5 months

Table 1. Inspection Parts and Items of each Inspection[4] Two Inspectors

To implement a robotic inspection by GenSPIDER®, only two

Disassembly of generator small parts such as manholes andendbells is required to allow inspectors access to the generator.

Mitsubishi Electric TAs (inspectors) are required.

The number of disassembly parts is different according to each

• Inspector A : Operator

Operates GenSPIDER® and carries out tests with Robot

generator’s design.

Control Unit outside of the generator.

The respective positions of the inspectors are shown in Figure 2.

• Inspector B : Installer

Installs GenSPIDER® into the air gap on each slot inside of thegenerator.

Inspector A

Robot Control Unit

Inspector B

GenSPIDER®
Figure 2. Positions of Inspectors for Robotic Inspection

4

G e n S P I D E R®

Mitsubishi Electric Generator Robotic Inspections

3. Beneﬁts

Robotic inspection by GenSPIDER® gives customers the following benefits.

（1）Condition Based Inspections vs Calendar Based Inspections
Customers can carry out GenSPIDER® inspections regardless ofcombustor inspection period. Therefore, customers canonly requires a one week generator outage, it is possible toascertain the interior condition as well as detectturbine inspection type. Because the GenSPIDER® inspection

implement robotic inspections more often and accurately

complete the GenSPIDER® inspection even within theabnormalities in the short term.

（2）Maintenance Cost Reduction

Frequent interior condition monitoring enables customers tothe right timing means continuous avoidance of forced

shortening of the inspection period and reduction of loss

occurrence of extra expenses and unexpected extensions ofplan appropriate periodical inspection schedules. This leads tooutages. Preparing necessary spare parts prevents thedue to generator outage. Carrying out periodical inspections atoutages for major inspections with the rotor pulled out.

（3）Accurate Trouble Shooting and Planning Future Maintenance
Robotic inspections by GenSPIDER® can provide valuable

information as to the condition of the generator without theused to plan corrective maintenance in more depth whilelessening the probability of in-service failures.

need for costly rotor out inspections. This information can be

4. Robotic Inspection Capabilities
Contents of the inspection and examples of the results are shown below:[1] Visual Inspection

GenSPIDER® is equipped with an LED light and a tilted mirror

Camera can inspect the rotor ventilation hole and the stator core

installed in an axial direction. This way the GenSPIDER® is able toabnormalities is essential in order to discover issues present

which can be rotated 360 degrees in front of the remote camera

bore surface without rotor removal. Early detection of anytake clear images of the stator and rotor in a 180 degree

before they result in major failures. Examples of detected

position, even in the dark inside the generator. The Remoteabnormalities are shown in Figure 3.

ScratchStator core

Scratch on stator core

Foreign material

Stator wedge

Foreign material on stator wedge

Figure 3. Examples of Detected abnormalities

5Rotor wedge

Misalignment

Misalignment of vent holeG e n S P I D E R®

Mitsubishi Electric Generator Robotic Inspections[2] Stator Wedge Tapping

Stator Wedge Tapping can be used to check the wedge tightnesstightness. A wedge tapping schematic is shown in Figure 4.

GenSPIDER® consists of three components: a hammer whichwedges have been conducted by engineers who then judged thewithout the rotor being pulled out. The tapping mechanism of

Traditionally, inspections of degrees of looseness in stator

vibrates the stator wedge, a motor which drives the hammer, andresults quantitatively. However, GenSPIDER® quantifies thean accelerometer which detects vibrations on the stator wedges.

looseness as numerical data. Accumulating inspection results

GenSPIDER® is also equipped with a cam mechanism. Installing

and analyzing trends enable customers to evaluate thethe cam driving motor axially on GenSPIDER®’s body results in acondition of components in stator core slots. From thesethinner body and assurance of sufficient vibration torque. As aresults, the number of required spare wedges can be prepared inresult, GenSPIDER® is currently applied to many kinds ofadvance of the next outage. Results of a stator wedge tapping

generators, providing accurate measurement of stator wedge

inspection are shown in Figure 4.

AccelerationsensorHammer

Stator wedge

Ripple spring
Wedge tapping schematic

Tight

Slot number

Wedge number

Stator coil
Result of stator wedge tapping inspection

LooseFigure 4. Wedge Map (stator wedge tightness distribution)[3] EL-CID

The EL-CID (Electromagnetic Core Imperfection Detection) test is

help avoid serious accidents, and it can be effective in

used to determine the integrity of the inter-laminar insulation in

identifying core issues prior to major damage during

EL-CID detects the stator core layer short without the rotor being

detection of layer short are shown in Figure 5.

the stator core and identify underlying eddy-current issues.

operation. An image of an EL-CID test and an example of apulled out. Early detection of stator core abnormalities canExample: Detection of layer short at stator core
Layer short due todamage of stator core

Excitation circuit

Short circuit detection

Figure 5. EL-CID Test6

G e n S P I D E R®

Mitsubishi Electric Generator Robotic Inspections

5. Robotic Inspection Equipment
Main equipment and tools of robotic inspection - Figure 6 and 7.
Detailed specifications of GenSPIDER® - Table 2.
Traveling mechanism★Stable measurement
due to low vibration
travelingWeight:
3 kg approx.

600 mmHeight:19.9 mm

Tapping mechanism★Higher reliability forassessing wedge
tightness

300 to 480 mm(Adjustable)

Figure 6. Exterior of GenSPIDER®

Robot Dimension

Robot Controlling /Monitoring Software

Robot Control Unit

Figure 7. Exterior of Inspection Tools（1）GenSPIDER®

Length600mm [23.6 in]Width

300 to 480 mm [11.8 to 18.9 in](Adjustable)

Height19.9mm [0.78in]

Robot Weight

3kg [6.6 lbs]

Operating Temperature-10 to 50 ℃ [14 to 122 ℉]

Power SupplyAC 100V to 240V (50Hz/60Hz)

Table 2. Specifications of GenSPIDER®

（4）Robot Control Unit

GenSPIDER® has a remote camera, stator wedge tapping andRobot control unit converts stator wedge tapping signals

traveling mechanism. It runs axially on the generator statorfrom analog to digital and supplies electricity to thecore and conducts inspections.

GenSPIDER®.

（2）Robot Controller（5）EL-CID Unit (Option)

The robot controller controls the remote camera, stator

The EL-CID unit excites the generator stator core and controls

wedge and traveling mechanism in GenSPIDER® through aEL-CID testing.

cable connected to GenSPIDER®.

（3）PC for Monitoring and Data Storage

Remote camera images, as well as stator wedge tapping andEL-CID test results are shown on the Monitoring PC. Results ofeach inspection are saved digitally.

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Mitsubishi Electric Generator Robotic Inspections

6. Summary• Robotic inspections enable frequent generator interior• GenSPIDER® is compact and can be applied to most Mitsubishi

inspection to be implemented within a short period without

Electric and Non-Mitsubishi Electric Generators.

rotor removal. Mitsubishi Electric offers subsequent future

maintenance and recommendation work for the customer’s• GenSPIDER® capabilities

next inspection depending on the results.

（1）Visual Inspection（2）Stator Wedge Tapping（3）EL-CID Test

List of Figures

Figure 1. Classiﬁcation of Stator Wedge Tapping

3

Figure 3. Examples of Detected abnormalities

5

Figure 2. Positions of Inspectors for Robotic Inspection

4

Figure 4. Wedge Map (stator wedge tightness distribution)

6

Figure 5. EL-CID Test

6

Figure 6. Exterior of GenSPIDER®

7

Figure 7. Exterior of Inspection Tools

7

List of Tables

Table 1. Inspection Parts and Items of each Inspection

4

Table 2. Speciﬁcations of GenSPIDER®

78Mitsubishi Electric Generator Robotic Inspections“GenSPIDER ”®

https://www.mitsubishielectric.com/en/products-solutions/energy/index.page
Head Office

Tokyo Building, 2-7-3 Marunouchi, Chiyoda-ku, Tokyo 100-8310, Japan

Energy Systems Center

1-1-2, Wadasaki-cho, Hyogo-ku, Kobe 652-8555, Japan＊GenSPIDER is a registered trademark of Mitsubishi Electric Corporation in Japan and USA, and is a trademark of other countries.

Safety information
Carefully read the operating instructions before usingand use only as specified.
In accordance with the Foreign Exchange Act, the export of strategic materials (orservices) included in this product requires an export (or service transaction) licensefrom Japan’s Ministry of Economy, Trade and Industry.

GS-0-202003 Printed in JapanISO 9001
CertifiedThis product has been
designed and manufactured
under a quality control systemcorresponding to ISO 9001,
the international standard for
quality control systems.

Published March 2020.
Specifications subject to change without notice.