stator visual inspection - frame 6 users...

AGTServices, Inc.Generating timely repair solutions

2019 Frame 6 User’s

Conference

2 GE Frame 6/6A3 “Minor” Outages,

Turned to Majors with Field Rewinds

Presented By:

Jamie Clark – AGTServices

www.agtservices.com

http://www.agtservices.com/


Agenda Summary

• Unit Details

• Unit Inspection History

• Unit “B” Minor – Fall ‘18

• Unit “A” Minor – Spring ‘19

• Findings/Root Cause

• Field Rewind

• Additional Stator Work

• Unit “C” Plans – Fall ‘19


Unit Inspection HistoryYear Unit A Unit B Unit C STG Findings

2001 Minor Major Minor B EW greasing, wedge greasing. C

partial rewedge, EW greasing

2002 Major Major B End Wedge Rewedge, STG Full

Rewedge

2003 Forced Forced A Repair/Replace 2 bottom bars, B

water ingress, no issues.

2007 Minor Noted more turn insulation migration

2008 Minor

2009 Minor Mag Particles, Rub Ring wear

2011 Minor Minor EW Greasing

2012 Minor EW Repairs w/ field in

2013 Minor Bus bar heating, Minor Grease

2015 Major Stator cleaned, field insulation

migration

2018 Minor Turned Major, Field RW, Rewedge

2019 Minor Turned Major, Field RW, Rewedge


Minor Inspection Scope (Both B-A)

• Outer end covers removed

• GAC in place

• Field installed

• Borescope aided visual inspection

• Standard Stator Electrical Testing

• Standard Field Electrical Testing

• Standard, limited disassembly, brushless exciter tests


Unit “B” Summary Findings

Global, aluminum

metallic particle

contamination

from rub ring

wear.



Rub Ring

Inner Oil

Deflectors

Contamination Ingress:

• Aluminum Particles

caused by rubbing of the

Inner Oil Seals or Inner

Ring.

Possible Contributors:

• Field Vibration

• Tilt Pad Bearing Wear.

• Alignment ??

Rub Ring



• GE – 6A3 - S/N: 336X402

• Significant Amount of End Turn Insulation Migration

End Turn Insulation

FIELD WINDING:


Unit “B” Summary Recommendations

Generator Field – To Remove Metallic Particles from Winding:• Remove field from stator.

• Perform a complete rewind with a new Class F Insulation.

• Perform a HSB with Running Electrical Tests.

Duration: Rewind – 21 Days / With HSB – 28 Days

Brushless Exciter: • Remove Diodes and Fuses.

• Clean.

• Replace All Fuses with New. Test & replace any bad Diodes.

• Replace Insulators and Hardware with new.

• Replace missing hardware from GFD.

• (Owner to supply Parts).

Stator – To Remove Oil Contamination & Assess Wedge System:• Clean Windings.

• Perform a Complete Wedge Tightness Survey – Perform Rewedge, if necessary.

• Ultimately, a full stator rewedge was required.


Unit “B” Rewind

Global, and GROSS, turn

insulation migration


Unit “B” Rewind

Significant End Winding

Elongation/Distortion


Unit “B” Rewind

Numerous End Creepage

Blocks Broken


Unit “B” Rewind

Top Coil To Coil Connectors

Undersized, Top Turn

Distortion From Soft Copper

FACTORY DEFECTS


Unit “B” Rewind

Numerous Slot Armors

Damaged/Compromised, and

numerous turn insulation

migration or cracking


Unit “A” Summary Findings

No Rub Ring

Aluminum

Contamination,

but GLOBAL and

GROSS turn

insulation

migration


Unit “A” Summary Findings

Second Verse, Same as the

First…but Worse!


Unit “A” Rewind

End Creepage Blocks Broken

– Same as Unit “B”


Unit “A” Rewind

Main Lead Leaf Broken and

Spun Up. Numerous slot

armors nearly worn through

near slot exit.


Unit “A” Rewind

Slot Armor Patch

FACTORY FIX


Unit “A” Rewind

Numerous Areas of Turn

Insulation Breaks and Pulling

Away


Unit “A” Rewind

Turn Insulation Severe

Enough to Expose Copper

Turns


Unit “B” vs “A” Differences and

Similarities

Condition Unit “B” Unit “A”

Aluminum Contamination Yes No – but present in ‘03

Loose Distance Blocks Yes Yes

Turn Insulation Migration Yes Yes

Creepage Block Breaks Yes Yes

Top Turn Distortion/Soft Cu Yes No

Turn Insulation Crack/Splits Yes Yes

Main Lead Cracks No Yes

Coil Crossover Undersize Yes Yes

Slot Armor Damage Yes Yes (worn)

Also “Patched”

End Turn Distortion Yes No


GE 6A3 Generator Field

Rewind


GE 6A3 Rewind Complete


GE 6A3 Rewind Complete….

But What About the

Stator(s)???


Stator Endwindings

Unit B Unit A


Stator Connection Rings

Unit B Unit A


Stator Axial Support Hardware

Unit B Unit A


Stator Wedge System

Unit B Unit A


Stator Wedge System

Only 21% are tight

Unit B


Stator Wedge System

80% are tight, so marginal. Due to

desired duration until next major,

rewedge recommended and approved

Unit A


Summary

Stator Area Unit B Unit A Comments

Endwinding Greasing Greasing Global cleaning,

partial block/retye

Stator Core No Issues No Issues

Wedge System 79% loose 20% loose Rewedge req’d

Buss/Lead Connections Minor retape Replace

some leads

Electrical Testing Passed Passed


Stator Repairs and Rewege

(similar for both)


Stator Repairs and Rewege


Conclusions/Summary

• Most 6A3’s at/beyond 30 year service life

• Oil is the enemy!

• Unit “C” at this site is in the same boat – Fall’19 Plans

• Many “minor” inspections turning into MAJORS

• Get your units baselined NOW, and fix it as a SYSTEM

• Cycling Duty is negatively impacting BOTH field and

stators

• Stator rewinds are next – 8-12 week winding cycle!

• Add 24-28 days to wind it!!

stator visual inspection - frame 6 users...

Documents