Nathan Griffiths - MJB International

41
www.mjbi.com THE IMPORTANCE OF CARRYING OUT GE FRAME ROTOR OVERHAULS & CONDITION ASSESSMENTS MJB International

Transcript of Nathan Griffiths - MJB International

Page 1: Nathan Griffiths - MJB International

www.mjbi.com

THE IMPORTANCE OF CARRYING OUT

GE FRAME ROTOR OVERHAULS &

CONDITION ASSESSMENTS

MJB International

Page 2: Nathan Griffiths - MJB International

CONTENTS

1. ROTOR OVERHAUL & CONDITION ASSESSMENT.

2. CRITICAL INTERNAL COMPONENTS ONLY ACCESSIBLE DURING FULL

ROTOR DESTACK

3. ISSUES FOUND & RECTIFIED FOLLOWING ROTOR DESTACK.

4. METALLURGICAL INSPECTIONS / NDT DURING DESTACK.

5. ROTOR OVERHAUL FACILITY – CAPABILITIES / EQUIPMENT REQUIRED.

6. SUMMARY / CONCLUSIONS

2

Page 3: Nathan Griffiths - MJB International

ROTOR OVERHAUL &

CONDITION ASSESSMENT.

SECTION 1

3

Page 4: Nathan Griffiths - MJB International

ROTOR OVERHAUL &

CONDITION ASSESSMENT

CONDITIONS THAT LIMIT THE LIFE OF THE ROTOR INCLUDE;

• Maintenance Practices

• Operating History

• Foreign Object Damage

• Low cycle fatigue cracking

• Crack initiation / Crack growth

• Material aging / properties

• Creep rupture

THE EFFECTS OF THESE ON THE ROTOR AND ITS COMPONENTS CAN LEAD TO;

• Blade thinning, pitting, erosion

• Disk / Wheel Corrosion

• Creep

• Turbine Wheel Erosion = excessive bucket movement

• Vibrations due to fouling inside the rotor

• Cooling air paths clogging = overheating of HGP parts

EVENTUALLY = ROTOR FAILURE = PROLONGED DOWNTIME + RISK TO

SAFETY OF PLANT & STAFF. 4

Page 5: Nathan Griffiths - MJB International

ROTOR OVERHAULS

NOT TO BE IGNORED

5

Heavy corrosion on compressor

wheels body.Missing & Damaged Blades Corrosion on distance pieces

Non-standard Balance Weights from

previous overhaul, carried out by

others.Material Blocking Cooling Holes Broken Through Bolt Nut

Page 6: Nathan Griffiths - MJB International

ROTOR OVERHAUL &

CONDITION ASSESSMENT

This presentation will discuss the importance of Rotor Overhauls & Condition

Assessments for GE Frame Industrial Units (standard tech – B / E Class) utilising MJB’s

extensive rotor overhaul / condition assessment experience:

• 62 x Frame 3002 Rotors

• 157 x Frame 5001 Rotors

• 57 x Frame 5002 Rotors

• 85 x Frame 6 Rotors

• 9 x Frame 7 and 9 Rotors

Other GT rotors overhauled include Siemens V64.3 and ABB11D4/5.

Other rotor experience: MHI & Dresser Rand Centrifugal Compressors, Steam Turbine

Rotors & Generator Rotors (incl. full rewinds).

6

Page 7: Nathan Griffiths - MJB International

CRITICAL INTERNAL COMPONENTS

ONLY ACCESSIBLE DURING FULL

ROTOR DESTACK

SECTION 2

7

Page 8: Nathan Griffiths - MJB International

GE FRAME ROTOR ASSEMBLY:

MAIN COMPONENTS

8

MAIN ROTOR COMPONENTS

Compressor Turbine

Forward stub shaft

Discs

Compressor thru bolts

Aft stub shaft

Marriage bolts

Distance piece / Forward stub shaft

Turbine wheels

Wheel spacers

Stud assembly

Aft stub shaft

To carry out full inspection and condition assessment of rotor components, it is

necessary to:

• Fully destack the compressor and turbine rotor

• Mechanical and Metallurgical Inspections of critical internal components

When the rotor assemblies are destacked issues can be corrected immediately.

Page 9: Nathan Griffiths - MJB International

GE FRAME ROTOR OVERHAUL

WORKSCOPE

9

OVERHAUL WORKSCOPE SUMMARY

1. Incoming Inspection:

• Rotors are externally inspected and prepared for inspection.

• Cleaning, dimensional checks, run-out and balance checks implemented.

Additional / Emerging Works Options will be confirmed - such as: Under Cut of

Journal’s / Thrust collars etc.

2. Compressor / Turbine Rotor Destack:

• Compressor / turbine rotors will be disassembled to their sub assembly components

and visually and mechanically inspected.

3. Condition Assessment – (if required)

• Additional NDT’s – Discussed in further detail later in this presentation.

Page 10: Nathan Griffiths - MJB International

GE FRAME ROTOR OVERHAUL

WORKSCOPE

10

OVERHAUL WORKSCOPE SUMMARY

4. Compressor / Turbine Repair:

Refurbishment of components will be performed and includes;

• Repair of journals and thrust collar

• Repair of dovetails

• Repair of rabbet areas, marriage areas, rims etc.

• Compressor re-blade

5. Compressor / Turbine Reassembly:

Following inspection and repair procedures, the compressor and turbine rotors will be

reassembled utilizing new hardware.

Customer is welcome to witness key stages of rotor assembly, final balance and run-

out checks.

Page 11: Nathan Griffiths - MJB International

ISSUES FOUND & RECTIFIED

FOLLOWING ROTOR

DESTACK

SECTION 3

11

Page 12: Nathan Griffiths - MJB International

COMPRESSOR THRU

BOLT CORROSION / PITTING

ISSUE:

• Thru bolts - subject to moisture =

corrosion pitting.

• Corrosion could result in failure

and high levels of unbalance

during operation.

CORRECTIVE ACTION:

• Replace component.

• Only discovered / resolved

following a full rotor destack.

12

Page 13: Nathan Griffiths - MJB International

RABBET, BORES AND RIMS FIT WEAR

(DISCS, WHEELS, COUPLING AREAS):

ISSUE:

• Critical these precision interfaces

are maintained to ensure run out

tolerances are achieved.

• If these become loose in service,

high levels of unbalance could

occur.

CORRECTIVE ACTION:

• Re-establish by machining andcoating or installing patch rings.

• Only discovered / resolvedfollowing full rotor destack.

13

Page 14: Nathan Griffiths - MJB International

INTERNAL COOLING

PASSAGE BLOCKAGES:

ISSUE:

• During operation the rotor ingests

huge quantities of air into the

compressor.

• Environment & Air Filtration issues

= blocked internal cooling passages

= reduced cooling air flow =

premature deterioration of HGP

Parts.

CORRECTIVE ACTION:

• Cleaning & blow through.

• Only discovered / resolvedfollowing full rotor destack.

14

Page 15: Nathan Griffiths - MJB International

COMPRESSOR BLADE MIGRATION:

ISSUE:

• The spacer holding compressor

blade in position overcomes

staking during start up / shut

down, irregular operating events

causing blade tip contact.

CORRECTIVE ACTION:

• Remove and rework the

spacers

• Only resolved following full

rotor destack.15

Page 16: Nathan Griffiths - MJB International

COMPRESSOR WHEEL

DOVE SLOT CRACKING:

ISSUE:

• Compressor Wheel Dovetail

Cracking can result in loss of

material causing FOD to

compressor blading & downstream

components.

CORRECTIVE ACTION:

• Blend dovetail cracks.

• Only resolved following a full

rotor destack.

16

Page 17: Nathan Griffiths - MJB International

THROUGH BOLT CRACKING

ISSUE:

• Through Bolt Nut Failure.

• Example: Fr 5/2 D DLN HP Rotor.

• Resulted in High Vibration.

• RCA determined nuts incorrectly

heat-treated.

CORRECTIVE ACTION:

• Replace all through bolts & nuts.

• Only resolved within a Rotor

Overhaul Facility.

17

Page 18: Nathan Griffiths - MJB International

FR 9 & FR7 2nd STAGE

DISCOURAGER SEAL DAMAGE

ISSUE:

• FOD & Distortion.

• Allows increased levels of hot

gases to enter into rotor's cavities.

CORRECTIVE ACTION:

• Replace with New Discourager

seal.

• Preferably resolved within a

Rotor Overhaul Facility.18

Page 19: Nathan Griffiths - MJB International

METALLURGICAL INSPECTIONS /

NDT DURING DESTACK

SECTION 4

19

Page 20: Nathan Griffiths - MJB International

CONDITION ASSESSMENT

TESTS & ACTIVITIES

• Rotors operational life is finite.

• Exceeding rotor life can result in failures that can damage

the entire turbine.

Condition Assessment NDT:

• Requires rotor to be destacked to gain access to the critical

areas / components.

• Assess material condition to mitigate risk of rotor failure.

20

Page 21: Nathan Griffiths - MJB International

CONDITION ASSESSMENT

TESTS & ACTIVITIES

21

1ST, 8TH & 16TH STAGE COMPRESSOR WHEELS:

Replication & hardness testing

Ultrasonic inspection 100% surfaces

Magnetic Particle inspection 100% surfaces

Eddy Current Inspection 100% surfaces including bores, fir trees, radii and fillets

DISTANCE PIECE:

Replication & hardness testing

Ultrasonic inspection

Magnetic Particle inspection

Eddy Current Inspection 100% surfaces including bolt holes, radii and fillets

1ST, 2ND & 3RD STAGE TURBINE WHEEL:

Replication & hardness testing of bores and fir trees

Ultrasonic inspection 100% surfaces

Magnetic Particle inspection 100% surfaces

Eddy Current Inspection 100% surfaces including bores, fir trees, radii and fillets

FWD & AFT SHAFTS:

Ultrasonic inspection 100% surfaces

Magnetic Particle inspection 100% surfaces

Eddy Current Inspection 100% surfaces

XRF for material analysis on all components

Page 22: Nathan Griffiths - MJB International

CONDITION ASSESSMENT

TESTS & ACTIVITIES

VISUAL INSPECTION:

• To examine appearance of rotor surfaces

• As received condition and after cleaning/blasting.

• Examine surface deposits, corrosion, pitting etc. on

rotor, rotor blade surfaces.

SCALE/DEPOSIT ANALYSIS:

Deposits on surfaces of rotor & blading are collected to

determine detrimental elements such as Vanadium,

Potassium, Sulphur etc.

HARDNESS TEST:

• Another method of determining creep damage.

• Changes in hardness can indicate of stress rupture.

• Numbers can be correlated to material ultimate &

yield stress levels.22

Page 23: Nathan Griffiths - MJB International

CONDITION ASSESSMENT

TESTS & ACTIVITIES

EDDY CURRENT TESTING:

• Performed on turbine wheel, bridge areas, bore hole and stress critical areas.

• Can reveal presence of surface cracks.

ULTRASONIC FLAW DETECTION:

• Performed on the rotor surfaces to detect presence of material flaws, defects or in-depth

cracks.

• High frequency sound waves are introduced into a material.

• Reflected back from surfaces or flaws.23

Page 24: Nathan Griffiths - MJB International

CONDITION ASSESSMENT

TESTS & ACTIVITIES

MATERIAL VERIFICATION BASED ON XRF ANALYSIS:

• Checks the chemical composition of rotor material.

• Locations = compressor wheels, turbine wheels,

spacers, and distance piece.

MAGNETIC PARTICLE INSPECTION:

Performed on the rotor surfaces to check

for presence of surface or sub-surface

cracks.

24

Page 25: Nathan Griffiths - MJB International

CONDITION ASSESSMENT

TESTS & ACTIVITIES

IN SITU-METALLOGRAPHY / REPLICATION:

• Replicas taken in known high stress points /areas.

• Examined by Light Optical Microscope & ScanningElectron Microscope (SEM).

• Gold or silver sputtered prior to examining in SEM.

Microexamination will Indicate:

• Major carbide transformations.

• Creep voids and Microcracks (SEM).

Determines Indications of:

• Grain structure change.

• Stability / Comparisons with any previous conditionassessment or a new rotor / component.

25

Page 26: Nathan Griffiths - MJB International

EXAMPLE OF ISSUES FOUND

26

Phased Array testing to Stage 1 & 2 Compressor Wheels to check nature of defect found

during ultrasonic flaw detection.

• Revealed cluster indications.

• Inherent defects from the manufacturing process (possibly inclusions).

• Measured lengths in the range of 10 to 16 mm.

Defect Areas Located with

Ultrasonic Testing in Compressor

Wheel

Page 27: Nathan Griffiths - MJB International

EXAMPLE OF ISSUES FOUND

EXAMPLE OF ISSUES FOUND DURING CONDITION ASSESSMENTS :

27

SEM showing Carbide Precipitation in Turbine wheels after 200K+ hrs.

Page 28: Nathan Griffiths - MJB International

CONDITION ASSESSMENT

TESTS & ACTIVITIES

Success of condition assessment also depends on operating data available,

such as:

• Operating Hours

• Number of starts and stops

• Fuel Fired with fuel analysis

• Any previous failure history

• Any replacements/ refurbishments carried out.

Test results obtained during a rotors full overhaul / condition assessment will

be co-related with the data provided to arrive at the factual condition of the

rotor material and its re-usability.

28

Page 29: Nathan Griffiths - MJB International

ROTOR OVERHAUL FACILITY

– CAPABILITIES / EQUIPMENT

REQUIRED.

SECTION 5

29

Page 30: Nathan Griffiths - MJB International

CAPABILITIES / EQUIPMENT

REQUIRED.

30

ROTOR OVERHAUL & CONDITION

ASSESSMENT FACILITIES:

Facility should be fully equipped with state of the

art equipment allowing implementation of:

• Complete Inspection

• Condition Assessment

• Overhaul

All performed under one roof = total control &

ownership of scope of work, from receipt through to

dispatch, with no compromise in quality.

Including capabilities to carry out associated

repairs including Bucket Repair, to ensure lead

times are kept to a minimum.

Page 31: Nathan Griffiths - MJB International

CAPABILITIES / EQUIPMENT

REQUIRED.

31

HORIZONTAL LATHES:

Various capacities up to 30 tonne / 12 metre

bed length to carry out incoming run out

checks.

HORIZONTAL BALANCING:

Various horizontal balance capacity up to 50

tonne / 9.5 metre bed length to carry out

incoming and final rotor balance checks to

OEM specification.

Page 32: Nathan Griffiths - MJB International

CAPABILITIES / EQUIPMENT

REQUIRED.

CRANES:

Various overhead cranes capacity up to

60 tonne / 12 metre hook height.

STANDS / THROUGH BOLT

STRETCHING EQUIPMENT:

Rotor stands, turning, destack / restack

fixtures and tooling for all GT Frame

sizes up to Fr 9E rotors.

32

Page 33: Nathan Griffiths - MJB International

CAPABILITIES / EQUIPMENT

REQUIRED.

CLEANING:

Abrasive blast cleaning of compressor &

turbines wheels to remove engine deposits.

(Blast cleaned with 220-aluminum oxide.)

IN-HOUSE LABORATORY:

The workshop repair facility requires support

of an in-house metallurgical laboratory

enabling complete condition assessment.

33

Page 34: Nathan Griffiths - MJB International

CAPABILITIES / EQUIPMENT

REQUIRED.

WHEEL RUN OUT / STACKING SEQUENCE:

Paragon Circular Geometry Inspection System:

• Utilised by OEM during new rotor manufacture.

• Superior to less accurate wheel run out tables.

Each surface measured approx. 540,000 times,

yielding resolutions to approx. 0.125 microns

Paragon makes all calculations re: Roundness,

Concentricity, Run-Out , Flatness & Parallelism

Plots best wheel position = straightness &

minimizes Total Indicated Runout (TIR) = reducing

rotor imbalance & potential for increased vibration

during operation.34

Page 35: Nathan Griffiths - MJB International

CAPABILITIES / EQUIPMENT

REQUIRED.

35

COMPRESSOR BLADE REMOVAL & RE-BLADE:

COMPRESSOR BLADE TIP GRINDING:

Blades machined as per specification to ensure

correct clearance once the rotor is installed back

into the GT casing and for optimum compressor

efficiency.

Page 36: Nathan Griffiths - MJB International

CAPABILITIES / EQUIPMENT

REQUIRED.

VERTICAL BALANCE MACHINES:

Vertical Balance Machine removes

requirement to use 2 x mandrel system

that introduces inaccuracy.

Vertical balance machines custom

designed with expanding mandrels &

high degree of accuracy & repeatability.

Specially designed / manufactured with

sole purpose of balancing GE Frame

Compressor & Turbine wheels.

36

Page 37: Nathan Griffiths - MJB International

CAPABILITIES / EQUIPMENT

REQUIRED.

ADDITIONAL / OPTIONAL ROTOR REPAIR PROCESSES:

• Thrust Collar Reclamation - repair the collar and return it to original dimensions.

• Under Cut bearing journals - Journal undercutting can be implemented to

customer demands.

• Under Cut Thrust Collars - Thrust collar modification to accommodate new tilting

pad bearing design.

• Probe Track Burnishing – This process incorporates diamond tip machining to

accommodate surface finish required for vibration pick ups

37

Page 38: Nathan Griffiths - MJB International

CAPABILITIES / EQUIPMENT

REQUIRED.

BUCKET REPAIR & COATING CAPABILITIES:

38

Page 39: Nathan Griffiths - MJB International

SUMMARY / CONCLUSIONS

SECTION 6

39

Page 40: Nathan Griffiths - MJB International

SUMMARY / CONCLUSIONS

• Rotor Failure = High Cost implications + Prolonged Downtime + Risk to Safety of Plant &Staff.

• Rotor failures can damage the entire turbine.

• Critical internal components of a rotor are only accessible during full rotor destack.

• When the rotor assemblies are destacked issues can be corrected immediately.

• Rotor overhaul / condition assessment ascertains whether a rotor is suitable to return toservice, based metallurgical examinations / NDT to confirm material condition / suitability.

REQUIRED FACILITY EQUIPMENT / CAPABILITIES:

• Fully equipped with state of the art equipment allowing for Complete Inspection, ConditionAssessment & Overhaul.

• All performed under one roof = total control / ownership of the scope of work from receiptthrough to dispatch, with no compromise in quality.

• Capabilities to carry out associated repairs including Bucket Repair, to ensure lead times arekept to a minimum.

40

Page 41: Nathan Griffiths - MJB International

www.mjbi.com

THANK YOU