lm series compressor damage mechanisms &failure analysis - olivia chung, quest integrity

LM Series Compressor Damage Mechanismsand Failure Analysis

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16th Annual Australian Gas Turbines Conference

Olivia Chung26 November 2015

LM Series Compressor DamageMechanisms and Failure Analysis

www.QuestIntegrity.com2

Overview

• Introduction to the GE LM family of aero-derivativeengines.

• Damage mechanisms.

• Failure analysis methodology.

• Service bulletins.

• Case studies.


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General Electric LM aero-derivative family

• LM = Land (or) Marine version of General Electric aviationturbine:

– Military engines:• LM1500 – aero-derivative of J79 turbojet.• LM1600 – aero-derivative of F404 turbofan.

– Civil engines (CF-6, itself based on the military TF39)• LM1800/2000/2500/2500+/2500+G4 – All based around CF6-6

turbofan.• LM5000 – aero-derivative of CF6-50.• LM6000 – aero-derivative of CF6-80C2.• LMS100 – hybrid of CF6-80C2/E1 supercore + MS6001F LPC.


• The LM2500 is available in 3different versions:– The LM2500

• 24 MW of electricity at 60 Hz with athermal efficiency of 36 percent atISO conditions.

– The LM2500+• 29 MW of electricity at 60 Hz with a

thermal efficiency of 38 percent atISO conditions.

– The LM2500+G4• 33-37 MW of electricity at 60 Hz

with a thermal efficiency ofapproximately 40 percent at ISOconditions.

LM2500


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• Legacy machine, with less than 60units in fleet.

• LM5000 engine types:– LM5000PC.– LM5000PC STIG.– LM5000PD STIG.

• Power output: approximately 37.5MW.

• Package can be up-graded toLM6000.

LM5000


• LM6000 engine types– LM6000PA (SAC, standard).– LM6000PB (DLE, emission reduction).– LM6000PC (SAC, standard).– LM6000PD (DLE, emission reduction).– LM6000PF (DLE, emission reduction).– LM6000PG (SAC, standard).– LM6000PH (DLE, emission reduction).

• Power output: approximately 43 to 53 MW.

LM6000


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• The LMS100 derived from the CF6-80E, CF6-80C2 and from the frame6FA gas turbine (boostercompressor).

• LMS100 (60Hz) Power Output:– SAC 116.2 MW.– DLE 103.3 MW.

• 20-stage axial compressor:– 6 low pressure stages.– 14 high pressure stages.– 43:1 compression ratio.

• Off-engine air-to-water intercooler.

LMS100


• If it went wrong with a CF6-type engine, it can gowrong with a LM aero-derivative engine!

• Some issues shared between LM5000 and LM6000(similar HPC design).

How does this relate to failure analysis?


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How and Why failures occur

• Main damage mechanisms incompressor (how it happened):– Foreign object damage (FOD).– Domestic object damage (DOD).– Low cycle fatigue (LCF).– High cycle fatigue (HCF).– Corrosion/pitting.– Wear.

• Causes of failure (why it occurs):– Design.– Manufacturing/ Quality.– Installation.– Operation.– Maintenance.


• Where do you start?– Restricted investigation

• Limited time available fordowntime.

• Limited access.• As instructed by OEM.

– Full failure investigation• Sets of components are

available for examination.• Some flexibility in undertaking

replacement of failedcomponents/ downtime.

• As instructed by OEM.

Failure analysis methodology


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1) Collection of background information.2) Undertake examination - restricted or full.3) Review results with respect to background information to

determine the damage mechanism(s) and (root) cause ofthe failure.

• Primary objectives:– To understand how the failure occurred and what caused the

failure.– To prevent further failures from occurring.

Stepped approach to failure investigation


Typical tasks for failure analysis

Activity Restricted Examination Full Examination

Visual examination/fractography

Photos, portable digitalmicroscope. Photos, optical microscope, SEM.

NDT Videoscope, borescope, UT, MPI,ET. Videoscope, UT, MPI, ET.

Dimensioning/measurements

Manual, laser scanning, surfaceroughness, pit depths.

Manual, laser scanning, surfaceroughness, pit depths.

Chemical analysis Collect deposits for EDX, portablePMI/ XRF.

Collect deposits for EDX, XRF,XRD, OES.

Metallurgical examination Metallurgical replication. Sectioning of components formetallurgical samples.

Hardness testing Portable (macro) hardness testing. Macro/ micro hardness testing ofmetallurgical samples.

Materials testing N/A Tensile, creep, fatigue, creep/fatigue crack growth, Charpy.

Engineering assessment FEA, FFS, fracture mechanics. FEA, FFS, fracture mechanics.


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• Operating history: number of starts andhours since overhaul and since new.

• Maintenance and replacement history.

• Condition monitoring records.

• Borescope and other inspection reports.

• Vibration records.

• All history relating to any previous orrelated failures; include all failures ofcomponents in the proximity to thisfailure.

• Unusual occurrences and anomalousoperation conditions.

• Service bulletins.

Background information required for a failureanalysis


Service Bulletins

• Product advisories highlighting changes, modifications and/orupgrades for a fleet of engines.

• The intent is to provide information on known issues andprovide engineering solutions for these known issues toimprove reliability of the engine i.e. minimise the risk ofcomponent/ engine failure.

• Information is presented with respect to the compliance level,category and timing code (i.e. likelihood of risk associated withengine integrity).– Consequence of not implementing the Service Bulletin will

generally be the same (forced outage).


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• Compliance levels are defined as follows:– F = Field

• Work identified may be accomplished in the field by trained on-sitemaintenance personnel or a GE Service Representative. TheseBulletins may also be accomplished at an authorized service centre.

– D = Depot• Work identified in SB must be accomplished at an authorized service

or repair centre.– F/D = Field/Depot

• These Bulletins may be accomplished in the field but require theinstallation of a part/accessory that was reworked/modified at anauthorized service or repair centre.

• For example when a part/accessory is modified to that can only beperformed at an authorized service or repair centre. Thepart/accessory may be removed and shipped to an authorizedservice or repair centre for modification. The original modifiedpart/accessory or rotatable exchange may be installed in the field.

Service Bulletins: Compliance level


Service Bulletins – Category

• Category levels are identified as:– O = Optional

• Identifies product improvements that may be beneficial to some, but not necessarily all,customers.

• OEM recommends implementation at customer's discretion or when an opportunity arises.

– R = Routine• Identifies product improvements or inspections that primarily enhance product life,

operating characteristics and/or reduce life cycle maintenance costs.• OEM recommends implementation in accordance with the Timing Code for the Bulletin,

generally during routine, scheduled maintenance.– C = Campaign

• Identifies product improvements or inspections that primarily enhance product reliability.OEM recommends implementation in accordance with the Timing Code for the Bulletin,normally implemented at first opportunity during scheduled or unscheduled maintenance.

– A = Alert• Identifies product improvements or inspections to ensure product safety and enhance

product reliability. GE recommends immediate action by the customer to plan andschedule implementation in accordance with the Timing Code for the Bulletin. Completedat first opportunity during scheduled or unscheduled maintenance. Implementation mayalso be required prior to a specific operating time or cycle limit.


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Implementation Timing Timing Code

Prior to start-up/engine operation 1

At first opportunity (next shutdown or periodicinspection at latest) 2

At first opportunity prior to Time/Cycles (TSN/CSN)limit 3

At first exposure of EMU/Module 4

At component part exposure 5

At component part repair or replacement 6

Optional 7

At next depot visit 8

Service Bulletins- Timing codes


Case Studies

• LMS100 booster compressor vane failure.

• LM5000 HPC Stage 3 blade failure.


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• Predominantly limited to on-site non-destructive examination.– Visual examination.– Chemical analysis using a

portable XRF analyser.– Rubber replication (to enable pit

depth measurements).

• Borescope inspection carried out. Unithad done 8222 fired hours at the timeof inspection. Failure occurred in early2013.

• One S1 vane liberation found in lowercasing.– Located approximately 50 mm

from the vane tip.

Case Study 1: LMS100 booster vane failure


• Damage mechanism: High CycleFatigue.

• Factors contributing to the failure:– Operation: the booster compressor

is wet and corrosion of vane carrierchanged vane frequency (“lock up”).

– Design: the vanes installed on thebottom half casing were moresusceptible to corrosion build-up.

Case Study 1: LMS100 booster vane failure

• Improvements to the booster have been made, including a material change tothe vane carrier.

• A Service Bulletin was reported to have been released in late 2013.


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Case Study 2: HPC Stage 3 blade dovetailfracture

• Overview:– One Stage 3 blade liberation.– Total hours of unit: over 40,000

hours.– Last maintenance outage

carried out 3500 hours prior tofailure to correct vibrationissues.

– Vibration free period since.– Extensive damage to VSV

linkages reported.– Reported as inspected by GE 1

hour before failure.– Set of Stage 3 blades submitted

for examination.


• Visual examination:– Beach markings.– Initiated from front right

corner of dovetail.– Crack arrested.– Fatigue re-initiated on left

hand side.– Surface coating spalled on

dovetail.– All other blades

consequential damage.



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• NDT:– Remaining blades from set

inspected using the Eddy Currenttechnique.

– No cracks indications detected.

• SEM Examination:– Beach markings observed on the

fracture.– No fatigue striations detected.



• Metallurgical Examination:– Crack turned towards foot.– No evidence of inherent material

defect.

• Hardness Testing:– No abnormal readings.

• Chemical Analysis:– EDX analysis results

consistent with Ti 6Al-4V alloy.– Surface deposits on dovetail

consistent with an anti-frettingcoating.


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HP Case Study 2: HPC Stage 3 blade dovetailfracture

• Damage mechanism: Fatigue crack in dovetail of blade.

• Numerous causes of failure:– Off schedule VSV operation.– Loss of anti-fret coating.– “Edge of Contact” fretting.– “Tip clang” during stalls.– Fouling of blade/dovetail.

• Common to CF6, LM5000, LM6000 HPC– At least 10% of LM5000 fleet.– At least 11 LM6000 units (~1% of fleet).– Affects HPC S3-S5 (and maybe one instance of S6).

• Re-designed as per SB229– But failures since, with no evidence of off-schedule VSV or loss of

coating etc.


Service Bulletin LM6000-IND-229


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Summary

• Failures observed for CF6- type civil engines can also occur foraero-derivative engines.

• A review of operation and historical information and ServiceBulletins is essential to understanding how and why a failureoccurred, in additional to undertaking analysis.– Service Bulletins can contain key information for understanding

how and why failures occur. Engineering solutions andmodifications to fleet-wide engine reliability issues are identified.

– Note the timing code, category and compliance level of ServiceBulletins.

• Review Service Bulletins proactively rather than reactively aftera failure has occurred.


Thank You

• Olivia Chung:

Office: +64 4 978 6630Direct: +64 4 978 6636Mobile: +64 21 911 352Fax: +64 4 978 9930Email: [email protected]

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