Download - When Bad Things Happen to Good Turbines
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When Bad Things Happen to Good Turbines
PAL Turbine Services, LLC
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ALFRED SHUMAN - Senior Staff Engineer Engineering Specialties
Gas Turbine Maintenance CMU Modifications Product Service Engineering Technical Training
Experience 41-years gas turbine experience
Senior Consulting Engineer for PAL Turbine Services since 2000
GE Field Engineer Lead Technical Training Specialist, FEP GE Service Supervisor, Baltimore, MD GE Senior Installation Engineer, Futsu Japan site for
14 MS9001E STAG plants (5-year project) Performed numerous major overhauls on GE model
series including MS5001, 6001, 7001
Education
E6, Machinist Mate, Class A, US Navy Submarine Nautilus
AAS Mechanical Design Engineering, Wentworth Institute of Boston, MA
GE Training Programs: Field Engineering Program (FEP) Gas Turbine Maintenance Schools Six Sigma Training
PAL Turbine Services, LLC Office: 518-371-1971 Fax: 518-371-1756
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Note That Some of the Examples Shown are from Not Only MS-6001B Units, but also MS-5001N and MS-7001EA Units
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Bolting Issues
1. Plated Bolting 2. Rusted Bolting
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World War II Liberty & Victory Ships
These ships were the first to be built completely welded with no use of rivets Components for ships built modularized in many different
locales and then welded together at the assembly shipyard This process drastically reduced the time to build these
ships at a time when the Allies were desperate for war materials
Some of the issues of Embrittlement, due to temperature along with contaminants and also with an excess of Hydrogen in the welds, led to significant failures of hulls during launching
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Launch of Liberty Ship from Dry Dock
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Catastrophic Failure of Launched Hull Due to Embrittlement
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Successfully Built Liberty Ship Helping the Allies War Effort
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Case #1 Cadmium & Zinc Plated Bolting
Do not use Cadmium plated bolts in the combustion, hot section or exhaust.
Above 4500 F the cadmium melts & attacks the grain structure of the bolts and the bolt fails.
The failure mode is called Liquid Metal Embrittlement and it is similar in nature to Hydrogen Embrittlement.
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Failed Cadmium Plated Bolts
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Failed Cadmium Plated Bolts & Nuts
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Combustion Can Cover, with Fuel Nozzle & Pigtails, Blew Off
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Collapsed Liner & Flow Sleeve
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Discussion of the Root Cause of
this Failure
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Case #2 Rusted Bolting in Inlet Ducting
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Rusted Bolting in Inlet Ducting
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Inlet Bellmouth Bernoulli Effect: Pressure Drop Produces Increase in Flow Velocity All GE Heavy Duty GTs produce a Velocity increase of Mach 0.5 Typical 295 lb/sec (1,062,00 lb/hr)
Velocity = Mach 0.5
Why Does Foreign Object Damage Occur So Rapidly Within the Flange-to-Flange
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Pond And Lucier, LLC
Pressure & Temperature Across Gas Turbine Typically, the Delta-P Across the Inlet Throat Results in a Delta-T of 230F
T4 = 1000 F P4 = 14.7 psia
T1 = 59 F P1 = 14.7 psia
T2 = 450 F P2 = 196 psia
Flame Temp = >3000 F
T3 = 2035 F P3 = 196 psia
1 2
3 4
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Collateral Damage From Failed Bolting
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Collateral Damage From Failed Bolting
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Collateral Damage From Failed Bolting
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Discussion of the Root Cause of
this Failure
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During reassembly, ensure that crew understands to report when something gets dropped into an open turbine. No one will be fired or censured for
dropping something into the machine as long as it is promptly reported.
Two case histories of when bad things happened because of dropped/missing parts
Cautions with Open Casings
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Case #3: MS-7001EA after a HGP & subsequent restart
Units MW output was significantly less then before the outage.
Pcd read higher than expected, but output was still lower than expected.
Significant testing indicated a problem in the Turbine section.
Decision made to open Combustion system in order to inspect Stage 1 Nozzle
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View of Stage 1 Nozzle from inside Wrapper
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Damage which Choked Nozzle (Note how TE is pushed upstream)
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Note how TE is pushed upstream
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Damage as Viewed from Turbine
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Bucket Denting & Splatter
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1st Stage Bucket F.O.D.
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2nd Stage Bucket Splatter & F.O.D.
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Setting Pressure Ratio (PR)
Nozzle Throat Dimension The Tightest Orifice in the Hot Gas Flow Path
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Typical Nozzle Throat Dimension Check Points
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Damage which Choked Nozzle & caused High Pcd
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1st Stage Nozzle F.O.D. & Buckling
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1st Stage Nozzle Impact Zone
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Discussion of the Root Cause of
this Failure
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Case #4: MS-6001B After Major Inspection
Complete Major Overhaul, with replacement of all HGP parts along with a refurbished CDC Inner Barrel.
Performance was ~9% lower than before the outage.
Significant testing & a borescope inspection
Unit reopened
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Borescopic View of Stage 1 Bucket Airfoil
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Borescope View of Stage 2 Bucket Shroud
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Note Gouges on Inside of Inner Barrel
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Close up of Gouges in Inner Barrel
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Distance Piece Interface with Stage 1 Wheel
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Stage 1 Bucket Pressure Side Deposits
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Stage 1 Nozzle Inner Sidewall Deposits
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Stage 1 Nozzle LE & PS Deposits
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Stage 2 Bucket Shroud Tip deposits
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Discussion of the Root Cause of
this Failure
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Case # 5: Effects of Turbine Clearances
Being Too Tight
Rubs & Consequential damage are most often a low speed event.
Damage usually occurs during very first start-up after outage.
Make sure that you fully understand the true costs of trade offs made during reassembly.
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Effects of Turbine Clearances Being Too Tight
Power Plant Users often believe that, since they are going to change out Turbine Nozzles and Buckets during an outage, it is not important to take all of the Internal Clearances when opening the unit and again, when closing the unit.
They believe that they can save outage time by not expending the effort to take accurate readings and compare them to what they were at the last outage; such a belief quickly becomes a False Economy.
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Effects of Turbine Clearances Being Too Tight
Turbine, Compressor, and Bearing Clearances are indeed where the rubber meets the road.
The OEMs Design Engineers view the Clearance Diagrams with their specific tolerances as the Bible for setting the performance and reliability parameters for any Heavy Duty Gas Turbine.
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Effects of Turbine Clearances Being Too Tight
It is crucial that the person taking the clearances not only has a good understanding of how and where to take the clearances accurately, but also understands that this task is one of the most important of the outage.
Adherence to the designed tolerance range affects optimum performance. You must review all of the before/after clearances; the Turbine is speaking to you. If you understand the inseparable dimensional relationship between the Rotor and the Stator during various phases of operation, then you can determine where to make judgments as to where to go outside of the optimum clearance envelope. PAL Turbine Services, LLC
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MS6001 Turbine Clearance Composite
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Bucket to Honeycomb Shroud Clearance
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Correcting Clearances Below Minimum Values on Stage 2 and 3 Buckets
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MS-6001B Stg 2 Shroud Rub
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Stg 2 Bucket Shroud Rail Rubbed Off
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Comparison of Buckets
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Discussion of the Root Cause of
this Failure
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Effects of Ignoring Recommendations Case #6
MS-6001B Stage 2 Bucket Shroud lift phenomenon Unit was open for a HGP Customer chose not to follow OEMs TIL
recommendation to change to new buckets due to potential cracking on airfoils.
Customer installed a set of buckets from another unit on site which had shown marginal shroud lift readings.
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What it Looked Like at First Outage
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What It Looked Like at 2nd Outage
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Stg 2 Bucket Stubs
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Stg 1 Buckets are only lightly damaged
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Collateral Damage to Exhaust Frame Outer Barrel
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Collateral Damage to Exhaust Frame Outer Barrel
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Collateral Damage to Exhaust Frame Outer Barrel
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2nd & 3rd Stage Stator Damage
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2nd & 3rd Stage Stator Damage
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Discussion of the Root Cause of
this Failure
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Corrosion Case #6
Contaminating reagents can enter the gas path via: Ambient air Fuel (oil/gas) Diluents/Misting/Evaporative Cooling
Contaminants from all sources are additive in concentration & impact
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Stage 1 Nozzle Exposed to Boiler Carryover in Steam Injection Attemperation
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Stage 1 Nozzle Exposed to Boiler Carryover in Steam Injection Attemperation
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Stage 1 Nozzle Partitions
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Discussion of the Root Cause of
this Failure
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Case #7: Rush to make-up lost time in MS6001B Major Inspection Schedule leads to the Law of Unintended Consequences Results in an Order of Magnitude more lost time along with replacement and/or rework of Critical Components
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View of S1 Vane Through VIGVs & R1 Blades
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Damage to Stator Dovetail Slot Along with Rubs & Dings to Blades & Vanes
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Arrows Show Where Retaining Keys Should Be Locked in Place
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Note Rubbing Damage to Dovetail Slot Caused by Rotation of Blade Rings in Service
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Note Damage to Stator Vanes & Blade Ring
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Discussion of the Root Cause of
this Failure
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Conclusions & Recommendations
Hug your Gas Turbines! Treat them well, especially during outages! Confirm that Proper Form, Fit, & Function
parts are being used as replacements! If schedule is causing an inordinate rush
stop to think, review situation, and act accordingly! Work Safely & Work Smart!
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Conclusions & Recommendations
Account for every single tool removed & every part installed properly before closing up Gas Turbine!
Following Good Engineering Practices will always trump False Economy!
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Centuries of experience In maintaining gas turbine generators
When Bad Things Happen to Good TurbinesSlide Number 2Bolting IssuesWorld War II Liberty & Victory ShipsLaunch of Liberty Ship from Dry DockCatastrophic Failure of Launched HullDue to EmbrittlementSuccessfully Built Liberty ShipHelping the Allies War EffortCase #1 Cadmium & Zinc Plated BoltingFailed Cadmium Plated BoltsFailed Cadmium Plated Bolts & NutsCombustion Can Cover, with Fuel Nozzle & Pigtails, Blew OffCollapsed Liner& Flow SleeveDiscussion of theRoot Cause of this FailureCase #2 Rusted Bolting in Inlet DuctingRusted Bolting in Inlet DuctingInlet BellmouthBernoulli Effect:Pressure DropProduces Increasein Flow VelocityAll GE Heavy Duty GTsproduce a Velocityincrease of Mach 0.5Typical295 lb/sec(1,062,00 lb/hr)Pressure &TemperatureAcross Gas TurbineTypically, the Delta-PAcross theInlet ThroatResults ina Delta-Tof 230FCollateral Damage From Failed BoltingCollateral Damage From Failed BoltingCollateral Damage From Failed BoltingDiscussion of theRoot Cause of this FailureCautions with Open CasingsCase #3: MS-7001EA after a HGP & subsequent restartView of Stage 1 Nozzle from inside WrapperDamage which Choked Nozzle(Note how TE is pushed upstream)Note how TE is pushed upstreamDamage as Viewed from TurbineBucket Denting & Splatter1st Stage Bucket F.O.D.2nd Stage Bucket Splatter & F.O.D.Setting Pressure Ratio (PR)Typical Nozzle Throat Dimension Check PointsDamage which Choked Nozzle & caused High Pcd1st Stage Nozzle F.O.D. & Buckling1st Stage Nozzle Impact ZoneDiscussion of theRoot Cause of this FailureCase #4: MS-6001B After Major InspectionBorescopic View of Stage 1 Bucket AirfoilBorescope View of Stage 2 Bucket ShroudNote Gouges on Inside of Inner BarrelClose up of Gouges in Inner BarrelDistance Piece Interface with Stage 1 WheelStage 1 Bucket Pressure Side DepositsStage 1 Nozzle Inner Sidewall DepositsStage 1 Nozzle LE & PS DepositsStage 2 Bucket Shroud Tip depositsDiscussion of theRoot Cause of this FailureCase # 5: Effects of Turbine Clearances Being Too TightEffects of Turbine Clearances Being Too TightEffects of Turbine Clearances Being Too TightEffects of Turbine Clearances Being Too TightMS6001 Turbine Clearance CompositeBucket to Honeycomb Shroud ClearanceCorrecting Clearances Below Minimum Values on Stage 2 and 3 BucketsMS-6001B Stg 2 Shroud RubStg 2 Bucket Shroud Rail Rubbed OffComparison of BucketsDiscussion of theRoot Cause of this FailureEffects of Ignoring RecommendationsCase #6What it Looked Like at First OutageWhat It Looked Like at 2nd OutageStg 2 Bucket StubsStg 1 Buckets are only lightly damagedCollateral Damageto Exhaust FrameOuter BarrelCollateral Damageto Exhaust FrameOuter BarrelCollateral Damage to Exhaust Frame Outer Barrel2nd & 3rd Stage Stator Damage2nd & 3rd Stage Stator DamageDiscussion of theRoot Cause of this FailureCorrosion Case #6Stage 1 Nozzle Exposed to Boiler Carryover in Steam Injection AttemperationStage 1 Nozzle Exposed to Boiler Carryover in Steam Injection AttemperationStage 1 NozzlePartitionsDiscussion of theRoot Cause of this FailureCase #7:Rush to make-up lost time in MS6001B Major Inspection Schedule leads to the Law of Unintended Consequences Results in an Order of Magnitude more lost time along with replacement and/or rework of Critical ComponentsView of S1 Vane Through VIGVs & R1 BladesDamage to Stator Dovetail Slot Along with Rubs & Dings to Blades & VanesArrows Show Where Retaining KeysShould Be Locked in PlaceNote Rubbing Damage to Dovetail SlotCaused by Rotation of Blade Rings in ServiceNote Damage toStator Vanes& Blade RingDiscussion of theRoot Cause of this FailureConclusions & RecommendationsConclusions & RecommendationsSlide Number 84