Thermoplastic Labyrinth Seals in Centrifugal Compressors -15 years of experiences

John K. Whalen, PE

TCE/Turbo Components & EngineeringJim Allen

Nova Chemicals CorporationJonathan D. Cardell

DuPont Packaging & Industrial PolymersJohn R. Dugas

Consultant

553

Thermoplastic Labyrinth Seals

n Thermoplastics used in compressors for over 20 years now.

n The two most common thermoplastic materials used are:q PolyAmide-Imide (PAI) trade name Torlonq Polyetheretherketone trade name PEEK

554

Thermoplastic Labyrinth Seals

n Benefits of Thermoplastic Sealsq Efficiencyn Design with reduced clearances

q Reliabilityn Maintain clearance during transient rubsn Forgiving during hard rubs (gall resistant)n Can be more corrosion resistant

q Ease of installation

555

Introductionn Labyrinth Sealsq Basics, leakage, use in centrifugal compressors

n Thermoplasticsq Types, properties, use in centrifugal compressors

n Upgrade payback calculationsn Case Historiesq Canadian ethylene plantq Texas ethylene plant

n Conclusions

556

Labyrinth Seals

n Seal an area of high pressure from an area of low pressure

n Clearance seals they do leakn Seals typically upgraded in a centrifugal

compressorq Eyeq Shaft or Hubq Balance piston

557

Labyrinth Seals Compressor Seals558

Labyrinth Sealsn Centrifugal compressor seal impact on

efficiency.q Assume leakage is linear with clearance.q Assume 4% of the compressor efficiency loss is

attributable to internal labyrinth seals.q If we reduce clearance to then leakage will

reduce to --> 2% efficiency gain.q If all major compressors in a 2 billion lb/yr

ethylene pant are upgraded this can save $700,000 per year in energy savings.

559

Labyrinth Seals

n How to reduce seal leakageq Reduce clearance and ensure it stays reducedq Metallic seal rub can cause problemsn Open seal boren Vibrationn Rotor damage (galling)

q Polymer seal rubs are forgivingn Clearance integrityn Not likely to induce rub related vibrationn Typically do not damage rotor

560

Metallic Seal Rubs 561

Polymer Seal Rubs562

Thermoplastics

n Define Thermal Property Terms n Polymer Typesq Thermosetsq Thermoplasticsn Amorphousq Torlon

n Crystallineq PEEK

563

Thermoplastics

n Thermal Propertiesq Tg Glass transition temperatureq Tm Melt temperatureq CUT Continuous Use Temperatureq HDT Heat Deflection Temperatureq DMA Dynamic Mechanical Analysisq CLTE Coefficient of Linear Thermal Expansion

564

Thermoplasticsn Tg Glass transition temperatureq Temperature at which the polymer softensq Below Tg polymers are rigidq Above Tg polymers are rubberyq At Tg CLTE increases significantlyq Above Tg strength and modulus drop offq Loses memoryq For labyrinth seals operation at or above the Tg

should be avoided.

565

Thermoplastics

n CUT Continuous use temperatureq Based upon UL testsq Temperature a polymer can be exposed to for

100,000 hours before losing its strength. q Accounts for thermal agingq Increases brittleness q Does not impact installed seal performanceq Only a concern in high temperatures (300-350 F)

566

Thermoplastics

n HDT is the Heat Deflection Temperatureq Per ASTM D-648, the temperature at which a

standard test specimen ( typically 0.5 W x 5 L x 0.5 Thick) under a load of 264 psi will deflect 0.010 or 5%

q Essentially the HDT is the temperature at which the flexural modulus of the polymer is reduced to 100,000 psi.

n DMA (Dynamic Mechanical Analysis) is a measure of the stiffness at temperature.

567

DMA Plot for Various Thermoplastics568

Thermoplastics

n CLTE (Coefficient of Linear Thermal Expansion)q Describes how the size of a part will change with

changes in temperature.q The smaller the materials CLTE, the more

dimensionally stable a part made from that material will be as temperatures are varied

q For most polymers the CLTE increases with temperaturen Must be accounted for in close tolerance applications

569

CLTE Plot570

Relative Thermal Properties571

Thermoplastics

n Chemical Attack Depends onTemperatureConcentrationPressureTime

572

PEEK Chemical Resistance

As a Semi crystalline polymer, PEEK is highly resistant to chemical attack BUT will be attacked by concentrated (over 30%) strong acids at high temperature:

Sensitive to: Unaffected by:

Chromic Acid Acetic Acid, 10% ConcHydrofluoric Acid Amines Nitric Acid HydrocarbonsSulfuric Acid Chlorine Dry & Wet

573

Torlon Chemical Resistance

As an amorphous polymer, Torlon is less chemically resistant than PEEK.

Sensitive to: Unaffected by:

Amines ( -NH2) Automotive Trans. FluidsAmmonia (-NH3) Aliphatic Hydrocarbons(Butane)Oxidizing Acids Aromatic Hydrocarbons ( Toluene)Strong Bases ( OH) Halogenated Hydrocarbons Chlorine Dry & wet such as: Methylene ChlorideSaturated Steam

> 300F

574

Engineeringn Data required includes:q Process make up for compatibility analysisq Suction and discharge temperatures and

pressuresq Speed for centrifugal growth calculationsq Cross sectional drawing of compressor

showing impeller and seal arrangementq Actual sealing diameters, from recent

inspection reportq Sample seals or seal drawingsq Bearing clearance

575

Engineeringn Calculations performed:q Polymer properties at operating temperatureq Thermal expansion of impeller, seal, and

diaphragmq Centrifugal growth of sealing surfaceq Resulting operating seal clearancen Size operating clearance equal to bearing clearancen For barrel compressor use 1.5 times bearing

clearance

576

Engineering

n Low temperature applicationsq Since CLTE is high the seals will contract more

than surrounding components this must be accounted for.

q Must ensure hook will not bind up in diaphragm.

q Successfully applied by authors at negative 150 degrees F suction temperature.

q Extrapolate mechanical properties.

577

Tensile Strength vs. Temperature578

Tensile Modulus vs. Temperature

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

0 100 200 300 400 500

Temperature (F)

Mo

du

lus

(p

si)

PAI

PEEK 1030

PEEK 1331

579

Compressive Strength vs. Temperature

0

10000

20000

30000

40000

0 100 200 300 400 500

Temperature (F)

Str

en

gth

(p

si)

Torlon

Aluminum

580

Upgrade Payback Calculations

n A common rule of thumb for estimating compressor performance gains is to use to % per impeller.

n Based upon experience this is conservativen Use the % number if the balance piston

seal is included in the project

581

Upgrade Payback Calculations

n Items brought up during this discussion;q I expect to see efficiency gains after a turnaround.q How to break out overall gains when several things

were done that should improve efficiency.q I cant measure my compressor efficiency

accurately enough to quantify the gains.n Use past experienceq See the two case histories that follow.

582

Case Historiesn Case 1: Canadian Ethylene Plantq Chow and Miller: Optimizing performance of an

ethylene plant cracked gas compressor train.n 10th Ethylene producers conference

q Whalen and Miller: An ethylene plant benefits from polymer labyrinth seals.n Turbomachinery International, 1998

n Case 2: Texas Ethylene Plantq Whalen and Dugas: Upgrading centrifugal

compressors with polymer seals in an ethylene plant a case history.n 29th Turbomachinery Symposium, 2000

583

Canadian Ethylene Plant

n 1996 Outage Ethylene 1n Installed Torlon in two cracked gas

compressors and the propylene compressorn Propylene seals are very large q 45 bore 1st stage eye, 36 bore balance piston

584

Canadian Ethylene Plant

n Ran 4 years - to 2001q Checked clearances in one machine still in specq Buttoned up and running today

n Ran 5 years - to 2006q Checked clearances still in specq Buttoned up and running todayq Expect to run for 6 years

585

Canadian Ethylene Plant

n 1998 Outage Ethylene 2n Installed Torlon in all three cracked gas

compressors and the ethylene compressorn 2002 outage still in specn 2007 outage still in specn All major compressors in both units are now

running polymer seals.

586

Canadian Ethylene Plant 1996 outage587

Canadian Ethylene Plant 1996 outage588

Canadian Ethylene Plant

n Historical trouble fitting the babbitt lined balance piston sealq Machined teeth off balance pistonq Went with Torlon stationary teeth

n Significant reduction in installation timen No drop in performance

589

Torlon Tooth Scrapping Tool

Relatively clean service but some seals were fouled

590

Shaft Seal as removed after 4 and 5 year runs 9 year total run time reinstalled will run another 6 years

591

Eye Seal as removed after 4 and 5 year runs 9 year total run time

592

Canadian Ethylene Plant

n Some seals were damaged when removedn These (5) were sent to vendor for analysisq All from charge gas service

n Vendor found very little drop off in propertiesq Seals ran for 9 yearsq Visually looked goodq Slight embrittlementq Tg constant no polymer degradation

593

Canadian Ethylene Plant

n Reported:q 2-3% increase per compression stage with the

installation of thermoplastic seals.q The rotating equipment specialists at the Joffre

site believe that the use of thermoplastics is important in optimizing performance, increasing run lengths, and reducing turn around costs.

594

Texas Ethylene Plantn Major ethylene producern Has six primary compressor trainsq Boosterq Charge gas (3 bodies) q Propylene refrigeration (2 bodies) q Ethylene refrigerationq Purge propyleneq Methane (2 bodies)

595

DuPont Cracked Gas Train596

DuPont Cracked Gas Train

36,000 hp turbine driving three compressor bodies

Upgraded 1st stage and 2nd/3rd stage compressors in 1999

Also upgraded both propylene, the ethylene, and the purge propylene

compressors in 1999

Upgraded last case in 2005

597

Texas Ethylene Plant

n Introduction to polymer sealsq Started investigating early 1990sq Talked to several usersq Decided to upgrade and evaluate one compressorn 10,000 hp boostern Upgraded in 1997

598

Texas Ethylene Plant

n Booster compressorq Plant can run w/o boosterq Used 3% efficiency upgrade for justificationq Installation went smoothly (only real work

performed that would effect efficiency)q After upgrade realized:n 3.1% flow increasen 2.7% steam flow reduction

q Decided to upgrade remaining compressors

599

New Polymer SealNewly Coated Rotor600

New Polymer SealNewly Coated Rotor601

Texas Ethylene PlantUsed Booster Compressor Shaft Seal

602

Texas Ethylene PlantUsed Charge Gas Compressor eye Seal

603

Texas Ethylene Plant

n Fouling more of an issue at this facilityn Replaced charge gas seals in 2003 and 2008q Too fouled and could not clean

n Inspected and reused refrigeration compressor seals in 2008q Very clean serviceq 9 year run (since 1999)q Seals in spec

604

Texas Ethylene PlantConclusions

n It is estimated that overall plant capacity increased 5% due to the polymer seal upgrades

n Reliability increased due to forgiveness of polymer seals compared to aluminum

n Plant is extremely pleased with this upgrade project

605

Conclusion

n The cases presented here represent up to 15 years of experience running polymer seals in critical turbomachinery.

n Analysis of material removed from service after 9 years demonstrated very low levels of material degradation. q Indeed other seals were reinstalled and will run for

another 6 years or longer before being reevaluated.

606

Thermoplastic Sealsn Labyrinth Sealsn Thermoplasticsn Engineering an Upgraden Upgrade payback calculationsn Case Historiesq Canadian ethylene plantq Texas ethylene plant

n Conclusions

607

DISCUSSION GROUP T1

ON

TURBOMACHINERY OPERATION AND MAINTENANCE

Joe Moreno, Coordinator

Rainer Kurz, Coordinator, is Manager of Systems Analysis and Field Testing for Solar Turbines Inc.,

in San Diego, California. His organization is responsible for conducting application studies, gas compressor

and gas turbine performance predictions, and site performance testing. He joined Solar Turbines Incorpo-

rated in 1993, and has authored more than 70 publications in the field of turbomachinery.

Dr. Kurz attended the University of the German Armed Forces, in Hamburg, Germany, where he re-

ceived the degree of a Dipl.-Ing., and, in 1991, the degree of a Dr.-Ing. He was elected as an ASME Fellow

in 2003.

Mike Pepper, Coordinator, is Chief Machinery Engineer for ExxonMobil Upstream, based in Houston,

Texas. As a Senior Consultant and mentor for the worldwide machinery community, he supports the Pro-

duction, Development and Research divisions of the company. He has 34 years O&G experience, through

working onshore, offshore, Middle East, Africa, Far East, North America, and the North Sea. He has broad

experience in Oil & Gas production, including power generation, water and gas injection, high pressure

sour gas and LNG production. He specializes in gas turbine and centrifugal compressor performance analy-

sis and currently focuses on research and qualification of new technology applications in machinery.

Mr. Pepper received a B.Sc. in Mechanical Engineering (1976) from Portsmouth, UK, and is registered

as a C. Eng, Eur Ing and a member of FEANI.

Charles R. (Charlie) Rutan is Senior Engineering Advisor, Specialty Engineering, with Lyondell

Chemical Company, in Alvin, Texas. His expertise is in the field of rotating equipment, hot tapping/plug-

ging, and special problem resolution. He has three patents and has consulted on turbomachinery, hot tap-

ping, and plugging problems all over the world in chemical, petrochemical, power generation, and polymer

facilities.

Mr. Rutan received his B.S. degree (Mechanical Engineering, 1973) from Texas Tech University. He

is a member of the Advisory Committee of the Turbomachinery Symposium, and has published and/or pre-

sented many articles.

Bryan Barrington is a 1994 graduate of Texas A&M University and currently works as a Principal

Machinery Engineer in LyondellBasells corporate engineering group. He is responsible for turbomachinery

at locations along the Texas Gulf Coast.

608

T40LTCDSLecturesT40LECT1LECT2LECT3LECT4LECT5LECT6LECT7LECT8LECT9/

LECT10LECT11LECT12

Turbo40TutorialsTUTT1TUTT2TUTT3TUTT4TUTT5TUTT6TUTT7TUTT8CONSEQUENCES OF POOR INLET FILTRATIONErosionFoulingCorrosion

FILTRATION CHARACTERISTICSFiltration MechanismsFilter Efficiency and ClassificationFilter Pressure LossFilter Loading (Surface or Depth)Face VelocityHigh Velocity SystemsLow Velocity Systems

Water and Salt Effects

COMPONENTS OF A FILTRATION SYSTEMWeather Protection and Trash ScreensAnti-icing ProtectionInertial SeparatorsMoisture CoalescersPrefiltersHigh Efficiency FiltersSelf-Cleaning FiltersStaged Filtration

OPERATING ENVIRONMENTCoastal, Marine, or OffshoreLand Based EnvironmentDesertArcticTropicalRuralLarge CityIndustrial Area

Temporary and Seasonal Contaminant SourcesSite LayoutSite Evaluation

LIFE CYCLE COST ANALYSISLife Cycle Cost BasicsConsiderations for an Inlet Filtration SystemPurchase Price/Initial CostMaintenance CostAvailability/Reliability of Gas TurbineGas Turbine Degradation and Compressor WashingPressure LossFailure/Event Cost

SUMMARY

TUTT9

Turbo40CaseStudiesCaseT1CaseT2CaseT3CaseT4In-house Engineering for Resolution of Chronic 4th Stage High Discharge Pressure Limitation on Carbon-dioxide Reciprocating Compressor Problem StatementAnalysisSlide Number 4AnalysisAnalysisAnalysisAnalysisAnalysisAnalysisSlide Number 11Conclusion

CaseT5CaseT6Advanced Vibration Analysis on Gear Box Train and vibration elimination by Udayashankar P. Eng., MBA,CMRPSuncor EnergyMachine Train configurationBrief HistoryProblem descriptionAnalysisRectificationConclusionsMachine Train ConfigurationSlide Number 4Unit DetailsBrief History-7K-20 Gear box Brief History ( Continued)Problem DescriptionSlide Number 9AnalysisAnalysisAnalysisAnalysisRectification- Action PlanEfforts MadeSlide Number 16Animation- ODS of the Gear BoxSlide Number 18Slide Number 19Slide Number 20Slide Number 21Slide Number 22Slide Number 23Gear Box Vibration Before/ After correctionConclusions

CaseT7CaseT8Investigation of Engine Vibration for Natural Gas Gathering and TransmissionBackground16-Cylinder Natural Gas Engine Mounted on Foundation at Another LocationCompare to 12-Cylinder Natural Gas Engine Mounted on SkidEquipment for Case HistoryEngine Compressor SystemVibration Measurement on Damper End of EngineVibration Measurement atMiddle of Engine FrameSummaryModel for Operating Deflection Shape (ODS) MeasurementODS Iso ViewODS Top ViewODS End ViewODS End ViewRecommendationsFinite Element Analysis (FEA)Example of Kick Brace With Insufficient Stiffness (Different Unit)Proposed Modifications Add Gussets to Skid Under EngineEngine Skid ModificationsAfter Modifications Performed

CaseT9CaseT10Slide Number 1ObjectivesContentsTurbo-Expander - ApplicationTurbo-Expander ComponentsThe Beginning of ProblemsFailure Modes ExperiencedFailure Mode 1 Axial Shuttling (Surge Failure Z12)Failure Mode 1 Axial Shuttling (Surge Failure Z12)RCA Work/ CA CompletedFailure Mode 1 - Current Status Unit #1 TECFailure Mode 2 Transfer Function ChangedAMB/Rotor Dyn TF Measuement In FieldFailure Mode 2 Transfer Function ChangedA1 - Typical Transfer Function PlotsA2 Unit #1 TF Change at High FrequencyA3 Unit #1 Controller Modified to Counter TF ChangeB1 Unit #2 TEC Unstable Vibration following TF ChangeB2 Unit #2 TF Changed at Low FrequencyB3 Unit #2 Machine Center Section Root CauseSummarySlide Number 22

CaseT11Slide Number 1Speed Signal Deterioration at High Speeds in Electronic Governor and Trip Systems 40th Turbomachinery Symposium Case StudyBackgroundDrawing of Bracket, Speed Gear and Probe ConfigurationAxial View of Speed Gear, Probes and BracketPlan View of BracketBackgroundSystem CharacteristicsSystem Characteristics (contd)Problems Appear. . .And Disappear . . .Slide Number 12Speed Signal IssuesSpeed Signal IssuesBracket Deformation Due to Thermal StressSpeed Probe Voltage OutputSpeed Signal IssuesSignal Voltage ReductionSignal Strength Reduction SummaryLessons LearnedLessons Learned (contd)Lessons Learned (contd)Lessons Learned (contd)DisclaimerBackup SlidesCalculation of Approximate Signal LossProbe Test ResultsShop Test DataSignal Before and After Patch

CaseT12Slide Number 1OutlineIntroductionProcess OverviewProcess OverviewCompressor Design & ConstructionReverse Rotation EventsCause of Reverse RotationCause of Reverse Rotation Cause of Reverse RotationPossible Impacts of Reverse RotationMitigating Actions. Phase 1 CompressorsMitigating Actions. Phase 2 CompressorsSlide Number 14Lessons LearnedConclusionsSlide Number 17Slide Number 18Slide Number 19

CaseT13Beating Effect Caused by Two Closely Spaced Mechanical Frequencies Observed on Two-Shaft, Gas Turbine Drive Two Shaft Gas Turbine ConfigurationCross section of a similar two-shaft gas turbinePhoto of Gas Turbine/Compressor EnclosurePhoto of Gas Turbine-CompressorBackground InformationVibration Response AnalysisBeating IssuesResulting Graphs: Set 1Resulting RMS Graphs: Set 2Investigation of System and AnalysisZoom Analysis Results from PT Speed SweepFrequency AnalysisThree (3) similar gas turbines at the site were running at the time of this comparative analysis. Here is a plot showing GP vibration at various locations along the three engines analyzed. Note: Turbine B below is the engine described in the case study. Notice that for some unknown reason it transmits the highest level of GP vibration to the power turbine end.SolutionConclusions and Lessons LearnedQuestions?

CaseT1440th Turbomachniery SymposiumAbstract Slide Number 2Slide Number 3Slide Number 4Slide Number 5Slide Number 6Slide Number 7Slide Number 8Hammering Test for PedestalSlide Number 10Slide Number 11Slide Number 12Slide Number 13The eigenvalue problem is solved.Slide Number 15Slide Number 16

CaseT15 (2)Thermoplastic Labyrinth Seals in Centrifugal Compressors -15 years of experiencesThermoplastic Labyrinth SealsThermoplastic Labyrinth SealsIntroductionLabyrinth SealsLabyrinth Seals Compressor SealsLabyrinth SealsLabyrinth SealsMetallic Seal Rubs Polymer Seal RubsThermoplasticsThermoplasticsThermoplasticsThermoplasticsThermoplasticsDMA Plot for Various ThermoplasticsThermoplasticsCLTE PlotRelative Thermal PropertiesThermoplasticsPEEK Chemical ResistanceTorlon Chemical ResistanceEngineeringEngineeringEngineeringTensile Strength vs. TemperatureTensile Modulus vs. TemperatureCompressive Strength vs. TemperatureUpgrade Payback CalculationsUpgrade Payback CalculationsCase HistoriesCanadian Ethylene PlantCanadian Ethylene PlantCanadian Ethylene PlantCanadian Ethylene Plant 1996 outageCanadian Ethylene Plant 1996 outageCanadian Ethylene PlantTorlon Tooth Scrapping ToolShaft Seal as removed after 4 and 5 year runs 9 year total run time reinstalled will run another 6 yearsEye Seal as removed after 4 and 5 year runs 9 year total run timeCanadian Ethylene PlantCanadian Ethylene PlantTexas Ethylene PlantDuPont Cracked Gas TrainDuPont Cracked Gas TrainTexas Ethylene PlantTexas Ethylene PlantNew Polymer SealNewly Coated RotorNew Polymer SealNewly Coated RotorTexas Ethylene Plant Used Booster Compressor Shaft SealTexas Ethylene Plant Used Charge Gas Compressor eye SealTexas Ethylene PlantTexas Ethylene Plant ConclusionsConclusionThermoplastic Seals

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