View
13
Download
0
Category
Preview:
DESCRIPTION
Thermoplastic Labyrinth Sealsin Centrifugal Compressors -15 years of experiences
Citation preview
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
Return Channel
Diffuser
Note: Arrows denote leakage paths.
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
As Installed
' 1
During Rub
Galled Shaft
After Rub
Polymer Seal Rubs562
As Installed
During Rub
After Rub
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
., :::s :::s
"C o_ ::E -U>
(.)~ --E S c
~ c
1400 1200 1000 800 600 400 200
0 -100 0 100 200 300 400
Temperature (F) - PEEK (15%CF) -Torlon (O%CF) - Tori on (30% CF) - Fluorosint
500 1600
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
-~50 ~--------------------------~---------~ // ~@~----------------~/~~-----LL 30 / / ~ +=~;;;;~=~~~~;;~L~===:_== :E 20 c;
- - - - - - -- - ~ - - - -- -~ 10+---------------------------------------
-w 0 +----~. --~.~--~.----~.----~. ----~,--~,--~, 1-...J -200 0 -100 0 100 200 300 400 500
Temperature (F)
1- Torlon - - Aluminum - PEEK(30%CF) - PEEK(15/oCF) I
Relative Thermal Properties571
800
600
F 400
200
0 Tm HOT Tg
Torlon
CUT PEEK
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
40,000 -,----~------------------------- -- .._ ; ~
~. 30000+------------------~~,-------------------------.r:. ' .
~ ' ~ 20,000 +----------------------__.._, ____________________ _ ~ ' ~ - ' ~ 10,000 ~~~~~~~~~~~~-~~~~~~~~~~~~~~~~~~~~~~~~~~
0 +-----~----~----~~----~----~----~.----~ 0 100 200 300 500 600 700
Temperature (F)
1- Torlon - PEEK (30 /o CF) - - Aluminum - PEEK (15% CF) I
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
TurboDG_TurboDGTSC_Layout 1Turbo40TACProfessional Staff_Layout 1Turbomachinery Laboratory
Recommended