Gas Seal Course Customer 112003 04a

11© 2003 John Crane EAA

Dry Gas SealsDry Gas Seals

Examples ofExamples of

Your SealsYour Seals


33

44

55

66

77


99

1010

1111

1212

1313

1414


1616

1717

1818





Commissioning Commissioning ProcedureProcedure

2121

Commissioning Procedure

General preparationGeneral preparation

Ensure free shaft rotation with coupling Ensure free shaft rotation with coupling

disconnecteddisconnected

Ensure Bursting Discs have been replacedEnsure Bursting Discs have been replaced

Check buffer gas system - is it on and Check buffer gas system - is it on and

functioning?functioning?

2222

Commissioning Procedure Static TestsStatic Tests

Inboard sealInboard seal Open primary leakage line valveOpen primary leakage line valve Pressurise casing incrementally to 5 bar g maximumPressurise casing incrementally to 5 bar g maximum Measure & record leakage at each increment (Page 23)Measure & record leakage at each increment (Page 23) Pressurise casing to 7 bar g (If Pressurise casing to 7 bar g (If belowbelow operating operating

pressure)pressure) Leakage should rise quickly – indicates static lift-off Leakage should rise quickly – indicates static lift-off

Outboard sealOutboard seal Close valve in primary leakage lineClose valve in primary leakage line Pressurise casing to 5 bar g maximumPressurise casing to 5 bar g maximum Measure & record interspace pressure (Page 23)Measure & record interspace pressure (Page 23)

Will gradually rise if outboard seal operating correctlyWill gradually rise if outboard seal operating correctly Depressurise outboard seal Depressurise outboard seal beforebefore compressor casing compressor casing

2323


Dynamic testDynamic test Fully open primary vent valveFully open primary vent valve Commence normal start-up proceduresCommence normal start-up procedures Gradually close primary vent valve to obtain Gradually close primary vent valve to obtain

interspace pressure of 0.5 bar ginterspace pressure of 0.5 bar g Record inboard leakage rates (Page 25)Record inboard leakage rates (Page 25) Compare against guaranteed values (Page Compare against guaranteed values (Page

8)8) Rejection criteria is 3 times guaranteedRejection criteria is 3 times guaranteed Continue recording leakage for 4 hours (at Continue recording leakage for 4 hours (at

half hour intervals)half hour intervals)

2424


Operation & MaintenanceOperation & Maintenance

Virtually no maintenance requiredVirtually no maintenance required

Continue monitoring leakage (daily)Continue monitoring leakage (daily)

Check for oil in atmospheric vent lines Check for oil in atmospheric vent lines

(monthly)(monthly)

During prolonged shutdown / staorage, During prolonged shutdown / staorage,

blank all connecting portsblank all connecting ports

2525

Examination – Test Number 2

And now for the And now for the examination!examination!

It is a multiple choice It is a multiple choice test papertest paper

PointsPoints 11 correctcorrect 00 don’t don’t

knowknow -1-1 incorrectincorrect

There may be more There may be more than one correct than one correct answer - tick them answer - tick them allall

Time allowed: 45 minutesTime allowed: 45 minutes



Installation TestInstallation Test

2727

Dry Gas Seal Installation - Test

1. What should be used to lubricate the 1. What should be used to lubricate the bore of the compressor housing?bore of the compressor housing?

A. Silicone greaseA. Silicone grease

B. Anti-seize compoundB. Anti-seize compound

C. NothingC. Nothing

2. What should be used to lubricate the 2. What should be used to lubricate the compressor shaft/rotor?compressor shaft/rotor?




2828


3. During installation, seal setting plate 3. During installation, seal setting plate screws should be:screws should be:

A. TightA. Tight

B. Slackened by 1/8 turnB. Slackened by 1/8 turn

C. Very looseC. Very loose

D. RemovedD. Removed

4. Compressor rotor should be set:4. Compressor rotor should be set:

A. In normal running positionA. In normal running position

B. Towards non-drive endB. Towards non-drive end

C. Towards drive endC. Towards drive end

2929


5. The seal should be “exercised”5. The seal should be “exercised”

A. Before installation in compressorA. Before installation in compressor

B. After installation in the compressorB. After installation in the compressor

C. It must NOT be exercisedC. It must NOT be exercised

6. A reference dimension between 6. A reference dimension between compressor rotor and compressor compressor rotor and compressor casing should be taken or checked:casing should be taken or checked:

A. Before seal installation onlyA. Before seal installation only

B. After seal installation onlyB. After seal installation only

C. Before, during and after installationC. Before, during and after installation

D. Reference dimension not importantD. Reference dimension not important

3030


7.7.If the installation tool jacking nuts become If the installation tool jacking nuts become tight:tight:

A. Use a longer spanner to give better A. Use a longer spanner to give better leverageleverage

B. Undo nuts and try to withdraw sealB. Undo nuts and try to withdraw seal

C. Stop, think, investigate, then take actionC. Stop, think, investigate, then take action

8. A failed seal should be:8. A failed seal should be:

A. Jacked out quickly as it is stopping A. Jacked out quickly as it is stopping productionproduction

B. Removed with more care than with the B. Removed with more care than with the installation of a new seal.installation of a new seal.



3232


1. What should be used to lubricate the bore 1. What should be used to lubricate the bore of the compressor housing?of the compressor housing?








3333


1. What should be used to lubricate the bore 1. What should be used to lubricate the bore of the compressor housing?of the compressor housing?


B. Anti-seize compound – very small amountB. Anti-seize compound – very small amount






3434


1. What should be used to lubricate the bore of 1. What should be used to lubricate the bore of the compressor housing?the compressor housing?








3535



A. TightA. Tight








3636



A. TightA. Tight








3737



A. TightA. Tight








3838











3939











4040











4141









4242









4343








B. Removed with more care than with the B. Removed with more care than with the installation of a new seal – it may stick!installation of a new seal – it may stick!



Dismantling andDismantling and

Re-assemblingRe-assembling

4545

Hands-on Exercise 3

S/38644S/38644 S/39397 S/39397 S/38006S/38006 S/39923S/39923T28AT+LabyT28AT+Laby T28ATT28AT Small T28ATSmall T28AT T28XPT28XP

1. Disassemble and re-assemble seal 1. Disassemble and re-assemble seal (Only disassemble/clean/assemble (Only disassemble/clean/assemble inboardinboard seal unit) seal unit)

2. Install 2. Install oneone new tolerance strip in new tolerance strip in bore of main sleevebore of main sleeve

3. Re-assemble seal3. Re-assemble seal

CC DD BB AA


Seal Failure Seal Failure AnalysisAnalysis

4747

Failure Statistics - Returned Seals

80% - significant contamination80% - significant contamination 50% - contaminant was hydrocarbon50% - contaminant was hydrocarbon

liquid from process gasliquid from process gas lube oil from bearingslube oil from bearings

10% - solids / particulates10% - solids / particulates from pipeworkfrom pipework from process gas (incorrect filtration)from process gas (incorrect filtration)

4% - chloride based from the process gas4% - chloride based from the process gas 2% - free water from the process gas2% - free water from the process gas 14% - unknown contaminants14% - unknown contaminants

4848

Hydrocarbon Contamination

Oil from bearingsOil from bearings Ensure barrier seal is fitted between seal Ensure barrier seal is fitted between seal

and bearingsand bearings Ensure barrier gas is switched on before Ensure barrier gas is switched on before

oil system (30 minute delay)oil system (30 minute delay) Ensure oil system is switched off before Ensure oil system is switched off before

barrier gas system (30 minute delay)barrier gas system (30 minute delay) ProblemProblem

High temperature from shearing liquid - High temperature from shearing liquid - mating ring fracturemating ring fracture

Burnt oil deposits block grooves and/or Burnt oil deposits block grooves and/or cause hang-up of balance diameter sealcause hang-up of balance diameter seal

4949

Hydrocarbon Contamination

Hydrocarbons from Process GasHydrocarbons from Process Gas

Efficient coalescing filtersEfficient coalescing filters

Heat the filtered gas to overcome the Heat the filtered gas to overcome the

Joule-Thompson effectJoule-Thompson effect

5050

Other Contaminants

Water - corrosion of metal and carbideWater - corrosion of metal and carbide

drop-out from process gas, often at drop-out from process gas, often at pressurised stand-still conditionspressurised stand-still conditions

Chloride CorrosionChloride Corrosion

salt water entrained in process gassalt water entrained in process gas

All can be designed for - these were all All can be designed for - these were all unexpected contaminantsunexpected contaminants

5151

Liquid Contamination

5252

Other Causes of Failure Reverse RotationReverse Rotation

face contact can occurface contact can occur bi-directional seal (Type 28BD) can be bi-directional seal (Type 28BD) can be

suppliedsupplied occasional low speed acceptable with occasional low speed acceptable with

Type 28AT and Type 28XPType 28AT and Type 28XP Reverse PressureReverse Pressure

face contact can occurface contact can occur at high speeds - mating ring fractureat high speeds - mating ring fracture can be designed for static reverse can be designed for static reverse

pressurepressure consider pressurised double sealconsider pressurised double seal

5353

Other Causes of Failure Incorrect FittingIncorrect Fitting

axial alignment axial alignment (working length ± 0.5 (working length ± 0.5 mm)mm)

rotor in correct positionrotor in correct position accurate shimsaccurate shims

contamination from fitting lubricantscontamination from fitting lubricants incorrectly fitted tolerance ringsincorrectly fitted tolerance rings damaged o-rings / polymer ringsdamaged o-rings / polymer rings

O-ring damage during runningO-ring damage during running chemical attackchemical attack thermal attackthermal attack explosive decompressionexplosive decompression

5454

Contact Damage

Mating Rings

Not acceptable.Not acceptable.Must be replaced.Must be replaced.Investigate HOW / WHY?Investigate HOW / WHY?

5555

Mating Rings

5656

Mating Rings

5757

Mating Ring Contact - Causes

5858


No liftNo lift Forced contactForced contact

5959


No liftNo lift Forced contactForced contact

Hang-upHang-upBlocked groovesBlocked grooves

DirtDirt

Blocked filterBlocked filterWrong filter sizeWrong filter sizeNo filterNo filter

Why/How?Why/How?

Check control systemCheck control system

Before start-up.Before start-up.Settle-out pressureSettle-out pressure

Start-upStart-upproceduresprocedures

Typical Example Typical Example of a Failure of a Failure Analysis Root Analysis Root Causes TreeCauses Tree

InstallationInstallation(Exercise?)(Exercise?)

Chemical attackChemical attackBal. diameter o-ringBal. diameter o-ring

Thermal attackThermal attackBal. diameter o-ringBal. diameter o-ring

CondensateCondensate

Joule-Thompson?Joule-Thompson?

Dew pointDew point

Bal. diameter wearBal. diameter wear

MisalignmentMisalignment

Thrust wornThrust wornDirtDirt

CokeCoke

Bearing OilBearing Oil

Buffer gasBuffer gassupply & timingsupply & timing

Labyrinth or Type 82Labyrinth or Type 82

ClearancesClearances

6060


Forced contactForced contact

Hang-upHang-up

AssemblyAssembly

Reverse rotationReverse rotation

TurbiningTurbining

Driver reversalDriver reversal

Wrong sealWrong seal

Thermal GrowthThermal Growth

No liftNo lift

Typical Example Typical Example of a Failure of a Failure Analysis Root Analysis Root Causes TreeCauses Tree

InstallationInstallation

Shim sizeShim size& position& position

Seal at correct end?Seal at correct end?

Reverse pressureReverse pressure

Check flare pressureCheck flare pressure

Check operating Check operating proceduresprocedures

Check buffer Check buffer gas pressuregas pressure

Thrust bearingThrust bearing

Check DE/NDE biasCheck DE/NDE bias

Check position Check position and conditionand condition

Was rotor in running position Was rotor in running position when seals were installed?when seals were installed?

6161

Mating Rings

Not acceptable, especially with Silicon Carbide.Not acceptable, especially with Silicon Carbide.Must be replaced.Must be replaced.Investigate HOW / WHY?Investigate HOW / WHY?

Chips xx

xx

xx

6262

Mating Rings

Heat Checking

Very rare, but can be Very rare, but can be seen on tungsten seen on tungsten carbide. Not acceptable.carbide. Not acceptable.Must be replaced.Must be replaced.Investigate HOW / WHY?Investigate HOW / WHY?

6363

Mating Rings

6464

Mating Rings

Pitting

Tungsten carbide can be Tungsten carbide can be attacked by contaminants. attacked by contaminants. Can sometimes be re-Can sometimes be re-lapped.lapped.In most cases, will have to In most cases, will have to be replaced.be replaced.Investigate HOW / WHY?Investigate HOW / WHY?

6565

Mating Rings

Chloride attack on Chloride attack on Tungsten CarbideTungsten Carbide

6666

Mating Rings - Chloride Attack

6767

Mating Rings

Groove Deposits

Can be cleaned, but Can be cleaned, but usually needs re-lapping usually needs re-lapping and re-grooving.and re-grooving.Check for heat-crazing Check for heat-crazing and contact.and contact.Investigate HOW / WHY?Investigate HOW / WHY?

6969

Primary Ring

Contact

Contact is unacceptable. Contact is unacceptable. Can cause excessive heat, Can cause excessive heat, melting the metal filler in melting the metal filler in the carbon.the carbon.Must be replaced.Must be replaced.Investigate HOW / WHY?Investigate HOW / WHY?

7070

Showing Inside Diameter Primary Ring/Mating Ring Contact

Primary Ring

Not acceptable. Replace Primary Ring.Not acceptable. Replace Primary Ring.Investigate HOW / WHY?Investigate HOW / WHY?

7171

Showing large particle marking. The face must be lapped backShowing large particle marking. The face must be lapped backto remove all trace, checked for thickness and re-processed.to remove all trace, checked for thickness and re-processed.

Probably needs replacing.Probably needs replacing.Investigate HOW / WHY?Investigate HOW / WHY?

Primary Ring Damage

7272

Showing light gramaphoning with no depth, due to particles.Showing light gramaphoning with no depth, due to particles.Cosmetic, and acceptable.Cosmetic, and acceptable.

Cosmetic Marks

7373

Primary Ring

Normal Wear

Acceptable Acceptable “scuffing” marks.“scuffing” marks.

Radial scratches Radial scratches must be lapped must be lapped out.out.

7474

Showing light circumferential marks caused by particles Showing light circumferential marks caused by particles trapped between seal and facetrapped between seal and face

Cosmetic Marks

7676

Showing scuffing where particles have passed through the Showing scuffing where particles have passed through the seal.seal.

This is acceptable.This is acceptable.

Cosmetic Marks

7777

Showing surface discolouration which is due to the manufactureShowing surface discolouration which is due to the manufactureof the primary ring blank.of the primary ring blank.

This is acceptable.This is acceptable.(Not to be confused with oil blistering).(Not to be confused with oil blistering).

Cosmetic Marks

7878

Primary Ring

Radial Cracks

This is rare. Check that it This is rare. Check that it is a crack and not a is a crack and not a scratch. Must be scratch. Must be replaced.replaced.Investigate HOW / WHY?Investigate HOW / WHY?

7979

Primary Ring

Chipping

VeryVery small chips on the ID of the carbon are small chips on the ID of the carbon are acceptable provided they can be blended in.acceptable provided they can be blended in.

Small chips on the OD are acceptable provided they Small chips on the OD are acceptable provided they can be blended in.can be blended in.

Large chips require the primary ring to be replaced.Large chips require the primary ring to be replaced.

Investigate HOW / WHY?Investigate HOW / WHY?

BlendBlend

8080

Showing a small chip which may be blended out and accepted. Showing a small chip which may be blended out and accepted.

Chips

8181

Showing a larger chip encroaching onto the sealing dam.Showing a larger chip encroaching onto the sealing dam.Primary Ring must be replaced.Primary Ring must be replaced.


Chips

8282

Primary Ring

Oil Blisters

Not acceptable.Not acceptable.Must be replaced.Must be replaced.Investigate HOW / WHY?Investigate HOW / WHY?

8383

Labyrinth – Chloride Attack

8484

Type 28XP Carrier - Contact

8585

O-Rings

Nicks and Cuts

8686

O-Rings

Explosive Decompression

8787

O-Rings

Thermal Damage

8989

Polymer Seals

Better explosive decompression and corrosion resistanceBetter explosive decompression and corrosion resistance

They require careful handling.They require careful handling.

9090

Sliding Damage

Polymer Seals

Typical of damage to Typical of damage to be found on seal OD be found on seal OD polymer rings in Type polymer rings in Type 28XP seals.28XP seals.Must be replaced.Must be replaced.

Investigate HOW / Investigate HOW / WHY?WHY?

9191

Damaged Spring

Polymer Seals

Spring holds seal open to Spring holds seal open to enable pressure to enable pressure to energise the seal.energise the seal.Must be replaced.Must be replaced.


9292

Metal Parts

Scored Bore Check critical areas Check critical areas (o-ring grooves, (o-ring grooves, tolerance ring grooves tolerance ring grooves and landings).and landings).

Polish out marks with Polish out marks with fine emery paper, but fine emery paper, but do not damage edges do not damage edges of tolerance strip of tolerance strip grooves.grooves.

Check compressor Check compressor shaft and clean up shaft and clean up carefully.carefully.

Check that correct Check that correct lubricant is being used, lubricant is being used, and used sparingly.and used sparingly.

Investigate HOW / Investigate HOW / WHY?WHY?

9393

Galling

Metal Parts

Often caused by Often caused by misalignment during misalignment during fitting or removal.fitting or removal.

Check condition of Check condition of compressor shaft and compressor shaft and take remedial action.take remedial action.

Repair may be possible, Repair may be possible, but distortion may but distortion may cause problem to re-cause problem to re-occur.occur.

Replacement is Replacement is generally advisedgenerally advised

9494

Metal Parts

Dents, bumps, hammer marks, distortion

Bore must be perfectly

round

SquareSquare

ParallelParallel

9595

Metal Parts

Fretting and Pitting

Contaminants in the gas can cause pitting.Contaminants in the gas can cause pitting.

The balance diameter is critical and pitting is not The balance diameter is critical and pitting is not acceptable.acceptable.

Must be replaced.Must be replaced.


9696


CC

AA

TT

leanlinessleanliness

ccuracyccuracy

imeime

9797

Dry Gas Seals

When:When:

1.1. Installing a sealInstalling a seal2.2. Removing a sealRemoving a seal3.3. Disassembling a sealDisassembling a seal4.4. Assembling a sealAssembling a seal

STOPSTOP if anything starts to get tight if anything starts to get tight

9898


leanlinessleanlinessCC

AA

TT

SS

ccuracyccuracy

imeime

top!!top!!

9999

Apply “CATS” and you can . . .

Produced by John BlaberProduced by John Blaber


Technology Technology DevelopmentsDevelopments

MaterialsMaterials

102102

High ModulusHigh Modulus

Good dry frictionGood dry friction

Homogeneous materialHomogeneous material

Good Thermal conductivityGood Thermal conductivity

Lower internal stressesLower internal stresses

Higher StabilityHigher Stability

Fracture ToughnessFracture Toughness

Existing Existing CarbonCarbon

Desirable AttributesDesirable Attributes SiliconSilicon

CarbideCarbide

Diamond like coatingDiamond like coating

Cranite Primary Ring Material

103103

Cranite Material - Attributes

Composite of Silicon Carbide & CarbonComposite of Silicon Carbide & Carbon High elastic modulusHigh elastic modulus

Reduced radial and toroidal deflectionsReduced radial and toroidal deflections

High thermal conductivityHigh thermal conductivity Reduced thermal distortionsReduced thermal distortions

High stabilityHigh stability Negligible residual distortionNegligible residual distortion

Good dry frictionGood dry friction Retains excellent carbon performanceRetains excellent carbon performance

104104

High ModulusHigh Modulus

Good dry frictionGood dry friction

Homogeneous materialHomogeneous material

Good Thermal conductivityGood Thermal conductivity

Lower internal stressesLower internal stresses

Higher StabilityHigher Stability

Fracture ToughnessFracture Toughness

Existing Existing CarbonCarbon

Desirable AttributesDesirable Attributes SiliconSilicon

CarbideCarbide

Diamond like coatingDiamond like coating

Cranite 2000CraniteCranite

20002000

105105

Cranite 2000 - Benefits Higher pressure capabilityHigher pressure capability

Controlled face distortionControlled face distortion Controlled radial deflectionsControlled radial deflections Reduced operating gapReduced operating gap Stiffer fluid filmStiffer fluid film

Reduced leakageReduced leakage Highly stable, repeatable at any pressureHighly stable, repeatable at any pressure

Excellent stop/start face performanceExcellent stop/start face performance No need for coatingNo need for coating

Field serviceableField serviceable

107107

Cranite 2000 DevelopmentDynamic IB leakages, cranite versus carbon faces @ 6000 rpm.

0

20

40

60

80

100

120

140

20 40 80 120 160 200Pressure / bar g.

Le

ak

ag

es

/ l

.min-1

Cranite 2000

Carbon

Dynamic Tests - Leakage Comparison

109109

Cranite Stop-Start & Slow Roll Tests Over 2100 stop-start cycles ( spring load )Over 2100 stop-start cycles ( spring load ) Over 50 hrs slow-roll @ 100 rpm Over 50 hrs slow-roll @ 100 rpm

0

1000

2000

3000

4000

0 5 10 15Time (min)

Sp

ee

d (

rpm

)

110110

Improved Silicon Carbide Material Increased TRS - 25%Increased TRS - 25% Increased fracture toughness - 40%Increased fracture toughness - 40% Improved availabilityImproved availability Adopted as Preferred Standard SiC Q1/99Adopted as Preferred Standard SiC Q1/99

111111

> Cranite FacesCranite Faces

> Improved seat material

Large Diameter Cranite Seal Tests

10.375” seal for Nam Groningen10.375” seal for Nam Groningen

112112

Improved Carbon 6 Month Development program6 Month Development program

Carbons tested to 250 barCarbons tested to 250 bar Residual distortion measuredResidual distortion measured Improved grade reduced distortion by 70 %Improved grade reduced distortion by 70 %

Carbon 1 Carbon 2 Carbon 3 OriginalCarbon

5.437"

7.125"

Re

sid

ua

l d

isto

rtio

n L

ev

el

113113

Improved Carbon Material Improved processingImproved processing

Reduced PrepressurisationReduced Prepressurisation

Less residual distortionLess residual distortion More uniform presentation angleMore uniform presentation angle Higher StabilityHigher Stability Reduced sensitivityReduced sensitivity

Improved reliabilityImproved reliability More stable leakageMore stable leakage Face shadowing eliminatedFace shadowing eliminated

114114

Improved Carbon Tested on pilot jobs Q3/98Tested on pilot jobs Q3/98

Introduced on high pressure jobs Q4/98Introduced on high pressure jobs Q4/98

Adopted as standard for all Adopted as standard for all seals Q1/99seals Q1/99

Improved production processImproved production process Prepressurisation offlinePrepressurisation offline Cycle time reduced Cycle time reduced

from 3 days to 3 hoursfrom 3 days to 3 hours

Documents

Gas Seal Course Customer 112003 04a