Post on 04-Apr-2018
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Advancements in Dynamic Sealing Technology
Mechanical SealsOil Seals Bearing I solators
David C. Rober t s, P.E.
I ndust rial Engineer
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By the end of todays discussion we will be
1. What are the 3 most common dynamic sealing
2. What is the primary theory of operation behindradial lip seal technology?
3. How have advancements in elastomer material
science improved radial lip seals?
4. What are the advantages to utilizing bearing
isolator technology?
5. What is the key limitation of both labyrinth seals &bearing isolators?
6. What is the primary application for mechanical
7. What is one of the critical factors in successfulmechanical seal applications?
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Dynamic Sealing Applications
Differ from static sealing applications in that the equipments mov ng
Static sealing applications may have fluid movement, butthe machine members do not move
The most common dynamic sealing application is a rotary
machine i.e. a shaft rotates as it is supported by bearings Reciprocating applications are less common i.e. a
hydraulic application where a shaft strokes through aho sin
Our focus today will be on rotating applications
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Dynamic Sealing ApplicationsSome dynamic sealing applications
There are many, many more !
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Dynamic Sealing ApplicationsThe basics
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What are the 3 most common dynamic
Mechanical SealsRadial Lip Seals Bearing I solators
a a p ea s a. .a. o sea s; uses ynam c ru er p to engage s a tsurface
Bearing I solat ors Hybrid labyrinth seal design, provides non-contact
Mechanical Seals Utilize hard mechanical faces (and other technologies)to provide a high pressure seal for severe sealing applications
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Radial Lip Seal Theory of Operation Hydrodynamic sealing
between shaft & seal lip Oil film (meniscus) is actual seal
Oil film reduces wear, friction,
and power consumption m epen ent on sea p
geometries & shaft surfaceconditions
en m s no presen , grea erseal wear (abrasion) occurs
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Radial Lip Seal Theory of Operation The shaft surface finish isCRI TI CAL to li seal erformance
Seal Dam Most lip seals require a 10-20 inRa shaft surface finish (some designsrequire finer surfaces)
LubricationEnvironment
Surface hardness must be no lessthan 30 Rockwell C (some designs
require harder surfaces)
Meniscus
(0.00018)
(0.0046mm)
perpendicular to the axis of shaftrotation
a
the peaks-n-valleys of the finishedsurface
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Elastomer Material Science
Commonly used lip seal materials are:Nitrile Rubber NBR acr lonitrile butadiene
Hydrogenated Nitrile (HNBR)
Silicone (VMQ)
Fluoroelastomer (FKM, commonly called Viton)
Common formulations
Easy to manufacture
Large allowable tolerance
Engineered ElastomersSpecialized formulation
More difficult to manufacture
Emphasis of performance
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Elastomer Material Science
Engineered Elastomers focus on improving
Factors include:Chemical compatibility
emperature res stance
Abrasion resistance
Retention of physical properties over time
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Improving Elastomer Abrasion Resistance
Taber Wear Test measures abrasion resistance:
A precisely measured disc is subjected to a grindingprocess for a specific number of cycles
The amount of material lost is measured and compared toother samples
The lower the taber wear number the better
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Improving Elastomer Abrasion Resistance
Advances in elastomer formulations have lead tosi nificant im rovements in abrasion resistance
Better abrasion resistance leads to longer seal lifeand thus longer equipment uptime (MTBF)
NBR elastomerimprovements:
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Improving Elastomer Abrasion Resistance
Improvements in HNBR & FKM elastomers:
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Improvements in Retention of Mechanical
Focus on retention of propertiesin service 25
Hardness Change (points)
Examines:HardnessTensile Strength -5
0
5
10
15
20
Tensile Change (%)Taber Wear Factor*
% Elongation
Wear Width
Abrasion Resistance
How well are these ro erties
-25
-20
-15
-10
maintained over time?Elongation Change (%)Wear Width (in (x100))
Volume Change (%)
Mill-Right N (48713)Nitrile (49706)
Perfection
* ASTMD4060 Taber Wear Index Factor
ASTM 903 Oil Immersion (70hrs @ 200F (93C))
KLOZURE 4-Hour Dry Run
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Bearing Isolators Non-contact seals
Tradit ional Labyrint h Seal Uses complex pathway to separate
Bearing I solator Seal Uses basic labyrinth technology
Rotor moves with shaft, while statorremains static in bore
,differential, and drain back designs tomaximize sealing effect
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Advantages of Bearing Isolator Seals
Can run on soft shaft materials
or finer Can run dry
rov e ot o retent on ancontaminant exclusion
Reduce power losses due to friction
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Bearing Isolator provide significant power
Testing conducted at Garlock shows
at start up and 285 watts in normaloperation
consume 150 watts at start up and 120watts during normal operation
service life of bearing isolators can beup to 65 times longer than that oftraditional li seals
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Advances in Bearing Isolator Technology
Bearing isolator incorporating
For use in very dirty, dustyenvironments
contamination, preventing
migration into bearing system
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Advances in Bearing Isolator Technology
Split bearing isolators
without costly equipment teardown
to repair (MTTR)
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Limitations to bearing isolator technology
Because bearing isolators are,
they are subject to a commonlimitation:
Shaft
LABYRINTH SEALS CANONLY BE USED IN NON-FLOODED APPLICATIONS
Level
Oil
Oil level must be below lowestopening in labyrinth pathway
Housing
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Limitations to bearing isolator technology
Examples of flooded applications:
Shaft
Submerged
Oil LevelShaft Garlock isOil
Level
developing aflooded isolat or
design!
Housing Housing
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Mechanical Seals
The primary applications for
stuffing boxes Often replaces compression
applications
Other applications includes, ,rotary fans, food processingequipment, and more
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Mechanical Seals
Stuffing Box ImpellerDischarge
Bearing Frame
Suction
Mechanical Seal
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Mechanical Seals
Most mechanical seal designs
faces to form a dynamic seal Faces must be lapped very
bands)
Common materials used are, ,
silicon carbide
Elastomers form internal static
Springs or metal bellows load theseal
Basic Mechanical Seal Design
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Mechanical Seals
More specialized designs use
Hardened sleeve providesrunning surface for lips
Garlock PS-II Design
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Critical factor for mechanical seal
One of the most critical factors
performance are the PROCESSCONTROLS used to regulate theseal
Various types of process controlinclude:Barrier Fluids
Buffer Fluids
Controlled Flush
Controlled Quench
Convection SystemsQuench & Drain
Stand pipes
Example of Convection System
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Review
1. What are the 3 most common dynamic sealing technologies?
Radial Lip Seals, Bearing Isolators, Mechanical Seals
. a s e pr mary eory o opera on e n ra a p sea
technology? Hydrodynamic Sealing3. How has improvement in elastomer material science improved
of physical properties
4. What are the advantages to utilizing bearing isolator technology?
Non-contact seals, dry running, reduced power consumption
5. What is the key limitation of both labyrinth seals & bearingisolators? Cannot be used under flooded conditions
6. What is the primary application for mechanical seals? Pump
stu ng oxes7. What is one of the critical factors in successful mechanical seal
applications? Process controls
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For more information...
GARLOCK SEALING TECHNOLOGIES
PALMYRA, NY 14522
Ph: 1-877-427-5625
. .
www.garlock.com
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