07 february 2005 m j stanway a primer on dynamic sealing or, how to keep water from messing up all...

07 February 200507 February 2005 M J StanwayM J Stanway

a primer on a primer on dynamic sealingdynamic sealing

or, how to keep water from or, how to keep water from messing up all your cool moving messing up all your cool moving

contraptionscontraptions

07 February 200507 February 2005 dynamic sealingdynamic sealing M J StanwayM J Stanway

O-ring(Parker Handbook)[McMaster 3180]

FlexiSeal(Parker Handbook)[McMaster 3244]

Magnetic Coupling(IEEE Papers)

[K&J Magnetics]

SealingMethods

STATIC DYNAMIC DYNAMIC


O-ring (static seal)O-ring (static seal)

• Specifications and help Specifications and help from from Parker O-ring Parker O-ring HandbookHandbook

• Male gland seals usually Male gland seals usually preferablepreferable

Easier to machine external Easier to machine external groovegroove

Less likely to damage seal Less likely to damage seal during assemblyduring assembly

• BUT prone to failure in BUT prone to failure in rotating applicationsrotating applications


FlexiSealFlexiSeal

• Specifications and help Specifications and help from Parker Flexi-Seal from Parker Flexi-Seal HandbookHandbook

• ““C” shaped open o-ring C” shaped open o-ring with enclosed springwith enclosed spring

• Used by SeaGrant in Used by SeaGrant in thrusters and other thrusters and other reciprocating sealsreciprocating seals

• Sold as “Spring-loaded Sold as “Spring-loaded PTFE seals” in McMaster PTFE seals” in McMaster (pg. 3244)(pg. 3244)


FlexiSeal installationFlexiSeal installation

• ““heel first” 2-part heel first” 2-part gland seal advisablegland seal advisable Open end of seal Open end of seal

faces higher pressurefaces higher pressure Easy to machineEasy to machine Easy to assemble Easy to assemble

without damaging sealwithout damaging seal

• Other options include Other options include step-cut glands step-cut glands with/without snap ring with/without snap ring retainerretainer


Magnetic CouplingMagnetic Coupling

• Good for thrusters, Good for thrusters, not high enough not high enough accuracy for accuracy for positioning actuatorspositioning actuators

• Simple concept, Simple concept, potentially difficult potentially difficult designdesign

• COMPLETELY COMPLETELY separated from fluid separated from fluid by casing materialby casing material


Magnetic CouplingMagnetic Coupling

• 2-3 manufacturers 2-3 manufacturers make something make something currently that currently that MIGHTMIGHT workwork

• WHOI uses them for WHOI uses them for thrusters on thrusters on somethingsomething

• Might be able to Might be able to design and fabricate design and fabricate our own at low costour own at low cost


MC Design ConsiderationsMC Design Considerations

• Use neodymium for high Use neodymium for high strength to volume ratiostrength to volume ratio

• Possible source: K&J Possible source: K&J Magnetics - $7.50 for 100 Magnetics - $7.50 for 100 (1/4 x 1/8 x 1/16)(1/4 x 1/8 x 1/16)

• Even number of magnets, Even number of magnets, same on inner and outer same on inner and outer rotorrotor

• Alternate poles around Alternate poles around rotorsrotors


MC Design ConsiderationsMC Design Considerations

• Rotor that sits inside Rotor that sits inside in coupling would be in coupling would be wet sidewet side allows for thin wall allows for thin wall

thickness in endcap thickness in endcap between magnets (that between magnets (that part is in tension)part is in tension)

possible quick-possible quick-disconnect propsdisconnect props

• Endcap most likely Endcap most likely AluminumAluminum


Other waterproofingOther waterproofing

• PottingPotting Solid materialSolid material InsulatesInsulates Reduction in powerReduction in power Good for sensors, not Good for sensors, not

actuatorsactuators

• Oil pressure Oil pressure compensationcompensation Can have power lossCan have power loss System can be bulky & System can be bulky &

expensiveexpensive


Seals in our ROVSeals in our ROV

Static SealsElectronics Housings

O-ring(Parker Handbook)[McMaster 3180]

Dynamic SealsManipulator

&Thrusters

FlexiSeal(Parker Handbook)[McMaster 3244]

Dynamic SealsThrusters

Magnetic Coupling(IEEE Papers)

[K&J Magnetics]

SealingMethods

questions?NOTE: pictures taken from Parker, Magnetic Technologies Ltd, Magnetic Materials and Components, and Bluefin Robotics

07 february 2005 m j stanway a primer on dynamic sealing or, how to keep water from messing up all...

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