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a primer on dynamic sealing

a primer on dynamic sealing. or, how to keep water from messing up all your cool moving contraptions. STATIC. DYNAMIC. DYNAMIC. O-ring (static seal). Specifications and help from Parker O-ring Handbook Male gland seals usually preferable Easier to machine external groove

Samuel
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a primer on dynamic sealing

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  1. a primer on dynamic sealing or, how to keep water from messing up all your cool moving contraptions M J Stanway

  2. STATIC DYNAMIC DYNAMIC dynamic sealing

  3. O-ring (static seal) • Specifications and help from Parker O-ring Handbook • Male gland seals usually preferable • Easier to machine external groove • Less likely to damage seal during assembly • BUT prone to failure in rotating applications dynamic sealing

  4. FlexiSeal • Specifications and help from Parker Flexi-Seal Handbook • “C” shaped open o-ring with enclosed spring • Used by SeaGrant in thrusters and other reciprocating seals • Sold as “Spring-loaded PTFE seals” in McMaster (pg. 3244) dynamic sealing

  5. FlexiSeal installation • “heel first” 2-part gland seal advisable • Open end of seal faces higher pressure • Easy to machine • Easy to assemble without damaging seal • Other options include step-cut glands with/without snap ring retainer dynamic sealing

  6. Magnetic Coupling • Good for thrusters, not high enough accuracy for positioning actuators • Simple concept, potentially difficult design • COMPLETELY separated from fluid by casing material dynamic sealing

  7. Magnetic Coupling • 2-3 manufacturers make something currently that MIGHT work • WHOI uses them for thrusters on something • Might be able to design and fabricate our own at low cost dynamic sealing

  8. MC Design Considerations • Use neodymium for high strength to volume ratio • Possible source: K&J Magnetics - $7.50 for 100 (1/4 x 1/8 x 1/16) • Even number of magnets, same on inner and outer rotor • Alternate poles around rotors dynamic sealing

  9. MC Design Considerations • Rotor that sits inside in coupling would be wet side • allows for thin wall thickness in endcap between magnets (that part is in tension) • possible quick-disconnect props • Endcap most likely Aluminum dynamic sealing

  10. Other waterproofing • Potting • Solid material • Insulates • Reduction in power • Good for sensors, not actuators • Oil pressure compensation • Can have power loss • System can be bulky & expensive dynamic sealing

  11. Seals in our ROV questions? NOTE: pictures taken from Parker, Magnetic Technologies Ltd, Magnetic Materials and Components, and Bluefin Robotics dynamic sealing

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