Transcript a primer on dynamic sealing - MIT's Remotely

a primer on dynamic
sealing
or, how to keep water from messing up all
your cool moving contraptions
07 February 2005
M J Stanway
Sealing
Methods
O-ring
(Parker Handbook)
[McMaster 3180]
STATIC
07 February 2005
FlexiSeal
(Parker Handbook)
[McMaster 3244]
DYNAMIC
dynamic sealing
Magnetic Coupling
(IEEE Papers)
[K&J Magnetics]
DYNAMIC
M J Stanway
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
07 February 2005
dynamic sealing
M J Stanway
FlexiSeal
•
•
•
•
07 February 2005
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
M J Stanway
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
07 February 2005
dynamic sealing
M J Stanway
Magnetic Coupling
•
•
•
07 February 2005
Good for thrusters,
not high enough
accuracy for
positioning actuators
Simple concept,
potentially difficult
design
COMPLETELY
separated from fluid
by casing material
dynamic sealing
M J Stanway
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
07 February 2005
dynamic sealing
M J Stanway
MC Design Considerations
•
•
•
•
07 February 2005
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
M J Stanway
MC Design Considerations
•
Rotor that sits inside
in coupling would be
wet side


•
07 February 2005
allows for thin wall
thickness in endcap
between magnets (that
part is in tension)
possible quickdisconnect props
Endcap most likely
Aluminum
dynamic sealing
M J Stanway
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
07 February 2005
dynamic sealing
M J Stanway
Seals in our ROV
Sealing
Methods
O-ring
(Parker Handbook)
[McMaster 3180]
FlexiSeal
(Parker Handbook)
[McMaster 3244]
Magnetic Coupling
(IEEE Papers)
[K&J Magnetics]
Static Seals
Electronics Housings
Dynamic Seals
Manipulator
&
Thrusters
Dynamic Seals
Thrusters
questions?
NOTE: pictures taken from Parker, Magnetic Technologies Ltd, Magnetic Materials and Components, and Bluefin Robotics
07 February 2005
dynamic sealing
M J Stanway