Transcript Document

MAGSEAL 101
DESIGN INFORMATION
Rotary face seal that utilizes magnetic attraction force to
positively mate the optically flat seal faces.
Magnetic attraction force variation is kept to a minimum as it
controlled by the internal air gap for maximum service life.
Magnet is magnetized through the diameter so that the magnetic
circuit is closed at the outside diameter of the seal case. It is
directionalized (anisotropic) for maximum magnetic energy and
stability.
Components are freely mounted on elastomers that prevent seal
face distortion and are positive secondary seals. They secure the
magnet in the housing or retainer, provide rotation of the seal case
and dampen system vibrations.
Axial shaft movement is taken up by the rolling action of the seal
case o-ring within the groove.
Radial shaft movement can be accomplished increasing the
diametrical clearances to ensure positive seal ring contact.
O-ring quality in accordance with AS 871 for positive secondary
seal.
Temperature range is limited by the elastomer
Special designs available for high pressure or pressure reversal or
large axial shaft movement.
1.
The magnet ring is magnetized through the diameter so that the magnetic circuit (flux) is closed at the outside
diameter of the seal case. The flux lines extend radially from the magnet’s outside diameter to the outside
diameter of the seal case and this magnetic circuit results in only minor stray flux.
2.
The magnetic attraction force applies a mechanical load on the seal case mating face (seal ring) to ensure
positive contact when there is no applied system pressure.
3.
In order for any ferrous debris to be attracted into this magnetic field it must pass though this field due to
either oil flow or gearbox windage. The magnetic field strength degrades to less than 3 gauss at a distance of
.5 (12.7 mm) for a typical gearbox MAGSEAL. Any debris that becomes entrapped in this magnetic field will
be retained and therefore prevented from migrating to the primary mating face.
4.
The seal case o-ring friction drive is designed so that a significant force (greater than the magnetic attraction
force) is required to slide the o-ring along the shaft.
STRAIGHT HOUSING BORE
O-ring roll or twist during installation may prevent the magnet/mating ring from
seating squarely against the bore shoulder thus putting the mating face out of square
relative to the axis of rotation (shaft). Seal leakage as a function of shaft speed is
indicative of an out of square mating face.
REVERSE TAPER DESIGN
TAPER ON MAGNET
TAPER IN HOUSING
Compression force from o-ring provides a resultant axial force to seat the magnet
squarely against the shoulder
HIGH PRESSURE MODEL 20
Higher pressures require that the seal ring mating face be in the balanced
condition. Balanced condition is achieved by making the seal ring contact
area (seal ring OD to seal ring ID) greater than the area exposed to pressure
(seal ring OD to shaft balance diameter).
PRESSURE REVERSAL
P1
Pressure greater
than P2 or 30 PSI
max less than P2
P2
Pressure 30 PSI
max greater than
P1 or less than P1
Magnet is retained in the housing
with a non-magnetic retaining ring.
The seal case drive o-ring contacts
an external shoulder.
The hydraulic force from the
system pressure acting on the seal
ring mating face is always positive
(closing the seal face) regardless of
which side has the higher pressure.
STANDARD MAGSEAL
AXIAL SHAFT
MOVEMENT .010
SPECIAL MAGSEAL
LARGE AXIAL SHAFT MOVEMENT
UP TO .05 WITH LARGER CROSS
SECTION O-RING AND SPECIAL
GROOVE WIDTH ALLOWS O-RING
TO ROLL WITHIN GROOVE WHILE
PROVIDING POSITIVE ROTATION
AND SEAL FACE CONTACT.
SEAL DESIGN / PERFORMANCE COMPARISON
MAGSEAL
STAMPED CUP
MECHANICAL SEAL
LOW UNIT (FACE) LOAD WITH MINIMUM
VARIATION DUE TO INTEGRAL MAGNET
ATTRACTION FORCE, REDUCES POWER
CONSUMPTION, HEAT GENERATION AND
THEREFORE INCREASES SEAL LIFE.
HIGH UNIT (FACE) LOAD (30%-50% GREATER) WITH
LARGER VARIATION DUE TO COMBINATION OF
INTEGRAL SPRING AND OPERATING LENGTH
TOLERANCE, INCREASES POWER CONSUMPTION, HEAT
GENERATION, AND THEREFORE REDUCES SEAL LIFE.
EFFICIENT HEAT DISSIPATION DUE TO THE USE OF
MATERIALS WITH A HIGH COEFFICIENT OF
THERMAL CONDUCTIVITY AND CONSTANT OIL
CIRCULATION FROM THE ROTATION OF THE SEAL
CASE.
SPRING CAVITY TRAPS OIL THAT CAN TURN INTO COKE
WHICH COMPROMISES THE EFFECTIVENESS OF THE
WAVE SPRING AND THE O-RING DUE TO THE LARGE
MASS OF CARBON WHICH HAS A LOW COEFFICIENT OF
THERMAL CONDUCTIVITY.
MOUNTED ON ELASTOMERS THAT DO NOT
ADVERSELY AFFECT SEAL FLATNESS AS WELL AS
DAMPING SYSTEM VIBRATIONS THUS
ELIMINATING SEAL FACE CHATTER AND WEAR.
MATING RING IS CLAMPED WHICH MAY ADVERSELY
AFFECT FLATNESS AS WELL AS TRANSMITTING SYSTEM
VIBRATIONS DIRECTLY TO THE SEAL FACE THUS
RESULTING IN SEAL FACE CHATTER AND WEAR.
TYPICAL MAGSEAL MILITARY AND
COMMERCIAL AIRCRAFT APPLICATIONS
Missile and Small Engine Main Shaft
Engine and Air Frame Accessory Gearboxes
Main Transmissions
Intermediate and Tail Rotor Gearboxes
Auxiliary Power Units
Starter Motors and Pneumatic Starters
Generators and Alternators
Air Drive Units and Air Turbine Motors
Constant Speed Drives
Fuel Pumps and Controls
Hydraulic Pumps and Motors
Wing Flap and Slat Actuators