Magnetic liquid rotary seals
The
Principle of Magnetic Liquid Seals
Among the numerous effects specific to magnetic liquids, such as levitation,
selflevitation, surface instabilities, movement induced by a rotating
magnetic field etc., in the case of magnetic liquid seals the most important
is the possibility of positioning of a certain quantity of magnetic liquid
by a nonuniform magnetic field.
The magnetic force proportional to the field gradient and the liquid magnetization,
will maintain the magnetic liquid in the prescribed space, against forces
due to gravitation, centrifugal effects or pressure differences.
The gap between the rotating shaft and the fixed part of the seal, which
is included in the magnetic circuit of a permanent magnet, a strongly
nonuniform magnetic field is created.
The magnetic liquid introduced in the gap will take the form of "O"
rings around the shaft, perfectly sealing the space between the parts
in relative movement.
The magnetic liquid seals may be used only for gases. They are unchangeable
in the cases when one need a perfectly tight vacuum feed through or a
perfect rotating seal for toxic, radioactive or very expensive gases at
moderate pressures.
Magnetic
liquid presentation ( video)