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The Omnitrol Pneumatic Liquid Level Control is a
magnetically actuated precision-made on/off pneumatic
instrument, which incorporates the use of a magnetically
controlled switch actuator in conjunction with specific
displacer configurations to provide liquid level indication and
control. It is designed to operate under the corrosive and
vibrating conditions associated with petrochemical industrial
applications such as scrubber level control on level gas
compressors for maintaining specific liquid levels and/or for
high or low safety alarm indication.
The air switch can be supplied with any single stage (600
series) Omnitrol unit, with the exception of the Series 250.
With the use of an adaptor kit it may be field retrofitted to
any standard housing electric switch unit.
The air switch is mostly commonly used for applications
such as those found in offshore drilling and in the area of
gas compression and compressor protection. In addition,
the air switch is well suited where electrical power is not
available or where hazardous conditions exist. The positive
magnetic coupling allows this unit to be used in areas of
high vibration. The fast action and large port size provides
fast response to liquid level changes. The three port, nonbleed
design also conserves instrument air, or gas.
At low liquid level, the magnet arm is tilted upward. In a
direct acting control as illustrated, the magnet arm forces
the actuating screw to push down against the actuating
arm, which forces the ball to seal against the supply port.
The output port is open to exhaust. This position is held by
the “Constantly Engaged Magnetic Field”. As the liquid
level rises, the inner magnet assembly rises and forces its
way through the outer magnetic field. The sudden reversal
of the magnetic field causes the magnet arm to move down
which opens the supply pressure to the output and closes
the exhaust.
The control can be made reverse acting by placing the
actuating screw in the opening provided on the opposite
side of the pivot. This will cause the control to increase
output pressure on lowering liquid level. The magnet arm
can be moved up and down by hand, and the optional supply
and output gauges will indicate if the change from direct to
reverse acting has been made correctly.
The output connection to the operation is always open, either
to the exhaust or the air supply. See the reverse side for
Table A, which illustrates the difference between direct and
reverse acting
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