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Left
drawing shows a typical Magnetic Level Gauge, used in level
control of any kind of fluid. The Magnetic Level Gauge is the
instrument to read a level indication in whatever plant or operating
conditions giving free maintenance, preventive security against
leakage, environmental safety, sure and trouble free application
with chemically aggressive, pollutant, harmful or poisonous,
inflammable or explosive, optically similar fluid interface.
Our very wide range of Magnetic Level Gauges allows to have
the proper instrument for any kind of plant or specific purpose.
Our world patented system includes a float able to float both
in high density fluid or in low density fluid up to 0.4 specific
gravity. But more! You can have low specific gravity and high
temperature and pressure together (i.e. water/steam of H.P.
vessels). Well! We manufacture a float able to float and to
resist with external pressure of 210 bar at 370 ºC!
And more! Do you need Remote Direct Reading? We have it, as
a completion of Magnetic or Glass level Gauge. Are you looking
for a Transmitted Remote Signal? We can supply a sensing element
able to transduce the signal to LED, Analogical or Recording
Instruments that you can have in Control Room.
DESIGN
In a vertical chamber (tube of suitable diameter connected by
stub ends to the vessel) there is a float containing a permanent
magnet -fixed by means of special patented device that permit
to the magnet a 360º rotation- placed exactly on liquid
level line.
Magnetic action of permanent magnet in the float generates rotation
of a set of small permanent magnets enclosed in small cylinders
-contained in indicating scale- which cylinders, having different
colours in the North and South pole, can rotate on their horizontal
axis.
So the scale appears of one colour (i.e. white) over chamber
area taken by gas and of another colour (i.e. red) over chamber
area taken up by liquid phase.
The chambers of the Magnetic Level Gauge are dimensioned according
to ASME B31.1 and B31.3.
The chamber is connected to vessel with flanged, threaded or
welded ends. Usually, between the instrument and its connecting
ends valves are fitted to consent shut-off piping and to disassemble
the level gauge without empting the vessel or shutting off the
plant. Drain valves can also be fitted on the top and bottom
of level gauge.
MAGNETIC
LEVEL GAUGE OPERATING PRINCIPLE
Operation of Magnetic Level Gauge is based on some elementary
physical principles:
The principle whereby liquid in communicating vessels is always
at same level;
Archimede's principle according to which a body immersed in
a liquid receives a buoyancy equal to the weight of displaced
liquid; The principle of attraction between North and South
poles of two permanent magnets and that of repulsion between
like poles.
This principle has two applications in the magnetic level gauge:
first between the magnet in the chamber float and every single
magnet of the indicating scale: second between the magnets of
the indicating scale.
The
cylindrical magnet "A" in the float is able to turn
horizontally on the axis "B" like a compass needle,
so that magnetic force is always free to best orientate itself
towards the magnetic scale, in which small cylinders "C",
rotating vertically on their axis "D", contain smaller
cylindrical magnets fitted in orthogonal position to rotation
axis.
Cylinders No. 1 & 2 are in stable position, as cylinders
4 & 5, because the magnetic chain between their magnets
is well oriented "N-S-N-S"; cylinder No. 3 is in not
stable position because North Pole "N" of the bigger
magnet "A" inside the float attracts the South Pole
"S" of the smaller magnet inside the cylinder. The
same cylinder tries to rotate clockwise because its "N"
pole would reach the "S" pole of cylinder 2. Imagine
now that fluid, growing in the level gauge, pushes up the float.
The float magnet, going upside, will approach the cylinder 4,
attracting its "S" pole, and so, after clockwise rotation,
it will be in the same position as now the cylinder 3. Same
cylinder 3 will be in that case free to complete rotation clockwise,
and its position will became stable as cylinder 1 & 2. And
so and so with growing of the liquid level. The same, with inverse
rotation of small cylinders, happen when the float goes down.
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