Magnetic Liquid Level Gauge
The left drawing shows a typical BONT® Magnetic Level Gauge, used in level control of any kind of fluid. The Magnetic Level Gauge is the instrument to reads 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 us 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 resist with an 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, Analog, or Recording Instruments that you can have in the 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 using a special patented device that permits the magnet a 360º rotation- placed exactly on a liquid level line. The magnetic action of the permanent magnet in the float generates rotation of a set of small permanent magnets enclosed in small cylinders-contained in indicating scale cylinders, having different colors in the North and South poles, which can rotate on their horizontal axis. So the scale appears of one color (i.e. white) over the chamber area taken by gas and of another color (i.e. red) over the 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 a 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 emptying the vessel or shutting off the plant. Drain valves can also be fitted on the top and bottom of the level gauge.
MAGNETIC LEVEL GAUGE OPERATING PRINCIPLE
The operation of BONT Magnetic Level Gauge is based on some elementary physical principles:
- The principle whereby liquid in communicating vessels is always at the same level
- Archimedes’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 the North and South poles of two permanent magnets and that of repulsion between like poles.
- This principle has two applications in the BONT 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 can 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 the rotation axis.
Cylinders No. 1 & 2 are in a 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 a stable position because the 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 down, will approach cylinder 4, attracting its “S” pole, and so, after clockwise rotation, it will be in the same position as now cylinder 3. Same cylinder 3 will be in that case free to complete rotation clockwise, and its position will become stable as cylinders 1 & 2. And so and so with the growth of the liquid level. The same, with inverse rotation of small cylinders, happens when the float goes down.
Remote Direct Reading (RDR) Magnetic Gauge
With the use of electronic sensors remote direct reading from afar is easily achieved with the RDR Magnetic Gauge. The system may be connected to a cherry system, LED connector, or a Transducer with an Analog converter for connection to a digital device or indicator. The system can be installed on any boiler or tank. Only two connections are sufficient for installation.
