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Working principle of magnetic level indicators and its trouble shooting

Author:vacorda    Source:vacorda.com    Date: 2019-10-15 10:30:31

The magnetic flap liquid level indicator can be used in various types of tower, tank, tank, ball-type containers and boilers and other equipment of the medium level detection. The magnetic flap level meter can be high-sealing, leak-proof and suitable for high-temperature, high-pressure, corrosion-resistant occasions. It makes up the glass plate (tube) liquid level gauge indicating poor clarity, easy to rupture and other defects, and the whole process of measuring no blind area, clear display, large measuring range.

installation diagram of magnetic level indicator

The magnetic flap level meter can be used to directly observe the level of the medium in various containers. It is suitable for the oil, chemical industry and other industrial fields of liquid level indicator, the liquid level meter structure is simple, observation is intuitive, clear, non-clogging, no leakage, easy installation, easy maintenance.

First. Working principle of magnetic level indicator

The UHCmagnetic flap level indicator is made up of measuring body, dual-colored display cylinder, ruler, top & low flange, magnetic ball and transmitter (4-20mA).Based on buoyance principle, the magnetic ball in the body of the level gauge is up or down with the liquid level changing and makes dual-colored turning to show the level of medium. Each cylinder is with two-color axisymmetric structures. The distance of two cylinders is 10mm. Red side of display cylinder indicates liquid and white side display cylinder indicates air. Besides measuring liquid level, it also could measure the interface of the two kinds of liquid.

working principle of magnetic level indicators                   working principle of magnetic level gauges

Second. Factors to be considered when selecting

(1). Measuring objects, such as the physical and chemical properties of the medium under test, as well as the operating pressure and temperature, installation conditions, the speed of fluid level change, etc.

(2). Measurement and control requirements, such as measurement range, measurement (or control) accuracy, display mode, on-site instruction, long distance indication, interface with computer, safety anticorrosion, and reliability and construction convenience.

(3). Also take into account the demagnetization of magnetic materials, demagnetization causes the liquid level gauge cannot work properly, the measurement results may not be allowed.

Third. Magnetic flap level indicator indicates inaccurate


(1) The container is always running, but the liquid level of the container is always at a certain point.

(2) The container increases or decreases the load, and the liquid level of the container does not change.

(3) The local level gauge does not match the pressure difference level gauge on the indoor display.


(1) The water in the container rises or falls too fast, that is, the float rises or falls too fast, and the magnetic flap does not have time to flip.

(2) The center of gravity of the magnetic flap is not at the center point. When the magnetic float rises, the magnetic float is reversed. When the magnetic float rises again, the flap returns to the original position state, and there is no water level state.

(3) The water contains too much impurities in the container and is adsorbed on the magnetic floating surface. The magnetic floating magnetic force is lowered, and when the magnetic floating rises, the flap cannot be rotated.

(4) The liquid phase conduit of the water is clogged differently, so that the actual water level in the container rises. Maglev does not rise with it.


(1) Try not to raise or lower the water level in the container too quickly.

(2) The water level gauge magnetic flap, the center of gravity is not at the center point. The manufacturing quality does not meet the standard and should be replaced.

(3) If the water quality is unqualified, it should be washed regularly.


(1) There should be no solid impurities and magnetic impurities in the cylinder of the liquid level gauge to avoid jamming and weakening buoyancy.

(2) According to the medium, the main conduit can be cleaned regularly to remove impurities from the sediment.

(3) When cleaning the level gauge or when replacing the float, open the drain flange. When loading the magnetic float, pay attention to the heavy end with the magnetic end facing up and not flipping.

(4) For low-temperature type and liquefied gas special-purpose products, the main body of the liquid level gauge adopts vacuum jacket insulation, so be careful not to damage the jacket during installation and use, so as not to affect the product quality.


Fourth, the display panel is abnormal

The causes of this failure

(1) The gap between the flap and the guide rail is unreasonably or too small, resulting in excessive friction and the flap is not turned over;

(2) The distance between the display panel and the pontoon is too large, and the driving force of the magnetic steel of the float is insufficient, so that the flap does not reverse;

(3) The magnetic steel in the flap is too small or the magnetic force disappears, resulting in the flap not being turned over or flipped abnormally;

(4) Impurities such as water or dust penetrate into the display panel, which makes it difficult to turn the flap;

(5) If the ambient temperature is too low, the medium will freeze and the float will not move. The flap cannot display the liquid level normally.

Fifth, the local display is normal, the remote transmission display is not normal

Reasons for this type of failure

(1) The domestic glass tube reed switch is fragile, and the dry reed tube is short-circuited or open circuit, which may cause remote transmission abnormality;

(2) Resistance welding;

(3) The metal contact gap of the reed switch is small. When the temperature of the medium is too high, the metal foil expands when it is heated, and the closed state is easy to occur;

(4) The pressure exceeds the rated value, resulting in damage to the switch.


Sixth, remote transmission and magnetic flaps do not move

Phenomenon 1: The float is stuck, causing the display panel to be incorrect. There are usually several reasons:

(1) When the float is used for a period of time, the float may get stuck due to the presence of impurities and cannot rise or fall;

(2) The installation angle of the pontoon is less than 87 degrees, causing the inclination to affect the up and down movement of the float;

(3) The float is stuck due to its magnetic adsorption of iron filings or other contaminants;

(4) If the ambient temperature is too low, the medium will freeze and the float will not move.

Phenomenon 2: The float is damaged, causing the display panel to be incorrect. There are usually several reasons:

(1) The design of the float is not correct due to the strength, so that when it is under pressure, it will be recessed into the inside and become smashed;

(2) There is no penetration or leakage welding at the weld, which causes the weld to crack when the float is under pressure, and the float enters the water;

(3) The float is demagnetized due to long use time or long-term high temperature, which makes it unusable;

(4) The magnetic steel in the float is loose, causing the float to fail to work.


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