A magnetic level gauge is a commonly used instrument for detecting the liquid level in various towers, tanks, troughs, spherical containers, and boilers. It is developed and manufactured according to the original Ministry of Chemical Industry's standard for magnetic level gauges, HG/T21584-95, after assimilation and innovation based on similar products both domestically and internationally.
The magnetic level gauge connects to the container being measured via flanges and interfaces, forming a communicating vessel. The liquid level in the communicating vessel is consistent with that in the container. The measurement mechanism involves measuring the liquid level in the communicating vessel to obtain the liquid level in the container. The float in the main measuring chamber of the magnetic level gauge is designed based on the specific gravity of the liquid to ensure it floats on the surface. As the liquid level rises and falls synchronously with the liquid level in the container, the magnet inside the float interacts with a magnetically attached flipper or flap outside the chamber, allowing the observer to indirectly monitor the liquid level change. The panel of a magnetic level gauge is normally red and white, but yellow and black are also available. Both colors have a very high contrast, making them very eye-catching and easy to observe.
Features
Simple structure, robust and reliable, durable, virtually maintenance-free, suitable for long-term outdoor installation and use;
The measured medium is completely isolated from the level gauge display, level sensor, and magnetic switch;
Wide operating pressure range, withstands pressures from vacuum to 42MPa;
Wide operating temperature range, suitable for temperatures from -190℃ to +425℃;
Unaffected by the physical and chemical state of the measured medium, such as conductivity, dielectric constant, foam, pressure, temperature, evaporation, boiling, and bubbles. Widely used for measuring the levels and interfaces of various corrosive, flammable, explosive, toxic, highly radioactive, agitated, and contaminated liquids;
Optional single-pole single-throw (SPST) and single-pole double-throw (SPDT) passive bistable magnetic switches for high/low liquid level, interface control, or alarm functions. Unlimited number of magnetic switches;
Optional reed switch level sensor or capacitive two-wire level sensor, magnetostrictive level transmitter, outputting 4~20mA ADC (or with HART protocol) signal for remote centralized measurement and control;
Two-wire level sensor can be equipped with LED digital display for easy nighttime observation.
Advantages
Magnetic level gauges offer several advantages, primarily including:
Wide Applicability: Magnetic level gauges can measure the level and interface of various media, such as petroleum, acids, alkalis, and other corrosive substances.
Diverse Installation Options: The installation method of magnetic level gauges can be selected according to actual needs, adapting to containers of different shapes and installation locations.
Excellent Vibration Resistance: Magnetic level gauges maintain stable operation even in environments with significant level fluctuations.
Comprehensive Functionality: Magnetic level gauges integrate on-site indication, remote transmission, and alarm control switches, offering comprehensive functionality to meet diverse usage requirements.
Intuitive Reading: Readings from magnetic level gauges are highly intuitive. Through color contrast and the large flap, readings are clear even at long distances.
Applications
Magnetic level gauges are widely used for level detection in various towers, tanks, troughs, spherical containers, and boilers. The magnetic level gauge's excellent sealing performance, vibration resistance, low maintenance, and low repair costs make it an ideal instrument for level detection.
In summary, the magnetic level gauge plays a vital role in the development of industrial automation and intelligentization due to its wide applicability, diverse installation methods, excellent vibration resistance, and intuitive readings. It is believed that with technological advancements and continuously increasing application demands, the magnetic level gauge will continue to be innovated and improved, making an even greater contribution to the development of global industry.
Common faults and their causes in the application of magnetic level gauges
Magnetic level gauges often experience faults during practical applications. The causes of these faults are varied, ranging from single-component failures to simultaneous failures of multiple components. Below is an analysis of common faults and their causes in the application of magnetic level gauges:
Fault 1: Local display normal, remote transmission abnormal. Analysis of causes: Generally, there are several reasons for this fault. The following are some common causes: 1. Poor soldering of the resistor. 2. Pressure exceeding the rated value, causing damage to the switch. 3. The domestic glass tube reed switch is fragile; short circuit or open circuit of the reed switch causes abnormal remote transmission. 4. Under excessively high medium temperature, the metal sheet expands due to heat, and because the metal contact gap of the reed switch is small, it is prone to closing.
Fault 2: Neither the remote transmission nor the magnetic level gauge moves. This fault is usually caused by a float malfunction, mainly manifested in the following two ways: I. Float damage leads to incorrect display panel indication. Reasons for float damage in the magnetic level gauge include: 1. Incorrect float strength design, causing it to cave in under pressure. 2. Incomplete or missed welds, causing the weld to crack under pressure, allowing water to enter the float. 3. Demagnetization due to prolonged use or high temperatures, rendering it unusable. 4. Loose magnets in the float, preventing it from functioning properly.
Fault 3: Float jamming leads to inaccurate display panel indication. Common reasons for the float jamming in the magnetic level gauge include: 1. Low ambient temperature, causing the float to freeze and prevent normal movement. 2. The float's installation angle is less than 87 degrees, causing tilting and affecting the float's vertical movement. 3. The float attracts iron filings or other contaminants due to its own magnetism, causing it to become stuck and unable to move normally.
4. Due to poor sealing, impurities seep in and become stuck on the float, preventing it from rising or falling.
5. When the magnetic level gauge passes through a steel platform, a lag in level measurement occurs near the platform, resulting in no change in the level.
Finding the cause is half the battle. Through the above analysis of common magnetic level gauge malfunctions, we have basically found solutions. We can then address the specific problems based on the malfunction and its cause.
Troubleshooting Magnetic Level Gauge Malfunctions:
I. Display Panel Malfunctions:
1. The distance between the display panel and the float is too large, resulting in insufficient driving force of the magnetic float's magnet, causing the level gauge to fail to rotate.
2. The gap between the level gauge and the guide rail is improperly designed (the gap may be too small), leading to high friction and preventing the level gauge from rotating.
3. The magnet in the level gauge is too small or has lost its magnetic force, causing the level gauge to fail to rotate or rotate abnormally.
4. Water or dust or other impurities seep into the display panel, making it difficult for the level gauge to rotate.
5. Low ambient temperature causes the medium to freeze, preventing the magnetic float from moving and the level gauge from displaying the liquid level correctly.
II. The magnetic level gauge displays normally locally, but the reed switch remote transmitter displays abnormally:
1. Domestic glass tube reed switch remote transmitters are fragile and prone to short circuits or open circuits, leading to abnormalities;
2. Poor soldering of the resistor;
3. The metal contact gap of the reed switch remote transmitter is too small. When the medium temperature is too high, the metal sheet expands when heated, resulting in a closed state;
4. Pressure exceeds the rated value, causing switch damage.
III. Both the reed switch remote transmitter and the magnetic level gauge are abnormal, exhibiting the following two manifestations, usually indicating a magnetic float failure:
Common malfunction phenomenon of magnetic level gauge 1: The magnetic float is stuck.
Magnetic floats getting stuck usually has the following causes:
1. After a period of use, the magnetic float may become stuck due to impurities, preventing it from moving.
2. The installation angle of the float cylinder is less than 87 degrees, causing tilting and affecting the vertical movement of the magnetic float.
3. The magnetic float's own magnetism attracts iron filings or other contaminants, causing it to become stuck.
4. The ambient temperature is too low, causing the medium to freeze, preventing the magnetic float from moving.
5. The magnetic level gauge is too close to the steel platform when passing through it. Therefore, special attention needs to be paid to the distance between the level gauge's connecting pipe wall and the platform's cut edge when installing it through a steel platform. Based on field experience, a distance of approximately 100mm is sufficient to ensure that it does not affect the magnetic float.
Common Fault Phenomenon Two: Damaged Magnetic Float.
Magnetic float damage is usually caused by the following reasons:
1. Insufficient strength of the magnetic float, causing it to dent and collapse under pressure;
2. Incomplete or missed welds at the joints, causing the weld to crack under pressure and allowing water to enter the magnetic float;
3. Demagnetization due to prolonged use or long-term high-temperature operation;
4. Loosening of the magnets in the magnetic float, rendering it inoperable.
Recommendations for using magnetic level gauges:
When putting the level gauge into operation, pay special attention to opening the upper gate valve first, then the lower gate valve. This is because the bottom of the connecting pipe of the magnetic float level gauge is equipped with a thrust spring to protect the float; otherwise, the large differential pressure may shatter the float, rendering the level gauge unusable. When using the level gauge, be especially careful not to use a strong magnet to pull the float up and down outside the connecting pipe for inspection, as this will cause the magnetic float to become magnetized and change its polarity, or even weaken its magnetism, making it difficult to function properly.
