Top Mounted Magnetic Level Indicator
Simple principle of mechanics and magnetism harnessed to offer an absolutely safe, reliable and trustworthy level indicator for dangerous and toxic liquids under high pressure and temperature. As the liquid level rises in the tank, the float is lifted up due to buoyancy. The float carries a stem attached to it and on the other side of the stem a magnet is fixed. The float stem moves inside an SS enclosure. External to this enclosure is a glass tube, which carries the magnetic follower (Red in Colour).
Due to magnetic attraction, the magnet on the float stem and the magnetic follower are coupled and move in union. As the float moves along with the liquid, the follower also moves inside the glass tube, and the position of the follower can be read against the scale.
Introducing the Top-Mounted Magnetic Level Indicator
The top-mounted magnetic level indicator is an industrial instrument that is applied in the continuous level measurement of liquids in tanks or vessels. It is installed vertically on the top of the tank and gives a visual and clear indication of the level of liquid present by the use of magnetic coupling technology. This kind of level indicator is particularly appropriate in those applications that deal with hazardous, corrosive, or pressurised liquids where non-invasive measurement is critical.
Introduction:
Definition:
A top-mounted magnetic level indicator is a level measurement device, based on a float, that has a magnetically coupled indicator to show the liquid level externally without direct contact.
Working Principle:
The level of the liquid is sensed by a magnetic float inside the tank. This float has a powerful permanent magnet that magnetically drives an external indicator inside a transparent tube or on a scale outside the tank.
Installation:
It is mounted on the head of the tank or vessel, and the float is in the liquid; the indicating scale is external.
Non-Intrusive Indication:
The indicator is not in contact with the process liquid, so it can be used in high-pressure or dangerous areas.
Applications:
Also used in chemical plants, refineries, water treatment systems, and food and beverage industries to provide reliable and maintenance-free level indication.
Advantages:
Loud and constant level indication
No power is needed to provide simple visual indication.
It is appropriate in high-temperature and high-pressure settings.
Able to work with corrosive and toxic liquids
Principle of Top-Mounted Magnetic Level Indicator
A top-mounted magnetic level indicator is a non-contact form of level-measuring instrument that is mostly applied in continuous measurement of liquid level inside a storage tank or process vessel. It operates on the basis of magnetic coupling and buoyancy.
Operation Principle:
Float Mechanism:
A float with a magnet on board is suspended in a stilling well or in the liquid itself.
The float rises and falls according to the height of the liquid in the tank.
Magnetic Coupling:
The float has a permanent magnet.
A magnetic follower or indicator strip is fixed to a guide tube (or housed) outside the tank.
The float magnet creates a magnetic field as it moves up or down, and this field is coupled to the external indicator.
Level Indication:
The external indicator is linked with the float to move in the same direction, in real-time, indicating the level visually.
In other designs, the indicator can be a pointer-type system or a rotating flap system (which changes color as the level changes).
Top Mounting:
The complete assembly is mounted on the top of the tank, and thus it is suitable in closed vessels and underground tanks or pressurized systems.
Uses of Top-Mounted Magnetic Level Indicator:
Magnetic level indicators Top-mounted Magnetic level indicators are common in continuous level indications of liquids in several industries. They are designed in a non-intrusive and robust manner, which makes them particularly well suited to harsh or demanding environments. These are important applications:
Process Industries Storage Tanks
Applied to chemical, pharmaceutical, and petrochemical plants to observe the level of liquids in the storage tanks.
Can be used with toxic, corrosive, or flammable liquid, as the magnetic coupling lets the reading be done externally without direct contact.
Vertical or underground tanks
Very suitable on deep or vertical vessels where side mounting is not possible.
Routine in oil depots, refineries, and utility tanks.
Dangerous and High-Pressure Areas
Applied under extreme pressure or in hazardous areas (ATEX-rated areas) because the indicator is hermetically sealed and safe.
Water and Wastewater Treatment
Placed in clarifiers, settling tanks, and sludge tanks to monitor real time.
Makes sure that the level is accurately detected despite the dirt, foamy, or viscous liquids.
Marine and Offshore Applications
Widely applied in ballast tanks, fuel tanks, and lubrication oil reservoirs on board ships and on offshore platforms.
Food and Beverage Industry
Appropriate to tanks that contain dairy, juices, beverages, and process water, particularly when they are made of sanitary-grade materials.
Cryogenic and High-Temperature Services
Applied in tanks that contain liquid nitrogen, LPG, ammonia, and other cryogenic gases.
It is constructed to be insulated and use materials that resist high temperatures.
Top-Mounted Magnetic Level Indicator Float Selection
The choice of float is a major factor when it comes to designing a specific and dependable Top Mounted Magnetic Level Indicator (MLI). The float is made to sense the liquid level and conveys the information to the outside indicator or transmitter through magnetic coupling. When it comes to the choice of the float, the following parameters are taken into account:
Major Float Selection Criteria
Specific Gravity
Essential to float buoyancy.
The float should be capable of floating on the process liquid reliably.
Minimum Specific Gravity: Standard specific gravity is 0.35, although special floats can be manufactured to lower specific gravity.
Pressure and Temperature
Decides the material and the thickness of the float and the wall.
Stronger materials are needed against high pressures (e.g. stainless steel 316L).
Thermal expansion may be an issue due to the high temperatures and special welding may be needed.
Chemical Compatibility
The float material should also be incompatible with the process liquid so it does not corrode or break down.
Common materials SS304, SS316, Titanium, PTFE-clad stainless steel or Hastelloy Corrosive services.
The Size of Tanks and Tank-Mounting Limitations
The float diameter and length should be able to fit in the tank nozzle and move freely without hindrance.
Long floats may be divided into segments or special-sized to fit narrow tanks.
Measurement of interface (Optional)
When applied to interface two immiscible liquids, the float should be built depending on the difference of densities of two layers.
Strength of Magnetic and Coupling
Float should have a permanent magnet powerful enough to activate the external magnetic flaps or transmitter.
A ring or bar magnet is usually placed inside the float, and oriented so as to be aligned with the indicator system.
The benefits of Top-Mounted Magnetic Level Indicator are:
This is applicable to Deep Tanks:
It is suited ideally to tall vertical tanks or underground storage tanks because the top can be used to measure the level without side access.
Non- Invasive Level Indication:
The fact that the float in the tank is magnetically coupled to the indicator on the outside of the tank means that the liquid does not come into direct contact with the external indicator- this makes cleanup and safety more effective.
Leak-Free Design:
The risk of leaks is lower, as there are no side process connections, which is more dependable when dealing with hazardous or toxic fluids.
Low Maintenance:
A smaller number of moving parts, and the enclosed structure of the indicator mechanism, translate into less maintenance and increased operating life.
Durable and weather-proof:
These indicators are usually constructed to be used outdoors and are therefore weatherproof and environmental friendly.
Remote and visual monitoring can be done:
Top-mounted magnetic level indicators are also easily incorporated with transmitters or switches, thus providing remote monitoring and control of level.
Safe in High pressure/High temperature:
As the float and measurement mechanism is isolated, it can be deployed in pressurized or high-temperature applications.
No Power is required to provide Visual Indication:
Magnetic indicators give an immediate visual indication and do not need electricity, so can be used in remote locations or where power is limited.
Types
Top Mount Magnetic Float Level Indicator (Side Indicator)
Description: Mounted on the top of the tank; a magnetic float rises and falls with the liquid level and an external magnetic follower on a side indicator indicates the level.
Use: Tall tanks, underground storage tanks and reservoirs.
Top-Mounted Magnetic Level Transmitter ( Reed Chain or Hall Effect Sensor )
Description The float movement in this type energizes reed switches or hall sensors installed in a stem, and translates level into an electrical signal.
Usage: Remote monitoring or control systems (SCADA, PLC) integration.
Bypass Chamber Top Mounted Magnetic Level Indicator
Description: It is mounted at the top but is connected to a side bypass chamber to indicate visually by means of magnetic flags or flaps.
Usage: High-pressure, or high temperature tanks, requiring isolation of the measuring mechanism.
Top-Mounted Float & Tape Magnetic Level Indicator
Description: It involves a float attached to stainless-steel tape and pulley; the float contains a magnet inside that interacts with a magnetic dial on top.
Usage: Vertical tanks that are tall and side mounting is not practical.
Top-Mounted Guided Float and Remote Magnetic Indicator
Description: A float is directed through a stem and vertical movement of the float influences a distant magnetic scale or transmitter that is mounted outside.
Use: Hazardous, toxic or corrosive environments where it is not possible to observe directly.
Suggested Disposal of Top-Mounted Magnetic Level Indicator
Top-Mounted Magnetic Level Indicator disposal is to be performed with caution to protect the environment and adapt to local laws. A suggested disposal procedure would be the following:
Decontamination
Clean the unit by flushing.
All dangerous chemicals (e.g. chemicals, hydrocarbons) should be neutralized or taken out by following the Material Safety Data Sheet (MSDS) of the fluid utilized.
Disassembly
The indicator should be disconnected to the tank or vessel after the system is depressurized and drained.
Isolate large parts including:
Float
Chamber
Magnet assembly
Indicator scale
Electronics (when possible)
Material Segregation
Metals (stainless steel, aluminium): Recycle them as scrap metal.
Indicators or seals (plastics or polymers): Dispose of as per local guidelines of plastic waste.
Magnets: They can be recycled independently using magnet recovery programs or e-wastes.
Electronic components (in case of any): Send to e-waste certified recyclers.
Hazardous Waste Handling
The components that have been contaminated by the hazardous fluids should be taken as the hazardous waste and should be disposed of in the same manner.
Organize with licensed hazardous waste disposal site in case of necessity.
Documentation
Keep a list of the disposal procedure, particularly in case the degree indicator was utilized in the regulated sectors (chemical, pharma, oil and gas).
Retain disposal certificates of recyclers or waste handlers in case of an audit or compliance.
Environmental Compliance
Be sure to comply with:
Rules of local pollution control board
EHS (Environment, Health, Safety) policies practiced inside a company
Any relevant environmental regulations (e.g. Hazardous Waste Rules, E-Waste Management Rules in India)
FAQs
Top Mounted Magnetic Level Indicator is a kind of liquid level measuring device mounted vertically and fitted at the top of a tank or vessel. It measures liquid level without physical contact with the liquid by the use of a magnetic float in a guide tube.
The indicator is based on the principle of magnetic coupling. There is a float with a permanent magnet that rises and descends with the level of the liquid. This float is magnetically coupled to an external indicator (e.g. magnetic flaps, followers or switches) to give either a visual or electrical level indication, without penetrating the tank.
It is widely applied in underground tanks, sealed compartments, and dangerous areas where side mounting is impractical or where liquid pressure and vapor containment are paramount, as in chemical plants, refineries, and water treatment plants.
- Liquid has no direct contact with external components.
- Suitable for corrosive, toxic, or pressurized liquids.
- Very visible and dependable level indication. • Can be used with switches or transmitters to automate.
It can be applied to most clean fluids and corrosive and hazardous fluids. Nevertheless, it is not likely to work well in very viscous, slurry, and solid-laden liquids where the movement of floats can be limited.
These level indicators are top-mounted magnetic level indicators, and the process fluid is contained in a sealed chamber, so there is no risk of leakage or direct contact. This makes it safer to operate in hazardous, toxic, or high-pressure environments.
The magnetic coupling is of non-contact design, thus minimizing wear and tear. The indicator does not have any moving parts that are exposed to the process fluid, and this minimizes frequent maintenance and extends the operation life.
Such indicators are manufactured with tough materials and a sealed chamber and can be used in a very broad range of temperatures and pressures without affecting measurement accuracy.
Yes. The process fluid is kept in a fully contained, corrosion-resistant chamber so that the design is suitable to aggressive, corrosive, or viscous media without damaging the indicator system.
Top-mounted magnetic level indicators offer a direct and clear visual indication via a magnetic float mechanism and an external pointer, which is usually color-coded or flap-based, and therefore easy to read even remotely or in low light.
Magnetic level indicators Top-mounted magnetic level indicators are frequently found on storage tanks, underground vessels, and pressurized tanks where side access is limited or not feasible.
Yes, provided they are made of appropriate materials such as SS316, Hastelloy, or PTFE-lined, they can be used to measure the levels of corrosive or hazardous liquids.
Yes, interface levels between two immiscible liquids, e.g., oil and water, can be measured using top-mounted magnetic level indicators, particularly in dual-float designs.
Yes, when constructed using suitable high-temperature materials, they are intended to withstand high temperatures, particularly in the refinery or chemical processing setting.
Yes, most models may be fitted with magnetic switches, transmitters, or reed-chain sensors and remotely monitored levels and incorporated into SCADA or DCS systems.
The level indicator should be depressurized, drained of all process fluids, and thoroughly cleaned before disposal to eliminate the possibility of hazardous residues. The isolation of the system must be confirmed properly.
Yes, personal protective equipment (PPE) is required, and relevant plant or industrial safety measures ought to be observed, particularly when handling toxic or flammable materials that had been used by the instrument.
Yes, a number of parts, including the stainless steel body, float, and magnetic assembly, can be recycled as scrap metal. Nonmetallic components might require sorting and transport to suitable waste treatment plants.
It should be handled as a hazardous waste. It is important that the unit is decontaminated and disposed of in a manner that is compliant with local environmental requirements, which in most cases requires the services of certified hazardous waste disposal companies.
Disposal is to be done by trained maintenance staff or a qualified waste disposal contractor that is knowledgeable on the disposal of instrumentation and hazardous industrial parts, within the regulatory guidelines.
