Magnetic level indicators, or gauges, measure fluid levels. They employ a magnetic float that rises and falls with the level of fluid contained within an attached chamber. As the fluid level rises, so too does the float. The float's position is reflected by a magnetic flag or indicator that is isolated from the internal workings of the chamber. This design is useful for reasons that will soon become clear.

Examples of applications that use magnetic level indicators (MLIs) include industrial boilers, oil refineries, and storage tanks. Any industry that needs to monitor and control fluid levels, from power plants to paper processing firms, can make good use of these devices.

The article that follows describes some of the advantages that MLIs have over traditional glass gauges. It also provides an overview of how the devices work as well as the parts contained in them. Lastly, you'll learn how to select a magnetic level indicator that accommodates your company's needs.


Advantages Of Magnetic Level Gauge Technology

This technology is employed as an alternative to sight glass level gauges. It offers several distinct advantages that are necessary in certain applications. To fully appreciate them, it's important to be familiar with the design of conventional level gauges.

Older models made liberal use of glass (and sometimes hard plastic) for the construction of the fluid chamber. The level of the liquid contained in the chamber could be easily determined by visually observing the position of a floating object (the float). Its position could be observed through the chamber's glass wall.

Although this design is adequate for a wide range of applications, it's unsuitable for many others. For example, situations in which the process fluid is under extreme pressure or temperature require a housing that is much stronger than glass or plastic. Both materials can suffer a breach. Likewise, highly corrosive substances can potentially erode the walls of the chamber, allowing the fluid to escape. In addition, some applications involve chemicals that can cause glass to become foggy and nearly unreadable.

Magnetic level indicators are used to resolve these limitations. They improve safety through the use of a stronger chamber. The chamber's wall is much less likely to suffer a breach due to pressurized, extremely hot, or corrosive fluids. They also improve visual clarity by removing the risk that the process fluid will make the chamber's sight glass unreadable. That in turn means less maintenance is required to keep the devices in proper working order.


Summary Of How Magnetic Level Indicators Work

The operation of a magnetic level indicator is both simple and elegant. As should be clear from the discussion thus far, the device is comprised of a fluid chamber, a magnetic float, and an external flag, also magnetic. The flag is isolated in an external level indicator, which is attached to the outside of the fluid chamber.

As the level of the process fluid contained in the chamber rises, the magnetic float also rises. The chamber's wall is not magnetic. Nor is the external level indicator. This allows the magnetic flag to follow the path of the float as it rises and falls inside the chamber. Unless something interrupts the magnetic field shared by the flag and float, the levels of the two objects should remain identical.

Some MLIs are designed with an external flag that changes color if the level of the process fluid reaches a predefined height. Bright, fluorescent colors are advisable to make any changes more noticeable, particularly from a distance.


How To Select A Magnetic Level Indicator

Magnetic level indicators must be suited to the specific applications to which they are applied. Companies can narrow their options by taking into account the type of process liquid that is to be monitored and the conditions under which the fluid is contained. It's also important to identify the preferred design of the external indicator and the type of scale needed to accurately and easily measure fluid levels.

Another factor to consider is the type of accessories that may prove useful in optimizing control of the process fluid. Such accessories can include level switches, extra insulation, or transmitting sensors.

If a sight glass level gauge is ill-suited for an application due to reasons involving safety, visibility, or risk to the surrounding environment, a magnetic level indicator may offer a viable alternative. The most important thing to remember is that MLIs come in varying sizes and configurations. A specialist can offer expert guidance on choosing an assembly that helps your company meet your process control objectives.