Liquid level switches are used to regulate and monitor levels of free-flowing liquids within a confined space, and they're used to identify the point at which a liquid falls below a preset minimum or rises above a preset maximum level. This guide will touch on the applications and basics of a liquid level switch.
The use of liquid level switches in industrial applications is ubiquitous; however, they're also used in more common everyday applications than you might know. A coffee maker uses a liquid level switch to ensure your morning brew is done just right, while your car employs them to monitor a variety of automotive fluids, including gas, oil, and power steering fluid. In industrial applications, level switches are used in a wide range of capacities from water storage tanks and irrigation control to dialysis machines and more.
There are a variety of different types of liquid level switches that detect the set point level of a liquid, or the minimum/maximum level. They're designed to provide a continuous measurement of the liquid to ensure the level doesn't fall below the minimum or exceed the maximum levels. It's critical to have a level control monitoring solution in place to prevent flooding or run-dry situations which can lead to extensive damage and expensive repairs.
Some of the more common switches used are magnetic, conductive, and pneumatic. Here's a look at these three.
Magnetic Switches
These switches incorporate a magnetic float, which rises and falls with the liquid in the confined space. As the liquid and, by extension, the magnet reach a preset level, a reed magnetic switch activates. Typically, there's a switch near the top and at the bottom of the confined space, which allows for the detection of minimum and maximum levels of liquid. Often, these switches include a protective shield to protect the magnet from direct exposure to the liquid to ensure there's no interference with the continuous monitoring. Magnetic float level switches are often used in high-temperature applications, and by using a permanent magnetic float level switch and reed contact, the switching operation doesn't need a power supply, is non-contact, and is free from wear. Wherever liquids flow in and out of sumps, pressure vessels, or tanks, magnetic liquid level switches are used in industries ranging from shipbuilding, power generating equipment, food & beverage, and more.
Conductive Switches
This type of switch includes a very low voltage source of power, and can only be used with liquids which conduct electricity. Liquids such as acids, lyes, and solutions containing water are conductive and are detected very well, while combustible liquids such as oils, solvents, and fuels are nonconductive and can't be measured by conductive liquid level switches. With conductive switches, two electrodes are installed above the surface of a conductive liquid to be monitored. If the liquid level rises to the point where both electrodes are in contact with the liquid, the current circuit of a connected relay is completed by way of the two electrodes and the liquid, which activates the switch to operate. One key advantage of conductive liquid level switches is that if several switching points are needed, multiple electrodes can be used. With the added benefit of being solid state, they're a simple, cost-effective measuring principle that can provide multi-point detection with a single process connection. Common applications for conductive liquid level switches include high/low-level alarm indication and pump valve control, as well as run-dry and tank overfill protection.
Pneumatic Switches
These liquid level switches are commonly used with hazardous liquids, or in applications where using electricity is not viable or possible. Relatively cost-effective, pneumatic liquid level switches do not actually come in contact with the liquid. Instead, the pneumatic liquid level switch senses the level of a liquid, and compares that level with the preset desired level, or set point. It then produces a pneumatic signal that operates an actuator control valve. By operating the actuator and valve, the switch maintains the level at the predetermined set point. Pneumatic liquid level switches are commonly used in applications involving heavy sludge or slurry, for use with highly viscous liquids such as grease, as well as water-based and corrosive liquids.
Lastly, liquid level sensors aren’t the only instruments used in industrial applications where liquid storage and flow are essential to process. Flowmeters, pump control boxes, and sensors also play important roles in controlling and measuring levels and flow.
Product Compliance and Suitability
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