Level switches are tools used to measure and report the levels of liquids, fluids, and fluidized solids in transmission equipment or storage enclosures. Sometimes, they are also used to control these levels as well, which is why they may also be referred to as level control switches. In systems that measure but do not control levels, level switches may also be called level indicators or level sensors.
All level switches share a basic construction, which consists of a switching mechanism, which indicates material levels, a tube, and a few areas of connection. However, outside of this basic construction, level switches can be quite different from one another. First, level switches can be triggered by temperature changes, buoyancy changes, or pressure.
Of these triggers, the measure of buoyancy is the most simple and straightforward. One type of switch that uses buoyancy are float level switches. Used to measure liquid levels, float level switches consist of a buoy or float, which sits on the liquid, and an electrical circuit. As material rises and falls, the float moves along with it, and if and when the float reaches a certain point, it triggers an electrical circuit, which closes the switch and sends a signal to the switch’s control equipment. Read More…
Level switches can also be designed to measure either or both solids and liquids. Switches that measure with buoyancy, like float level switches, are an excellent example of liquid level switches. An example of a solid level switch is the spinning rotary level switch, which measures levels of granular solids at different levels inside storage containers. Spinning rotary level switches employ blades or paddles that rotate around an axis that stop only when they are interrupted by the presence of a solid. When this interruption happens, the control equipment receives the signal that the switch elevation has been reached.
In addition to these distinctions, some switches are mechanical, meaning they come into direct contact with the materials they measure, while others are nonmechanical, meaning they do not come in direct contact with the materials they measure. Examples of common mechanical level switches include displacer level switches, rotary tank level indicators, and float level switches. Nonmechanical level switches include the likes of optical level switches, capacitance level sensors and ultrasonic level sensors.
While they make many different types of level switches, there are a few specific types that level switch manufacturers make most often to fulfill industrial application requirements. These include float level switches, displacer level switches, chambered level switches, capacitance level sensors, ultrasonic level switches, and optical level switches.
Float level switches we already know. Closely related to them are displacer level switches, which also measure and monitor liquid level changes with the force of buoyancy. Chambered level switches are named after the casing, or chamber, in which their switch mechanism is encased. They are mostly used as liquid and solid level switches, but they can sometimes be used to also control flow of materials in and out of the container they are monitoring.
Capacitance level sensors use electrical signals to detect the presence of organic and aqueous liquids, solids, and slurries alike. Ultrasonic level switches measure level changes via the transmission and reflection of ultrasonic waves. Optical level switches or sensors are used to sense changes in levels of sediments, suspended solids, and liquids. They do so by projecting an infrared light from an infrared diode (LED) and noting changes in its transmission.
Level switch manufacturers can construct switches using a variety of materials. These include brass and stainless steel, as well as a number of plastics, including polypropylene and polysulfone. Brass switches are suitable for installation in vehicle storage tanks, hydraulic systems, transmissions systems, generators, and any other processes that involve the use of petroleum-based liquids.
Polypropylene and polysulfone are popular because manufacturers can produce them in a variety of colors, because they hold up well in acidic environments, and because they work well with lower temperature food processing and general purpose applications. They are installed in systems that monitor food and beverage processing, electroplating, and metal cleaning.
Also available in different shapes and sizes, level switches serve not only these applications, but others, such as: the level monitoring and control of refrigerant or oil levels in HVAC systems, the control of potentially dangerous chemicals found in processing applications, the monitoring of wastewater levels, the monitoring of powder and liquid food item levels during food production and packaging, and the measurement of drug ingredient bulk quantities.