Flow switches are used to monitor fluid or gas flow while it is passing through its valve body, then to send an electrical control sign if the flow rate is too high or too low. The signal is sent as a safety measure to another device, such as a pump, that will respond accordingly or to a switching unit within the valve body. This is an important safety feature because many processes will only operate within a certain range of flow rate, halting or becoming compromised if the flow rate exceeds or falls under that range.
While all flow switches are flowmeters, not all flow meters are flow switches because they are not all equipped with the ability to control the flow rate, but simply to measure it. Flow switches are utilized in a wide range of applications, including air conditioning, water treatment systems, water cooled equipment, liquid transfer systems, pump systems and industrial process control. Categorized by characteristics such as flow material, measurement type and design, flow switches are used in diverse industries including HVAC, industrial, pharmaceutical, food and chemical processing, water treatment and commercial.
There are many different types of flow switches, the most common of which include gas, liquid, volumetric and velocity flow switches. The first two types are characterized by the flowing material, whereas the last two are characterized by measurement type; thus, these types can intermingle such as a volumetric gas flow switch or a liquid velocity flow switch. Flow switches at their most basic consist of a valve body, sensing devices and a switching unit that is connected to a pipeline. Gas flow switches include materials such as air and steam and are most often used in HVAC applications. Liquid flow switches include a much longer list of materials, which includes water, lubricants, coolants, chemicals and slurries, and are vital to many industrial applications. Volumetric flow switches, on the other hand, can measure the flow of liquids or gases. The most important characteristic of a volumetric flow switch is that it measures the flow of the material based on volume per unit time, an example of which is cubic feet per minute. Conversely, velocity flow switches measure the flow rate of a moving material in terms of velocity, of which an example would be feet per minute.
Flow Switches - Sierra Instruments