Flowmeters: An Essential Tool In Substance Analysis Instrumentation
Flowmeters are essential tools in the realm of substance analysis instrumentation. From measuring the rate of flow in a pipeline and controlling it, to detecting changes in liquid, gas and steam media, to monitoring pressure and velocity, these devices can be versatile, reliable, and accurate. There are several variations of flowmeters available today, including turbine, rotameter, differential pressure, ultrasonic, vortex shedding, and magnetic types.
Turbine flowmeters measure liquid and gas flow rates through a rotating element that is either externally driven by the process fluid (a straight-run or variable area) or driven by an external force (a helical/tangential). Straight-run turbine meters are used for measuring clean liquids, whereas variable area meters are used for more complicated media such as slurries, solids, and other complex fluids. To provide feedback control on the variable flow rate, a torsionally driven turbine meter can be used.
Rotameters are used to measure volumetric flow rate. They consist of a tapered tube containing a float which moves up or down with the rate of flow. The float is made of a material with a specific gravity different than the flow media, which allows it to move in proportion to the rate of flow. Rotameters can also be used to measure gas flow as well, wherein the process gas is forced through a glass tube containing a bobbin full of beads whose displacement indicates the flow rate.
Differential pressure flowmeters measure flow rate using two pressure sensors, one downstream from the other. This type of flowmeter is often used to measure large volume flows of gas or liquid, or for very large industrial plants. Ultrasonic flowmeters measure the difference in transit time of sound waves passing through a pipe, and can be used to measure the differential pressure across the flow.
Vortex shedding flowmeters measure the vortices created by incoming flow through the use of a sensing element. This type of flow measurement is typically used in larger pipes and/or when lower accuracy measurements are required. Magnetic flowmeters measure the flow rate of electrically conducting liquids through a magnetic field. This type of flowmeter is ideal for measuring corrosive liquids and slurries.
While each type of flowmeter has its own advantages and disadvantages, all of them offer the same basic benefits: high accuracy and reliability, wide range of applications, low maintenance requirements, and easy installation. The selection of the right flowmeter for a particular application requires an understanding of the specific needs and requirements, as well as a thorough knowledge of the various types available, which will allow for the most effective solution.