Rotometers are flow meters named for the rotating float which functions as the meter's indicating element. A float moves up and down a tapered tube according to the rate of flow. Rotometers are typically used to measure low flow rates and are an economical method of indicating and controlling gas and liquid flow for several applications.
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Benefits of Rotometers
Rotometers come in simple and complex designs. Some rotometers can be equipped with multiple features for checking material properties such as temperature, pressure, viscosity and more. There are many advantages and disadvantages to rotometers. One of the major advantages to rotometers is the fact that these devices have a simple design with few components which makes it easy to mass produce. Most rotometer designs require no electricity to operate which makes it ideal for applications where electricity would be a hazard or in situations where no electricity is available. The placement of the tube is very critical because gravity is a key factor for proper functionality of the rotometer. Another disadvantage of rotometers is the accuracy of the readings become less reliable at low flow rates. Rotometers come with an excellent value in terms of repeatability and ease of use. These devices are quick to respond to any changes in the flow path. An example of a common rotometer can be found in the medical field. Medical personnel typically utilize a rotometer in oxygen regulators.
Rotometers consist of a float that moves vertically through a slightly narrowing tube. As fluid enters the bottom of the rotometer, the float is forced upward until the force is balanced by gravitational forces. Like peak flow meters, graduations are marked on the tube so that the level of the float can be aligned with a gradient to provide an accurate, fast and easy-to-understand flow rate reading. Rotometer tubes are read directly in standard cubic feet per hour of air. Rather than using a constant restriction area and a variable pressure differential, rotometers use a variable restriction and a constant pressure differential to measure flow. Rotometers may be designed to measure the flow rate of single or multiple streams. Single tube rotometers are usually mounted directly on the piping and they are used with non-corrosive materials. Single tube rotometers are used if there are special conditions for the measurement or when a basic flow meter will suffice. Multiple tube rotometers are mounted to a tripod base plate with feet to level the assembly. They may also be bench or wall mounted. This kind of rotometer takes measurements for flow rates of more than one stream of gas or liquid. Other variations are also available.
Applications of Rotometers
Typically, rotometers are used to measure smaller flows and the reading is usually done locally, although transmission of the readings is possible. Most rotometers are made of glass with markings on the outside so that flow readings can be taken visually, similarly to flow indicators; however, metal rotometers are also available. Rotometers are advantageous due to the simplicity of the device and the constant pressure drop they offer. Also, rotometers do not require straight pipe runs for installation so installation can be performed almost anywhere. The selection of the appropriate rotometer for a particular application requires attention to a few key details. These include which gas will be used, the required flow rate, the number of streams to be measured and whether a metering valve is included. Rotometers are favorable for their simplicity, versatility, accuracy, and ease of use. For all these reasons, rotometers are the flow meter of choice for many industries.
Rotometers are ideal for measuring the rate of liquids or gases which are being utilized for an application. Rotometers are equipped with a device called a “float” which rises and falls based upon the flow rate of the material. If the float is high then that means there is a greater force in the flow. These floats are engineered in different designs such as circular, triangular or elliptical. The float is housed in a special tube known as a tapered meeting tube. The diameter of a tapered tube gradually increases along the vertical axis of the device. Rotometers are crucial pieces of equipment when flow rate identification is essential.