Rotameter | Flow Meter for Industrial Gas Measurement

 In Measurement and Control of Natural Gas

In wrapping up our series on natural gas flow meters, there is one last meter-type worthy of mention, the rotameter. The rotameter is a traditional gas technology and may be used as an industrial flow meter to measure the volumetric flow rate of fluids in a closed tube. It is a variable area meter and provides a simple, precise, and inexpensive indication of flow rates.

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Principle of Operation

The rotameter’s principle of operation involves a float positioned in a tapered tube. The float raises with fluid flow and pushes down with gravity. The tube is usually glass, while the float is typically ceramic or aluminum. The height that the float lifts is proportional to the flow rate. With liquids, the float rises with buoyancy, but with gases, the float increases with velocity. The float reaches a mechanical equilibrium state when the upward force exerted by the fluid flow is equivalent to the gravitational force. Any fluctuation with flow upsets the balance, and the float moves up or down indicative of the flow rate. Because the float is gravity-dependent, it is essential to install the meter vertically.

Rotameters are used in process industries as an industrial meter and may monitor gas at plants or in labs or filtration loading.


The mechanical nature of the rotameter is such that no external power is necessary to run the device and if the float is metal, its position can be transferred to an external indicator and observed remotely. Needing no external power is particularly beneficial in a hazardous location with flammable gases since there is no power associated with running the meter. The rotameter is inexpensive and usually highly resistant to thermal shock or chemical action. The rotameter has an extended measurement range with reasonable accuracy in low and medium rates, low-pressure loss, and is easy to install and maintain. The meter is also easy to read.


The meter’s housing is glass and is subject to breakage, so it is not a tough flow meter particularly in a process or industrial environment. Because gravity impacts the reading, the meter must be installed vertically. The rotameter’s scale will only be accurate for the specific fluid and conditions where the meter is calibrated. While a magnetic float may be available having the meter adapt to machine reading is often challenging.

Rotameter Manufacturers

  • Brooks
  • Voegtlin
  • Malema
  • Voegtlin

Natural Gas Flow Meter

Linc Energy Systems does not represent a rotameter line. If you are looking for an industrial flow meter for natural gas, perhaps one of our other product offerings could be beneficial. Message us now with your project needs.

Need assistance with a gas flow meter?

You may find helpful our article, 4 Things to Consider Before Selecting a Gas Flow Meter Technology.

Photo by Owain.davies [CC BY 3.0 (], from Wikimedia Commons


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