Complete guide on Rotameter and its benefits?

A Rotameter is a device you can use to measure the volumetric flow rate of fluid inside a closed tube. To get the flow rate when using a Rotameter, the falling and rising action of a float in the tapered tube occurs. The Rotameter device operates on the principle of thrust force brought by fluid and the force of gravity.

Construction of a Rotameter

Rotameter devices consist of the tapered tube plus afloat inside them. A scale is fitted on the tapered tube on the surface. But the scale may also be placed adjacent tapered tube based on the purpose. The tapered tube is positioned inflow conduit vertically with a conical shape inside. The quantity of fluid monitored is defined by the height of float that goes up. You are supposed to use glass tubes for measuring both gases and liquids. 

For the fluid with high pressure and temperature, you can use metallic tubes. When it comes to floating, stainless steel floats are recommended. You may go for aluminum to lead floats. The shape of a Rotameter float shape varies depending on the use and density of your fluid. 

How a Rotameter works

The fluid you seek to monitor enters from the bottom part of the tapered tube. Once that happens, some fluid will strike into the Rotameter float bottom. From there, it passes aside the float. The float will then experience two forces from the opposite direction. There will be a gravitational force downward and a drag force upward.

The fluid you are monitoring will move the Rotameter float upward against gravity. Up to a given point, the flowing area hits a level where all the pressure-induced force on the floating body matches the weight of the float. The Rotameter float reaches equilibrium once the area around the float produces enough drag that is equal to the buoyance weight.

When float weight and gravity are constant, then the distance displaced by float upward will be relative to the velocity of the fluid flowing via the tapered tube.

Things to consider when selecting a Rotameter 

You are already convinced that a Rotameter will be a great solution to the flow metering problem. Besides, you may have analyzed the benefits of a Rotameter and found them appealing. So, before going to a Rotameter distributor to select a device that matches your application, there are many factors you need to consider. These includes:

1. Fluid type

Knowing the nature of the fluid to be monitored will help to get the right choice of a Rotameter! Do you intend to measure the flow rate of steam, gas, or liquid? It will be vital to understand it all. Is the liquid highly corrosive or not? When you are aware of fluid type and nature, it will be easy to select a Rotameter that suits the application. 

2. Fluid viscosity

A change in fluid viscosity may affect how a Rotameter works. Ensure you understand your fluid and its viscosity. That will help you purchase a device that is compatible with the viscosity of your fluid for accurate results.

3. Valve requirements

Before making the final choice of a Rotameter, consider valve requirements. Are you going to use a needle for inlet or outlet flow? 

4. Maximum and minimum operating pressure and temperatures

You will find a Rotameter that is sensitive to temperatures and pressure. Any slight change in temperature and pressure may affect how your Rotameter works. Before you can buy the device, consider the temperatures and pressure of the fluid you are going to measure and match with the operating minimum and maximum temperature and pressure of your device. 

 5. Cost of a Rotameter

Apart from buying costs, you will incur installation and maintenance costs. It will be vital to consider all those costs when selecting a Rotameter. Go for an affordable Rotameter that offers accurate results.

Benefits of Rotameter

It saves the cost of external power.

A Rotameter doesn’t require an external source of power. That helps to avoid any cost that comes with using external energy to measure fluid flow rate.

You can use a Rotameter to measure gas and liquid flow rate.

Do you seek to monitor the flow rate of gas or liquid? All is taken care of by a Rotameter. You can use it to get an accurate flow rate of both liquids and even gases.

A Rotameter is suitable for measuring the flow rate of the corrosive fluid.

Are you dealing with corrosive fluids? A Rotameter will be the ideal device to use to monitor the flow rate. It is made in a way that it can measure a corrosive fluid and give reliable results. 

It offers a low-cost flow metering solution.

Many devices to monitor flow rate exists in the market. But they aren’t cheap. For some, buying cost, installation, as well as maintenance costs are very high. However, a Rotameter won’t cost much, yet it will give you accurate flow rate results. 


Get a Rotameter, and you will solve an issue related to the flow metering problem. The device is suitable for measuring both gas flow and liquid flow rate. A Rotameter operates in a float-tapered tube system to determine fluid’s flow rate. 

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