A flowmeter has a single job: to measure the rate (or volume) of fluid that passes through it. The tool is used in a variety of applications, from the fuel pump at your local gas station to pressurized containment systems in chemical plants. It's used to monitor a fluid's flow rate so the process manager can decide whether adjustments are warranted.

When it comes to flowmeters, precision accuracy, while helpful, isn't always necessary. Much depends on the requirements of the application. For example, precision measurements would presumably be more important in a laboratory or chemical treatment plant than a vineyard. That's worth noting since greater precision comes at a higher cost.

We'll explain the mechanics behind a flowmeter below. You'll learn about its basic operation as well as how to choose the right device for your particular application. We'll also cover a few precautionary notes regarding its installation.

How A Basic Flowmeter Works

The basic flowmeter has 3 simple components:

1. a flow tube through which the measured fluid passes
2. a float that rises and falls with the rate of flow
3. a scale that allows the manager to instantly identify the flow rate

The flow tube is tapered. Positioned vertically, its lower end has a smaller diameter than its upper end. Thus, a uniform rise of the float indicates a faster flow rate. The higher the float rises, the more fluid that passes through the flow tube. Eventually, the float reaches a high enough point where the increased diameter of the tube allows fluid to pass by the float unhindered.


How Float Density Affects Flow Capacity

Flowmeter floats are available in a variety of materials, including glass, tantalum and carboloy (an alloy containing carbon and cobalt). The type of material dictates the float's density. The density influences the rate at which the float rises in the flow tube; denser materials rise more slowly than lighter materials. That in turn affects the associated flow rate.

Choosing a different float density isn't the only way to influence an application's flow capacity and allowable flow rate. A smaller or larger float can also be used to the same end. As long as the variable (tapered) diameter of the flow tube is left unchanged, a different-sized float will affect flow capacity.

Another option is to change the size of the flow tube. The greater its tapered diameter, the greater its flow capacity.

Choosing The Right Size Flowmeter For The Application

The size of the flowmeter should reflect the type of fluid being measured. Different fluids pose different densities, pressures and temperature ranges. For that reason, it's important to evaluate the flow specifications and conditions of the application before making a selection.

It's not enough to distinguish between gas, air and liquid. The type of gas, air and liquid must be taken into account to ensure the flowmeter performs as expected.

Precautionary Notes On Installing Flowmeters

As noted earlier, flowmeters are installed in a vertical position. That's important because the float is dependent on gravity. While its rise and fall within the flow tube is influenced by the force of the measured fluid, gravity is an essential ingredient in its operation.

It's also important to make sure the flow tube remains free of fluids that are not intended to be measured. For example, a flowmeter intended to measure the flow rate of gas should not contain water. Likewise, a flowmeter intended the measure the flow rate of water should not contain gas. The presence of unwanted fluid in the flow tube will negatively impact the flowmeter's accuracy.

Being familiar with how flowmeters work is helpful when it comes to selecting a model for your application. Having said that, if you have any questions regarding which model is best-suited for your needs, our support staff can provide answers. We're committed to providing the tools and services you need to streamline your operations.