How To Make a Fan Performance Curve

Fan Curve Development for Centrifugal Fan Applications

The fan performance curve shows the pressure and flow rate that the fan will produce for any system connected to it. The actual fan performance is dependent upon the detail design of each system. System designers calculate process air requirements, and the fan application engineer selects fans to meet those requirements, which are graphically represented by a fan curve.

We can plot a fan performance curve for any given specification, from horsepower to temperature to static pressure. For this demonstration, we’re using static pressure versus airflow volume.

Collecting Data Points to Plot a Fan Performance Curve

Any curve is simply a series of points plotted on a graph and connected to extrapolate a solid curve. To get those data points, we need to measure the element we want to plot at the minimum, maximum, and several points in between.

In this case, we are measuring fan static pressure (y-axis) relative to airflow volume (x-axis). To get the various points that will form the fan performance curve, we vary the airflow volume and take readings of fan static pressure at each volume level created.

For this fan performance curve, we take our measurements of static pressure (an indication of the air flow resistance inside the fan) using a Pitot Tube at a specified distance from the fan outlet toward the middle of the duct.

We change the volume of airflow using metal plates to vary the size of the fan outlet. To get the maximum reading, we measure without a metal plate covering the fan outlet. To get the minimum, we use a solid plate that covers the outlet completely. Once we have an appropriate number of data points plotted on the graph, we can connect them to form the fan static pressure performance curve.

chart showing a fan static pressure curve and a brake horsepower curve

What We Do with the Fan Curves

We provide the fan curves to application engineers installing centrifugal fans into industrial applications. The fan performance curves for the fan in question are necessary for them to complete the installation and operate the fan efficiently.

Hear it from an Application Engineer

Senior Application Engineer Chet White demonstrates the process of measuring and plotting a fan performance curve in this 5-minute video.

When you’re ready to start your project, reach out and connect with one of our application engineers to discuss the details of your specifications.

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