At AirPro, one of the most common questions we get from customers is: How can I reduce static pressure in my system?
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Imagine you have a regular light switch and a dimmer switch for a light bulb. A regular switch only has “on” and “off,” while a dimmer lets you control how bright the light is. A VFD is like a dimmer switch for a fan motor – it lets you control the fan’s speed. Changing the fan’s speed with a VFD also changes the motor’s horsepower (its ability to do work) and torque (its turning power). Let’s break it down for centrifugal fans (the most common type).
Impeller Types for Centrifugal Fans
New for 2025 is a regular feature on basic fan knowledge from Chet White, our Sales and Marketing Manager. This month we look at the various types of impellers for centrifugal fans.
Fan Wheels: The Basics
One of the coolest things about building fans is understanding industrial fan applications. At AirPro, we build all types of fan wheels depending on customer needs. So why one fan type over another? It all has to do with application.
Reasons for Measuring a Fan
Generally, there are two reasons to measure a centrifugal fan – the user wants to retrofit the fan (or parts) or replace it with a new fan. In either case, accurate measurements are critical to replicating the system currently in place, especially if no drawing is available. If possible, separate or isolate the fan from the system to access key measurement points. If duct work on the inlet or outlet is in the way, this could impact measurement accuracy.
The Centrifugal Fan Basics
The most basic answer to the question, “What does a centrifugal fan do?”, is that it moves gas (air), drawing it into the inlet, turning it 90 degrees, and blowing it through the outlet to exit the fan. It moves a higher static pressure than an axial fan, which moves air and gas straight, in one direction. Without air movement inside buildings – whether a room (like in Chet’s example in the video), a house, or an industrial manufacturing facility – things would get dicey. If you were to be trapped in a small room with no ventilation, only breathing in your own exhaled air, you could only survive for so long. Imagine what would happen in a manufacturing facility where there are many other gases and particles at play! If that is all the information on centrifugal fans you were looking for, feel free to stop reading now. For a little more on how they work, carry on.
Why and How to Vary Speed in an Industrial Centrifugal Fan
A variable-speed fan is just what it sounds like. In this case, we’re talking about an industrial centrifugal fan that is capable of operating at more than one speed. That means it can run above or below the constant motor speed specified. There are several reasons why you would need a variable-speed fan, several ways to do it, and a few things to be careful to avoid when operating at varied speeds.
Use a Damper to Add Resistance and Reduce Airflow
If you want to reduce a fan’s air volume and horsepower without adjusting speed, then you can use a damper to add system resistance. The damper can be installed on either the inlet or outlet side of the fan, and you can determine the best location based on your specific application and your fan performance curve. More often than not, we’ll recommend placing the damper at the outlet as the most cost-effective way to simply add resistance.
5 Steps to Find and Fix Industrial Fan Performance Problems
Troubleshooting and addressing fan performance issues can feel overwhelming, but with the five steps outlined below and the help of a trusted application engineer either remotely or on-site, you can find the solutions you need for your operations.
Things to Check When Running Your Fan for the First Time
When your new industrial fan or blower arrives at your facility from the manufacturer, it should already be tested and ready for fan installation. But that doesn’t mean there’s nothing more to do to ensure it operates properly! Whether it sits idle awaiting installation or goes right into service, there are several important things to check when running your fan for the first time.
3 Ways to Clear Debris from an Industrial Fan
Sometimes the most simple things like cleaning get overlooked, potentially leading to many more serious issues. It’s important to properly clean a blower wheel, as material buildup on a wheel can cause vibration and damage your fan. Even “clean air” may contain various particles and debris. A simple cleaning procedure can keep your fan healthy and decrease downtime.
Industrial Fan V-Belt Installation, Alignment, and Tensioning
Many industrial fans operate using a v-belt drive. The constant motion and friction make it very important to ensure proper fan belt alignment and tension upon installation and during routine maintenance. Getting this right will help extend the life of the fan belt. Proper installation is based on the specifications in the installation and operation manual (IOM).
Common Types of Fan Bearings Explained
No matter what kind of centrifugal fan you have, you can be sure that it has bearings in its connection to the motor. The bearings enable movement in this heavy-duty industrial machinery. There are two configurations and three common types of fan bearings, which we will outline below.
Back to Basics: Explaining Centrifugal Fan Airflow
There’s more to a centrifugal fan than blade structure (versus axial) and function (to move process air and other materials as part of a larger system). Centrifugal fan airflow is at the core of how it works.