At Pelsue, we believe in selecting the right tool for the job. And when you need to do the important work of ventilating your workspaces, it helps to understand the difference between axial and centrifugal (sen-TRI-fuh-gl) blowers.
These two most prominent types of industrial blower each have different advantages. Having either one is crucial to ensuring a safe workspace, but which one is right for you?
To help you make an informed choice, we wanted to put together a handy introduction guide. We’re going to over the major differences between our Axial and Centrifugal blowers and compare their performance in hypothetical situations.
But first, it’ll help to go back to a very basic question.
No doubt some of you read that and think, “Well…because we need to be able to breathe.”
You are, of course, correct. But there are several different factors that go in to making the air in a confined space breathable.
When you ventilate a confined space, you’re not only adding breathable air into a space, you’re forcing potentially harmful air out.
As we discussed in one of our previous posts, the air in confined spaces can contain large, even hazardous concentrations of those harmful gases. Along with using gas monitors before entering and while working in a confined space, employing ample ventilation to purge toxic gases is key to ensuring worker safety.
Ventilation also makes air more breathable by purging it of dust and other particles. Not only do these small bits of solid matter floating in the air make breathing harder, they also carry with them an increased risk of explosion.
Blowers can also be positioned to bring cool air into a confined space while pulling out warm air (or vice versa). Workers can experience heat stress in indoors just as easily as outdoors. Lowering the temperature of warm spaces is important for both worker safety and comfort. You can magnify the impact of this by using a portable air conditioner or heater in combination with your blower.
Ventilating your confined workspace is an obvious choice. But what kind of blower is right for the job? That’s a little more complicated.
The Right Blower for You
Let’s start with the upshot. Centrifugal blowers offer more power and faster purge times (the length of time it takes to fully exchange the air in a given space). Axial blowers are more affordable and require less power to operate.
As with so many other tools, there’s no simple, direct answer to the question: which one is better? Centrifugal and axial blowers are each suited to different crews and situations.
Axial blowers get that name because they move air along an axis. The fan blades on an axial blower rotate around the axis, drawing in and pushing out air parallel to that axis.
In contrast to axial blowers, centrifugal blowers put out air perpendicularly to their intake. The air is then usually directed through a series of ducts and tubes, which creates a constant output pressure.
Centrifugal Blowers: Better Flow Rate Means Faster Purge Time
The main advantage of centrifugal blowers is that they maintain a higher air flow rate than axial blowers. When attached to a hose with one 90 degree bend, our centrifugal blower has a certified flow rate of 1,360 cubic feet per minute (cfm), compared to 492-586 cfm for our Steel Axial Blower (depending on the model).
Centrifugal blowers have another easy-to-overlook advantage, namely that they’re generally more portable than axial blowers. Since axial blowers operate in one direction, they’re limited in how small they can be. A centrifugal blower, on the other hand, can produce higher pressure airflow in smaller space by forcing the air through its ducts.
Axial Blowers: Easier to Buy, Less Expensive to Run
Axial blowers, though, have other advantages which shouldn’t be dismissed. Axial blowers are considerably less expensive to purchase than centrifugal blowers. Since ventilation is crucial for safe work environments, the affordability of axial blowers is important for smaller organizations with more demanding budgets.
Axial blowers generally have the advantage when it comes to power consumption. While centrifugal blowers will purge a given area 2.5x faster, their gasoline engines require more power to do so. Our axial blowers run off electric power and consume less proportionally. This advantage shrinks as the size of the confined space increases, but for most spaces you encounter on the job, axial blowers cost less to operate.
How to Calculate Purge Time
That brings us to a very important point about your blower: your purge time will vary no matter what type of blower you choose.
The dimensions of your workspace and the potential presence of hazardous gases both have significant effects on your total purge time.
These variances can make judging the right purge time tricky. Fortunately, we have a tool to help. Our handy Purge Time Reference Chart is available on our website for you to gauge the appropriate purge time based on the size of your workspace and flow rate of your blower. All you need is a straightedge.
Just place your straightedge on the left–hand side along the “manhole size” axis (this is measured in cubic feet, so be sure to have a measurement of that before you begin). Then, align the straightedge along the right-hand side “effective blower capacity” axis. Where your straightedge intersects the diagonal axis is the recommended minimum purge time.
For spaces where hazardous gases are present, purging time should be increased by 50%. And, as always, gas monitors should be used before entering and while working in any confined space.
Properly ventilating your workspace is one the most important safety measures in confined space work. Choosing the right blower and allowing ample time to use it are crucial to doing the job correctly.
At Pelsue, we’re dedicated to providing you with the tools to keep your workers safe. Whether it’s our heaters, gas monitors, or blowers—both kinds—we design everything as if it would be used by our own family. We put every ounce of care and attention we have into everything we make so you and your crew gets home safe.