Waiting on fan manufacturers to get quotes back to you can be stressful. Frequently, you do not have the time — days or even hours — to wait for a quote. Fan buyers have another option though: Most industrial fan/blower companies offer fan selection software, available via the Internet on company websites, or offered as a program to be installed on your computer. No matter the source though, it is important to do two things before using the selection software to find the appropriate fan for your application.
• Learn the Products. When making a fan selection, you typically get several options for fans that may meet the desired performance. Naming conventions vary from vendor to vendor, so you should access the company’s website or call and request information on product types to narrow down your search within the selection software. Whether you have a need for radial bladed fans, industrial exhausters or backward inclined, high-efficiency fans, find out what the company you’re considering calls that type of fan, and what it is capable of handling, before accessing that company’s selection software. It will make selecting fans much easier.
• Learn How to Navigate the Selection Software. Now that you know the names of the products and have reasonable confidence that the chosen fan company manufactures the type of fan or blower that you need, the next step is to understand how to make a fan selection with that vendor’s selection program. Is there a manual on how to use the software? If not, contact a sales engineer to take you through a fan selection over the phone or by webinar.
Once you understand the products and the software, the following advice should help you understand five facets of the fan selection process.
Performance Data Input
Every fan selection begins by entering the desired performance data. Volume and differential static pressure are absolutely critical, as every following step is driven based upon these two numbers. Assuming that air is the gas going through the system, the next critical information includes airstream temperature, site elevation and inlet static pressure. These three numbers combine to give an approximate air density based on 0.075 lb/ft3 at standard conditions. Finally, select the desired fan arrangement, discharge orientation and rotation.
If you are dealing with cold airstreams at startup, cold start temperature is a critical number because the air likely will be denser than the air at operating temperature is expected to be. Knowing the possible air density at startup could lead you to change your motor selection.
After entering the performance data, the next step is selecting a fan. If you learned about the fan manufacturer’s product offerings and fan selection software, this should not be too difficult. Armed with the knowledge necessary to select your desired fan, the only challenge here is to choose the correct fan size. If the fan selection program allows it, try sorting by what is most important to you. For instance, if efficiency is of utmost importance, sort the selections by static efficiency. Likewise, if fan speed is critical, sort by speed. Once you have decided on which fan is best for your application, move on to the fan curve.
This step gives the most detail regarding what you can expect from the fan that was chosen. The fan curve should show the intersection between the system resistance curve and the static pressure curve. This intersection point will be the air volume (x-axis) and static pressure (y-axis) entered in the performance data step. This point then will project onto the horsepower curve so you can know what motor size will be necessary to operate the fan in your system.
While the figures for this article include the predicted sound level, it may or may not be included on the fan curve page using some selection software packages.
If you already have approximate fan dimensions in mind for your particular system, this may be the most important of the five selection software steps. While you cannot get full-scale CAD drawings through a selection program, you should be able to get critical mounting dimensions such as inlet diameter, outlet dimensions (rectangular or round), centerline height, width and height. For engineers looking to design a fan into their system, this may be the only reason you use fan selection software. It is important to understand the first two steps so you can successfully make it to this point.
Using fan selection software to price the fans needed for your project can save you valuable time. It is critical to understand what is required for each fan arrangement when making pricing selections. For instance, in order for an Arrangement 1 (belt-driven fan with motor mounted separately) fan to function properly, it needs a motor, V-belt drive, OSHA guards and unitary base in addition to the basic fan parts. Comparatively, an Arrangement 4 (direct drive with fan wheel mounted to the motor shaft) fan only requires a motor in addition to the basic fan parts. Additional items such as an inlet box, spring vibration isolators, or damper may be available depending on which selection software you are using. Once you have successfully priced the fans required for your system, you have the freedom to move forward.
Not all selection software packages include the above five phases. Make sure to first learn the fan selection software, as advised early in this article, so you are fully aware of what each selection software package offers.
Web Exclusive: Understanding the 5 Phases of Fan Selection Software