Induced Draft Fans for Industrial Applications

Induced Draft Fan Applications

Induced draft fans (ID fans) often process air in harsh conditions including high temperatures, acidic airstreams, and other extreme exhaust gases. They focus the volume and pressure at the inlet of the fan to pull air and other materials or elements through the system, extreme conditions can require special attention to imbalance, excessive vibration, temperature, maintenance, and operating costs, but they can also operate at higher efficiencies relative to forced draft fans,

The induced draft fan is situated above the bundle, creating negative air pressure to draw the air through to the next step of the process, which could be another application like a dryer or an air treatment system for pollution control. It could also be the exhaust to the outside air. They can work in concert with forced draft fans to maintain efficient and steady air pressure.

Your induced draft fan application environment and airflow will dictate fan selection and specifications. Scroll or hyperlink down to find Application Featured Products, Case Studies, and further application details as follows:

Primary Industries
Fan Selection & Specification
Arrangements, Accessories, & Design
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Primary Industries for Induced Draft Fans

Induced draft fans are found across industries. However, because they are instrumental in processing air, gas, and materials under harsh conditions, you can be sure you’ll need an induced draft fan in any or all of these industries:

Agricultural Processing
Automotive OEM
Building Materials
Chemical Processing
Food Processing
Glass Manufacturing
Metals & Mining
Oil & Gas
Paint & Surface Coatings
Pharmaceuticals
Power Plants
Printing, Packaging & Labeling
Pulp & Paper
Rubber & Plastics
Semiconductor & Electronics
Wastewater Treatment

Selection & Specification of Induced Draft Fans

As mentioned above, induced draft fans typically operate at higher efficiencies relative to forced draft fans, though it depends on the nuances of your application. They also have better process control and stability with reduced exposure to elements like wind, rain, and hail. Select and design your fans based on function, flow, and pressure. Here’s a quick overview of the top fans for each main function:

Typical Types of Induced Draft Fans

Fan Arrangements

Fan Arrangements indicate how the motors mount to and drive the fan. For induced draft fans, we typically use a direct drive arrangement. Usually, Arrangement 4 or Arrangement 8, unless the blower is very large, in which case we might specify an Arrangement 7:

Arrangement 4 – Direct Drive with an overhung impeller. A low-cost arrangement, the fan wheel mounts directly on the motor shaft.

Arrangement 4V / Top Mount – Direct Drive with an overhung impeller. The wheel also mounts directly on the motor shaft, but in a vertical position.

Arrangement 7 – Direct Drive with a center-hung impeller. The motor is directly coupled to the fan shaft with a bearing on either side of the fan wheel. Involves a bearing on either side of the fan wheel and is supported by the fan housing.

Arrangement 8 – Direct Drive with an overhung impeller. The fan shaft is directly coupled to the motor shaft with a flexible coupling.

Fan Accessories & Design

The same harsh conditions (high temperatures, acidic airstreams, and other extreme exhaust gas) that make induced draft fans the right choice also make them critical components of operations, and present risks to your fan’s health. If harsh environments present higher threats to your fan’s health, then it’s probably safe to assume your maintenance and operating costs will be higher.

Frequent vibration and temperature testing, fan cleaning, bearing lubrication, and higher power consumption are some of the factors you may want to consider when selecting your induced draft fan. For example, choosing a fan with high static efficiency may significantly lower your operating costs.

Here are just some of the accessories and features you may see In induced draft fan applications:

Flex Connectors to accommodate shifting during rapid temperature change
Spring Vibration Isolators to protect the fan from excessive vibration
Inlet Silencer for noise control on the fan inlet
Inlet Vane Damper, Variable Frequency Drive (VFD), Outlet Damper, or a combination for volume and pressure control
Inlet Filter or Screen to keep the airstream clean and avoid damaging the dampers
Inlet Box if space is tight for the ductwork
Purge Shaft Seal helps prevent hot air from getting to the bearings through the shaft hole opening
Vibration and temperature sensors to monitor bearing and fan health and prevent unplanned outages
Split Housing for easier maintenance access to the fan wheel and shaft.
Proper installation and maintenance to ensure safe startup and operations

Talk with Our Application Engineers

If you feel overwhelmed by all this information, don’t despair! We have a team of application engineers who are happy to talk with you and select the best fan for your application. You can call 715-365-3267, email [email protected], or send us your information, and one of our engineers will connect with you.