When Process Upsets Become Equipment Failures: Why Industrial Fan Selection Must Consider the Unexpected
An industrial fan can be perfectly selected, properly installed, and operating exactly as designed, and still experience catastrophic failure.
How?
Because most fan selections are based on normal operating conditions, while many of the most severe mechanical loads occur during abnormal events.
Emergency shutdowns. Closed dampers. Blocked ductwork. Control system failures. Operator error.
These scenarios may only occur once during the life of a system, but they're often responsible for the most expensive failures.
At BA Associates, we've found that successful fan applications aren't just about selecting the correct airflow and static pressure. They're about understanding what the fan may experience throughout its entire operating life.
A Fan Designed for 75°F… Operating Above 500°F
One recent case study illustrates this concept perfectly.
A stainless-steel centrifugal fan was selected for ambient air service with a design temperature of just 75°F. After only a few months in operation, the fan wheel had warped, the protective coating had failed, and vibration levels had increased dramatically.
At first glance, the conclusion seemed obvious.
The fan must have been undersized or improperly designed.
The investigation revealed something entirely different.
The Fan Didn't Fail. The Operating Conditions Changed.
During an emergency elsewhere in the facility, an upstream isolation damper remained closed while the fan continued operating for several hours. With nowhere for the air to go, the fan became dead-headed and continuously recirculated the air trapped inside its housing.
Without moving fresh air through the system, the fan lost one of its primary cooling mechanisms.
The trapped air continued absorbing energy from the rotating wheel until internal housing temperatures exceeded 500°F—despite the incoming air being only 75°F.
The resulting damage included:
A distorted fan wheel
Failed protective coatings
Excessive vibration
Premature equipment failure
The original design conditions hadn't changed.
The operating scenario had.
This Isn't Unique to One Manufacturer
Whether we're working with Hartzell Air Movement or Garden City Fans (formerly Howden Garden City and now part of American Fan Company), one engineering principle remains consistent:
Industrial fans are only as reliable as the systems they're installed in.
We've seen installations where performance issues were caused by:
Isolation dampers closing unexpectedly
Emergency shutdown sequences
Field modifications made after installation
Added duct losses
Restricted inlets
Process changes that increased system resistance
Control logic allowing fans to operate against closed dampers
In nearly every case, the fan was responding exactly as physics dictated.
The surrounding system created the problem.
Thinking Beyond the Fan Curve
Fan selection software does an excellent job predicting performance under known operating conditions.
What software cannot predict is every possible upset condition a facility may experience years after startup.
That's why application review should include questions such as:
Can dampers close while the fan remains energized?
What happens during an emergency shutdown?
Could maintenance personnel isolate the system while the fan continues operating?
Are process temperatures capable of changing dramatically during abnormal events?
Does the control sequence adequately protect rotating equipment?
These discussions often uncover risks that aren't visible on a fan performance curve.
Engineering for Real-World Reliability
In the case study above, the solution wasn't selecting a larger fan.
Engineers redesigned the rotating assembly using higher-temperature materials, including high-strength stainless steel and Inconel where required, while increasing the design temperature from 75°F to 550°F to provide additional safety margin during upset conditions.
It's an important reminder that mechanical design and materials of construction can be just as critical as airflow and efficiency.
Why Early Application Review Pays Off
At BA Associates, we work with consulting engineers, OEMs, contractors, and industrial facilities throughout New England to review industrial ventilation applications before equipment is released for manufacturing.
Representing both Hartzell Air Movementand Garden City Fans gives us access to decades of engineering expertise across a broad range of industrial applications, from corrosive process exhaust and high-temperature ventilation to heavy-duty centrifugal fans used in demanding manufacturing environments.
Rather than simply matching a fan to a performance point, we work with customers to evaluate the entire system:
Operating sequences
Process conditions
Damper arrangements
Temperature excursions
Material compatibility
Maintenance accessibility
Emergency operating scenarios
Those conversations often prevent problems that would otherwise surface months—or years—after startup.
The Takeaway
Every industrial fan will eventually experience conditions that weren't part of its original design point.
The question isn't whether abnormal operating conditions will occur.
It's whether the equipment has been selected and engineered to survive them.
Whether your application calls for a Hartzell fan, a Garden City heavy-duty centrifugal fan, or another industrial air movement solution, taking the time to evaluate the complete operating sequence, not just the airflow requirements, can dramatically improve reliability and reduce lifecycle costs.
If you're planning a new project or troubleshooting an existing ventilation system, BA Associates can help review your application, identify potential risks, and recommend solutions that perform not only during normal operation, but when the unexpected happens.