Pitfalls #6 – Flexible connectors and high temperature: not just about vibration
We were recently asked, on a high-temperature installation: can you skip the flexible connector between the fan and the duct, to simplify installation?
The short answer is no — and the reason goes beyond what’s usually assumed.
The best-known role: isolating vibration
This is the function most people associate with a flexible connector: mechanically decoupling the fan from the duct, so the machine’s vibrations don’t transmit to the rest of the installation. That’s real, and it’s often the only reason we hear when a customer considers doing without one.
The lesser-known role: absorbing thermal expansion
At elevated temperature, steel expands — roughly 1 mm per metre of duct per 100°C. Over a line several metres long, cumulated across the full length, that movement becomes far from negligible.
That movement has to be absorbed somewhere. Without a flexible connector between the duct and the fan, it transmits directly onto the inlet or outlet flanges — and from there to the housing, potentially reaching the shaft and bearings. It’s not an immediate failure, but an added mechanical stress, repeated with every heating and cooling cycle, on components that weren’t designed to take it.
That’s what we explained to this customer: a flexible connector isn’t just a vibration damper — it’s also what lets the duct move without forcing against the fan.
Key takeaway
On a high-temperature application, the question isn’t only “does it vibrate?” but also “does it move as it heats up?”. Both call for the same answer: leave a point of flexibility between the fan and the duct.
Not sure about an existing or planned installation? Let’s talk.