Large air moving fans used in air cooled heat exchangers or cooling towers sometimes “wind-mill” while powered off. Wind-milling occurs when back drafts cause fans to rotate backwards when out of service. This can present safety concerns to personnel working in the proximity of the fans. It can also damage fan structures and belt drive systems when the units are powered on and the counter-rotating fan inertia energy is quickly dissipated and absorbed by the structure and power transmission system.
The Gates Draftguard product eliminates these issues. It consists of a strong one-way clutch that mounts directly to QD bushing sizes E, F and J and TaperLock bushing sizes 3020, 3525, 3535 and 4030 or directly to fan shafts. With Draftguard mounted and the torque arm secured, fans can no longer counter-rotate, but are free to rotate normally when powered on. This eliminates system start-up shock loads and enables technicians to perform maintenance operations on belt drive systems without concern of unexpected backwards movement.
Draftguard is a great product to consider when drive shaft counter-rotation causes safety concerns. Draftguard also reduces the chance of structural damage and synchronous belt tooth jumping when high inertia and counter-rotating fans are started.
For more information, contact Gates Product Application Engineering at 303-744-4947 or firstname.lastname@example.org.