FD Fan Blade Protection and Balance

The challenge

A forced-draft fan feeding a furnace pulls particulate-laden air across its blades hour after hour, and that particulate wears the blade tips down and roughens the faces. As the metal comes off unevenly, the rotor falls out of balance and starts to vibrate, which loads the bearings and shakes the whole assembly. The worn, roughened blades also drag against the air stream and move less of it, so the fan no longer delivers the airflow the furnace needs to run. Left to keep wearing, the imbalance and the lost airflow force the fan, and the furnace behind it, out of service.

Our approach

We take the rotor down and strip the blades to clean metal so we can see exactly where the tips and faces have worn. We rebuild the worn tips and faces cold with a Belzona composite, putting the metal back where the particulate took it and bringing the blade geometry back toward its original shape. Then we lay an erosion-resistant coating across the blade surfaces, smooth enough to cut the drag and tough enough to take the particulate. With the geometry rebuilt evenly across the blades, the rotor comes back toward balance, and the smooth surface restores the airflow the furnace needs while giving the blades a wear face that holds up.

1. Assess and stripWe pull the rotor and strip the blades to clean metal to see where the tips and faces have worn and how far the rotor has gone out of balance.
2. Surface preparationWe blast the blade surfaces to a clean, profiled metal so the rebuild composite and the coating bond properly.
3. Rebuild tips and facesWe rebuild the worn tips and faces cold with a Belzona composite, working with no heat so the blades see no distortion.
4. Coat the wear facesWe apply an erosion-resistant coating across the blade surfaces, smooth to cut drag and tough enough to take the particulate in the air stream.
5. Balance and return to serviceWe confirm the rebuilt geometry brings the rotor back toward balance, then hand the fan back ready to feed the furnace.