Important checks during Preventive Maintenance Program of Cooling Tower Fans to prevent breaking of FRP blades of Cooling Tower fans during start up.
Ensure that annual CT fan PM check list contain following points also in addition to all other points which maintenance engineers are following in their work place. Any abnormality must be thoroughly examined and necessary repair /maintenance if required shall be carried out to ensure the reliability till the next annual PM opportunity:
1.Inspect for any loose or missing bolts in the fan shaft bushing,the fan hub, and the fan shaft bearing(s).
2. Check the fan blades for looseness, first by twisting the blade
by hand, and then by moving the blade tip up and down. There should be no play or slippage.
3. Inspect each blade for excessive scale build-up that could cause vibration.On FRP blades, consider cleaning the blades and applying a coating of
UV inhibiting paint if the blades are showing signs of UV attack/deterioration.
4.Carefully check the aerodynamic fan blades surfaces ,shanks/shrouds thoroughly for any cracks or damage or severe pits which may become potential reason for breaking of FRP blades during start up.In case of severe pits,replace blades.
5. Ensure that any weep holes in the end of the blades are open and clear.
This is a must so that water does not accumulate in the hollow blade of fans
causing fan imbalance.
6..Check blade track to be sure all blades are running in the same plane.
7..Check individual fan blade pitch to be sure all blades are pitched at the same
angle.If uncertain, measure the pitch with an inclinometer.Check torque on all fan blade clamp bolts. Record pitch angle in your records.
8.Confirm the fan seal disc is in place and all attaching bolts are properly torqued.
9. Confirm the fan tip clearance to the fan stack is uniform around the fan stack.
Clearances are within the design value. Adjust fan stack to proper clearance.
10. Rotation: Turn the fan by hand to ensure that it moves freely with
no rough spots, binding, or other malfunctions that could cause
vibration or fan motor overload. While rotating the fan, check the
blade tracking.
11. Direction of Rotation: On initial start-up, or if the fan motor has
been rewired, bump the fan motor and note the direction of
rotation. It should rotate in the direction indicated by the arrow on
the fan cowl.
12. Operation: On initial start-up, run the fan in the manual position for
several minutes and check for any unusual noises or vibration.
