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Fan service generally resolves itself into three items; bearings, drive, and guard. Always disconnect the power supply before working on equipment
a. Bearings Fans used on Dust Control Systems usually use a paddle or backward inclined wheel, and are in the medium pressure category. As such they will normally use a double-roller, heavy-duty, pillow-block bearing.
These bearings are not designed to allow axial movement, therefore they are normally installed with one fixed and one floating. On APSCO fans the fixed bearing is located near the fan scroll and the floating bearing at the drive end. As the temperature of the fan shaft changes, the axial movement is taken up by the outboard bearing without imposing additional axial stresses. Keep this in mind when replacing bearings.
Bearing maintenance reduces to proper and timely lubrication. During the summer months, grease these bearings every 60 days with a medium weight industrial purpose grease.
During the winter months, grease the bearings with a light weight general purpose grease every 30 days. In winter, the flywheel weight of the fan wheel, together with the friction in the bearings when cold, imposes a high starting torque for the fan motor. If you can reduce this starting torque you will prolong the life of the equipment, and reduce the starting ampere draw of the motor.
Do not overgrease the bearings. Most often these bearings have a seal to prevent dirt from entering and thereby reducing bearing life. If you overgrease, you run the risk of breaking these seals, thereby creating the exact opposite effect of what you are trying to accomplish. Usually one to two gun strokes is sufficient. You can generally tell if and when you are applying extra pressure to the seals when the gun resistance suddenly increases as you are applying the grease.
b. V-belts Check and replace V-belts as necessary. If the V- are worn, broken, or glazed, they should be replaced. If your system has multiple belts they should be replaced with matched sets, or equivalent. Always ensure that you have the correct belt or belts for your pulley or sheave.
Make sure that shafts are parallel and sheaves are in proper alignment.
Belts should never be forced over sheaves. More belts are broken from this cause than from failure in service. Always loosen the motor slide mount or adjustment so that the belts can be installed easily by hand. Then tighten the belt or belts as illustrated. Check belt tension after 8 hours of operation. Do not use belt dressing.
c. Guards are for everyone's protection. Keep them firmly and properly bolted in place. Disconnect your power source to the fan motor whenever working on this equipment. What more can be said? My uncle lost his right leg to a farm tractor power take-off with the guard removed! One of our shop welders lost three fingers on his left hand to one of our fans, when the guard was removed! Safety is everyone's business.
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