Changing Shaft Speed
All belt driven fans with motors up to and including 5 hp (184T max.) are equipped with variable pitch motor pulleys. To change
the fan speed, perform the following:
1. Loosen setscrews on driver (motor) pulley and remove key, if equipped.
2. Turn the pulley rim to open or close the groove facing. If the pulley has multiple grooves, all must be adjusted to the
same width.
3. After adjustment, inspect for proper belt tension and alignment.
Speed Reduction
Open the pulley in order that the belt rides deeper in the groove (smaller pitch diameter).
Speed Increase
Close the pulley in order that the belt rides higher in the groove (larger pitch diameter). Ensure that the RPM limits of the fan and
the horsepower limits of the motor are maintained, which can be read on the motor nameplate.
Pulley & Belt Replacement
1. Remove pulleys from their respective shafts.
2. Clean the motor and fan shafts.
3. Clean bores of pulleys and coat the bores with heavy oil.
4. Remove grease, rust, or burns from the pulleys and shafts.
5. Remove burrs from the shaft by sanding.
6. Place fan pulley on the fan shaft and motor pulley on its shaft. Damage to the pulleys can occur when excessive force
is used in placing the pulleys on their respective shafts.
7. Tighten in place.
8. Install belts on pulleys and align as described in the
Belt and Pulley Installation
section.
Bearing Replacement
The fan bearings are pillow block ball bearings or flange bearing assembly, depending on type of fan. An emery cloth or file may
be needed to remove imperfections in the shaft left by the setscrews.
Fig. 10 – Bearing Assembly
NOTE: In applications where contact with the exhaust poses a serious contamination is a factor, the bearings can be removed
with the wheel and inlet cone staying in place. In this case, the shaft must be held in place with suitable straps or bracings firmly
secured around the bearing support frame. The shaft must be supported to restrict any lateral movement of both shaft and
impeller. In this case, review but skip steps 2, 4, 6, & 14 .
1. Mark the position on the shaft of both bearing races, setscrews, and the wheel and pulley.
2. Mark the location and orientation of the inlet cone. Note the clearance between the wheel and the inlet cone.
3. Remove the fan pulley.
4. Remove the inlet cone. Remove the wheel from the shaft – a 2-jaw puller may be needed.
5. Remove bearing hold-down bolts.
6. Remove shaft and bearings as one unit.
7. Remove anti-corrosion coating from the shaft with a suitable degreaser.
8. Remove the bearing from the shaft using a bearing puller. If a bearing puller is not available, tap on the bearing with a
wood block and hammer to remove it.
9. Smooth and clean the shaft and bearing bore thoroughly.
10. Place the bearings into position making sure they are not on a worn section of the shaft. Tapping the inner ring face
with a soft driver may be required.
Do not hammer on the housing
.
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