Adjusting Fan Blade Pitch
The trial pitch is the calculated setting for design conditions
Note(water rate , heat load, air density, and brake horsepower). The trial pitch is provided by SPX Cooling Technologies (see page 2).
BLADE | STRAIGHT | BEVEL |
TIP | EDGE | PROTRACTOR |
| | PITCH ANGLE |
| Section | |
1–Select a position on the fan circumference and rotate each blade to this common location when setting or checking blade pitch. Sup- port the blade tip to maintain a common rotation plane while setting the fan pitch. The pitch is set within 2″ (51mm) of the blade tip by placing a bevel protractor on top of a parallel sided straight edge that extends across blade width as shown in Figure 6.
2–Pull the blade outward so the safety shoulder is in contact with the blade clamp, then set the pitch. See Figure 5. Blades should be within ± 1/4° of the desired pitch angle. After the de- sired setting is obtained, progressively tighten the C\v″ hex nuts to 120 ft·lbƒ (163 N·m) torque. Recheck the pitch angle. If required, loosen the hex nuts and reset the pitch as necessary until the proper pitch angle is obtained with the C\v″ hex nuts at 120 ft·lbƒ (163 N·m) torque.
3–Repeat step 2 for all blades.
4–Check the vertical blade-tip track variation. The allowable vertical variation from a reference plane is ±1″ (25mm). If a blade’s tip track is out of tolerance, loosen the C\v″ hardware and change the blade tip support location higher or lower as required to adjust the tip track. Recheck blade pitch angle.
