How to adjust the angle of large fan blades?

Hainanquwei gave a good answer on the eighth floor. Generally, if it is new, it will be numbered during installation. If the old and new blades are installed together, weigh the blades to see if they are the same. The angle adjustment is generally at the top of the blades. Just use a universal angle ruler and a steel plate ruler to measure at 20mm. The general angle is 9 to 11 degrees. One additional point: In addition to the above factors, the angle of the fan blades must also consider process requirements and motor current. The second question asked by the original poster: Adjustment of the gap between the fan blades and the air duct? The general requirement is not less than 10mm, but it should not be too large to affect the air volume.