How To Check Cooling Tower Fan Blade Angle

Here is a clear and practical guide on how to check the blade angle of a cooling-tower fan, using standard field methods.

 ✅ How to Check Cooling Tower Fan Blade Angle

Cooling-tower axial fans rely on correct blade pitch (angle) to produce the proper airflow (CFM). An incorrect angle can cause low performance, high vibration, motor overload, or noise.

You can check the blade angle using one of the following methods:

Method 1 — Using a Digital Inclinometer (Most Accurate)

Tools Needed

* Digital angle finder / digital inclinometer

* Ladder or platform (if required)

* Fan lock-out/tag-out (LOTO)

Steps

1. Shut down and lock out the fan

Ensure the fan cannot start accidentally.

2. Place the inclinometer on the blade surface

* Choose a spot near the blade’s mid-span (not at the tip or root).

* Place the gauge on a flat portion of the blade.

3. Zero the inclinometer

* Many techs first zero it on the hub or on a horizontal frame section.

4. Read the blade pitch angle

Record the angle displayed. This is the blade pitch relative to horizontal.

5. Repeat for all blades

Ensure all blades have the same angle within ±0.5°.

Method 2 — Using a Manual Protractor + Level (Traditional Method)

Tools Needed

* Mechanical protractor

* Straightedge

* Spirit level

Steps

1. Lock out the fan.

2. Place a straightedge along the blade surface.

3. Use the protractor to read the angle between:

* The straightedge (follows blade surface)

* A horizontal reference (using the spirit level)

This method is less precise but works for older installations.

Method 3 — Manufacturer Markings on Hub (If Provided)

Some cooling-tower fans (e.g., Marley, EVAPCO, Liang Chi) have:

* Pitch reference lines on the hub

* Slot positioning that corresponds to known angles

Steps:

1. Align the blade’s root to the marked index.

2. Read the corresponding angle from the manufacturer chart.

Method 4 — Measure Chord Line Angle (Engineering Method)

If no flat surface exists (some FRP blades are curved):

1. Measure two points along the blade’s chord line (leading to trailing edge).

2. Use a jig or angle gauge to determine the angle of the chord line relative to horizontal.

Used mainly when accuracy is critical.

 ✅ What Is the Correct Blade Angle?

Typical cooling-tower axial fan pitch: 14°–32°

Depends on:

* Fan diameter

* Motor HP

* Airflow required

* Manufacturer specifications

Never change blade pitch without verifying motor amperage limits.

⚠️ Important Safety Tips

* Always lock out/tag out before touching fan blades.

* Use proper fall protection around towers.

* Ensure the fan cannot freewheel from natural draft (block the fan if necessary).