Why do fans surge?

What causes a fan to surge?

As long as the outlet pressure of the blower is greater than the downstream pressure, the blower operates smoothly and efficiently. If the blower is slowed down enough or the downstream pressure rises suddenly beyond the capacity of the blower surge will occur.

What is fan cavitation?

If there is a restriction of the available air above the blades for the fan to draw upon, this can create a vacuum effect and begin to draw the same air that is being displaced down, back up to the top of the fan. This results in a “cavitation” effect and impedes the performance of the fan.

How do fans increase pressure?

For a fan, it is based on the average air velocity at the fan outlet. As the velocity of the airflow increases, the velocity pressure increases. The total pressure developed by a fan is the sum of its static pressure and its velocity pressure. The acoustic energy emitted by a sound source.

What is rise to surge?

The achievable rise to surge is directly influenced by the required compressor operating range. The HRTS is a measure of the rise in the head (at constant speed) when the operating point moves toward the surge line. Other common terms related to HRTS include pressure rise to surge, and pressure ratio rise to surge.

What causes a fan motor to seize?

The most common cause of fan motor seizure is lack of lubrication to the bearings. Usually there is no provision to lubricate the bearings because, according to the manufacturer, the bearings are “permanently” lubricated. However, even simple experience shows that the lubrication is not permanent.

How do you overcome cavitation?

Some tips to prevent cavitation due to vaporization include:

  1. NPSHa > NPSHr + 3 ft or more safety margin.
  2. Lower temperature.
  3. Raise liquid level in suction vessel.
  4. Change out pump type.
  5. Reduce motor RPM.
  6. Use impeller inducer.
  7. Increase diameter of the eye of impeller.


Which fan type is well suited to handling high particulate airstreams?

Radial fans
Radial fans are industrial workhorses because of their high static pressures (upto 1400 mm WC) and ability to handle heavily contaminated airstreams. Because of their simple design, radial fans are well suited for high temperatures and medium blade tip speeds.

What is fan curve?

Fan curves are simply graphs showing fan performance, normally with air volume on the horizontal “x” axis, and pressure on the vertical “y” axis. … For a fan driven by an electric motor, the input voltage remains the same throughout the test.

How does a fan airflow work?

Centrifugal Fan Airflow and How the Centrifugal Fan Works Here's how centrifugal fan airflow works: An induced draft centrifugal fan pulls the air, fluid, gas, and any particulate through the system into the inlet. The blades rotate to move the air to discharge through the outlet at a 90° angle.

Do fans increase air pressure?

A fan increases the static pressure on it's outlet and can also decrease the static pressure on the inlet slightly. Even though very slight in comparrison, a fan is technically a compressor. The static pressure rise is usually in the order of inches of water.

What is a surge curve?

surge consists of total flow oscillations around the whole rotor. • the surge curve is the zero slope points of the characteristic curves.

How do you fix a seized fan?

0:311:41Fixing a seized oscillating fan motor – YouTubeYouTube

How can you tell if a fan motor is bad?

5 Signs That Indicate a Failing AC Fan Motor

  1. The fan won't start even though the AC is on.
  2. The fan continues to run, even when shutting off the AC.
  3. The fan is on but rotating very slowly.
  4. The fan runs intermittently.
  5. There's a rattling or buzzing noise coming from the condenser unit when the fan is turned on.


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