Maintenance Of Centrifugal Fans

By Author: Neel Rao
Total Articles: 119
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Like any other piece of industrial machinery that undergoes rigorous use and plays an important role, centrifugal fans need to be inspected regularly. Particularly, the fan surfaces and the impeller tend to collect deposits which reduce the efficiency of the fan and often result in vibration and imbalance.

However, it is to be kept in mind that only the minimally necessary amount of cleaning should be carried out and it should be done very carefully. Any harshness in the cleaning process may damage the airflow surfaces and surface finish. The type of cleaning would depend on the current situation of the fan and how rigorously it is used.

Warning: The electrical supply must be completely shut off and the lockout procedures followed before initiating the process. To prevent the wheel from rotating by any means, the rotating assembly should be blocked too.

Inspection
When a new centrifugal fan is installed, it should be inspected every few hours. The frequency of inspection can be gradually reduced in the order of daily, weekly, bi-weekly, and then monthly.

Visual Inspection Of The Fan
It ...
... is essential to take a detailed look for any signs of damage to the fan blades or structural deterioration. In industries where the fans are run continuously, these inspections are usually made annually. However, if even an annual inspection isn’t possible, it is necessary to carry out maintenance inspections during any short shutdown.

Inspection Of The Fan Motors
One of the most visible signs of motor failure is unexpectedly low. However, low amperage might also indicate the fan assembly requires maintenance. Other than these, you might also want to check if the motor is running in the right direction and ensure that the condenser fan isn’t cycling too rapidly.

Cleaning The Fan Blades
The fan would become less efficient if the blades of the impeller get dirt-coated. Usually, effective filtration systems can keep out most of the dirt. However, it is still wise to carry out at least one inspection every year. As the blades of the impeller in the forward curved fans are scoop-shaped, they particularly tend to collect dirt. Even if it is a small fan, cleaning the blades might require about an hour as the impeller need to be taken off.

Lubricating The Bearings
The sleeve bearings must be lubricated twice or thrice a year as they are metal-to-metal running surfaces. The bearings should be labeled with the recommended lubricant type and the lubrication intervals. You might want to keep in mind that the bearings cannot be re-greased. In case if a bearing generates excessive heat, noise, and vibration, it is likely to fail soon. This usually happens when the bearings get several years old and when it does, the bearing cassette needs to be replaced.

Adjusting The Belts
The belts in the centrifugal fans need to be protected from dripping oil, chemicals, and oil mist. If the belts aren’t protected and are constantly exposed to oil and chemicals or aren’t adjusted properly, they tend to wear out and need replacements more often than usual. If the belts are too tight, they would pressurize the fan shaft bearings and the motor excessively. This may cause either the belt or the bearing to fail. Loose belts wear out easily and cause the fan to lose torque by slipping off.

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