Fan Maintenance to Achieve the Design Airflow

The airflow requirement for an industrial process broadly depend on the operational conditions, material to be handled and system resistance. When airflow of a fan system is not adequate, typically industries seek alternatives such as increasing the fan speed or replacing it with a bigger capacity equipment.

To avoid facing issues associated with system airflow, industries have to ensure proper working of their centrifugal fan system. By employing certain maintenance procedures such as checking fan mechanical conditions and performing periodic inspection of system components, the issues with system airflow can be rectified.

Belt inspection
When belts wear or tend to loose tension, they result in reduced fan speed making the system inefficient. Inspecting and replacing belts and faulty drive components for insufficient belt tension and misalignment is important, to maintain required airflow and minimize the risk of energy losses.

Clean air-stream surfaces
Fan system cannot perform as designed when there is a contaminant buildup on the blades and other fan surfaces. Especially, when fans are used in ventilation application to remove the airborne pollutants, there is a possibility of heavy particulate accumulation which may disturb the airflow. Inspection and cleaning of the fan systems has to be done regularly to avoid the issues associated with fan performance.

Leaks in air supply ducts
Leaks are developed when a fan system experiences high vibration levels or when there is a crack or gap in the duct work. When there is a leakage, a part of discharged air from centrifugal fan flows through the gaps where there are poorly fitted joints or worn flexible connectors. To avoid losses in the airflow it is essential to inspect the duct work regularly and identify the leaks that are contributing to reduced system performance.

Check the direction of wheel rotation
Centrifugal fans can be bi-directional fans with straight blades rotating in both the directions or uni-directional with blades fixed at an angle to the shaft rotating in one direction. But, when centrifugal fans rotate in incorrect direction, opposite to the normal design of rotation it will suffer with reduced airflow and system performance.

Improper inlet cone to wheel fit
It is essential to adjust the fan wheel position to provide the proper inlet cone overlap. The purpose of the inlet cone is to convey air to the fan wheel. Any displacement in the fan assembly, shifting the position of the cone away from the wheels may result in loss of airflow.

Check for clogged filters or coils
Clogging of filters occur when there is an accumulation of debris due to indoor moisture or water intrusion into the filter. The hard accumulation of dust and debris on the filters and coils can act as an obstacle for the airflow. If moisture or dirt accumulation are found, filters need to cleaned or replaced.

Inspect dampers for proper installation
Dampers act as control devices for restricting the airflow in an industrial process. When dampers and vanes are used at the inlet, it is essential to install them in such a way that they are open in the same direction as the fan rotation. Verify the installation of dampers to make sure they are not located too far from the inlet of the fan. Also, check if dampers are completely open, otherwise it may obstruct the air entering into the fan system.

Check airflow losses due to system effect
There could be performance deficiencies due to system effect if there are any obstructions or sharp changes in the direction of the airflow at the fan inlet or outlet. To prevent poor airflow through the fan system avoid situations like improper ductwork at the inlet or outlet, placing inlet or outlet too close to the wall or bulkhead, improper or defective installations of dampers etc. If possible keep the duct-work straight at the inlet or outlet to minimize the system effect.