Choose Your Air Blower
An air blower, also known as a centrifugal fan, is a mechanical device for moving air or gases.
How do Air Blowers Work?
A blower is a machine used for moving gas with a moderate increase of pressure, or in other words, a more powerful fan. A blower is able to push air in any direction you want it, as the angle of the blades of the air blower can be changed. Air blowers are used in the industry in the following ways:
- To generate a specific quantity of air flow
- Build pressure generated by an air flow to compensate for pressure drops
Several applications require a specified quantity of air. However, it may not be feasible to place an air blower at the point of application. In such cases, the generated air flow is guided to the point of application. As the air flows along the pipe, there is resistance to the air flow and hence, a pressure drop. The air pressure generated must be increased by an amount equivalent to the expected pressure drop, otherwise the amount of pressure received at the point of application would be too low due to air resistance and friction.
How to choose an Air Blower for your needs?
There are 3 factors to consider while choosing a fan or blower:
- Fan type: Fan types can be broadly classified into two – centrifugal blowers and axial fans. A centrifugal blower receives air through the blower housing inlet and discharges it in a perpendicular direction through the outlet. An axial fan takes in air through a propeller and discharges it in the same axial direction. It is used as an inline duct type of wall fan. However, an axial flow fan cannot be used to convey material.
- Total airflow: Airflow is measured in cubic feet per minute (CFM) or cubic metres per hour. If you are using a blower to convey material, you must ensure that the CFM of the duct or hose pipe is high enough to allow the material to have a velocity to move forward. Otherwise, the material may settle down in the pipe.
- Static pressure: Static pressure is caused by friction or resistance to airflow in the pipe or duct. It is measured in inches of water gauge (SPWG) or in Pascals (Pa). It is the sum of all the pressure drops through the entire pipe in the inlet, outlet, filters, control dampers, louvers and all other components in the system that cause resistance to airflow. If the static pressure on the inlet of a blower exceeds 15” SPWG, a correction for suction pressure must be made. This process is called rarefaction.
Air Blower Maintenance and Repair
Periodic maintenance of blower parts, at least once a year, is essential for proper and efficient operation of the blower. The following parts should be regularly checked for maintenance:
- Hardware: Blower and hardware for foundations should be checked for tightness. All set screws and taper lock bushing bolts should be tightened to the threshold torque values. Loose screws should be thrown away and set screws should never be used more than once. Knurled, cup point set screws should be replaced with a nylon locking patch.
- Blower Bearing Lubrication: Blower bearings have to be lubricated all dry and clean applications where blower air temperature is -29°C to 49°C. High temperature applications require high temperature grease in the blower bearings. It is important not to over grease the blower bearings. Generally, 1-2 shots should suffice. A hand-operated grease gun at no more than 40 PSI can be used. Carefully lubricate blower bearings when the blower is running.
- Wheel Balance: Blower wheels are assembled at the factory but additional trim balancing is required after the blower is assembled. Trim balancing is always necessary for all replacement wheels. Chemicals and air stream materials can cause corrosion of blower parts. Blower wheels can be balanced by grinding off material from cast aluminium wheels, adding balancing weights for steel and fabricated aluminium wheels and using balancing clips for forward curved wheels.
- Vibration: Excessive vibration can cause premature motor and blower bearing failure which can lead to failure of the blower. If any major vibrations are present, they should be corrected before the blower is put back into operation. Common causes of vibrations are wheel imbalance, mechanical parts being loose, bearing failure, poor blower inlet, misaligned sheaves and belts and foundation stiffness.
- Fan Shaft and Bearing Replacement: The blower shaft and bearings should be designed to tolerate the maximum load and operating conditions for each blower model. When bearings are being replaced, it is strongly recommended to replace the blower shaft at the same time.