Industrial Exhaust Fans

The most practical and commonly used types of plant ventilation are:   

* Power Roof Ventilators or Exhaust fan   

 In order to eliminate excessively hot air, you generally have to have powered wall or roof exhausters. This type of fan should assist in controlling air pressure in the building regardless of whether it’s positive or negative pressure.   

* Supply Fans or PRVs. 

Many buildings have exhaust PRV’s because they are capable of exhausting dust, fumes, smoke and other contaminants that can’t be prevented in the running of the business. This results in the buildings being under an extremely negative pressure. This problem can be solved by using supply fans or what’s known as “make-up” air ventilators.     

* Air Circulators. 

 If workers suffer from discomfort and the exhaust and supply air needs have been properly installed and engineered, air circulation is usually the problem. Workers then get additional comfort of the air circulating over them and they don’t suffer effects from the hot air being removed from the building. 

Industrial fans are grouped into tube axial, propeller and vane axial styles, which each have different traits. The simplest type is the propeller fan because it has only a propeller and a motor. Tube axial is like propeller fans except they have a venturi around the propeller that decreases the vortices. Vane axial fans come with vanes that run behind the propeller to make the swirling flow straight.      

Ventilators and air moving fans use power from a motor to create a volumetric air flow at a specific pressure, and are thought of as low-pressure air pumps. Torque is converted by the propeller from its motor (usually a brushless DC or AC induction motor) to raise static pressure across the fan’s rotor and to give the air particles increased kinetic energy.   

The main differences between the fan and the blower are the pressure and flow properties. Blowers produce air that flows perpendicular to the axis, while fans produce air that flows parallel to the blade axis. This enables fans to give a higher flow rate that works against low pressure whereas blowers produce a somewhat lower flow rate that’s working against high pressure. Squirrel cage type centrifugal blowers have a curved backwards wheel or a curved forwards wheel.    

Restriction of the air-flow is another big difference in the mechanism. In blowers there is an opposite effect on the same exact motor driving the fan blade. For example, the motor’s load lowers when the motor dives the squirrel cage blower. The blower will speed up as the system gets clogged. The motor’s load will increase and the fans go slower when then air flow system gets clogged in fan blades.