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// BLOWERS AND FANS

The pump is the heart of any laser fume extractor (pardon the pun!) it controls the rate of airflow through the machine, vital to ensure all the filters work at maximum efficiency. Pumps are rated by the amount of airflow they generate In laser fume machines, this is typically between 200 and 5000 cubic metres per hour.

The most common pump type is known as a centrifugal motor, or (squirrel cage fan) which utilises a spinning fan or impeller to generate a vortex this sucks air in one end and blows it out the other as per the model below. In Laser fume applications an electrical direct drive is employed for simplicity rather than a belt drive application.

There are again two ways in which a pump is utilised within in a machine. And it all lies within the control system.

Many smaller, cheaper laser fume extractors use a constant rated pump, which pulls air at a set rate all the time. The major downfall is that as filters become blocked, the resistance on the pump increases. If the rate of airflow does not change all that happens is a reduction in vacuum at the extraction end, causing contaminants to leech into the atmosphere.

What is required therefore is a system with either a very high rated pump, or preferably one which is variable rated, also known as closed loop control.

Closed loop control is system whereby the airflow at the extractor end is constantly monitored. When a new filter is installed air resistance will be very low, visa versa - when blocked the resistance will be very high. This system therefore adjusts motor speed to compensate, ensuring that the vacuum remains a constant. However this system can only be used if the filter media has been reinforced to accommodate such high pressures, so to avoid ruptures.

Many companies have thought of this in their units but it always worth querying this. For a lot of applications simple systems will suffice, but for high energy, complex laser fumes the correct system must be installed, rather than the most economical.