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While it is good and necessary to consider dust characteristics, conveying velocities, filtration efficiencies, explosion protection scenarios etc. it seems all too common for designers to either ignore or make assumptions about the actual pressure drops within the process machinery to which they connect. This is probably due to the lack of easily available information from many manufacturers of process machinery.

When air flow requirements are shown on the installation drawings they usually lack the pressure required to draw that air flow through the machine. The pressure drop is left to the be determined by the customer or dust collection system designer and all too often a “guess” is used. That method can work when the passages are larger such as with most woodworking equipment but when, for example, dealing with packaging machinery with ½” and smaller passages snaking through the equipment, it is not all that reliable.  A recent example of this was a packaging machine having a calculated pressure drop approaching 16 INWG.

Determining the facts is important. This can be done by sizing and measuring all of the passages within the process equipment and performing the calculations or by connecting a test rig and determining the pressure required to achieve the desired airflow. While both methods can be time consuming or even tedious, the long term benefits of this investment can actually determine the success or failure of the dust collection system’s performance.