If your air velocity is too low in your ductwork you could get dust dropping out in straight runs.  And dust collecting in ductwork is not a very good idea. 

• It is a fire / explosion hazard. If your system has a low dust loading, small enough that there isn’t enough material to support an explosion (below MEC), dust collecting in the ductwork could put the system above the MEC, thereby making the system an explosion hazard.
• Dust collecting in the ductwork causes the effective diameter of the ductwork to decrease. This causes the pressure drop through the system to increase, which will decrease the airflow through the system.  Lower airflow will cause more dust to escape the pickup hoods, thereby causing greater housekeeping, maintenance, etc.
• Dust building up in ductwork will also cause your ductwork to weigh much more. Depending on the weight the supports were designed for, if too much dust builds up, your ductwork could fall down, thereby possibly creating a dust cloud that could be explosive.

If the air velocity is too high, the static pressure of your system will be high.  This will require you to operate the exhaust fan at a higher speed.  This could increase the noise, power used and wear and tear.  High air velocity could also increase the erosion of the ductwork, thereby developing holes in the ductwork which will leak air into the system and decrease the actual airflow at the pickup points.

Watch for our upcoming article on sizing of ductwork for your dust collection system.

If you are having operational issues on your dust collection system, contact Aerodyne at 440-543-7400 or dc@dustcollectorhq.com.