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Duct Design

  1. Aug 28, 2014 #1
    Hi, I just started my first job and I have to complete one unfinished project. This is a dust collector system and i have the ducting blue print but I am not sure how to calculate the friction losses in the ducting. I have the dust collector in place plus the ducting diagram, need some help with calculations. Dust collector has 40 HP motor and attached ducting

    Attached Files:

  2. jcsd
  3. Aug 28, 2014 #2


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    Staff Emeritus
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    The first thing you'll need to find out is something about the construction of the ducting itself: what kind of material is used, what sort of surface roughness you'll find inside.

    It's not clear from your diagram where the supply of air is and where it exits, but that can be corrected by showing a few arrows in the proper locations.

    What you have is a duct system with multiple branches. It's similar to say, a municipal water system, where one reservoir feeds multiple users thru a water main and branch system. You can calculate the flows in the branches of the system by iteration or by use of software to do the tedious calculations. But, in the main, you should pick up a textbook on Fluid Mechanics or Hydraulics (Streeter or White are two good references).


    Last edited by a moderator: May 6, 2017
  4. Aug 29, 2014 #3


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    In practice, all you need here is a spreadsheet and a ductulator (or other duct friction calculator). List the airflow and dimensions of every leg of the duct, read the friction loss off the ductulator, multiply by length, and add them all together.

    ....is there not someone at the company mentoring you?
  5. Sep 12, 2014 #4
    As a new hire and in a first time job, go ask questions. Think them through, but no one will expect a new hire to know what they are doing for all of it. They will want you to ask when you get stuck. After 30 years, I still go and ask questions. In truth, if you know all the answers, you are ready for more challenges.

    I have trained probably over 100 young engineers fresh out of school. The single most important thing for rookies to realize is they do not have all the answers and you must ask questions. No rookie has been fired for asking intelligent questions. Take a few minutes and talk to your mentor or supervisor. And take notes so you don't repeat.
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