Dave Dickey Forum Moderator 290 Posts
Re: Pitched-blade impeller direction27 April 2007 at 1:29pmThe direction of a 60-degree pitched-blade impeller, or any angle axial flow impeller, should be downward by your definition. The impeller should be about one impeller diameter (typically between 0.5 and 1.25 impeller diameters depending on liquid levels) from the bottom dish of the reactor.
Material, especially settling solids, will not be lifted from the bottom is the impeller is facing upward (pumping upward). A pitched-blade impeller facing downward (pushing downward) will give proper mixing, suspend solids, and give proper motion from the bottom to the top of the reactor. Definitely do not install the impeller facing upward, regardless of the direction of rotation.
I would like to know the direction of 60-degree angle pitch-blade impeller and whether it should be facing upward or downward while the agitation is in clock-wise direction. I also am seeking information on how much distance is required from the bottom dish of the reactor to the bottom impeller. As far as I know, if the pitch-blade impeller's angle is facing upward during its clock-wise rotation, the material lifts from bottom to top and gets radial and axial agitation to lift the reaction mixture. If the pitch-blade impeller's angle is facing downward during its clock-wise rotation, the material pushes down and may be not getting proper mixing effect. In either case what should it be?
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