We have a pilot mixing plant here on site. Ever since it was stripped down and rebuilt due to its PM schedule, it hasn't worked properly. We use the tank to mix a powder and a liquid. Now when it runs, no vortex is created (or be it a very poor one) and the powder does not go into solution, it just sits on the top of the liquid. We have tried moving the impeller up and down the shaft but to no avail. Unfortunately, the original dimension drawing are missing and so we do not know the original position of the impeller and its dimensions etc. Are there formula that might help us to determine the optimum position for the impeller etc. if we measure the various aspects of the tank, baffles etc.?
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Dave Dickey Forum Moderator 275 Posts
Re: Formula for position of impeller24 May 2006 at 1:29pmPowder incorporation is almost art as it is science. From the information given, PM should not have directly caused the problem. Possible solutions:
- Increase the mixer speed - that may have changed with maintenance.
- Increase the liquid level, so it extends above the top of the baffles, depends on the tank straight side and baffle length.
- Reduce the distance between the impeller and the liquid surface, this dimension has the greatest geometric effect on surface motion and vortex depth.
- Type of impeller - pitched-blade works best as upper impeller.
- Use multiple impellers - two impellers will increase surface motion and maintain mixing.
The problem is well understood, the correction is unusual, as described the process worked before.