Which Motor Need To Be Installed For High Viscous Applications

Consult a Process Engineer without delay. The power needed for a mixer is a function of many variables and viscosity is only one of them.

• It could be that the equipment is just too small for the job at hand.
• It could be that the agitator speed is too high.
• It could be that the agitator impeller is too large.
• It could be that the temperature is too low; viscosity varies strongly with temperature.
• It could be that the vessel's baffling is too large.
• It could be that the batch size is too large.
• Consider static mixers that install in a pipeline with no external moving parts. The process would need to change from batch to continuous, which might not be a bad thing.
• etc.

If the viscosity of your material is increasing to the point where it trips out the agitator motor (stiring motor?) then the rather obvious conclusion is that your motor is too small.

The problem is that maybe after 4 hours something may be happening to your existing motor that causes it to trip out. You need to make sure that all phases are well connected and that the motor has all three phases in use when it trips out.

A current clamp would be very helpful in determining if the full load suddenly went to "single phase" mode because of an open circuit. This would create the condition where all of the load was expressed on 1/3 of the motor. And when that happens the current will exceed the rated value, so it should trip.

Of course, if your batch of viscous material suddenly requires more horsepower then so be it. But if you could reduce the speed of stiring or whatever, then the load may stay within the parameters of the motor you are using.

If you do increase the size of the motor, you may experience mechanical failure in the hardware or mounting bracket. Think about this. Bigger may be better, but it may also be more dangerous.

I think before you start changing motors, you should make sure that you really have a sizing issue and a need for more power. Larger motors may require new power feed wires because the wire may be choosen for the 25 HP motor and nothing larger.

You MUST BE MORE SPECIFIC in your question as to what the parameters are within the total mixer system. You only get a good answer for your particular question if you give good information. I have a lot of agitator and reactor experience but I can't begin to answer your question.

Basic thoughts on my mind are: Is it a vertical blender with a vertical agitator or a horizontal agitator? Is it a cylindrical shaped reactor, a "V" blender, a ribbon blender, etc.? Is there heat put into the batch during the processing? What type of agitator is used, a "propeller" style with how many agitator blades, what diameter, do they mix upward, downward, vertical or at an angle? Are there fixed or adjustable "wings" mounted on the inside walls? What is the current agitator speed? "High viscosity" is only a "relative" measurement, is it high like very thick wall paper paste, milk curd, Elmer's Glue-all, spackling mix, silicone calking, wet cement mix, pumpkin pie filling, etc. Does the viscosity change as the process progresses? Is the material thixotropic (viscosity lowers with longer and/or more agitation)?

My past practices in the case of an "emergency" where the process has to get back in operation has been to throw a larger agitator on but only if I knew that this increase would not jeopardize the product or the equipment. Seat of the pants guide was up to 50% increase if there weren't any foreseen problems anticipated after a well thought out haz-op.

Some times there are success stories. We had a new 2,500 gal. vertical reactor with a vertical flat blade agitator and small internal wings for early manufacturing and development of a well known PVA based wood glue. Unfortunately the "home office" engineer decided that we only needed 25hp motor on the agitator and speed reducer vs. the local engineers saying at least 40 hp. 1st batch took 3 days in the new one instead of the 5 hours with the old reactor. I had a 50hp motor in the bone yard and we replaced the new motor with the bone yard one. Batch time now down to 4-1/2 hours! New coat of paint on the old motor made it look brand new. Just goes to show you that adequate brain storming with a degree of caution can out beat the "shiny pants" staff from the corporate office. Dirty hands solve more problems than clean hands with sharp pencils!

Good Luck, Old Salt