According to the impeller descriptions, the bottom (No. 1) impeller is 76" in diameter, has two blades 6" wide.  The sweep has almost no effect on the power requirements.  The No. 2 impeller is 40" in diameter with 4 blades at 45 degrees and 5" wide.  The No. 3 impeller is 77" in diameter with 4 blades at 45 degrees and 5" wide.  The No. 4 impeller is 40" in diameter with 4 blades at 45 degrees and 5" wide.  The No. 5 impeller is 77" in diameter with 4 blades at 45 degrees and 5" wide.
 
All of the impellers have unusually narrow blades.  Typical impellers have blades about 1/5 the diameter of the impeller.  These blade widths are 1/8 to 1/15 of the impeller diameter.  The narrow blades and relatively close spacing may make my power estimates less accurate than usual.
 
At 50 rpm and 25,000 cp, the following power values are calculated: No. 1 = 11.28 hp, No. 2 = 1.98, No. 3 = 19.02 hp, No. 4 = 1.98 hp, and No. 5 = 19.02 hp, for a total impeller power of 53.28 hp.  The close spacing of the impellers will reduce that total to between 40 hp and 45 hp so a 50 hp motor may not overload.  With the 50 hp motor, the torque is about 63,000 in-lbs.
 
At 45 rpm and 25,000 cp, the following power values are calculated: No. 1 = 8.33 hp, No. 2 = 1.52, No. 3 = 14.34 hp, No. 4 = 1.52 hp, and No. 5 = 14.34 hp, for a total impeller power of 40.05 hp.  The close spacing of the impellers will reduce that total to between 30 hp and 35 hp so a 40 hp motor may not overload.  With the 50 hp motor, the torque is about 50,400 in-lbs.
 
Obviously, the two 40" diameter impellers add little to the total mixing, only about 8% of the total power.  The additional metal and expense of those impellers may add little to the performance of the mixer.  The narrow impeller blades are rarely recommended for high viscosity applications.  Most high viscosity (25,000 cp) applications would use impellers with wide blades, at least standard blade widths (15" on 77" impellers).  The impeller diameters are large for any application, especially for the lower viscosities.  This mixer is unusual in many respects and the geometry should be tested in small scale with those viscosities to see if it will actual move the liquid, especially blending from top to bottom.


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