First determine the amount of horsepower suggested to effectively mix your material. 

The consideration in horsepower selection is batch turnover time (turnovers/min), viscosity of the mixture, and the size of the batch (and tank geometry). The table below can be used for basic selection in 80% of mixing applications. Selections from this chart will provide mixing/pumping turnover time of approximately 1 to 2 minutes. For rapid agitation, use the next larger size mixer. For help sizing a mixer please contact www.wmprocess.com with your mixture details and tank geometry

Some typical viscosities (at 70º F) are listed below for reference:

Water 1 cps
SAE 10 Oil 100 cps
SAE 40 Oil 250 cps
Varnish Coating 350 cps
SAE 60 Oil 800 cps
SAE 70 Oil 1000 cps
Tomato Ketchup3000 cps

After the mixer is chosen, you can then specify a shaft length and the number of mixing blades/impellers desired. The following illustrations show recommendations for mounting mixers and number of propellers required. For the best mixing action in tanks without baffles, mixer shafts should typically be mounted 10º to 20º off vertical centerline and 10º to 20º off the tank center line (to the right hand side of vessel).