Disperser Tip Speed

Normally blade speed for a high speed disperser is targetted at 5200 fpm (feet per minute).

Blade Speed (tip speed), measures how far a point on the outer most edge of the disperser blade travels in a given amount of time. You may remember from early math classes that the circumference (perimeter) of a circle is equal to:  

Circumference = π × D

 So if we take a 1 foot diameter (D) blade and turn it one complete revolution, a point on its edge would have travelled pi (π) 3.14 feet. By multiplying by rpm (n) we get the Tip Speed formula:

TipSpeed = π × D × n

where:

• Tip Speed - impeller tip speed (rpm)
• D - impeller diameter (ft)
• n - impeller rotation speed (fpm)

Disperser manufacturers target between 4000 and 6000 fpm (feet per minute) for the tip speed of their dispersers. As with blade diameter, there are advantages to varying the tip speed of these dispersion blades. Higher tip speeds may produce superior grinds in difficult to disperse products or counter insufficient flow in high viscosity batches. Lower speeds will reduce the vortex in low viscosity batches.

From an operator's perspective, one blade may function adequately in several different diameter tanks, resulting in less operator intervention.

Below are three Calculators addressing the most common uses of the tip speed equation.

• Tip Speed - calculating tip speed based on a know blade diameter and rpm.
• RPM - calculating rpm needed to develop a desired tip speed with a know blade diameter.
• Scale Up - Match the tip speed of one mixer to that of second disperser with differing blade sizes.

Tip Speed Calculator				When the speed of the disperser (rpm) is known, the blade diameter can be measured. With this information, the Tip Speed of the disperser blade can be calculated using the calculator on the left.
Shaft Speed (RPM)	Blade Diameter	Tip Speed (FPM)
Enter Values for RPM and Blade Diameter Tip Speed will be calculated.
RPM Calculator				A common problem is to determine the appropriate operating speed for a high speed disperser. With this calculator the target Tip speed can be entered as well as the current blade size. This calculator will display the required rpm.
Shaft Speed (rpm)	Blade Diameter	Tip Speed (fpm)
Enter Values for Tip Speed and Blade Diameter Shaft RPM will be calculated.
Scale UP				Whether moving from lab development to production or increasing/reducing batch size in respone to changing markets, batch scaling is a common and important process. Dispersion, unlike other mixing processes is typically not scaled by maintaining costant ratios of Torque/Unit Volume or Pumping rates, but by constant tip speeds. This calculator takes the parameters of Blade Diameter and RPM of one disperser and the blade diameter of the second disperser to provide target rpm of the new disperser.
Existing Disperser
Shaft Speed (RPM)	Blade Diameter
New Disperser
Shaft Speed (RPM)	Blade Diameter	Tip Speed (FPM)
Calculate comparable rpm for a second disperser, based on speeds of existing disperser.

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