How to Calculate Tip Speed for a Dispersion Blade
INDCO offers a variety of dispersion blades to meet the needs of your application. How does dispersion work you might ask? Dispersion works when particles hit the blade and are broken apart. In the intense turbulence surrounding the blade, particles hit one another at high speeds and are further broken. The area where these collisions occur, beginning at the blade and extending out about two inches, is called the “zone of attrition”. Beyond the zone of attrition, the now-broken material is thoroughly mixed and particles are dissolved or dispersed by the laminar flow set up by the blade. This flow is separated at the vessel’s wall, ensuring complete circulation.
To get the most from your dispersion blade, the diameter of the blade should measure about 1/3 the diameter of the vessel in which the blade will be used. The blade should be normally placed about one full diameter off the tank bottom. The maximum depth of the material should not exceed three times the diameter of the blade. The minimum depth above the blade should not be less than the amount below the blade. The disperser shaft should be positioned in the center of the container in a vertical position.
A common mistake is not running a blade fast enough to achieve optimum dispersion. Dispersion blades should generally be run at tip speeds of 2,500 to 5,000 feet per minute. Your precise tip speed can be determined by using the following equation: FPM = RPM x .262 x Blade Diameter (inches). The optimum action of a disperser is a combination of rotary and radial flow. A particle starting at the outer edge of the container should travel to the center of the vortex in less than 360 degrees.
Round vessels almost always provide better dispersions than square vessels because they have no “dead areas” in the corners. Contact INDCO for a quote on tanks or dispersion equipment at firstname.lastname@example.org.