Lube-Tech
Figure 3: (Left) Illustration of speed-controlled auger, steel ball feeding device, grease holding tank, and steel balls and (Right) photo of a 15 ft auger used in production
The use of solid media for cooling to replace water cooling has shown success in reducing the grease temperature by as much as 100°C in under 30 minutes with minimal mixing. This has also resulted in more stable grease, less shearing and in the case of aluminum complex grease a significant increase in yield.
The third improvement is in the selection of mixing vessels that are more suitable for use as finishing vessels.
3. Vertical vs. horizontal mixing/blending The need for more effective blending became evident when a private-label client of a grease manufacturer requested a special light blue colour grease. The grease is aluminum complex and prone to shear thinning if mixed or milled excessively. Figure 5 shows variations of vertical mix tank mechanisms. These designs have been in use for decades and are effective in mixing some products. But, for the semi-solid grease some vertical mixing designs are not effective. It is akin to trying to mix two different colour solid granules in a vertical tank. For mixing solids, the product needs to be physically lifted and turned in order to mix effectively.
Figure 5: Paddle Blenders for Blending granular materials, Aluminum Complex Grease on Paddles, and Horizontal Mixers designed specifically for blending grease
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.146 page 4
To mix solids like construction aggregate, different colour plastic pellets and the like, horizontal mixers are employed. Also called blenders, they include different designs such as ribbon blenders or paddle blenders. Experiments with thick greases have shown that paddle mixers present a more effective option for mixing. Paddle blenders use opposing paddles with different angles that act like a row on a rowboat. The outer paddles push the grease to one direction while the inside paddles push the grease the opposite direction creating an efficient mixing action. Additionally, since the mix tanks is usually not 100% full, the paddles lift the grease during half of the rotation, but the grease drops off the paddle surface due to gravity when the paddle are near vertical position. Horizontal blenders do occupy more floor space than vertical tanks do. But, for finishing grease especially when small amounts of additives or dye are to be mixed, they reduce mixing time, reduce shear in shear unstable greases and result in energy and time savings.
Figure 4: Variations of vertical mixing arms in vertical mix tanks
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LUBE MAGAZINE NO.175 JUNE 2023
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