Processing, April 2019
increases production but may fail to capture economies of scale With every square foot of oor space occupied by numerous small mixers the associated labor costs also go up when they really dont need to if only a larger mixer is used instead Minimize the frequency of mixing and cleaning cycles to hit production targets while avoiding costly overtime 3Consider if semi continuous mixing is appropriate for your process For example many mixing systems up to 500 gallon capacities can be supplied in a change can design Using multiple interchangeable vessels with a single mixer one tank could be at the loading stage another under the mixer another at the discharge step and yet another at the cleanup stage This arrangement maximizes both machine and labor utilization Another practical feature of the change can design is the ability to dedicate each vessel to a particular formulation or product color simplifying the cleaning procedure 4Pay attention to control system design A well designed control system is another crucial component in optimizing labor related to the mixing operation At the same time it o ers many other important bene ts Higher product yield less rejects especially for applications that are highly process sensitive Lower production cost not only due to less labor but also because of less waste and energy consumption Shorter cycle time Delays attributed to frequent rework incorrect mixing instructions and weighing errors are signi cantly reduced if not eliminated Longer service life An appropriate control system provides electronic soft start for the agitator s overload protection and other features that help prevent premature wear and mechanical failure Proper routine maintenance and calibration can also be programmed into the programmable logic controller PLC recipe controls so operators are less likely to overlook such procedures APRIL 2019 www processingmagazine com 29 Figure 1 One bay of the Ross plant in Port St Lucie Florida This facility holds one of the worlds largest inventory of specialty mixers and blenders for immediate rental or purchase All images courtesy of Charles Ross Son Company Figure 2 Ross Multi Shaft Mixers supplied with interchangeable vessels that also serve as holding tanks prior to the packaging step After each mixing cycle the vessel containing nished product is simply pulled from under the mixer and tted with a custom cover while another vessel is rolled into the mixing position The cover for the holding tank is secured via quick acting clamps and suitable for 2 psi inert gas purge An impeller agitator mounted to a tri clamp port on the cover prevents any settling or separation
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