The science behind scale-up

Posted by andy_admin 07/08/2018 0 Comment(s) Engineering Case,Job Reference,News,

One of Silverson Machines' unique selling points is the ability to scale up our mixing equipment from the laboratory to full scale production models. With over 70 years' practical experience in scaling up, we offer unrivalled know-how and expertise, and time and again, we have found scalability is a deciding factor when customers are looking to purchase a mixer.

Many of our competitors sell production scale equipment but do not offer laboratory mixers, or conversely some offer high speed laboratory mixers that have no production equivalent. Silverson offers the largest range of capacities from a single manufacturer - from 1 ml laboratory units up to some of the largest disintegrator systems on the market - and because all our equipment is manufactured to the same precision engineered tolerances we can offer scalable results across our entire product range.

When specifying pumps or agitators it is possible to predict the machine required with a high degree of certainty. But with high shear mixers, especially rotor/stator mixers, this process is more complicated and is still very much based on a practical approach rather than a theoretical one.
Some years ago Dr. Niraj Thapar, then working in the R&D Department at Silverson UK, wrote a paper on the science behind the ability to scale-up and the number of factors that have to be taken into consideration.
It is clear that the scale-up of rotor/stator mixers is dependent on various parameters including tip speed, energy dissipation, shear frequency and throughput, so the development of a clear set of rules is not straight forward. Silverson has worked with a number of academic institutions including the University of Maryland's High Shear Mixing Research Program, the British Hydromechanics Research Group and several UK universities to try to develop a more scientific understanding of the operational parameters of rotor/stator mixers. They are looking to find ways to apply this knowledge to scale-up due to growing expectation from customers for scientific data (similar in nature to that given for pumps and agitators) to help them make better informed decisions when specifying mixing systems.

While this research is in its infancy, Silverson is able to draw upon acquired experience and knowledge along with use of instruments such as particle size analysers, viscometers and Rheometers to recommend appropriate product scale mixers with an increasing degree of certainty, putting us ahead of other rotor/stator mixing companies who do not have the experience or knowledge of this principle.

The full article looks in detail at the various parameters in rotor/stator mixing that must be considered when scaling up and can be downloaded below.