Many companies design or modify their agitation processes based on a single viscosity figure.
The result? Oversized agitators that consume too much energy, or worse, undersized ones that won’t move the product.
- Wasted time
- Product out of specification
- Wrong investments
The solution lies in understanding what the correct viscosity value is for sizing an agitator.
Having the tools to properly characterize it and design the agitation system you really need is the starting point.
In the design and optimization of industrial processes with agitators, one of the most critical and yet most misunderstood parameters is product viscosity. At Vak Kimsa, we have found that many agitation problems originate from poor characterization of this fundamental parameter.
What is viscosity?
Viscosity is the resistance a fluid offers to movement. It is a physical property that determines how easy or difficult it will be to move our product inside the tank. It is usually expressed in centipoise (cPs) or centistokes (cSt), and its value can vary enormously depending on the type of fluid: from 1 cPs for water to thousands of cPs for products such as jams, creams or adhesives.
Viscosity is not a single value
A common mistake is to treat viscosity as a constant. In reality, except in Newtonian products (such as water or mineral oils), viscosity depends on two critical factors: temperature and applied shear. This means that the same product can present very different viscosities depending on working conditions.
This variability is especially important in pseudoplastic or thixotropic fluids, where viscosity decreases with increasing shear rate. Therefore, measuring viscosity under static conditions or at incorrect speeds can lead to significant errors in agitator sizing.
What is the correct viscosity data?
Here lies the key to the problem: we need to know the product’s viscosity at the actual working speed of the agitator. The solution is to perform viscosity curves that relate shear rate to the product’s dynamic viscosity.
At Vak Kimsa, we offer our customers the possibility of carrying out these rheological studies. Through viscosity curves, we can accurately determine the real viscosity of the product at the agitator’s operating rpm.
Solutions to agitation problems
If your product is not moving correctly with the current agitator, don’t give up. Now you know the importance of having reliable viscosity data. With this information, we can offer you the best solution:
- Analyze the current agitator: Either with our Smartvak-Vakcal calculation software or if necessary by performing an Ansys simulation, we can analyze the behavior of your agitator and see how to get the most out of it with the properly characterized product.
- Modify the current agitator or a new one: If the current agitator cannot handle your product, we will propose the necessary modifications. There will be cases where this will be possible without changing the agitator, but in others a new agitator will be essential.
- Implement multi-agitator systems: Even in very demanding applications, it may be necessary to install two agitators in the tank: one to move the entire volume of product and another to perform the specific process (dispersion, emulsion, etc.). We will study it and always propose the simplest viable solution.
Conclusion
Viscosity is much more than a number on a technical sheet. It is a dynamic parameter that must be measured under actual working conditions. Investing in a good rheological study can be the difference between an efficient process and a chronic agitation problem.
At Vak Kimsa, we are ready to help you obtain the correct data and optimize your processes.
Feel free to contact us for further information.
