Stirring processes are common processes upstream of production or even core processes. Reproducability and reliability are two of the most important buzzwords.

Mixing processes become really effective and, above all, intelligent with the right control that regulates the process precisely.

Part 1 of our two-part series shows you which factors can be important for the stirring process. Be it to ensure quality or to optimize work steps. From this we conclude the need for regulation and intelligent control.
Part 2 (to follow shortly) explains how a control can work and what options there are. This clarifies: How do I guarantee reproducibility and reliability in the long term? How do I achieve this without using a lot of staff? How does it work with pneumatic and electric agitators?

Before we get in: Of course, our experts are always available to answer your individual questions. Simply contact us at +1 (850) 462-2730 or info@ptm-mechatronics.com or use our contact form.

Let’s start with the question of why constant stirring or stirring up can be important in production processes:

A large number of intermediate or end products that come in the form of liquids or textures are mixtures. Ultimately, they consist of several ingredients. These are homogenized into one another in the stirring process, such as chocolate or fruit gum mass in the food industry, creams or serums in cosmetics or paints in the chemical industry. If we take the example of paint, these are binders, pigments, oils, resins, fillers, additives and solvents.

Some of these mixtures, such as the said paint, quickly separate into their individual components as soon as they are no longer stirred. Therefore, they either have to be stirred continuously or stirred up before being used or bottled.

Which factors are important for the stirring process?

The stirring process is subject to some passive and some active aspects that should be taken into account in order to obtain an all-round good result. We would like to list these below. We will present you with questions that you could ask yourself.

Viscosity of the substance being stirred

The viscosity of a substance can change in the course of the mixing process. This can have several reasons:

1. In the course of the manufacturing process, different substances with different viscosities are homogenized into one another. Substances with a lower viscosity make the mix more fluid, those with a high viscosity tougher.

2. Take the example of stirring paint: The solvent is a volatile component in the mixture. It evaporates. This makes the viscosity of the paint increasingly tough. Solvent is poured in and the paint becomes more liquid again.

Questions: How can I measure the viscosity continuously? How can I adjust the speed of the agitator to the different conditions? How much solvent has to be added in the example of the lacquer stirring in order to restore the perfect viscosity? How can the stirrer replenish the solvent completely independently?

The level in the stirring tank changes

1. The level in the stirred tank can change due to the evaporation of the substances, as already mentioned above.

2. For further use or for filling, part of the content is removed, for example via a suction lance or a filling system. Or further components are added to the content so that the fill level rises.

The level significantly influences the speed of the agitator. When the contents are removed, the resistance at the impeller decreases and the speed increases unintentionally. The result could, for example, be foaming due to excessive stirring or an increase in shear forces. By adding content, the resistance increases again. The agitator has to develop a higher torque in order to keep the homogeneity constant.

Questions: How do I get the agitator to detect a lower and higher level and automatically adjust the speed and torque?

Air consumption – potential cost savings

1. Depending on the application, an agitator uses more or less compressed air. There are also striking differences in consumption between different types of agitators, such as the energy-intensive vane motor and the economical radial piston motor. High savings potential can be used here if the consumption of compressed air is measured.

2. Some media do not have to be constantly stirred, for example only shortly before consumption or filling. This results in pauses in stirring, for example at night. In this way, the consumption of compressed air can be minimized, which is reflected not only in the environmental balance, but also in the costs.

Questions: How do I measure my air consumption exactly and how do I always adapt my process to the framework conditions in an energy-saving way?

Different substances, different work steps

1. Agitators become particularly flexible if they can stir different substances. Different speeds or torques may be required for this, which must be set accordingly on the agitator.

2. Some processes consist of successive work steps. For example, if a liquid ingredient is added first, then a solid one. These two steps require different speeds in order to produce a homogeneous mass.

Questions: How can an agitator perform different work steps automatically one after the other without the use of personnel? How do I avoid having to manually set different standardized work steps each time? How can I adjust an agitator to standardized agitation requirements for different substances without having to readjust each time?

Individual control is the answer to all of these questions. PTM mechatronics offers the eco-Control, a central monitoring and control system. On the one hand, it reliably evaluates all necessary measured variables and, on the other hand, enables them to be precisely controlled. The unit can be easily and uncomplicatedly integrated into any higher-level process automation system via common interfaces in order to receive regular status and feedback messages there. This means that the stirring process is no longer an opaque process, but systematized, controlled and safe.

Have we piqued your interest? Then don’t miss our 2nd part, which deals in detail with the functions of a control system and shows the possibilities of comprehensive automation for both pneumatic and electric agitators. Part 2 will follow shortly.

Of course you don’t have to wait that long. You are also welcome to ask us your questions on the subject now. We would be happy to advise you personally on the use of an intelligent controller in your application. Contact our experts: +1 (850) 462-2730 or info@ptm-mechatronics.com.

Would you like to know more specifically on the subject of “stirring paint”? Then read our specialist article “Mixing paints efficiently and economically” in the JOT Journal for Surface Technology.

PTM mechatronics – we generate movement in special environments.