Getting Started With RheoStream®
This article introduces the practical aspects of installing and using RheoStream. Whether you will use RheoStream to monitor a continuous process or a batch process, the installation is simple. The viscosity data from RheoStream is fed directly to the factory control system.
Which benefits do you want from RheoStream?
With RheoStream, you can monitor the viscosity and make sure that the viscosity stays within limits and the process is in control. Having near-real-time information means that now viscosity is a parameter that can be automatically adjusted — no more waiting for manual analysis and no more re-processing or scrapping of off-spec material. You can also capture a complete log of the material produced, and you can gain new insight into the actual variations and sources of variation in the process. Eventually, you can produce more consistent quality to the benefit of your customers.
If you produce in a continuous process, you will avoid having to re-process an off-spec product. If you run a batch process, now you can set up automatic viscosity adjustment. That way, every batch is on specification the first time, and you do not have to wait for the manual measurement.
You can also use RheoStream as a much faster and fully automatic QC method. You save time and resources.
Remove human error from the equation. RheoStream measures the same way every time with higher precision than most QC procedures.
Where do you install RheoStream to get the full benefit?
In a continuous mixing process (e.g., liquid detergent or adhesive), install RheoStream on a pipe downstream of the mixer. A constant stream of new viscosity data can inform a regulation loop, e.g., to dose more or less of an ingredient that directly impacts viscosity. Ideally, the location of RheoStream is positioned shortly after the raw material dosing and mixing to minimize the total time of the regulation loop. Still, if viscosity keeps evolving as the liquid flows through the pipe, the position may have to be further downstream.
In a batch process, we recommend installing RheoStream directly on the batch mixer. To be precise, install it on the tank that determines the viscosity, i.e., where a final dilution or thickening happens. Alternatively, RheoStream can be installed on a storage/adjustment tank, as found in some paint factories.
At Fluidan, we are ready to discuss the best place to install RheoStream for maximum benefit in your specific process.
How to install RheoStream
RheoStream is a fully automatic capillary rheometer in a box (read more about RheoStream: A Fully Automated Process Rheometer. The box is the size of a large shoebox. It must be positioned right next to the pipe or tank where the liquid to be measured is inside. From here, RheoStream draws in a small sample (5 ml), carries out the measurement (see: https://fluidan.com/technology/), and expels the sample, then moves on to the following sample. The sample enters through a sample inlet tube fixed to the tank or pipe via a control valve provided with the instrument. There is also an outlet tube, leading the spent sample to a waste container. Finally, because RheoStream carries out automatic self-cleaning at intervals, there is also a connection to the cleaning liquid. The spent cleaning water is also collected in the waste container. Alternatively, all waste is led to a waste collection system, which is already present in some factories.
The cleaning liquid can, in many cases, simply be tap water or process water already present throughout the factory. If the liquid produced requires a particular cleaning method, there must be a suitable cleaning liquid supply. The cleaning liquid could, for instance, be a surfactant solution for lotions or a solvent for solvent-based coatings. Note: Solvent handling usually requires the ATEX version of RheoStream – a separate article will inform you about the ATEX version’s added features later.
RheoStream requires a 24V DC power supply, and it communicates via an ethernet cable.
The instrument box is mounted on a rack keeping RheoStream in the correct position.
Interfacing RheoStream to the factory control system
We configured RheoStream to provide the viscosity at one or more shear rates, measured on every sample. You need this information to flow immediately and seamlessly into the factory control system. Once the data is in the control system, it is logged and provides traceability to every batch. And more importantly, the data can be acted upon. If the viscosity is too high, dilute the liquid. If it too low, then thicken it. The control method all depends on how the specific production process is best managed.
As an example, paint is today very often deliberately made a bit too thick. Then the viscosity is analyzed manually in the QC lab. Once you know the viscosity, a dilution is calculated, and a volume of water is added. Then, after some mixing, a new sample is brought to the lab. Hopefully, the paint is now within the acceptance limit, but sometimes another round of dilution and measurement is needed. With RheoStream, the paint mixing could be done as today, but instead of taking a sample to the lab, RheoStream will send the control system’s viscosity data. The system calculates the dilution required, and the water needed is dosed automatically. Then, the following RheoStream measurements will show when the desired viscosity has been reached. The formerly manual adjustment cycle has now been done automatically and without waiting for the analysis. Work saved, time saved, and a very high 1st-time-right.
Read more about viscosity control of paints: RheoStream for Quality Assurance in Paint Production.
The interfacing of RheoStream can be done in two different ways, offered by Fluidan:
- The all-digital solution – OPC-UA: OPC-UA is a digital machine-to-machine communication protocol supported by virtually all automation providers globally. OPC-UA means Open Platform Communications – Unified Architecture.
Fluidan offers the software to make RheoStream act as an OPC-UA server. With this setup, the factory control system can be programmed to inquire for new viscosity data from RheoStream. A rich communication of commands, error messages and warnings can be transferred between RheoStream and the control system.
- The PLC solution: Viscosity data are communicated as analog 4..20mA signals. Other signals, such as error messages from RheoStream or start/stop/clean commands to RheoStream, are transmitted by simple 1/0 digital signals.
This setup requires a PLC (supplied by Fluidan) that converts the digital output from RheoStream to analog values and conveys the 1/0 signals.
Both solutions will require programming in the factory control system. Fluidan provides complete documentation of the solution – OPC-UA or PLC selected, and we stay in dialogue with your programmers until the interface is in place.