- Dosing pumps are used in a wide range of applications, but don’t offer the best accuracy
- Combining a flow controller to a dosing system can drastically improve dosing pump control, quality, and repeatability between batches
- Bronkhorst offers flows meters with built-in PID controllers that can automatically control dosing pumps, which improves accuracy and provides long-term cost savings
Improved Dosing Pump Control Using Flow Meters and Controllers
The major household companies around the world use liquid colorants (dye) for adding color to their products. These colorants are very concentrated and often only a small amount is needed to give the required color to the end-product. While they do not add anything to the cleaning properties, it makes the product more attractive and can help with brand recognition. Dosing pump control is critical for systems that need repeatable, uniform batches.
Major brands especially place great value on consistent coloring of their end-products. Therefore, repeatability is of major importance to make sure that there is no color difference between items on the shelves. Another important characteristic is accuracy. Since the colorants tend to be rather expensive, it is desirable to dose as little as possible for optimal effect. The more accurate the dosage, the less colorant will be used, thus minimizing waste.
Best Methods to Dose Colorants, Dyes, and Other Chemicals
The most common solution is using a pump to dose the dye. However, this is not a very accurate way of dosing. To improve accuracy, it is recommended to combine the pump with a flow meter. For example, a Coriolis mass flow instrument or an ultrasonic volume flow instrument may be used to improve the accurate flow of the dosing pump.
In many cases, a PLC / HMI controller will be used to control the speed of the pump. This is based on the measuring signal of the flow meter, and improves accuracy compared to using a stand-alone pump exclusively. But there is an even better way to optimize your process. Highly accurate dosing processes use a flow meter to control the pump using a powerful, on-board PID controller.
Benefits of Using Flow Controllers for Better Dosing Pump Control
Closed Loop Dosing Pump Control Systems Improve Accuracy
Aside from being very compact, one major benefit is that these flow instruments create a ‘closed loop’ system. So the flow will be immediately corrected if there is a change in back pressure. The dosing pump will run faster or slower almost instantly, which maintains the required accuracy.
Improved Stability of Dosing Pumps Increases Service Life
Furthermore, the dosing pump will run extremely stable on a moderate speed, which decreases wear, thus increasing its service life. This results in less down time of production equipment and therefore saves production time and costs.
Temperature and Pressure Independent Flow Measurement
Another advantage of ultrasonic and Coriolis flow instrumentation is that the measurement is independent of the fluid properties. This means recalibration or working with conversion factors is not needed which, again, saves time and money.
Low Flow Dosing Pump Control
When dosing liquid colorants, the use of an (ultra) low flow Coriolis or ultrasonic flow meter will give you the benefit of dosing undiluted dye. How? There is no need to mix the colorant with water to create a high enough flow. Undiluted dye is more concentrated and higher in quality than mixtures with water and also saves on water consumption.
Want to learn more about low liquid flows? Download our e-book.
Applications That Benefit from Using Improved Dosing Pump Control Methods
Other applications that encounter these challenges with dosing colorants are in production processes. For example, personal care products, production of fertilizers, and many more:
- Dosing of flavorings in the food industry
- Dosing of pharmaceutical agents in pharmaceutical production
- Dosing of liquid CO2 for foam extrusion in the chemical industry
- Controlled Bacterial Growth in Bioreactors