How flow meters can make your dishwashing more colourful?

February 27, 2018 Ron Tietge

We still often struggle with doing the dishes, and sometimes we just want our dirty dishes to magically disappear. If you do not have a dishwasher yet, you will definitely recognize this problem. However, manufacturers do their utmost best to make dishwashing as colourful as possible. You have probably noticed the large variety of detergents in your supermarket,  so many choices!  Mass flow controllers play an important role in the production process of these detergents.  Let me explain why…

Colouring detergents

Detergent itself is transparent or white in colour. To change this, a small amount of colourant (or dye) is added to detergent and that’s the colour you see in the bottle; often green, yellow or red. The colourant does not add anything to the cleaning properties, however, it makes it more attractive and it will help the user to recognize a certain brand.
For the manufacturer a consistent colour of the end-product is of major importance. Every flacon has to be the same colour, you should not see any colour difference between the flacons on the shelves  (as the colour is part of their company branding).

What would be an appropriate way to dose these colourants? Pump control can be your solution.


Using Coriolis mass flow meters for accurate dosing

Dosing colourants can be done by using a pump. However, since this is volume flow it is not always the most accurate way. In these kinds of applications accuracy, and moreover, repeatability are crucial for the production process.

Important requirements in applications using colourant are:
  • Accuracy: the colourants used are in fact highly concentrated and have to be applied in extremely low doses. Furthermore, the colourants are rather expensive; therefore accurate dosing of the liquid is very much desired as well.
  • Repeatability:  every flacon of detergent has to have the same colour, therefore the dosing of the colourant has to be consistent, always.
A better solution here would be to combine your pump with a Coriolis mass flow controller; it will give you the opportunity to control your pump and therefore a precise and traceable way of dosing your colourant.

mini CORI-FLOW Tuthill pump
mini CORI-FLOW mass flow meter with Tuthill pump

Pump control

The unique method of combining your pump with a Coriolis mass flow controller makes the pump dose mass flow instead of the usual volume flow. Since real mass flow is independent of the fluid properties of the colourant, the accuracy will be inimitable.

A PID controller makes it possible to control the speed of your pump. This can be done by an external PID controller (however, this can result in a slow response and slow control) or by a Coriolis instrument with integrated PID controller (a separate control signal will control the speed of the pump).

Read more about pump control in my blog about using pump control to optimize detergent colour.

Coriolis mass flow controller with integrated PID controller

Bronkhorst has a Coriolis instrument in its portfolio with integrated PID controller. The advantage of using a Coriolis instrument with integrated PID controller is the so called ‘closed loop system’.  The flow will be immediately corrected if there is a change in back pressure by making the pump run faster or slower almost instantly, keeping  up the required accuracy.

Additional benefit of this stable control method is that the pump is made to run on a moderate speed, decreasing wear and thus increasing its service life, resulting in less downtime of production equipment. Dosing mass flow instead of volumetric flow means high accuracy, for all your available liquids.


Other applications where you can encounter these challenges with dosing colourants/dyes  are in production processes of shampoos, soaps, fabric conditioner agents, (shaving) creams and tooth pastes.
In a previous blog, I shared my thoughts about how pump control can optimize our detergent colour.

Example response time Coriolis flow meter
Example of response time of a Bronkhorst Coriolis instrument (series mini CORI-FLOW) with pump. (red = set point, green = output and yellow is the fast control signal to control the pump).

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