Digital Dosing – A Solution-Oriented Concept From Grundfos - Grundfos

Precipitation, flocculation, neutralisation and disinfection are essential physico-chemical processes used in the treatment of water and wastewater. Application of the highly effective state-of-the-art chemicals now used in these processes needs to be precise, cost-effective and eco-friendly. Some of the chemicals are also very difficult to dose. Conventional dosing pumps are often unable to cope, but digital dosing pumps with cutting-edge drive technology and user-friendly operating software offer a solution.

The treatment of drinking water, industrial water and wastewater has come a long way in recent years. The chemicals used are now more highly concentrated or have higher viscosities. In addition to making the chemicals more effective, this also cuts users’ transport and storage costs. These developments throw up major new challenges for dosing technology and the companies using it:

-Smooth dosing of disinfectants and biocides subject to strong outgassing without interruptions due to the formation of air bubbles
-Cavitation-free and thus reliable dosing of viscous polyelectrolytes
-Reliable and highly accurate dosing of flocculants to keep chemical costs in check and avoid unnecessary environmental pollution

Conventional dosing pumps are often unable to meet these challenges, which has a negative impact on process quality and reliability.

There is a solution for these increasingly complex dosing applications – intelligent dosing pumps with new drive and adjustment mechanisms that keep processes operating precisely, reliably and cost-effectively, thereby making life easier for users.

The flow of traditional dosing pumps has always been adjusted by changing the stroke length or frequency. The stroke length can be changed either manually or electrically. The stroke frequency is adjusted electronically through the speed of the motor or start / stop operation, switching the motor or drive magnet on and off. Various combinations of these adjustment options are also possible.

Users often find it difficult to select the appropriate flow adjustment method and calculate adjustment parameters such as stroke rate, length, volume and frequency. What’s more, these methods are not without their problems. An inadequate stroke length can result in air voids or impair suction. Dosing gaps can occur at low stroke frequencies or during start / stop operation. This leads to non-continuous dosing.

The market has indicated that, difficult as it may be, it is time to move on and bid farewell to the current mindset in order to bring real innovations onto the market.

Grundfos ALLDOS introduced Digital DosingTM 10 years ago. Its latest generation of digital dosing pumps offers users state-of-the-art dosing and the ultimate in user-friendly operation with patented technologies, while still ensuring process reliability and energy savings.

The use of stepper motor/EC drives optimises control of the stroke speed and makes it extremely accurate. The duration of each pressure stroke varies according to the flow setting. The suction stroke time always remains constant but can be lengthened using the anti-cavitation function and thus adapted to the relevant needs. The decisive advantage here is that suction always takes place with the full stroke volume. This results in continuous dosing and lower pulsation in the dosing system – important factors in ensuring smooth pumping of outgassing media and in installations requiring longer suction lines. (Fig. 1)