An introduction to mechanical and digital dosing in municipal and industrial applications

An introduction to mechanical and digital dosing in municipal and industrial applications

Find out about the many benefits of digital dosing for dosing objectives of every level of complexity and how it is applied in municipal and industrial applications.

In an industrial sense, the definition of dosing is when quantities of chemicals are applied to a process fluid. Contrary to a single dose, dosing is the act of administering several doses in specific time intervals during a day. In this course, we’ll take a closer look at what dosing is, why it is important and how a newer form of dosing – digital dosing – brings a variety of benefits to the more traditional form of dosing.

But before we consider traditional and digital dosing, let’s quickly go over what dosing can be used for.

Dosing is used in all municipal and industrial applications including water utility, industrial process water, water and wastewater treatment and commercial buildings.

Additionally, it is used in processes that include disinfection, chemical dosing and filtration.

Common for these applications and processes is that the water needs to be checked on a regular basis to ensure that it maintains its level of quality. And this is where dosing comes into play. So, when the water quality is checked, it can then be topped up with chemicals to achieve the required water quality.

Traditionally, the way to handle this is by adding chemicals to the process when needed, typically based on a simple on/off trigger. When the pump receives the signal, it pumps chemicals at a constant predefined volume. This method is typical for mechanical dosing. And while it has its benefits, it also presents a variety of challenges.

One noteworthy downside to mechanical dosing when installed without an expensive frequency converter is its inability to deliver a variable, dynamic flow that meets the needs of various applications. This not only increases operation costs, it also wastes chemicals. Fortunately, there is a solution to this: Digital dosing.

Digital dosing pumps from Grundfos have a high turn-down ratio, meaning that more pump applications can be covered with fewer pump variants. This allows the pumps to easily be set up to handle other assignments with different flow requirements, and thereby deliver a dynamic flow according to the given needs. Digital Dosing automates the entire process.

An intelligent dosing pump is the ideal answer for dosing objectives of every level of complexity, providing users with precise, reliable and cost-effective dosing processes. Let’s take a closer look at how digital dosing overcomes the challenges and presents new opportunities and benefits for the users.

First of all, digital dosing ensures a much better dosing accuracy than mechanical dosing. The delivered accuracy is very high, regardless of whether we’re dealing with larger dosing quantities or smaller dosing quantities. That way, there’s a huge reduction in the waste of chemicals as the required dosing can be measured almost to perfection.

Secondly, digital dosing means that it’s no longer necessary to modify stroke length. This contributes not only to an improved dosing accuracy, but it also means that the suction capacity remains unaffected, which brings us to the next point.

In mechanical dosing, reducing the stroke length modified the suction capacity: the shorter the stroke length, the smaller the suction capacity, which led to problems with viscous fluids, suction height and installation difficulties. However, due to the internal stroke speed control implemented in digital dosing, dosing runs at a smooth, continuous rate and makes stroke length modification redundant. Thus, the aforesaid problems are no longer problems.

Another issue eradicated since the introduction of digital dosing is the risk of air-locks. In short, an air-lock happens when the dosing head is filled with gas that compresses and expands according to diaphragm movement, resulting in the non-displacement of any fluids. In a mechanical dosing process, this would result in problems with degassing liquids – such as sodium hypochlorite.

Additionally, it could lead to the operation being brought to a stop for the pump to be primed. However, thanks to digital dosing and its excellent handling of degassing fluids, this is no longer an issue.

Another benefit to digital dosing is the low cost of installation, since the need for components such as pulsation dampers and flowmeters is minimised. This makes potential service and maintenance cheaper, too.

Finally, there’s reliability. And digital dosing excels in reliability. Naturally, this high reliability ensures a smoother, trouble-free operation, which leads to a reduction of service and maintenance.

So, now that we’ve been through the advantages of digital dosing, let’s recap: Digital dosing brings a much higher level of accuracy, resulting in reductions in both chemical waste and on the energy bill.

Digital dosing systems set the stroke speed internally, making the need to adjust stroke length and stroke frequency redundant. Installation is cheaper thanks to fewer components. And finally, digital dosing performs flawlessly at both small and large rates.