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New Concept For Continuous Gravimetric Measuring and Dosing of Powders

New Concept For Continuous Gravimetric Measuring and Dosing of Powders
26 Oct 2022  |
"Continuous Manufacturing" is a trend that can no longer be stopped. Control devices (PAT) are evolving and, on the mechanical side, feeders that have to continuously deliver the right mass flow rate should evolve with it. But this is clearly not going as smoothly.

Loss In Weight?

So far, it is mainly Loss in Weight feeders that are used for this purpose, especially in the pharmaceutical industry because they can handle smaller flow rates accurately enough. The mechanical concept of these is already decades old, and despite miniaturization and improvements at the detail level, the structural disadvantages still remain a stumbling block for the further development of Continuous Manufacturing:

  • They are certainly accurate, but not at all “continuous”:
  • By striking a favorable balance between the ” dosing time ” and the “refilling process”, you try to smooth out the “dosing folds” for each powder so that the result resembles a continuously controlled system. This practically means that you actually need two different feeders in series per dosing position.
  • To make the dosing system “contained “, the different components have to be linked together with flexible bellows. This must be done carefully so as not to disrupt the operation of the load cell…nor do they contribute to the operator’s working comfort.
  • Consequently, changeover to a different product means that all components have to be taken apart and cleaned, possibly preceded by Wash in Place (WIP) if toxic powders are involved. Clean in Place (CIP) is almost impossible. Changeover is therefore a labour-intensive process lasting several days.
  • The devices are very sensitive to external vibrations, so their set-up is critical.

Dead-end street?

So, plenty of reasons to keep thinking about alternatives. The systems that really work continuously, such as weighing conveyors, Coriolis feeders and deflectors from heavy industry, have to give up when the flow rate becomes too small. It can be said that until today there is no concept on the market that is practically capable of accurately and continuously measuring or dosing the most diverse mass flow rates of powders.

But we have to move on!

It seems that gravity is the big stumbling block that can only be worked with in the low range through the use of high-tech devices and conditioned environments.

But do we really need them?
In the end, aren’t we only interested in dosing (kg/h or g/s) powder mass m?
Should we then remain blinded by that eternal acceleration g = 9.81 m/s2 … or may it be something else?

Our statement leading to a new concept:

“With a suitable acceleration, any mass flow can be continuously measured and thus dosed.”


With this as a starting point, we have now developed a prototype incl. HMI indeed demonstrates that this statement is true;

… as a dosing device by adding a metering valve (current range 0.3 to 15 kg/h):

Effect on a catch scale:

More features:

  • Very compact design due to the nature of the process
  • The device is self-adjusting if required without loss of powder.
  • The metered powder stream can be split into several outflows, each maintaining its accuracy, i.e., one device could supply several production lines or one outflow could be used to control the others. 
  • Robust hermetically sealed or contained system, suitable for toxic products; no casing required,
  • Connection of liquids and gases, overpressure or under pressure becomes possible.
  • Clean in Place (CIP) becomes possible.
  • Our concept theoretically allows a measurable flow rate down to zero so that micro-dosing is within reach.

The concept is patented. We think its simplicity makes it a useful next step in terms of Continuous Manufacturing and so we are looking for interested companies (food, pharma…) that can assess it and make it a commercial product.

See also link below:

new gravimetric powder dosing concept.mp4 on Vimeo

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With decades of experience in the mechanical design of production machines (Philips, 3D systems, Fette Compacting), I noticed a strange complex way of working regarding the accurate and continuous measurement and dosing of mass flows...

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