Blending Ratio Control
We bumped into a client that indicated their process specified a particular material ratio (i.e. 10:1) of materials A/B on an In-Line pre-blender. Additionally, the client also specified that an amount of A was required in the beginning and at the end of the blend since it was critical that material B could not be added by itself. In the past, the control system was programmed to control the ratio of the flows (as requested), where A was the Master and B was controlled to keep up to maintain the required Flow ratio. The Batch Brothers sensed some issues with this approach…
The problem they encountered was that upon completion of material B feed, too much or too little was left of Material A to flow solo as by requirements, this was due to the errors encountered by B trying to keep up with the Master Flow rate.
After better understanding the requirements the following solution was designed to ensure the best possible ratio control. Aside from the initial Solo of Material A (SiA) and final Solo of material A (SfA) addition required, the remaining amount of Material A (RaA) should be blended as homogeneously as possible with the required amount of Material B.
The Batch Brother’s Solution continuously calculated what the Ideal Flow ratio should be based on the actual amount of material remaining to be blended. By continuously updating this ratio the system could compensate for the errors incurred by not maintaining the EXACT ratio required as well as any error incurred in the addition of the initial solo feed of Material A.
The initial approach of maintaining a fixed Flow ratio setpoint did not allow the system to compensate for any errors incurred by the feed systems, by continuously recalculating the required ratio based on the amounts remaining, the system continuously corrects the setpoints and provided the most homogeneous possible product.
Batching Across America,
-The Batch Brothers
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