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Improving Biopharmaceutical Process: Level Control of Caustic Soda Solution

A Magnetrol Application Study:
A biopharmaceuticals company needed an accurate and repeatable level measurement of caustic soda solution, which was used to control the biopharmaceutical process of continuous fermentation.

The application had been originally equipped with a competitor’s float system, and due to the typical “lift-off” issues that accompany those systems, it only had a measurable level of 5″ (13 cm) above the bottom of the storage tank.

Because the storage tank was only 27.5″ (70 cm) high, and any leftover solution had to be discarded, it resulted in both wasted process media and loss of yield during fermentation.

The product temperature was about +77° F (+25° C), with a pressure of 18.9 psi (1.3 bar). The container was periodically sterilized at +249.8° F (+ 121° C) for 60 min.

Since the continuous fermentation was controlled by the addition of caustic soda solution, fermentation stopped when the storage tank was almost empty and the measurable level was near 5″ (13 cm).

Since the tank was not completely emptied after completion of a cycle, every additional liter could be seen as an increase in the overall yield.

The installation position of the level measurement was fixed; and to further complicate things, a non-standard flange was required.

Until recently, the customer was unsuccessful in finding a suitable measurement technology that would offer an increase in the yield or measurement range while utilizing the required installation location.

By utilizing an Eclipse® Hygienic Model 705 guided wave radar transmitter (GWR) with a single rod X7MF probe, the customer now has a solution for accurate biopharmaceutical process control.

The GWR probe was manufactured with a special flange to meet the installation requirements. This allowed for simple replacement of the Eclipse GWR transmitter on the vessel without modifications.

In order to ensure an increase in yield, the probe was bent by the customer at approximately 50% of the rod length at 45°. This allowed measurement down to the lowest point of the tank, which led to a significant increase in yield.

Furthermore, using the 20-point strapping table in the GWR transmitter, the vessel was accurately calibrated for tank volume.   This brought an additional advantage because the customer was then able to operate more efficiently, resulting in better control of the fermentation process.

By using ECLIPSE GWR technology, the customer has increased yield by about 20%.

Considering the cost of fermentation and production cycle of about one batch per week, the customer realized a payback period of less than two months.