Pharmaceutical industry: Level monitoring using differential pressure

In many processes in the pharmaceutical industry, reliable level monitoring is indispensable. Numerous solutions are available for this task. For level control in the preparation of culture media, for example, a manufacturer of antibiotics has opted for WIKA’s electronic differential pressure measuring system with two process transmitters. It operates with high accuracy and is also insensitive to ambient temperatures.
Level monitoring in the pharmaceutical industry can act as a quality indicator
Culture media are mixed from several substances. The production of such a nutrient solution for bacteria is an elementary preliminary stage for the production of active ingredients and drugs. The level monitoring in the process doesn’t only give the pharmaceutical industry an indication of the current level in the tank. Undeniable serves as an indicator for the correct mixing ratio and thus for the quality of the culture media.
The manufacturer of antibiotics mentioned at the beginning initially used differential pressure transmitters for level monitoring. This type of instrument has two process connections for the pressures P1 and P2. For level measurement, it is necessary to bridge the corresponding distance between the two measuring points. This is done with the help of capillaries.
Capillaries susceptible to fluctuating ambient temperatures
However, such a capillary connection is susceptible to fluctuating ambient temperatures, which, in turn, can affect the measurement accuracy. The antibiotics producer also learnt this for themself. They installed transmitters from various manufacturers, but without achieving any improvement. No instrument was able to compensate for the high ambient temperatures.
Of course, there are alternative methods of measurement. But for economic reasons, the pharmaceutical company had opted for differential pressure measurement for level monitoring. It provides the required accuracy, while the investment is significantly lower than other measuring methods, such as radar. The cost advantage also applies to level monitoring by means of electronic differential pressure measurement, which now guarantees the pharmaceutical company reliable level detection.
Electrical connection between primary and secondary instrument
The measuring system developed by WIKA under the model designation DPT-EL works with two process transmitters. They are arranged as a primary and secondary instrument. The connection between the two consists of a signal cable. It is therefore purely electrical and, consequently, insensitive to the ambient temperature. The primary instrument of the DPT-EL supplies power to the secondary instrument. The second transmitter can also be parameterised via the its display of the primary transmitter or the interface. Communication is via an internal bus.
WIKA has instrumented the measuring system for the pharmaceutical customer with two model IPT-20 process transmitters. Due to hygiene and safety requirements, the measuring instruments had to be connected to the process with an appropriate diaphragm seal, in this specific case, model 990.22 with sterile connection. Such a measuring arrangement provides an accuracy of up to 0.1 percent of span.
Conclusion
With electronic differential pressure measurement, level monitoring in the pharmaceutical industry receives a highly accurate measuring solution which can be applied flexibly. It is particularly suitable for level measurements where differential pressure measuring instruments with capillaries reach their limits, i.e. in the case of fluctuating ambient temperatures or greater distances for pressure transmission. In cases of high static pressures versus small differential pressures, on the other hand, conventional differential pressure measurement is recommended.
Two process transmitters (model IPT-2x or CPT-2x) are available for the DPT-EL electronic differential pressure measuring system, depending on the requirements; a combination of both is also possible. With both instruments, a specific measuring span can also be individually set via the turndown function.
The DPT-EL electronic differential pressure measuring system ensures both safe and highly accurate level monitoring in applications in the pharmaceutical industry. Its process transmitters, in combination with diaphragm seals for sterile applications, are connected by a signal cable.
Note
Further information on the measuring system described here can be found in our post “Electronic differential pressure measurement for level monitoring”. On the WIKA website you can also find technical details about the DPT-EL system and the corresponding model IPT-2x and model CPT-2x process transmitters. If you have any questions, your contact will gladly help you.
Also read our posts
Gravimetric level measurement in vessels
Level sensors – the agony of choice?
Pressure monitoring in the pharmaceutical industry with a universal instrument
Diaphragm seal system with diaphragm monitoring – also digital
You can also find out more about the turndown function of WIKA process transmitters in the following video:

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