Is the pressure in the tank correct?
Pharmaceutical companies are currently feverishly researching a corona vaccine. When this is produced on a large scale, the manufacturing process must be scrupulously clean. Monitoring the pressure overlay in tanks and storage containers plays a role, for example. If the gas pressure in the free part of the tank is not correct, process reliability suffers. Errors can reduce the quality of a product and lead to rejects. This would be particularly fatal in the case of vaccines.
The systems for pressure control in tanks in the pharmaceutical, food and beverage industries (Fig. 1) usually consist of a combination of sensors, valves, pressure regulators and controls; they are therefore usually made up of many components. The user usually purchases the components from different manufacturers and then combines his solution on site himself. This works, of course, but it also has a whole series of disadvantages that often only become apparent during practical operation. For example, smooth interaction of the individual components is not necessarily guaranteed. Longer signal processing times can then be the result. In addition, the space required by the individual components is often quite large, compressed air losses cannot usually be avoided, and cleanability and sterilization can cause problems.
Compact system from a single source
Bürkert Fluid Control Systems, headquartered in Ingelfingen, Germany, has developed a compact, hygienic system solution for pressure control in tanks that reacts very quickly to changes in temperature and filling quantity as well as to chemical reactions. The tank blanketing system increases process reliability, sensitive media can be protected or product quantities can be filled in precise doses. The compact solution requires little installation space, the components are perfectly matched, the system can be validated, is easy to retrofit and, last but not least, impresses with its good price/performance ratio.
The pressure overlay system consists of two bellows valves with integrated process controller, an internal air duct and a pressure transmitter. The bellows made of PTFE guarantees clean media separation, is FDA-certified and sterilizable. The common stainless steel base body of the system can be drained completely in vertical position and its low dead space design makes cleaning easy. Cleanability has been confirmed with a VDMARiboflavin test. Different industry-standard connections ensure easy integration or simple retrofitting in the respective process.
Automatic pressure control
The possible applications of automatic pressure control are wide-ranging and extend from fermentation processes and the filling of sensitive media under a protective gas atmosphere to the storage and delivery of water for injection solutions. The principle of operation is always the same (Fig. 2): When a medium is filled into a tank, the available volume for the inert gas, e.g. nitrogen, decreases. To keep the pressure superposition constant, i.e. to compensate for the increasing pressure caused by the rising medium level in the tank, a signal exchange takes place between the proportional valves and the pressure sensor installed in them and the relief port is opened to reach the preset superposition pressure. The second valve remains closed during this function. If the medium is then withdrawn from the vessel, e.g. at tapping points for WFI, the available volume for the protective gas increases. In order to then keep the preset pressure constant and to compensate for the drop in pressure due to the drop in the medium level, the second proportional valve now opens for the gas feed in accordance with the pressure sensor signal. The first valve remains closed during this function. In this way, the gas pressure is precisely and reliably controlled and a constant pressure superposition takes place.
