Feature sponsored by Flow, level & control T
he basic principle involved in pressurised vessels containing a liquid and a gas, says that as liquid is removed, the gas pressure drops. However, the gas pressure directly affects the dosing quantity, assuming the valve opening time
remains constant. It is therefore important to carefully control the gas pressure to ensure that a stable and reliable process is maintained.
HIGH-QUALITY PRODUCTS Take as an example, fermentation processes, which are used in the production of medicines and vaccines. As such, the manufacturing procedures are subject to very strict regulation and the fermentation process needs to be repeatable to the exact same criteria. Only in this way will a consistent, high-quality product be delivered. During fermentation, carbon dioxide is produced, while gases such as nitrogen or oxygen are added to the vessel. Maintaining the delicate balance requires precision gas control to ensure the quality of the final product. With the food and beverage sector, tank blanketing is used to retain product quality. For producers that bottle naturally carbonated mineral water, it is essential the water does not lose carbon dioxide during the storage and bottling processes. The gas pressure above the
water must be high enough to prevent the CO2 from being released, affecting the taste and reducing quality.
DELICATE PROCESS CONTROL Returning to the pharmaceutical sector, some manufacturing processes involve fragile molecules or cells, whose structure must remain intact. The centrifugal force of conventional pumps can damage the delicate ingredients if they are used for filling containers. Instead, a pressure- controlled measurement process offers precision and reliability as well as product integrity. At the same time, both industries discussed require hygienic conditions within the process equipment, which means clean-in-place (CIP) or sterilise-in-place (SIP) procedures need to be
CONTINUOUS GAS
PRESSURE CONTROL: ACHIEVING ULTIMATE PROCESS RELIABILITY
Many manufacturing processes in the food and beverage industry and pharmaceutical sector require careful control of pressurised vessels to ensure optimum product quality. Fermentation in bioreactors, tank blanketing in drinks production, or pressure transfer of fragile products are just a few examples where accurate gas pressure control is essential for process reliability. Kieran Bennett, industry account manager - Food & Beverage at Bürkert, looks at some of the key aspects of controlling gas pressure in vessels.
accommodated. This can cause some issues with proportional control valves, which over time suffer from reduced lubrication caused by aggressive CIP media. Further challenges are presented by the control infrastructure, whose design can affect process responsiveness. Centralised control systems, working through a PLC, can unwittingly introduce a delay of more than two seconds between the detection of a reduced pressure in the vessel and the corrective action restoring it to the nominal value.
20 INDUSTRY EXPERTISE
Having looked at the system requirements and some of the drawbacks with conventional designs, there is an opportunity to review the alternatives. Bürkert has applied its expertise in flow control equipment, with considerable experience in hygienic applications, to create local pressure monitoring and gas control systems. For liquids that need to avoid contact with air, inert gases may be used to maintain liquid stability. Bürkert’s control valve system is equally adept and well-suited to operating with other
October 2023 Instrumentation Monthly
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