Pressure monitoring in UHT plant without risk of contamination

Companies in the food industry use electronic pressure transmitters to monitor the pressure in a UHT plant. In order to optimise its process reliability, a manufacturer of dairy products has now upgraded its system to utilise the WIKA DMSU21SA pressure transmitter with integrated diaphragm monitoring. The previously installed measuring assembly leaked due to damage to the diaphragm, leading to consequent contamination of the product.
“Ultra-high-temperature” (UHT) processes are used to destroy unwanted microorganisms and at the same time to preserve the physico-chemical properties of the respective product – here milk – in order to increase the shelf life of the food. The UHT plant mentioned works with indirect heating via a heat exchanger. In this way, a large part of the thermal energy can be recovered and the process can be operated cost-effectively.
Pressure monitoring in UHT plant using flush-mounted pressure transmitter
Temperature, flow and pressure instrumentation is required to control heat transfer. In view of temperatures up to +135 °C and other challenging conditions, such as aggressive cleaning agents, flush pressure transmitters are used for pressure monitoring in UHT plant. Their diaphragms withstand normal process conditions over a long period of time without restriction.
However, pressure gauge 10 bar , caused, for example, by 24-hour operation in the production of dairy products, temperature changes, cleaning processes and subsequent steaming, can wear and damage even such a solid diaphragm, for example as a result of violent pressure surges (“water hammer effect”). The crack or perforation can allow pressure transmission fluid to seep into the process. Conversely, product gets behind the diaphragm, remains there and forms a new source of germs.
Significant losses after contamination of the product
The damage initially remains undetected because the sensor continues to function and measure. The contamination it has caused can have serious consequences. Because the product is no longer pure, the affected batch must often be destroyed once the damage has been detected. The processing of milk usually involves large quantities, 20,000 litres and more. Such an incident also causes a production downtime of several hours, plus the effort for cleaning and sterilisation and then the disposal of the contaminated product.
The DMSU21SA provides protection against contamination and immediate notification of any damage
The DMSU21SA process transmitter with integrated diaphragm monitoring is EHEDG- and 3-A- approved and can be supplied with all common sterile connections.
With the manufacturer mentioned above, the leak occurred at a measuring location directly at the heat exchanger. The company did not hesitate and exchanged all instruments in the process for WIKA DMSU21SA pressure transmitters with integrated diaphragm monitoring. The measuring system works with a welded double diaphragm, the space between which is evacuated.
If the diaphragm on the process side is damaged, the vacuum is released and the monitoring instrument (pressure switch) emits an alarm signal. The manufacturer is informed about the incident at the same time and can initiate countermeasures immediately. The second diaphragm keeps the process securely sealed until the damage has been repaired.
The instrument replacement is also made without much effort. This is because the DMSU21SA can be commissioned without any problems, based on the plug-and-play principle. The measuring system communicates via the HART® protocol and can therefore also be integrated into digitalised structures.
Note
Further details on the DMSU21SA can be found in our blog post “Diaphragm seal system with diaphragm monitoring – also digital” and on the WIKA website. There you will also find information on other measurement solutions for the food industry. If you have any questions, your contact will gladly help you.
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