In the food industry, aggressive liquids such as carbonic acid and alcohol pose a significant challenge to measurement technology. Standard materials can corrode under these conditions, impairing the accuracy and longevity of pressure sensors.
Challenges Posed by Aggressive Media
A manufacturer of automatic inline and laboratory liquid analyzers approached STS to find a durable and precise pressure transmitter. The media used, especially carbonic acid, increase the concentration of protons (H+), leading to hydrogen corrosion. Once the corrosion penetrates the sensor's membrane, it becomes unusable. Therefore, conventional stainless steel is insufficient for applications with high carbonic acid concentrations.
Specific Requirements in the Food Industry
The pressure sensor for this specific application in a filling plant must not only be highly corrosion-resistant but also capable of handling extremely low pressures close to vacuum. Since this application is part of the food industry, hygiene standards are very high. The near-vacuum conditions to which the equipment is regularly exposed are part of the sterilization process. Low pressures below 0 bar can compromise the integrity of pressure sensors, as the vacuum can pull the membrane out of its position in the sensor. This can lead to false readings or complete sensor failure.
Custom Solution with Hastelloy
Based on these requirements, STS developed a customized solution using the ATM.ECO pressure transmitter. An extremely corrosion-resistant Hastelloy steel was selected as the material. To ensure membrane stability under low-pressure conditions, a special adhesive was used to fix the membrane in place.
Results and Advantages
Since the pressure transmitter operates at room temperature in this application, no special temperature compensation was necessary. An accuracy of 0.25 percent of the full-scale value is more than sufficient for this application. The measurement range from 1 to 15,000 psi is perfectly suited for low-pressure measurements.
Conclusion
Choosing the right material and adapting the pressure sensor to the specific requirements of the food industry are crucial for preventing corrosion caused by aggressive liquids. Through the use of Hastelloy and special design measures, STS was able to provide a durable and precise solution for this demanding application.
