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Technical Aspects of Measuring Hydrogen Pressure and the Effects of Hydrogen Migration

Measuring hydrogen pressure accurately and safely is a critical aspect of various industries, including energy, manufacturing, and research. The unique properties of hydrogen, such as its small molecular size and high diffusivity, pose specific challenges to pressure measurement technologies. This article explores the technical aspects of hydrogen pressure measurement, focusing on the effects of hydrogen migration with different diaphragm materials and sensing technologies.

Pressure Pressure measurement on a H2 hydrogen production plant

Housing and Diaphragm Materials

316 Stainless Steel:

  • A specific grade of 316 stainless steel is commonly used for housing and diaphragm materials in hydrogen pressure sensors. This material is chosen due to its excellent resistance to corrosion and its ability to reduce the effects of hydrogen embrittlement. Hydrogen embrittlement occurs when hydrogen atoms diffuse into the metal, leading to a loss of ductility and potential failure under stress. The specific grade of 316 stainless steel used in pressure sensors minimizes this risk, ensuring reliable and long-term operation.  Example product: DMP 336 Pressure Transmitter for Technical Gases and H2 Applications

Ceramic Diaphragms:

  • Ceramic diaphragms are advantageous for hydrogen pressure measurement because they allow hydrogen to migrate without causing damage. Ceramics are generally impervious to hydrogen embrittlement, making them a durable choice. However, the migration of hydrogen through ceramic diaphragms into the environment must be carefully managed. Implementing systems to recirculate or safely vent migrated hydrogen is essential to maintain safety and accuracy. Failure to handle the migrated hydrogen properly can lead to measurement errors and safety hazards. Example product: DMK 331 Industrial Pressure Transmitter

Oil filled Stainless Steel Diaphragms with Silicon:

  • When using stainless steel diaphragms coupled with silicon chips that employ oil as a pressure transfer medium, there is a risk that hydrogen will diffuse into the oil cavity. This diffusion can cause hydrogen to act as an air bubble, leading to pressure measurement offsets. The presence of hydrogen bubbles in the oil alters the pressure transmission characteristics, resulting in inaccuracies. Regular maintenance and monitoring are necessary to detect and mitigate this issue. Additionally, using hydrogen-resistant oils or alternative transfer mediums can help reduce the impact of hydrogen diffusion. Example product: DMP 331 Industrial Pressure Transmitter for Low Pressure

Gold-Plated Diaphragms:

  • Gold plating on stainless steel diaphragms offers a solution to mitigate hydrogen migration and embrittlement. Gold is impermeable to hydrogen, preventing its diffusion through the diaphragm. However, this approach is limited to specific applications, such as the G1/2″ flush diaphragm on the DMK 331P series, and is only viable for pressures as low as 1 bar. Additionally, gold plating is costly, which can be a significant drawback for large-scale or budget-sensitive applications. Despite these limitations, gold-plated diaphragms provide a highly effective barrier against hydrogen migration and are suitable for high-precision measurements. Example product: DMK 331 P Industrial Pressure Transmitter

Conclusion

Accurate hydrogen pressure measurement is essential for various industrial applications, and addressing the challenges posed by hydrogen migration is crucial for sensor performance. By selecting appropriate diaphragm materials, implementing robust sensor designs, and conducting regular maintenance, the adverse effects of hydrogen migration can be mitigated. Advancements in materials science and sensor technology continue to enhance the reliability and accuracy of hydrogen pressure sensors, ensuring their effectiveness in demanding environments.