How to monitor whether equipment is suffering from high-temperature H₂ corrosion
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Considering the background of high-temperature H₂ corrosion in petrochemical hydrogen-related equipment discussed earlier, the current mainstream monitoring methods can be classified into the following categories: Conventional non-destructive testing methods; Visual inspection: Directly observing whether there are any abnormal signs on the equipment’s surface such as corrosion-induced discoloration or bulging. Ultrasonic thickness measurement: It accurately detects the thinning of equipment walls caused by corrosion, and is the most commonly used basic monitoring method. Radiographic inspection: It can detect hidden defects such as internal microcracks and decarburized layers caused by high-temperature H₂ corrosion. Special hydrogen damage detection methods – Microstructural examination: By taking samples and observing the degree of decarburization in the steel as well as the distribution of grain boundary cracks, it is possible to determine the level of corrosion damage. Hydrogen permeation test: The Devanathan-Stachurski dual-electrode cell method is used to measure the diffusion coefficient of hydrogen in the material, thereby evaluating the dynamic process of hydrogen intrusion. Ultrasound C-scan/phased array detection: Precisely locates the distribution of internal hydrogen-induced microcracks, enabling quantitative assessment of damage. The online real-time monitoring method relies on corrosion sensors to establish a data acquisition system that enables real-time measurement of parameters such as the corrosion rate of equipment and hydrogen concentration. It allows for dynamic tracking of the development trends of high-temperature H₂ corrosion without interrupting production, thus enabling early detection of potential issues.
The organizer’s summary and the additional insights from above are both very practical; especially the point regarding how the coupling agent is affected by high temperatures during ultrasonic thickness measurement – this is indeed something that is easily overlooked. I’d like to add another perspective: when selecting a monitoring solution in practice, in addition to temperature, pressure, and material as mentioned earlier, it is also necessary to take into account the equipment’s operational cycle and the costs associated with downtime. For example, radiographic testing and on-site metallographic replication often require temporary shutdowns or additional procedures (such as removing insulation or setting up scaffolding). If the equipment is still in operation, it is more advisable to use online ultrasonic thickness testing or magnetic particle inspection for a preliminary screening first, and to conduct more thorough inspections during the maintenance period. Additionally, if possible, it is recommended to determine the inspection frequency and threshold values by referring to relevant standards (such as NACE or GB/T specifications), as the acceptable amount of thinning varies greatly depending on the operating conditions. Of course, the actual implementation still requires a qualified testing agency to develop a plan, as it involves high-pressure hydrogen safety; if one is not sure about the details, it’s better not to draw conclusions hastily.