Classification of mixed media in pressure vessels – related issues
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There is a container with a working pressure of 0.2 Mpa, a diameter of 600 mm. The medium inside is a mixture of acetic acid and water, and the operating temperature is 105°C – this temperature reaches the boiling point of water but not that of acetic acid. The ratio of acetic acid to water in this mixture is not specified, and the design team is also unable to determine the exact composition of the medium. In such a case, should it be classified as a high-risk container? What if, in extreme cases, water makes up only 0.1% of the amount? How should it be classified? After all, there is a significant difference when the water content is 0.1% compared to 30%. We welcome all experts to share their opinions and discuss this! ! ! !
It is indeed difficult to classify containers without specific medium ratios. First, it is necessary to refer to **or industry-related pressure vessel standards, such as GB150, etc. Typically, pressure vessels are classified based on operating pressure, vessel size, operating temperature, and the hazard of the medium. Given that the acetic acid-water mixture operates at 105°C, which is below the boiling point of acetic acid but above that of water, it should be considered that the medium has a certain vapor pressure, which may lead to pressure changes and increase safety risks. Therefore, containers under such conditions should tend to be classified into a higher safety category. In extreme cases, such as when water accounts for only 0.1%, although its amount is small, its impact on the overall pressure and temperature still needs to be considered. Since it is not possible to determine the exact ratio of water to acetic acid in practice, to ensure safety, it is recommended to assess the situation based on the highest possible risk level and to implement appropriate safety measures, such as installing overflow or pressure release devices. In summary, due to the lack of detailed information on the composition ratios of the medium, it is recommended to adopt a conservative approach by classifying the container in a higher category and designing corresponding safety measures. At the same time, it is also possible to communicate further with the design institute to obtain as much relevant information as possible, in order to make a more accurate judgment. .
Yes, when the proportions of the components are not clear, the approach in monitoring and inspection is to focus only on the medium with the lowest boiling point among the mixed media (the liquid), and consider things from that point onward.
It is recommended to classify them directly, keep them under regulation – it’s safer that way. If the user is not happy/does not agree, ask them to provide the standard boiling point of the liquid.
Indeed, in inspection and monitoring, the treatment of mixed media typically takes into account the properties of the liquid with the lowest boiling point, to ensure that pressure vessels can operate safely under all circumstances. This method helps prevent risks that may arise from changes in composition ratios. When designing and evaluating pressure vessels in accordance with the strictest safety standards, potential safety hazards can be effectively avoided. Although this may result in a higher safety factor for the container design, in the long run it helps to ensure a safe and stable operating environment. Therefore, when the proportions of the components are not clear, it is a reasonable and safe approach to classify container types based on the liquid with the lowest boiling point in the mixed medium. .
When the ratio is unknown, or no clear agreement exists, or the ratio needs to be kept confidential, it is assumed that the content could range from 0.1% to 99.9%. The worst-case scenario is taken into account for classification purposes.