Discussion on the toxicity of media in pressure vessels
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This post was last edited by guoshu258 on 2019-4-24 at 11:14. There are a few questions: 1) Is the toxicity of the medium classified according to HGT20660, regardless of its concentration level? For example, if a medium contains 5 ppm of hydrogen sulfide or 20% hydrogen sulfide, its hazard level should be classified as highly hazardous. What level of concentration is considered minimal? 2) If the concentration level needs to be taken into account, how should mixed media with varying toxicity levels be classified? For instance, if a medium contains a gas that is extremely hazardous at 5 ppm, along with a gas that is moderately hazardous at 20%, how should the toxicity of such a medium be determined? 3) In HGT20660-2000, H2S is classified as moderately hazardous, while in HG/T20660-2017 it is classified as highly hazardous. This change requires adjustments to the manufacturing and testing requirements for many devices in the natural gas industry; therefore, some experts suggest that H2S should still be considered moderately hazardous. Even though HGT20660-2000 is no longer in use, is this still the case? 4) The meaning of A1.2.1 in the diagram isn’t very clear; could any teacher please explain it? The maximum allowable concentration for highly hazardous substances is less than 0.1–1.0 mg/m3; does that mean that concentrations below 0.1 mg/m3 are considered moderately hazardous, while those above 1.0 mg/m3 are considered extremely hazardous?
It seems that pressure pipelines have a more detailed definition
The concentration mentioned by the poster is not the same as the concentration specified in the standards
HG/T20660-2017 classifies many substances with moderate hazard as having high hazard. From what I’ve seen, all carcinogenic substances are classified as having high hazard, including common chemical solvents such as dichloromethane. This has a significant impact on the manufacturing cost of the equipment. At present, we try our best to design in accordance with HG/T20660-2017. However, sometimes, considering manufacturing costs and the financial capabilities of the equipment users, it is acceptable to use HG/T20660-2000 as per the current regulatory requirements; in such cases, equipment inspection will be no problem. But it will be a headache when the regulatory standards are revised next time. I wonder how you dealt with it. Additionally, regarding item A1.2.1 in the diagram, my understanding is that the poster may have made a mistake of reversing cause and effect; if a substance is highly hazardous, then its maximum allowable concentration should be less than 0.1–1.0 mg/m3. It’s not the case that just because the maximum allowable concentration of a certain substance is less than 0.1–1.0 mg/m3, it is automatically highly hazardous. For media not listed in G/T20660-2017, to determine their hazard level, one should use GBZ230 as a guide. It can be seen that in addition to the allowable concentrations, there are many other parameters to consider; however, since data is available for only some of these parameters, it is necessary to apply strict standards. As a result, the hazard level is likely to be classified as highly hazardous.
The classification in the tolerance specifications is based on HG/T20660-2000, and this HG/T20660-2000 includes the year of issuance. The HG/T20660-2017 version is not required. Regarding the issue of the maximum allowable concentration, I personally believe it should be considered in conjunction with A1.3.4 P102. When the medium type is classified as extremely hazardous and the concentration is less than 0.1 mg/m3, the design unit decides on it itself ； When the concentration is 0.1 mg/m3 or higher, it must be classified as extremely hazardous. When the medium type is highly hazardous and the concentration is less than 0.1 mg/m3, it can be disregarded ； When the concentration is between 0.1 and 1.0 mg/m3, consider it on your own ； When it is 1 mg/m3 or higher, it must be classified as highly hazardous. The same applies to the latter.
Refer to GB/T20801-2006
This part is quite frustrating – the two harmonization standards in GB150 and TSG21-2016, namely GB6479-2000 and HG/T20660-2000, are annoying. They were originally referred to as reference standards, and now there’s another harmonization standard? It’s hard to understand.
I’ve learned it.* Coordination standards must be followed.