Question: During pressure test inspections, what is the relationship between the ambient temperature and the temperature of the medium?
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I would like to ask everyone: during pressure testing, in the summer, the temperature of the medium is lower than the ambient temperature; I have measured this when I had time (in fact, the temperature is hardly measured during pressure testing – one simply assigns a value equal to the ambient temperature for that day). Is it the same in winter as well, where the temperature of the medium is lower than the ambient temperature? Has anyone actually measured it? How large can the actual temperature difference be? During the airtightness test, since compressed air is used, and the air compressor does work on the air, its temperature should be quite high. Therefore, I believe that the temperature of the compressed air during such tests is higher than the ambient temperature. I would like to verify whether this is correct.
In fact, there is no need to worry too much about these two temperatures; the pressure test focuses primarily on the actual temperature of the container’s metal walls, in order to prevent brittle failure.
The standard specifications now specify that for pressure testing, it is the temperature of the vessel wall that matters, not the temperature of the medium; this is indicated with parentheses in the standard text. According to the fixed capacity regulations, clause 4.7.6.1(5) explains it very clearly. In summer, the temperature of the vessel walls is high while the temperature of the medium is low, though not by much; moreover, it absorbs heat from its surroundings and thus warms up, so there should be no problem. In winter, the temperature of the vessel walls is low, while the temperature of the medium is high; moreover, the temperature of the surrounding environment is low, leading to a drop in temperature. At such times, it is important to pay attention to the temperature of the vessel walls, as it can easily drop below 5°C (for the three most common types of steel), which would not meet the standard requirements.
Page 150 provides detailed information; refer to page 338 of the standard
Thank you for your reply. It seems I still haven’t fully understood the concept of 150; I need to put in more effort reading books going forward. Thanks.