The issue of preparing product test plates individually under low-temperature and low-stress conditions
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There is currently a LNG jacketed vessel with an inner liner made of S30408 and an outer shell made of 16MnDR; the designed operating temperature is -32°C. The designers say that this represents conditions of low temperature and low stress. The current manufacturing method in the workshop involves preparing test plates for each individual unit. The question is: 1, according to 150. According to criterion 3-E, 16MnDR-32° meets these requirements, so it is not necessary to comply with the regulations for low-temperature vessels; in other words, it is not required to follow the standard for individual unit fabrication specified in clause 150.4 (Low-temperature Vessels)? 2. Due to the design temperature, a toughness test at -40° is required for the welds; therefore, an impact test must be conducted as part of the process evaluation. But for product test pieces that are tested one by one, is it necessary to perform an impact test on each of them as well? I beg the experts to help me understand this. . Thank you:hug::hug::hug:
The standard represents the minimum requirement; if the design documents specify that weld specimens of the product must be prepared, then such specimens must be made. Impact testing must definitely be carried out.
What about the first point? How should we evaluate the test plates of individual products under conditions of low temperature and low stress?
It states that each unit was checked one by one; what more is there to say?
If product welding specimens are to be prepared, the specimens must undergo impact testing.
Since the shell of an LNG jacketed vessel is not a pressure vessel, is it still necessary to prepare welding test pieces?
It’s this question: Is the casing design considered a pressure vessel? Looking at the design drawings for the enclosure, it operates at a negative pressure of 0.1 MPA; it is not considered a low-temperature vessel