Regarding the issue of design temperature
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True or False: The metal inner surface temperature of a pressure vessel is 200°C, the outer surface temperature is 160°C, and the metal temperature is 175°C; therefore, the design temperature determined is 180°C. ( ) Answer: Incorrect; the design temperature should be higher than the metal temperature, that is, it should be above 200 degrees. The defined design temperature is the metal temperature of a component under normal operating conditions (the average temperature across the metal cross-section of the component). Since the metal temperature is 175°C, the designated design temperature of 180°C is higher than 175°C; so why is that not acceptable? The temperature of the inner surface of the metal is 200°C; this merely represents the temperature of the inner surface, not the temperature of the metal itself. Could those who know more please explain this?
It’s not related to equipment manufacturing; for reference only. The temperature of the metal inner surface of a pressure vessel is 200°C, the temperature of its outer surface is 160°C, and the temperature of the metal itself is 175°C. Based on these values, the design temperature is set at 180°C. ( ) Answer: Incorrect; the design temperature should be higher than the metal temperature, that is, it should be above 200 degrees. The defined design temperature is the metal temperature of a component under normal operating conditions (the average temperature across the metal cross-section of the component). Since the metal temperature is 175°C, the designated design temperature of 180°C is higher than 175°C; so why is that not acceptable? In my opinion, this is something that isn’t clearly specified in the standards: the temperature of the inner surface of the metal is 200°C, the temperature of the outer surface is 160°C, and the temperature of the metal itself is 175°C – here it should be referred to as the average temperature of the metal
This one. . . I really don’t understand. . . I also think it should be right. . .
It should be no lower than the temperature of the inner surface of the metal. . . . . .
Yes. I think the same way. For this question, I also chose 180 degrees as the design temperature.
The design temperature refers to the average temperature assumed along the metal cross-section of the component, but this temperature should be higher than that at any point in the metal of the pressure vessel. If the temperature on the inner surface of the metal reaches 200 degrees, then the design temperature must certainly be above 200 degrees; otherwise, do you think it’s safe?
The standard understanding is correct, but in actual design the design temperature should be above 200°C....
By definition, 180 degrees is fine, but in practice, it may be necessary to take into account the fact that the temperature of the medium on the outer surface cannot be guaranteed during startup and shutdown; I’m not sure if this is a valid concern
The temperature of the metal inner surface of a pressure vessel is 200°C, the temperature of its outer surface is 160°C, and the temperature of the metal itself is 175°C; thus, the design temperature determined is 180°C. 1. The answer is wrong ； 2. Correct answer: Unknown. Because the \"temperature of the inner surface of the metal at 200°C\" could also refer to the average temperature of the inner surface, and the design temperature must not be lower than the highest temperature. Generally, depending on the fluctuations in the temperature of the process fluid, its maximum value should be selected along with a certain margin to ensure equipment safety. So the correct design temperature might be 205°C, 210°C. . . . . .
If the average temperature along the metal cross-section of the component is 180 degrees, while the given average is 175 degrees with an inner surface temperature of 200 degrees, then when the average is 180 degrees, the inner surface temperature must be greater than 200 degrees, what do you think?
Learn* a bit – isn’t it necessary to have some margin?