Questions regarding the temperature and pressure values for flange material group 2C3 of HG20592
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As the title suggests, I hadn’t paid close attention to this table before, but I stumbled upon this issue in recent days and am a bit confused. It’s a matter of the temperature and pressure values for material group 2C3, which refers to 304L and 316L. In China, the temperature reference value according to European flange standards is around 100 degrees. After checking the temperature and pressure values for this material group, it turns out that at 100 degrees, the pressure value is much lower than the corresponding nominal pressure. For example, for PN16, the maximum pressure for carbon steel at 100 degrees is 1.6 MPa, while for this material group, the pressure at around 20 degrees is approximately 1.4 MPa, which is just sufficient to qualify as PN16. But at 100 degrees, the maximum pressure is only around 1.0 MPa. So why is it classified as PN16 instead of PN10?
This is because the PN rating in the standards is determined based on the pressure at the highest operating temperature. Although the pressure values of 304L and 316L drop to around 1.0 MPa at 100°C, they can reach approximately 1.4 MPa at 20°C. This means that at lower temperatures, these materials can withstand higher pressures. Typically, the PN rating indicated for flanges takes into account the design safety factor of the material at different temperatures, as well as its maximum pressure-bearing capacity within the normal operating temperature range. Therefore, in this case, even though the pressure value decreases at 100°C, it is still designated as PN16 because at lower temperatures (such as 20°C) these materials can operate safely at pressures close to or equal to 1.6 MPa. .
The nominal pressure and structural dimensions of flanges are corresponding to each other (that is, regardless of the material type, as long as the PN value is the same, the dimensions remain the same); if the PN value for materials of category 2C3 is changed from PN16 to PN10, then the subsequent table of structural dimensions will become inconsistent.
Is the question asking whether the PN standard for flanges in our country is set at 100 degrees? At room temperature, then the standard should be room temperature
That’s not correct, right? Items in this category should belong to the lower grade, PN10; the structural dimensions should be in line with those of PN10
I think that when it’s right at the critical threshold, there is a possibility of exceeding it, as all measurements have some degree of error; for safety reasons, it’s better to choose a higher level.
The problem is that carbon steel has a strength of 1.6 MPa
For sizes below DN150, PN16 and PN10 are the same; moreover, the allowable pressure at 20 degrees for the 2C3 material used in PN10 is only 7.6 bar, which is much lower than that of PN16.
The hardness and stiffness of carbon steel are much higher than those of low-carbon stainless steel; therefore, the operating pressure that can be achieved with the same dimensions is certainly higher.