Design pressure of vacuum pipeline
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Design pressure of vacuum pipeline = full vacuum. Could someone please explain this? I’m not quite understanding it. Thank you.
Perfect vacuum represents the ultimate state of vacuum; actual operating conditions cannot achieve perfect vacuum, so it is sufficient to use perfect vacuum as the design pressure!
Vacuum pipes shall be designed to withstand external pressure; when equipped with safety control devices, the design pressure shall be the lower of 1.25 times the maximum difference between internal and external pressures or 0.1 MPa. In the absence of such safety control devices, the design pressure shall be 0.1 MPa.
This begins with the concept of units for vacuum, as the unit for vacuum is a negative value; its maximum value is negative one atmosphere, that is -0.1 MPa(g). Therefore, complete vacuum refers to the range from 0 to -0.1 MPa(g).