The expression issue for nominal pressure diameter
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Ask a stupid question. Normally, we can use the ASME standard to specify valve flanges, with inches followed by the nominal pressure, such as 3\" 300LB. It can also be denoted by the European standard DN80PN4.0. Is the notation DN80 300LB acceptable? If there are any relevant standards, please let me know; I haven’t tried it
I’ve seen valves with such markings on site; they’re so standard that it’s hard to tell
Are the valve flanges of these two expressions exactly the same?
Generally, 300LB is considered equivalent to 5.0 MPa, while 150LB is equivalent to 2.5 MPa; the specific details haven’t been carefully examined
I don’t think it works; it’s awkward. Although it can be understood, it gives off a sense of being irregular.
Once the valve is used at LB, there are restrictions on temperature... If MPa is used in place of LB, a reference temperature is required. The notation for 3’ and DN80 is different; 3’ denotes the outer diameter, and it is in imperial units ； DN80 denotes the inner diameter, and it is in metric units.
Both LB and PN have temperature requirements for this. There is doubt regarding the claim that 3\" refers to the inner diameter; although it hasn’t been measured, it certainly isn’t the outer diameter. I’ll go to the warehouse tomorrow to take actual measurements.
So the notation DN80 300LB is completely fine.