How to calculate the flange thickness of equipment at atmospheric pressure
Thread Content
Atmospheric pressure vessel, with a pressure of 30 KPa; the medium is steam, and it is made of 304 stainless steel. The cylinder wall thickness is 4 mm, with upper and lower end caps. There are equipment flanges, and the standard used for these flanges is 700-0.25; however, their thickness has been adjusted to 25 mm. Using SW6, it simply cannot pass the calculation, as the strength check fails. 1. Is this calculation accurate? 2. Is 25mm sufficient? The numbers are entirely my own estimates. 3. The thickness of the DN600 atmospheric manhole flange is 16 mm; by analogy, the thickness for DN700 atmospheric manholes is 18–20 mm. So 25 mm should be sufficient, right?
Since it is at atmospheric pressure, the flange strength is determined by the pre-tensioning condition. The flange size isn’t something you can decide arbitrarily just because you think 25mm is sufficient; it must be calculated. If passing is not possible, it is recommended to use bolts made of a material with lower strength, a smaller bolt diameter, and a reduced bolt circle diameter ； Additionally, softer gaskets could also be considered.
What was said upstairs is correct – the thickness of the flange cannot be determined arbitrarily; it must be calculated
Sw6 calculations generally fail. Moreover, the calculated thickness is greater than that of standard flanges at 0.25 MPa.
The standard flange type is made of Q345R material with a thickness of 25 mm and can withstand a pressure of 0.25 MPa; it’s normal that the strength of stainless steel is lower than that of Q345R
Mm. I just finished calculating it and it worked. Design pressure 0.03, temperature 130, flange Q345R, bolts 20#. 25mm is just enough for the calculation. . What I really mean is, how can we use the thinnest possible material? After all, this is at atmospheric pressure; in reality, such thick materials would not be used. Are there any empirical values available?
In reality, for carbon steel, we use one with a pressure rating of 0.25 MPa
What kind of gasket is being used? If it is a gasket made of winding material, the calculated value will definitely be higher than that of non-metallic gaskets such as those made of PTFE. For equipment operating at atmospheric pressure, if the medium is compatible with non-metallic gaskets, it is recommended to use such gaskets.
From my experience, for atmospheric pressure equipment, DN700 with S30408 flanges should have at least 30 mm. It’s not a requirement regarding strength, but rather stiffness: thin flange thickness makes leaks more likely. When the vacuum level in a vacuum system does not meet the required standards, it is often due to a leak in the sealing surface of the manhole.
In 2013, our company changed the flange size from the originally designed 1.6 to 1.0 due to funding issues; nothing went wrong as a result, so it became the norm.
Non-metallic rubber gaskets are used, with m=1.5 and y=0.