Working pressure: -0.02 MPa. How should the design pressure be determined?
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It is a separation device that uses a fan to draw in materials, creating a working pressure of -0.02 MPa inside the device. It does not have any safety relief mechanism. This device falls under the category of external-pressure vessels. Since the vacuum level is 0.02 MPa or greater, it cannot be classified as a normal-pressure vessel. Must the design pressure for this device be set at -0.1 MPa, that is, designed for a state of complete vacuum? Or can the design pressure be set at -0.03 MPa? According to HG/T 20580-2020, vacuum vessels, submersible vessels, and buried vessels are all classified as vessels under external pressure, as stated in the revision notes. However, in Table 4.0.2, which outlines the principles for determining design pressure, containers are classified only as pressure vessels and vacuum vessels. According to this table, the design pressure for such equipment must be set at -0.1 MPa. I’m asking members of forums for help – is there any other source that allows a design pressure value of -0.03 MPa?
Theoretically, it is designed at —0.1 MPa. If a negative pressure safety valve is installed, it can be designed according to the operating pressure of that valve
This post was last edited by Wen Bing on 2021-7-8 at 10:33. If there are no safety devices, -0.1 should be used as the design pressure. This is specified in GB150.1.
To ensure that the equipment can withstand the negative pressure under operating conditions, it is sufficient to leave a certain margin
I believe it is sufficient to set the design pressure higher than the fan’s maximum suction capacity, that is, to use -0.03 MPa for the design. Of course, HG/T20580 specifies -0.1 MPa.
Reference can be made to the standards set by the Ministry of Chemical Industry.
Do not write HG/T20580 for the design standards. The stress source does not have such capability, so there is no need to increase the design pressure of the equipment excessively.
This post was last edited by wanlirn on 2021-7-11 at 09:21. According to our company’s regulations, it should be calculated using a strength of 0.1 MPa, with a verification value of -0.1 MPa. This is how I understand it; after all, 0.1 MPa is already a very low value. Strength isn’t the main concern here – stiffness is. If we use 0.03 MPa, the thickness will be even lower. Moreover, there’s currently no definitive formula for calculating stiffness; values are determined based on experience. Therefore, it makes sense for the standard to specify that if the negative pressure is below 0.02 MPa, then -0.1 MPa should be used. . . In fact, the final actual thickness is determined by stiffness, so there’s no need to worry about it.
Are you from a design institute or a manufacturing factory? As long as it’s related to the three major oil companies or the two industrial sectors, I’ve never seen any design that doesn’t follow HG/T20580
An evaluation is needed, right? It has to be below the fan’s ultimate vacuum value. If a fan with better vacuum performance is installed later, it is necessary to assess whether it can handle the conditions