Must non-standard containers used for highly hazardous media use WN flanges?
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This post was last edited by 311yj on 2024-6-2 21:07. If it is a non-standard container (not a pressure vessel) that operates under negative pressure for vacuuming, with a pressure of less than 1 kilogram of positive pressure, then no classification is required. If the medium inside is a highly hazardous one, must the pipe flange necessarily be a WN long-neck butt-weld flange? Which specification contains this mandatory requirement? Will SO flanges work?
For custom containers containing highly hazardous media, the choice of flange type is primarily based on sealing performance and safety. WN long-neck butt weld flanges are generally recommended due to their high strength and excellent sealing performance. However, whether it is necessary to use it depends on the properties of the specific medium and the design specifications of the container. The use of SO flanges (sliding flanges) may also be feasible in some cases, but compared to WN flanges, they may have lower pressure resistance and sealing performance, especially under vacuum conditions or when the positive pressure is low. It is recommended to consult relevant engineers or review specific industry standards and safety regulations before making a decision. There is no unified standard that mandates the use of WN flanges; therefore, it is necessary to determine this based on the industry standards and safety requirements of the specific application. For example, according to standards such as ASME or API, there may be specific guidelines or requirements regarding the selection of flanges. In the absence of explicit specifications, for safety reasons, it is recommended to use flange types with higher performance. .
Article 4.2.4 of HG/T20583-2020 stipulates that wafer butt flanges should be used
I can’t remember which year it was, but there was a large tank whose outlet flange at the bottom failed to seal properly, resulting in an explosion that killed several people. As a result, regulations were imposed requiring that for hazardous materials, flanges of higher stiffness be used, along with gaskets featuring rigid inner and outer rings, as well as high-strength bolts. Later, for some reason unknown, the SO type was rejected; it was simply stipulated that the WN type must be used, and it had to be a grade III forging. Therefore, when dealing with highly dangerous explosives and the like, it is best to consider everything in accordance with WN.
In extreme, high-medium pressure, and high-temperature operating conditions, WN flanges are used, offering reliable strength, stiffness, sealing performance, as well as reliable manufacturing and inspection quality.
Class B welds have good load-bearing capacity; WN refers to Class B welds
In 1998, there was a leak incident at a liquefied gas tank in Xi’an; the cost differences resulting from differences in flange types should not have been that significant
It is clearly stipulated in Article 3.2.5, the Design Section, of the «Great Capacity Regulations».
There are no special requirements for manholes; just choose them according to the pipe outlet