Material issues for manway sections of pressure vessels
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This post was last edited by niuchangsheng on 2016-2-11 at 08:56. In the past, the manholes for containers in my unit were designed in accordance with standards such as HG/T21516 and 21517; for these manhole sections, steel pipes of types GB8163 or GB9948 were used. This time, while designing a container, I reviewed standard 21518 and found that no information regarding the pipe material was provided for the section components, whereas sheet metal was specified as the material. Upon checking other standards such as 21515 and 21516, it was found that the same specification applies there as well. I wonder if my colleagues also use pipes, or whether they choose sheets according to standards for rolling and welding. Addition: 1. If it follows the standard manhole structure but does not specify that it is designed in accordance with relevant standards such as 21517, is it permissible if the strength calculations meet the requirements? It’s obvious that we have a set of drawings; the structure of the manhole is entirely in line with HG/T21515 standards. However, these technical requirements do not mention that standard – is this appropriate? 2. The bolts and nuts used for manholes do not come with washers, but in our design we have intentionally added washers – isn’t that a bit redundant? After all, since there are standards to guide us, we should follow them – even if they are merely recommended standards. Standards inherently carry a certain degree of authority. With dishonesty, one can make excuses when problems arise, but failing to follow the standards essentially creates safety risks for oneself.
In my opinion, for commonly used pipes, whether they are in accordance with GB/T8163 or GB9948, the material is usually 20#, which can be considered equivalent to Q245R; therefore, the material code can be classified as Category II.
When designing, I choose tube section materials that are the same as those used for the equipment housing, using only forgings
First, you need to understand what category the container you are designing belongs to – is it at atmospheric pressure or under pressure? Fixed or mobile? Is it a conventional container or a heat exchanger? Secondly, regarding the use of pipes as shells, the regulations set by various standards differ! In some cases, certain pipe grades specified in certain standards are not allowed to be used for the shell; naturally, they cannot then be used for manway shells either! Finally, take a close look: the manhole standard 21515-2014 is intended for use on vessels at atmospheric pressure! ! !
What I’ve seen is that the manholes used in our facility are applied to pressure vessels, but their structure corresponds to that of manholes for atmospheric-pressure vessels as specified in standard 21515; moreover, no technical requirements state that these should be designed in accordance with 21515. So this must be considered an independent design, right? Manholes for atmospheric pressure vessels are not necessarily required to be used on such vessels; after calculations, they can be used as long as the requirements are met. If the standard for manholes is specified, the design must be carried out in accordance with the structure required by that standard!
Forged parts for tube sections? We have also never used forged cylinder shells.
The cost of forgings is a bit higher, right?