Why are manhole flanges made using flat-welded necked or butt-welded necked designs?
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Why are wafer flanges and butt-welded flanges with necks specified in HG/T21517-2014 and HG/T21518-2014 for manholes?
Why can’t plate butt welding be used? Is it because the stress on people moving in and out is considered to be high?
Although the manhole is not externally connected, it remains an opening and must still comply with the requirements regarding pressure, temperature, and the type of medium used.
There are also plate-type butt-welded flanges for 40-kilogram pipelines! Why do manholes have to have a neck? Those with necks are expensive!
According to the regulatory requirements, pressure vessels used to hold liquefied petroleum gas, media with extremely high or high toxicity, as well as highly permeable media with moderate toxicity, must be equipped with necked butt-welded flanges
It means that since these manholes are provided by the Ministry of Chemical Industry and are used for handling chemical substances, those with a neck are used; but if the substance is water, steam, or something like that, then a neck isn’t necessary Can I just create a non-standard one myself?
It’s completely possible. The standards should be reference standards, and when selecting materials, it’s important to pay attention to the differences between forgings and sheets.
Mm-hmm, thank you!