Is it reasonable to use forgings for standard PL pipe flanges?
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Today, let’s discuss a particularly boring and pedantic issue that was also talked about with other friends a long time ago: regarding the use of PL pipe flanges and flange covers in accordance with the HG/T20592-2009 standard – is it indicated in the drawings whether the components are forged or not? My friend’s opinion is: if we refer to the manhole standards. According to the manhole standards, both the PL flanges and flange covers are specified as steel plates, with no mention of forged products. He believes there must be a reason why the manhole standards are written in that way. According to the table in HG/T 20592-2009, it is stated that, in my opinion, using forgings is also an acceptable option. But my friend’s view makes sense as well; he said that all the PL flanges and flange covers he has seen are made of steel plates, and he has never seen any made from forgings. I think this is also a matter of market logic – after all, steel plates are cheaper than forgings! So, if we follow this philosophy, should our design adhere to market principles? Using sheet metal would have been sufficient to meet the requirements, but you chose forgings instead – isn’t that going against market principles? If considered in this way, writing about forgings might indeed not be appropriate. What do you all think?
Regarding whether to use plates or forgings, a friend’s analogy seems to me the most apt: PL flanges have a limited range of applications; both plates and forgings can be used. It’s like transporting manure – some use donkey carts while others use horses; both methods work, but people just smile at those who use horses
2# The analogy is really apt; either plates or forgings can be used, as long as they meet the allowable requirements at the corresponding temperatures. But from the user’s perspective and considering economic feasibility in design, panels should be used whenever possible. :D
In terms of manufacturing costs, it is advisable to use sheets as much as possible...
It’s hard to say exactly which option is cheaper; it depends on whether there is stock of steel plates available, or on the number of flanges needed. If there are just one or two flanges and no suitable steel plates in stock, then it’s better to use forgings.
Flanges should be purchased from specialized manufacturers.
If the steel plate meets the usage requirements, it should be selected for the design, in accordance with the principles of economic design. Standard parts should be purchased first; however, if they cannot be acquired due to quantity constraints or other reasons and no stock plates are available, forgings may be used as a substitute, requiring proper procedures to be followed for this substitution.