I have seen flange supports. They are pretty common of FRP pipe especially. And if you do support from the flange, it is generally a good idea to make a half circle plate that bolts to the flange and ends in a pipe shoe.
I added a page from the Maverick Applied Sciences pipe support catalog to show you what I am talking about. They are generally for FRP systems, but I have seen such things fabricated for steel pipes too.
Thanks,
Duncan
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Duncan McEwen, P.E., P. Eng.
SSOE
Senior Mechanical Process Engineer