I've done some searching on the forum but only turned up one post related to re-using old commercially available burners. I often see used Carlin or Beckett burners for next-to-nothing on Craigslist around here and it struck me that it may serve as a good base for a foundry burner. Have people tried this before? Good idea, bad idea? Seems to me that the fuel would have to be very clean and some extra care / thought may need to go into protecting the burner from radiant heat, especially once it was done firing and fuel wasn't flowing anymore. But otherwise, I'm seeing fuel rates that (anywhere from 1 to 7 GPH) that seem to map into the kinds of fuel rates used in decent sized home foundries...?
I have used a Beckett burner in an old poorly modified MIFCO furnace I had, yes the burner needs to be withdrawn once firing is complete as the radiant heat will damage the unit. It's a wonderfully convenient self contained unit with the fuel pump, blower, ignition etc all integrated. You can tune them by swapping nozzles which is nice. I had good luck with it, I don't recall much for downsides on it (fuel was a bit different, no propane tanks to freeze though!) but it has been many years since I have run that furnace, I need to dig it out of storage and rebuild it properly