I've sold Duo-Checks at my last job and know that these things just slow down flow. Never count on them for tight sealing. Saw many in the field that when they were removed from the line one or both of the plates were gone. Sometimes the center pin as well. There is a reason they are so...
Is this the Technical Paper you're wanting?http://files.engineering.com/getfile.aspx?folder=01e3551a-db31-45f7-9d82-802d94f40a6b&file=Failure_Analysis_of_Ball_Valves_(TP-12D-1).pdf