Re: D&RGW tender air valves

Rob:
I can't answer this with any real authority on D&RGW equipment other than within the context of what I was told regarding similar piping on C&S locomotives, specifically, #74, which was in service after 1945.
The C&S placed triple valves at this location on tenders. By the time the 74 was in service on the RGS in 1949, the FRA required that an air dump valve be located in case of emergency. The thinking was that the crew would dump the train air as they joined the birds.
I'm sure this air dump is at least part of what you are seeing, and I was told it was required on all locomotives. It was just a straight valve with an open end.