What is that metal band thing over the top of dome cars?

Can someone please tell me the purpose of that metal loop/band that I have seen over the top dome windows on most Great Dome cars.

Here it is as originally built on Amtrak 10031:

And here it isn't when Amtrak rebuilt the car (eliminating the vestibule too). You can see where it was once attached:

It looks like it's over the generator. Is it an exhaust pipe? Why isn't it needed anymore?

First guess: as built, the car had a diesel to power air conditioning etc, and that's the exhaust. Apparently Amtrak decided HEP could power the car adequately, so no more diesel.

bostontrainguy wrote:Can someone please tell me the purpose of that metal loop/band that I have seen over the top dome windows on most Great Dome cars.

Here it is as originally built on Amtrak 10031:

Dome 1.jpg

And here it isn't when Amtrak rebuilt the car (eliminating the vestibule too). You can see where it was once attached:

dome 2.jpg

It looks like it's over the generator. Is it an exhaust pipe? Why isn't it needed anymore?

In Indonesia there's nothing like it