Why two "exhaust stacks" for some steam generators?

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Why two "exhaust stacks" for some steam generators?
Posted by 7j43k on Thursday, October 12, 2017 6:05 PM

It seems like the roofs of most steam generator equipped F units have two vents, or whatever.  Clearly, one is the exhaust for the "fire".  But I wonder what the other is. I had been assuming it was an air intake.  But someone pointed out that the whole carbody was pretty open, so there was no need to bring in outside air from the roof. In addition, GN apparently did some of their own steam generator installations, and those have only the single exhaust.

So, I'm asking if anyone knows what's with the "extra" exhaust.  Or intake.  Or whatever.

 

Ed

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Posted by Firelock76 on Thursday, October 12, 2017 7:16 PM

Just guessing, but it could be a vent for the steam generator's safety valve.

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Posted by SD70M-2Dude on Thursday, October 12, 2017 10:31 PM

GMD1 roadswitcher with steam generator in the short hood:

http://www.railpictures.ca/?attachment_id=17034

One stack and the little hatch is right at eye level for someone exiting the cab.  Maybe it is an air intake, I'm not very familiar with diesel locomotive steam generators.

Greetings from Alberta

-an Articulate Malcontent

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Posted by Miningman on Thursday, October 12, 2017 10:58 PM

....and a "buried" hint for the Classic Quiz!

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Posted by SD70M-2Dude on Thursday, October 12, 2017 11:27 PM

Guess again, the passenger GMD1s were all B-B, only the freight ones were A1A-A1A.  Also they were not exclusive to one railroad, Northern Alberta had a few too. 

Back on topic, the Vapor-Clarkson diagrams near the bottom of this page seem to indicate a blower with an air intake at about the same height as the hatch seen on the GMD1's short hood:

http://rollymartincountry.blogspot.ca/2017/02/1967-confederation-train-documents-and.html

Greetings from Alberta

-an Articulate Malcontent

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Posted by blue streak 1 on Saturday, October 14, 2017 8:53 PM

Fooled me twice shame on me.  Thought your title meant electric generators on a steam loco ?

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