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Steam & Excursion > Whazzit? (8)

Date: 01/11/20 14:48
Whazzit? (8)
Author: LarryDoyle

Recognize this part?  Where would you find it on a steam engine?  Why was it implemented?  What did it do?  Do any engines in service today use it?



Edited 1 time(s). Last edit at 01/11/20 14:51 by LarryDoyle.

Date: 01/11/20 15:17
Re: Whazzit? (8)
Author: 2720

Looks like a pneumatic bell ringer!


Date: 01/11/20 15:19
Re: Whazzit? (8)
Author: NathanNon-Lifting

Superheater damper?

Date: 01/11/20 15:22
Re: Whazzit? (8)
Author: LarryDoyle

2720 Wrote:
> Looks like a pneumatic bell ringer!
> Mike

Mmmmmmm......    No.  Sorry.


Date: 01/11/20 15:25
Re: Whazzit? (8)
Author: LarryDoyle

NathanNon-Lifting Wrote:
> Superheater damper?

Yes, it is a superheater damper control.  Why would anyone want to do that?


Date: 01/11/20 15:31
Re: Whazzit? (8)
Author: NathanNon-Lifting

From what I understand, it’s a damper for the tubes controlled by the steam chest pressure. As the steam chest pressure rises (stronger exhaust) the damper closes off the flow of exhaust gas thru the tubes, forcing the majority of gas to travel thru the flues around the superheater units. This is an attempt to secure higher superheater temperatures.

...how did I do?

Edited 1 time(s). Last edit at 01/11/20 15:34 by NathanNon-Lifting.

Date: 01/11/20 16:54
Re: Whazzit? (8)
Author: callum_out

That's why they call it a "dead weight" device.


Date: 01/11/20 16:59
Re: Whazzit? (8)
Author: wcamp1472

A superfluous piece of 'jewelry".
The device was supposed to protect the superheater units from being melted by long flame tips, while sitting around...
The device OPENS an internal damper, opening the airflow over the Type A superheaters, thus adding heat to the steam
traversing the units..

The only times searing flames lick the ends of the superheater units is under a heavy draft through the firebed,
caused by a generous throttle opening, along with a heavy trailing train...

Thus, when slowing for a station, or just sitting around, there is insufficient draft to threaten the units.
The return bends are well recessed at the end near the rear flue sheet, units typically have the return bends 16" to 24"
shorter than the tube length.

The boiler water, though 'hot' ( near 400 deg F), the flames under a heavy draft can reach temps above 2800 degs F.
Thus, the water surrounding the flues is relatively 'frigid', ...2400 degrees colder than the flame tips..

So, there's absolutely NO CHANCE of endangering the units...with conditions of a low draft.  

The device operates from the steam supply at the cylinders.
With the fire/flame vehemence directly affected  by the draft up the stack, the flame length & temperature regulation is virtually automatic;
thus,  the units are always protected from temperature-endangerment...as the throttle gets closed when stopping, etc..

(Rarely applied after 1918...)


Edited 3 time(s). Last edit at 01/11/20 18:34 by wcamp1472.

Date: 01/12/20 03:44
Re: Whazzit? (8)
Author: LarryDoyle

wcamp1472 Wrote:
> A superfluous piece of 'jewelry".

Wes nailed it - Good One!.  Yet, nearly every new design engine built in the second decade of the 20th century had one, as it seemed to be to be a good idea at the time to close off the flues containing the superheater elements whenever the throttle was closed to prevent overheating the elements - these were all dome throttles at this time.  But, it was found to be unnecessary.

Front end throttles rendered them superfluous anyway, as with a front end throttle there is always steam present in the elements, and in fact it was found they really weren't needed on dome throttle engines, either.

When our 1906 2-8-0 DM&IR 332 was retrofitted with a superheater a damper was not included, though it kept its dome throttle.


Date: 01/12/20 15:27
Re: Whazzit? (8)
Author: nycman

Thanks for another lesson in steam technology.  This was a new one on me.

Date: 01/12/20 19:39
Re: Whazzit? (8)
Author: Earlk

If you want to see one in the wild, go to Cass and hunt up WM 6.  It has a (possibly functioning) superheater damper.  Against my wishes as Steam Project Manager for the Durbin & Greenbrier Valley RR when it assumed operation of the Cass Scenic RR, the "assigned" engineer of #6 spent over 2 weeks trying to get the superheater damper to function.  I enlisted the help of several other experts to back my proposal to simply block the damper open, but I was turn shot down by upper management because they didn't want to "rock the boat" and create unrest among Cass employees.  My response was "well, its your money, spend it if you like..."  I course it made me seem pretty impotent in the eyes of the Cass workforce.  It was the beginning of a long downward spiral they led to my departure 8 months later....

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