External reducing valves

Wed Feb 13 15:34:34 EST 2019

Bud,

Agreed. But I did find the attached drawing. Perhaps foreign material could damage the small choke point in the venturi  (i.e. steam nozzle)? Just a thought. But does it act as an air filter? I can’t exactly follow the air flow route because it seems only the inner surface of the rock-wool filled cylinder is perforated.

Also interesting to note how many classes of locomotives had these installed (or were at least tried).

John Garner

From: NW Mailing List [mailto:nw-mailing-list at nwhs.org] 
Sent: Wednesday, February 13, 2019 11:41 AM
To: NW Mailing List <nw-mailing-list at nwhs.org>
Subject: Re: External reducing valves

John, don’t know, but I doubt it.  What if a little dust was injected into the firebox, it was just sucked up the stack along with cinders and all.  Bud

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Sent: Tuesday, February 12, 2019 8:25 PM

To: nw-mailing-list at nwhs.org <mailto:nw-mailing-list at nwhs.org>  

Subject: RE: External reducing valves

Thanks Bud. Most helpful. Do you happen to know if the ‘cans’ hanging below each nozzle on the side of the firebox (S1a for example) were air intake filters?   John Garner

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Sent: Tuesday, February 12, 2019 6:51 PM
To: NW Mailing List <nw-mailing-list at nwhs.org <mailto:nw-mailing-list at nwhs.org> >
Subject: Re: External reducing valves

John,

The jets were controlled from the cab.  The position of the jets were along the firebox side and were staggered so that a jet on one side was not exactly opposite the other side.  I don’t know about being adjustable, but they did use a steam nozzle that drew air in through an orifice using the venturi (spelling?) effect.  N&W only used overfire air jets on yard engines and if the exhaust and draft was heavy the jets would be off, and if the engine was halted or working with the light exhaust and draft, the engineer could turn the jets to get more complete combustion.

Hope this helps,

Bud Jeffries

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Sent: Tuesday, February 12, 2019 12:19 PM

To: nw-mailing-list at nwhs.org <mailto:nw-mailing-list at nwhs.org>  

Subject: RE: External reducing valves

Bud,  Can you briefly explain the operation of these jets? Were they automatic or controlled by crew? Was air flow adjustable or just on/off? Was steam used as the power source to achieve the necessary air flow?     Thanks,   John Garner

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Sent: Tuesday, February 12, 2019 10:29 AM
To: NW Mailing List <nw-mailing-list at nwhs.org <mailto:nw-mailing-list at nwhs.org> >
Subject: Re: External reducing valves

N&W tested the use of overfire air jets for road service in 1944 with 2151.  With heavy exhaust creating very good draft in road service, the railway found that the jets gave no appreciable benefit.  Overfire air jets did find favor for use on locomotives in yard service where draft was much more sporadic and often not heavy.

Bud Jeffries

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Sent: Monday, February 11, 2019 4:54 PM

To: NW Mailing List 

Subject: Re: External reducing valves

Speed didn’t have anything to do with the use of overfire air jets.  Rio Grande had some big Baldwin 4-6-6-4s with overfire jets.

Their function was to kill smoke by introducing air over the fire to more thoroughly burn the fuel.  The first tests of them on the N&W were on a Z-1a (1352) and a W-2 0-8-0 (if I recall correctly the 680).  The tests were done at Bluefield Yard; the catenary was in full view.  There are at least two N&W photographs of the test.  I don’t know the date, but it was before the electrification was done away with.

Ed King

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Sent: Monday, February 11, 2019 3:02 PM

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Cc: NW Mailing List 

Subject: Re: External reducing valves

While on N&W steam : Most all the 0-8-0 switchers had over the fire air jets-- I'm guessing to aid in keeping a hot fire because of their slow mundane work vs the faster road locos had speed to help in firing. Is that the only reason for the jets ?  Ron Hash

On Monday, February 11, 2019, 6:38:15 AM EST, NW Mailing List <nw-mailing-list at nwhs.org <mailto:nw-mailing-list at nwhs.org> > wrote: 

Larry - 

You have a few things confused here.  Alco developed an intercepting valve about 1910 for Mallet locomotives which automatically started the locomotive out in simple operation – in other words, live steam from the throttle into all four cylinders.  In order for this steam at high pressure not to cause the front engine to slip because of the larger cylinders, a reducing valve was incorporated to limit the pressure of this steam going to the bigger low-pressure cylinders so the front engine wouldn’t be slippery.  All N&W’s Alco Mallets had this feature and it was adopted as the standard for all the Mallets built by Roanoke.  Starting out in simple was automatic.  Also provided was a so-called “emergency” valve which could be operated by the engineer to keep the intercepting valve from functioning – in other words, to keep the engine operating in simple cycle until a difficult situation could be dealt with.  This is not the same as the emergency valve incorporated into the air brake valve.

When the improved intercepting valve was developed (in the early 1950s, I believe – someone correct me if I’m wrong) an external reducing valve was used which appeared as a cylindrical gadget above the right high-pressure valve chest.  When this was done, control of the simpling function was no longer automatic but was given to the engineer in the form of a lever in the cab that he could use as conditions required.  But simpling still required the use of the reducing valve.

The so-called “booster” valve which added a measured amount of throttle steam to the receiver to increase the power of the low-pressure engine was a separate valve under the control of the engineer so as to increase the power of the low-pressure engine after the engine had been changed from simple at starting and low speed to give the engine a bit more power under difficult circumstances.  All the 2100-series Y’s got this feature.  None of the earlier ones did, nor did the Z’s.  As these features were developed, all the 2100s were retrofitted so that N&W had 100 locomotives of equal capability.  If you had the 2101 out on the side of the mountain with tonnage, you would not be any better off with the 2200.

These features made N&W’s 2100-series Mallets far and away more powerful than anyone else’s Mallets.  The Y-2 of 1918 pointed the way, and the USRA Y-3s and descendents were far and away faster than all the others.  When you consider that the horsepower curve of a Virginian AE 2-10-10-2 peaked out at 8 MPH and that of a Y-6 peaked out about 30 (at 5500 DBHP) you can see why N&W took the trouble to keep on developing the Y engines.  I know, the AE had ten thousand pounds more starting tractive effort than the 2100, but that figure was good for bragging rights and that was about all.

Hope this helps and is not tMI.

Ed King

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Sent: Sunday, February 10, 2019 8:29 PM

To: nw-mailing-list at nwhs.org <mailto:nw-mailing-list at nwhs.org>  

Subject: External reducing valves

N&W in early fifty’s started using the external reducing valves on the Y classes. Which enable them also to manually to control the intercepting valve and

put superheated steam into the LP receiver  While running it compound.  Anyone have an idea exactly  what locomotives actual got this modification? 

All Y6bs ??  I know some Y5s.   I have heard all Y6bs but at this late date seems to me to be improbable?  Thanks for any help.      

Thanks

Larry Evans

Kenova WV

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