Tunnel doors

[wjstix]

Generally diesels didn't present the problems steam did, some railroads that had electrified tunnels (like Great Northern) were able to tear down the wire once the railroad had gone all diesel.

In the west (again like GN) I don't think hoboes etc. were an issue, so I don't think that's why the tunnels had doors. It maybe some early tunnels in the east had doors for security / safety reasons, but normally doors (from what I've seen) were an indication that there was a blower system that needed the doors to work properly.

[cx500]

KCSfan

The purpose of the door at the west (N. Adams) end of the Hoosac was to prevent snow from blowing into the tunnel, I have always assumed that this was the reason for doors on those other tunnels which had them. The only tunnels that I know of with doors are all located in heavy snow country. I don't understand how doors would aid in exhausting smoke/fumes from a tunnel. It seems to me they would have the opposite effect and inhibit ventilation.

Mark

 

Where there is forced ventilation in a tunnel, ie fans, the doors can aid in providing the desired air flow.  The Mount MacDonald Tunnel in CPR's Rogers Pass has one door at the east portal, and another mid-tunnel at the ventilation shaft.  For ventilation purposes the tunnel is divided in two parts, each about 4.5 miles long. The fans are also at the east portal and mid-tunnel.

Once the last car of a westbound (upgrade) freight is clear of the east portal, the door closes.  The fan now sucks air down the mid-tunnel ventilation shaft, past the train, and out by a separate opening at the east portal.  If the door were not closed, the air flow would instead go in the east portal and immediately back out through the fan, it being easier to move an unobstructed column of air a few hundred feet long than one a few miles long against a piston (the train).

If there is no forced ventilation, then doors will prevent natural air circulation from clearing the fumes from the tunnel and are rarely used.  I suspect where they are in use, it is because of problems with ice build-up inside the tunnel, not snow.  In some areas, there is a lot of seepage of groundwater through the walls, which, particularly near the entrance, will freeze and start restricting clearance.  Closing doors once the tunnel air has cleared will keep the air temperature warmer and prevent or reduce the problem.  This will mostly be a useful procedure on lines with a limited number of trains.

John

[AgentKid]

KCSfan

I don't understand how doors would aid in exhausting smoke/fumes from a tunnel. It seems to me they would have the opposite effect and inhibit ventilation.

One way to think of it is:

The train going through the tunnel is the piston in a cylinder.

There is at least one vertical air shaft and often two, that act as inlet and exhaust ports.

The tunnel doors are the valves.

Every tunnel is different, but the train is either pumping out bad gasses or sucking fresh air as it moves, depending on the position of the doors.

Even the newest (I think) and longest tunnel in North America, the MacDonald Tunnel in British Columbia uses a variation of this system.

 AgentKid

 

[henry6]

I have heard of tunnel doors being used so that there was no head wind in some cases and would be opened as the train approached...it does appear that each tunnel has its own story or stories.

[KCSfan]

The purpose of the door at the west (N. Adams) end of the Hoosac was to prevent snow from blowing into the tunnel, I have always assumed that this was the reason for doors on those other tunnels which had them. The only tunnels that I know of with doors are all located in heavy snow country. I don't understand how doors would aid in exhausting smoke/fumes from a tunnel. It seems to me they would have the opposite effect and inhibit ventilation.

Mark

[Great Western]

 I enjoyed watching the vid of the Cascade Tunnel which was posted by Stix.  I also watched two others about the Moffat.  Fantastic!

[henry6]

Wasn't it a combination of heat build up and ability to get air for combustion?  But, yeah, that's why tunnel motors were needed.  Diesel fumes were also bad for passenger trains.  If not open windows, then it was air conditioning ducts sucking the fumes in and passing them around.  But wind, temperatures, hobos, various animals, et al, were reasons for doors on tunnels (curiously though, usually only at one end!).

[wjstix]

In tunnels, heat build-up could be a bigger problem than smoke for diesels, causing them to overheat...hence the birth of "tunnel motors".

[timz]

SP installed a couple of doors fairly late-- 1970s? One on the east end of Tunnel 28 on Donner, one on the west end of Tunnel 41 on Donner, and one on Tunnel 7 on the Cascade climb. No fans on any of those tunnels-- the point of the door was to force the tunnel air past the upgrade train, to help cooling.

[wjstix]

Cascade Tunnel in Action

[Deggesty]

In all of the articles I have read concerning tunnels and their doors, the doors are used in conjunction with clearing the the exhaust fumes from the engines (steam or diesel) out of the tunnels.

Johnny 

[Great Western]

 Thanks gentlemen for your prompt replies.  The one factor I overlooked, mainly due to the fact that it rarely falls below zero where I live, was the temperature factor.

Maybe one day the Google maps, which allow you to see some towns and streets at street level, will extend to the open country.  Then I can view all portals  of the 30 tunnels in the Tunnel District on the Moffat Sub. 

[wjstix]

Many long tunnels had ventilation systems with doors that opened and closed to help create a suction so the blowers could suck out the smoke from the steam locomotives. It dates back to at least the 1920's. Generally the tunnels had doors that slid up and and down and was automated. Once diesels came along, there wasn't as great a smoke danger.

Of course, some railroads facing one or more long tunnel chose to electrify those tracks, like the Great Northern did in the Cascades.

IIRC Gary Hoover did an MR article a few years back about how he created a working tunnel door system for his model railroad.

[pajrr]

I don't know if the Gallitzin Tunnels ever had doors. I do know that they had ventilation fans. I remembered seeing the remains of them years ago before the tunnels were enlarged. The little 3ft gauge East Broad Top had a roll-up style metal door on the Sideling Hill Tunnel to keep ice from building up in the tunnel. Another purpose of tunnel doors was to aid in exhaust smoke removal once a train had passed through. Sealing the tunnel doors and turning on the blowers would create a huge vacuum that would clear out all the smoke in a matter of minutes. It made the tunnel kind of like a big drinking straw. I have recently seen a big train go through the double tracked tunnel at Gallitzin that had 8 locomotives on the point, one of which obviously had a turbo problem. The locomotive was belching out thick black smoke. The blower fans at Gallitzin are long gone. Smoke from this train was still coming out of the west portal 15 minutes after the train had cleared up!

[henry6]

Tunnel doors were (are) quite common and have been right along.  Hoosac tunnel has doors at the west portal in N. Adams, MA, Belden Hill, near Bingahmton, NY on the CP,neeD&H had doors on its west end...however none of the tunnels in NJ or Metropolitan NY, nor O&W tunnels at Highview, Hawk Mt. and Northfield, as I remember, had doors.  Galitzen?  not sure.  But two of the factors were to maintain tempertures (especially in cold weather) and reduce the wind factors; I am sure tresspassing could also have come into play.

[Great Western]

 I have seen pictures, the Moffat Tunnel comes to mind, of railroad tunnels with doors and signals protecting these doors.

I wonder how old this practice is? 

Is it something new to do with Homeland Security or is it to keep critters out or maybe to assist ventilation fans clear fumes more easily.