Re-entering fire door?

[Anonymous]

I came across this term.
It is used in the following paragraph:
"This locomotive is fitted with a re-entering fire door and the very small amount of smoke issuing from the top of the stack showed the advantage of admitting air to the firebox above the fire and deflecting it downwards upon the bed of incandescent coal."
Can anyone explain what a re-entering fire door is?

[edblysard]

Sounds like a boiler door with a adjustable draft vent, which would allow you to adjust or add air flow on top of the fire, instead of allowing the stack draft to pull all of the air from the under the fire grate. Sorta like the little round adjustable door in your barbque pit.
I would imagine it would be used at slow speeds, or at a stop, when the stack draft or draw would be at a minimun, to keep the fire box from smoking up.
Opinion only, no refrence to back it up, except a lot of barbqueing time.
Stay Frosty,
Ed

[Anonymous]

When coal is burning slowly, it emits a lot of volitale fumes that are usually transformed into the "black smoke" that is familiar. When coal has an adequate draft, and high enough combustion temperatures, it really is a "clean-burning" fuel.
The key to firing coal is an equilibrium between coal being burned, and adequate oxygen for the fire. ( no air, lots of smoke ), The purpose of the introduction of fresh air over the top of the fire is to allow the volitales to ignite in the flues, before it goes up the chimney.
Todd C.

[Anonymous]

OK--
Now then, what is a re-entering fire door?
What does it do?
Is it different from a regular fire door?

[bfsfabs]

Todd, You mean a "re-entering fire door" is sorta like poor-man's overfire jets ? Something to introduce oxygen into the fuel rich exhaust stream to allow it to burn ?

I've never heard the term before, 'course that doesn't mean much.

Lowell

[edblysard]

Regular firebox door, with an adjustable vent in it, allows fresh air to be drawn into the fire box above the coals, allows the gases to burn cleaner. Draw or draft from the stack will pull fresh air into the firebox through the vent.
Like adjusting the flue in your fire place, close the flue, and the fire will smoke up due to lack of oxygen, open, the flue, the draft up the chimmey will draw fresh air from the room into the fire, allowing it to burn the hot gases given off by what ever type of fuel used.
As wood and coal heat up, both give off volitale or flammable gases, wood will excrete cresote also, very flammable. What you are watching burn is not the body of the coal, but the gas given off when the coal reaches a certain tempature.
As the coal heats up, its physical charateristics change, the heat turn the organic compounds into a gas, which burn away creating more heat, and the carbons are all thats left in the form of ash, almost pure carbon.
Ever notice its easier to keep a fire going than to start one? Because you have to heat the original fuel supply up to the point the organic compounds turn into a gas before they will ingnite, so you have to pre heat the fuel with some form of starter fire, newspaper, kindeling and such. Once the fuel reaches the correct temp, it begins to break down into it base compounds, and the oraganics will ingnite, if the correct amount of oxygen is present and a ignition source such as the rest of the "fire" is present. The hotter the fuel gets, to more gas it releases at a higher rate, creating a hotter enviroment for any other fuel added.
Watch a oil lamp wick. Note the wick takes a long time to burn away, but you fill the lamp several times before you ever have to replace the wick. The flame you see isn't the wick burning, nor is it the oil, but the gas created when the wick draws the oil up near the flame, and the heat from the flame turns the oil into a gas, which ignites from the already present flame. If you look closely, you can see the flame "dance: just above the wick, same with a wood or coal fire, if you look closely you can see the gases form and burn. In an enclosed area, like a firebox, these gases can exceed the correct ratio of oxygen to gas needed to burn hot or clean, so by introducing a supply of fresh air(oxygen) the mixture returns too the combustion point, ignites from the exsisting fire and burns.
Hows that sound?
Ed

[Anonymous]

A kind gentleman, Ted Talbot, a published authority in the U.K. about such matters was gracious enough to provide an answer to the question of "what's a re-entering fire door?"
Here's his reply--
"Now your query about 'a re-entering fire door' - I am not surprised you are puzzled by such a term. In fact, this fitting was much simpler than it sounds. The handle operating the firehole door was to the left of the door and was fitted with a ratchet. When the handle was vertical, the door was closed. When the fireman pulled the handle towards him, the door, which was hinged at the top, swung into the firebox - and so formed a flap. Air entering the firebox beneath it was therefore directed downwards.
The ratchet on the handle enabled the fireman to set the flap/door in any position he chose, so as to get just the amount of top air that he wanted. Of course, the drawback with this design was that it the engine was worked very hard, the temperature in the firebox rose sufficiently to heat up the door and distort it."
Many thanks to all who supplied answers.
I believe it was Oliver Wendell Holmes who said that the Americans and British are a people separated by a common language. That sure is true in railroading. For, while we use different terms, most of the replies to my query arrived at the same place.
Again, thanks for the help.