[Footnote: From a lecture before the Franklin Institute by C. John
Hexamer.]
There are few parts in fire construction which are of so much importance,
and generally so little understood, as fire doors. Instances of the
faulty construction of these, even by good builders and architects, may
daily be seen. Iron doors over wooden sills, with the flooring boards
extending through from one building to the other, are common occurrences.
We frequently find otherwise good doors hung on wooden jambs by ordinary
screws. Sliding doors are frequently hung on to woodwork, and all
attachments are frequently so arranged that they would be in a very short
time destroyed by fire, and cause the door to fall. In case of fire, a
solid iron door offers no resistance to warping. In an iron lined door,
on the contrary, the tendency of the sheet iron to warp is resisted by
the interior wood, and when this burns into charcoal, it still resists
all warping tendencies. I have seen heavily braced solid iron doors
warped and turned after a fire, having proved themselves utterly
worthless. It is needless to say that when wooden doors are lined, they
should be lined on both sides; but frequently we find so-called fireproof
doors lined on one side only.
Good doors are frequently blocked up with stock and other material, so
that in case of fire they could not be closed without great exertion; or
they have been allowed to get out of order, so that in case of fire they
are useless. This has been so common that it has given rise to the
jocular expression of insurance men, when they are told that a fire door
exists between the two buildings, "Warranted to be open in case of fire."
The strictest regulations should exist in regard to closing the fire
doors nightly. Frequently we find that although the fire door, and its
different parts, are correctly made, there are openings in the wall which
would allow the fire to travel from one building to the other, such as
unprotected belt and shaft holes. That a fire door may be effective, it
must be hung to the only opening in the wall.
The greatest care must be exercised to keep joists from extending too far
into the wall, so as not to touch the joists of the adjacent building,
which would transmit the flames from one building to the other in case of
fire. A good stone sill should be placed under the door, and the floor
thereby entirely cut. Sills should be raised about one and a half inches
above the level of the floor, in order to accomplish the necessary
flooding of the same. If stock must be wheeled from one building to the
other, the sill can be readily beveled on both sides of the wall,
allowing the wheels to pass readily over it. Lintels should consist of
good brick arches. When swing doors are used, they should be hung on good
iron staples, well walled into the masonry, and the staples so arranged
that the door will have a tendency to close by its own weight. The door
should consist of two layers of good one and a quarter inch boards,
nailed crosswise, well nailed together and braced, and then covered with
sheet iron nailed on, or if of sheet tin, flanged, soldered, and nailed.
Particular care should be taken to insert plenty of nails, not only along
the edge of the door, but crosswise in all directions. I have seen cases,
where the entire covering had been ripped off through the warping
tendencies of the sheet iron.
The hinges on these doors should be good strap hinges, tightly fastened
to the door by bolts extending through it, and secured by nuts on the
other side. Good latches which keep the door in position when closed
should always be provided. In no case should the door be provided with a
spring lock which cannot be freely opened, as employes might thereby be
confined in a burning room.
Sliding doors should be hung on wrought iron runways, fastened tightly to
the wall. Wooden runways iron lined, which we frequently see, are not
good, as the charring of the wood in the interior causes them to weaken
and the doors to drop. Runways should be on an incline, so that the door
when not held open will close itself. Care must be taken to have a stop
provided in the runway, so that the doors may not, as I have frequently
seen them, overrun the opening which it is to protect. Doors should
overlap the edges of the openings on all sides. Large projecting jambs
should never be used.
All doors contained in "fire walls" should have springs or weights
attached to them, so as to be at all times closed. Fire doors can be shut
automatically by a weight, which is released by the melting of a piece of
very fusible solder employed for this purpose. So sensitive is this
solder that a fire door has been made to shut by holding a lamp some
distance beneath the soldered link and holding an open handkerchief
between the lamp and link. Though the handkerchief was not charred, hot
air enough had reached the metal to fuse the solder and allow the
apparatus to start into operation.
These solders are alloys more fusible than the most fusible of their
component metals. A few of them are: Wood's alloy, consisting of:
cadmium, 1 to 2 parts; tin, 2 parts; lead, 4 parts; bismuth, 7 to 8
parts.
This alloy is fusible between 150° and 159° Fahr. The fusible metal of
D'Arcet is composed of: bismuth, 8 parts; lead, 5 parts; tin, 3 parts. It
melts at 173.3°. We can, therefore, by proper mixture, form a solder
which will melt at any desirable temperature. Numerous devices for
closing doors automatically have been constructed, all depending upon the
use of the fusible solder catch.
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