Protective Screens For Furnaces
: The Working Of Steel
Workmen needlessly exposed to the flames, heat and glare from furnaces
where high temperatures are maintained suffer in health as well as
in bodily discomfort. This shows several types of shields designed
for the maximum protection of the furnace worker.
Bad conditions are not necessary; in almost every case means of relief
can be found by one earnestly seeking them. The larger forge shops
have adopted fl
me shields for the majority of their furnaces. Years
ago the industrial furnaces (particularly of the oil-burning variety)
were without shields, but the later models are all shield-equipped.
These shields are adapted to all of the more modern, heat-treating
furnaces, as well as to those furnaces in use for working forges;
and attention should be paid to their use on the former type since
the heat-treating furnaces are constantly becoming more numerous
as manufacturers find need of them in the many phases of munitions
making or similar work.
The heat that the worker about these furnaces must face may be
divided in general into two classes: there is first that heat due
to the flame and hot gases that the blast in the furnaces forces
out onto a man's body and face. In the majority of furnaces this
is by far the most discomforting, and care must be taken to fend
it and turn it behind a suitable shield. The second class is the
radiant heat, discharged as light from the glowing interior of
the furnace. This is the lesser of the two evils so far as general
forging furnaces are concerned, but it becomes the predominating
feature in furnaces of large door area such as in the usual
case-hardening furnaces. Here the amount of heat discharged is
often almost unbearable even for a moment. This heat can be taken
care of by interposing suitable, opaque shields that will temporarily
absorb it without being destroyed by it, or becoming incandescent.
Should such shields be so constructed as to close off all of the
heat, it might be impossible to work around the furnace for the
removal of its contents, but they can be made movable, and in such
a manner as to shield the major portion of the worker's body.
First taking up the question of flame shields, the illustration,
Fig. 102, is a typical installation that shows the main features
for application to a forging machine or drop-hammer, oil-burning
furnace, or for an arched-over, coal furnace where the flame blows
out the front. This shield consists of a frame covered with sheet
metal and held by brackets about 6 in. in front of the furnace.
It will be noted that slotted holes make this frame adjustable
for height, and it should be lowered as far as possible when in
use, so that the work may just pass under it and into the furnace
Immediately below the furnace openings, and close to the furnace
frame will be noted a blast pipe carrying air from the forge-shop
fan. This has a row of small holes drilled in its upper side for
the entire length, and these direct a curtain of cold air vertically
across the furnace openings, forcing all of the flame, or a greater
portion of it, to rise behind the shield. Since the shield extends
above the furnace top there is no escape for this flame until it has
passed high enough to be of no further discomfort to the workman.
In this case fan-blast air is used for cooling, and this is cheaper
and more satisfactory because a great volume may be used. However,
where high-pressure air is used for atomizing the oil at the burner,
and nothing else is available, this may be employed--though naturally
a comparatively small pipe will be needed, in which minute holes
are drilled, else the volume of air used will be too great for
the compressor economically to supply. Steam may also be employed
for like service.
The latest shields of this type are all made double, as illustrated,
with an inner sheet of metal an inch or two inside of the front.
In the illustration, A, Fig. 102, this inner sheet is smaller,
but some are now built the same size as the front and bolted to
it with pipe spacers between. The advantage of the double sheet
is that the inner one bears the brunt of the flame, and, if needs
be, burns up before the outer; while, if due to a heavy fire it
should be heated red at any point, the outer sheet will still be
much cooler and act as an additional shield to the furnace man.