ACID CHAMBER WORK.
It is not my intention to give an elaborate description of how acids are
made or to attempt to describe all of the different fittings employed in
that work, because while all plants are similar in construction no two
are alike. For that reason I will confine myself to the methods employed
in handling lead in large quantities, as the lead used in this work
ranges in weight from 18 to 24 pounds to the foot and is therefore very
heavy to handle. These chambers are known as condensing chambers, and
their use is to catch and condense a mixture of sulphur and steam which
is blown into them through a large lead pipe. For that reason they are
usually built out of doors, and sometimes have a sort of temporary roof
built over them. Consequently in repairing they are easily gotten at,
which, by the way, is seldom necessary.
[Illustration:
_Fig. 37.—Method of Framing Chamber._
]
To begin with, the sheet lead should be purchased of such a width as to
make as few seams as possible. The bottom of the chamber for this lead
to lie upon should be made of 2-inch cypress plank, the same to be
tongued and grooved as for floors, and should be planed down, if
necessary, so that it will present a perfectly smooth surface for the
lead to rest upon, for if there are any uneven spots that is where the
lead will eventually crack. The frame work for the sides should also be
put in place before the lead work is started, or at least enough of it
to prevent dirt and other stuff from bothering the burner. One end of
the chamber, however, should be left open, so as to enable the workmen
to bring in the lead or other material. The sides should not be closed
up, but should be framed, as shown in Fig. 37, so as to allow the lead
to be securely fastened to the frame work, which should be made of heavy
stock, depending, of course, upon the depth and size of chamber, as they
are in all sizes, from 10 feet to 60 feet long and longer.
After seeing that this part of the work is all right, begin to place the
bottom in position. This lead should be cut large enough to allow of its
being turned up about 2 inches all around for tight tanks. The sides are
not burned to the bottoms of some chambers, but the bottom lead is
turned up different hights, depending upon how deep it is required to
carry the acid in the chamber, which is from 4 to 10 inches or deeper.
The studding should be notched out to allow the turned up lead to face
with the face of the studding, otherwise there would be a bend in the
side lead where it overlaps the sides of the bottom. The flat seams in
the bottom should be butted together, so as to give a perfectly smooth
surface, which will allow all the acid to be drawn off.
[Illustration:
_Fig. 38.—Chipping Knife._
]
[Illustration:
_Fig. 39.—(A) Strap Split and Bent in Alternate Directions. (B) Bevel
End of Strap._
]
It is rather a difficult task for some men to cut heavy lead straight.
This is easily accomplished by first marking a chalk line on the lead
where it is desired to cut it off; then, taking the hammer and chipping
knife, as shown in Fig. 38, dip the blade of the knife in water, lay the
blade square on the line and strike the back of the blade lightly with
the hammer. Mark the sheet the whole length in this manner. Then go over
it again and repeat the operation, making sure that the knife is held
straight. The blade of the knife must be kept wet or it will stick in
the lead and cause it to glance off sideways. After it is cut any uneven
spots can be planed off smooth with a small smoothing plane, set so as
to take off a very light chip. The lead should now be placed in position
and dressed smoothly by using a piece of pine, or other soft board, as a
dresser. This must be laid on any uneven spots and then pounded down
smooth with a heavy wooden mallet, after which the seams should be
shaved and burned at once; or if the seams are short and it is desired
to put in enough work one day to keep the burner busy the next, strips
of paper 6 inches wide should be pasted over the seams to keep the dust
out. Only the edges of the paper should be pasted, so that when ready to
burn all that will be necessary is to take hold of one end of the paper
and strip it off, leaving the seam clean and free from dust and paste
and ready to shave and burn.
[Illustration:
_Fig. 40.—Roll of Lead in Position._
]
After the bottom is finished the sides must be put in, in such a manner
as to have as few seams in an upright position as possible, as it saves
considerable time to burn them when horizontal. On small chambers or
tanks not over 10 feet deep the carpenter should make a staging wide
enough to receive two sheets of lead and as long as the tank is deep.
The bottom of the chamber should then be covered with boards, so as to
prevent damage to the lead. The staging is then brought in and set up on
horses, and the sheets of lead are cut off and laid on the staging. The
seams are lapped, shaved and burned, after which the lead tacks or
straps are cut and burned on, to support the lead when in position.
There are different ways of putting on these straps. For side lead I use
strips of the lead itself about 3 inches wide and long enough to lap
well onto the studding. My way is to split this strip about ½ inch deep
and bend the ends in alternate directions. The edges are then cut off,
as shown at A, Fig. 39, after which they are burned in place. These
straps should be spaced not more than 15 inches apart, and should be
placed in such a manner as to come on the upper side of the studding.
[Illustration:
_Fig. 41.—Clamp and Method of Applying._
]
Another method of putting on these tacks, and one which is most commonly
practiced, is to trim the end of the strip of lead as shown at B, Fig.
39. The strip is laid flat on the lead sheet, with the bevel end down,
and is then burned onto the sheet in that position, after which it is
bent over the studding and nailed. The exponents of this method claim
that a better job is done in that manner, as there is always a lifting
pull on the strap. I claim for the first method that there is more
strength in the lead seam, and that as the edge of the studding comes
directly under the strap it acts as a sort of shelf for the strap and
thereby becomes a strong brace. But it is probably only a matter of
habit, as they hold all right either way.
Now, after having the seams burned and the straps in place, the lead
must be put in position. This can be accomplished by any arrangement of
block and tackles, but if the chamber be very large it will be found to
be a saving of time and labor to rig up a derrick. This is not such an
expensive thing to do, as a carpenter is always on hand and most likely
all the material needed is already on the ground. This derrick should be
constructed with a swinging boom, so that it can be raised, lowered or
swung into any desired position.
[Illustration:
_Fig. 42.—Showing Staging in Position._
]
Now to raise the side lead into position: The derrick is hooked onto the
hook or rope that is on the upper end of the staging. It can then be
easily raised in position. If the tank be very deep, or if it should be
too narrow to follow this method, the sheet lead should be rolled up on
a piece of 2, 3 or 4 inch iron pipe, depending upon the weight of the
lead. This pipe should be long enough to project at least 6 inches from
both ends of the roll. Two timbers, long enough to cross the frame work,
should be obtained. About 18 inches from one end of each timber a notch
should be cut to prevent the pipe from rolling. These timbers must now
be placed across the frame work just over the place that is intended for
the lead. The whole roll can now be raised with the derrick and the ends
of the pipe placed in the notches. The lead can then be pulled down,
similar to pulling down a window shade, after which the tacks can be
burned on in place. This is shown at _a_, Fig. 40. Or if there be room
enough the piece of lead can be cut from the roll, dressed smooth and
have the tacks burned on while on the floor. The upper end of the lead
can then be rolled over and nailed to a piece of timber 2 × 6 inches or
heavier, and the derrick hooked onto this and raised in position. This
is the easiest method where there is room to do it. These are a few of
the methods used, but there are numerous other ways.
To place the top lead in position requires a staging, which can be built
as follows: Enough hooks should be made to properly support the staging,
shown at A, Fig. 41. Two timbers should be laid across the top of the
chamber, far enough apart to allow two strips of lead to be placed in
position at once. The hooks are now hooked over these timbers, while two
pieces of 3 × 3 or 4 × 4 are placed in the other end of the hook. Planks
are now laid over these timbers and the screws set up until the tops of
the planks come just level with the top of the lead—not higher, or else
they will prevent the joist from being placed in position.
The lead can now be cut off on the ground and hoisted up to the top,
where it becomes an easy matter to place it in position. The lead tacks
can now also be cut and burned on. They should be cut sufficiently long
to allow them to lap over the top of the joist, as shown at _a_, Fig.
42, where they should be nailed with large headed nails. It will be
noticed that the tacks are doubled up on the top lead and that they are
not set opposite each other. The joist can now be set and the tacks
nailed on, after which ropes can be tied onto the projecting ends of the
4 × 4 timbers and the whole staging be lowered to the floor at once.
This operation can be repeated until the whole top is on.
[Illustration:
_Fig. 43.—Lead Headed Nail._
]
It will be necessary to leave small holes between the lead seams at
intervals for the hooks to pass through. However, these can be burned
over at any time, and where the ends of the top should overlap the end
of the chamber the lead can be left turned up until the staging is
removed, after which it can be turned over and burned. The hooks are
made of ⅝ round iron and have a long thread cut on one end, so as to
allow for adjustment. The details are shown in Fig. 41. There are also
numerous fittings used in connection with these condensing chambers, but
they are all easily made and are too simple to take up space here in
explanation. Should it be necessary to use nails for any purpose on the
inside of the chamber, the heads should be dipped into a pot of melted
lead that has not quite set until the adhering ball of lead is about ½
inch in diameter, as shown in Fig. 43. These nails can be driven in
place and the lead burned to the sheet lead, which will prevent
corrosion.