Year: 1886

page_text: I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake, & Co, Patent Agents,
Southampton Buildings in the County of Middlesex do hereby declare the nature
of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:-
My present invention has relation to boilers or digesters to be used in the
manufacture of paper pulp.
As sulphurous acid, acid solutions, sulphites or bisulphites are commonly
employed in the digesting process, and as such process is carried on under con-
siderable steam pressure it is the usual custom to construct these boilers or digesters
of iron and to line them with lead. This lead lining has been applied to the
boilers and affixed therein in various ways, none of which, however, has proved
entirely satisfactory. The sudden changes of temperature to which these boilers
are subjected during the digesting process and the difference in expansion and
contraction between the iron casing and the lead lining, has the effect of causing
the lead to warp and curl up at various points, while it is strained and spread at
other points and eventually the lining becomes cracked or broken and the liquid
or vaporous acid in the interior, escaping through the fissures in the lead attacks
the iron casing.
The usual manner of detecting the leakage of any acid through the lead lining
is by scenting the sulphuretted hydrogen which may escape at some of the joints
of the iron casing.
The life of these boilers of digesters is usually not more than two or three weeks,
the replacement of the lead lining being then necessary.
My invention has for its object the provision of means for preventing as far as
possible any distortion, warping, or breaking and consequent leakage of the lead
lining in boilers or digesters used in the manufacture of paper pulp."

page_text: My invention has for its further object the provision of means for immediately
indicating by a sonorous signal the escape of any acid through the lead lining,
whether such acid be in a liquid or vaporous form.
My invention consists,
Firstly In constructing the boiler or digester in such manner as to leave a space
between the lead lining and the iron casing and maintaining an equal pressure on
both sides of the lead lining while the boiler or digester is in operation.
Secondly In the provision of an electric signal adapted to be automatically
operated upon the escape of any of the acid contents of the boiler through the
lead lining.
Referring to the accompanying drawing wherein Fig. 1, is a vertical central
section of a vertical stationary boiler embodying my improvement and Fig. 2, a
. detail.
A, designates the exterior iron casing of the boiler which is of the usual form
and construction and need not therefore be particularly described. B, designates
the lead lining. This lead lining is separted from the interior of the iron casing A,
by a space C, and maintained at that distance by means, either of rings of lead D,
which are formed integral with the lining B, or attached thereto in any suitable
manner; or by means of rings of iron E, which are formed integral with or attached
to the casing A.
In Fig. 2, I bave shown a means for securing the iron casing and lead lining
together and at the same time sustaining the rings D, or E, in position, such
means consisting of bolts F, passing through the casing, the lining and the rings.
The rings D, or E, whichever may be employed, can be made continuous all
around the lining in which case they should be provided with holes for the passage
of steam or water; or they may be replaced by a number of lugs or projections
arranged at proper intervals.
It is my design to maintain, constantly, an equal pressure upon the outside and
inside of the lead casing and in order to do so, attach a branch pipe to the steam
pipe which conveys steam to the interior of the boiler; which branch pipe I lead
into the space C, between the lead lining B, and the casing A.
This space may be kept full of steam alone, the pressure being the same as that
upon the inside of the lead lining or a quantity of water may be kept in the space
and the pressure of the steam upon the top of the water within and without the
lead lining will maintain an equilibrium.
If water is kept in the space it should be pure and the water of condensation of
the steam will probably be found sufficient for the purpose after the boiler has been
in operation for some little time.
Suitable pipes should be provided for the ingress and the egress of the solutions
used and the boiler is of course provided with the usual means for introducing
and discharging the material to be acted upon in the boiler.
At or near the bottom of the boiler are fixed two wires I, I, which pass through
the exterior casing A, and are insulated therefrom.
The inner ends of these wires are brought close together without contact and
their outer ends are connected to the terminals of an electric circuit in which are
included a battery K, and an electric signalling apparatus L.
OPERATION.
The apparatus being constructed and arranged as described, the material to be
digested and the desired acid solution introduced into the boiler; steam is turned on
and enters the interior of the boiler and also the [space C. An equilibrium of
pressure is thereupon established between the interior and exterior surfaces of
the lead lining which is maintained during the time of the contents of the boiler
are under pressure. The lead lining and the iron casing of course expand and
contract as the temperature increases or diminishes, but being separated from one

page_text: another by the space C, wherein the steain pressure is maintained as before
mentioned, there will be comparatively no bulging or warping of the said lining
and heuce but little tendency on the part of the same to crack or leak at any of
its joints or seams.
Should any leakage occur, the water of condensation into which the wires I, I,
project becomes acidulated and establishes a circuit between the two thereby
causing the alarm L, to be sounded and immediately notifying the operative in
charge of the boiler of such leakage.
Having described my invention, I claim :-
1st. In a boiler for digesting materials by the action of acids, the combination
with an exterior casing and an interior lining of lead, separated from said casing
by a space, of steam pipes leading into the interior of the boiler and into the space
between the lead lining and the exterior casing whereby an eqable steam pressure
may be maintained on each side of said lining, substantially as described.
2d. In a boiler for digesting by the action of an acid solution or vapor, the
combination with an exterior casing and a lining separated from said casing by a
space, of an electric signalling apparatus whose circuit terminals project into said
space, substantially as described.
3d. In a boiler for digesting materials by the action of acids the combination
with the exterior casing and an interior lining of an electric signalling apparatus,
adapted to be automatically operated upon the escape of acids through the lining
substantially as described.