other Fibrous Matters with Acid Solutions.
Year: 1888

page_text: Date of Application, 7th Dec., 1888
Specification Accepted, 15th Jan., 1889
or other Fibrous Matters with Acid Solutions.
1 ALFRED LUNDBERG of Sweden but now of Northfleet in the County of Kent,
Chemical Engineer, 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 :-
This invention relates to boilers of iron or steel for treating wood or other fibrous
matters for the production of pulp with such acid solutions, as necessitate the
application of lead to prevent the said boilers from being attacked.
Hitherto lead has been applied in such boilers chiefly as rolled sheet lead; but
owing to the frail nature of lead such a lining, though attached and upheld in
numerous places, requires much attention and often repairs and renewing.
33
The fact having been established by experience that the damage to a lining of sheet
lead results chiefly from movements in the lead, notably from the so called "creeping
caused by repeated heating and cooling, when expansion is favoured more in one
direction than in others, attempts have been made to curtail those movements in and
give more rigidity to the lead by combining the same with a perforated sheet of a
firmer metal (Makins Patent No. 5626 7th May 1885), the said combination being
brought about in such manner, that lead is cast round the perforated metal sheet
(preferably of iron or steel), by which operation sheets of lead are obtained tied, as
it were, to the more firm perforated metal sheet by means of leaden studs or rivets at
all the places where the metal sheet is perforated-but there only.
2 years previously Mōhlau of Düsseldorf in Germany (Pat. No. 1730 6th of April
1883) tried to solve the problem in a more thorough manner by fusing with the aid
of the oxyhydrogen flame lead direct on to the iron shell so as to form metallic
union with the iron shell, but in execution this method, which undoubtedly aimed
in a right direction, has been found to be fraught with enormous difficulties causing

page_text: the work to be unreliable, and for this reason and on account of the great difficulties
to repair defects, when they begin to show, the method has not answered
expectations.
.
It is important, that the term metallic union (the union between the elements of a
solid piece of metal or an equivalent union between two pieces of metal) should be
clearly distinguished from the combination between the lead and the perforated sheet
previously described (Makins Pat.), and which combination I should term metallic
contact.
The object of my Invention is to provide by a method easy of execution lead lined
boilers, in which no movements (creeping) can take place in the lead, and consists
in 1st making use instead of sheet lead of a compound sheet composed (see drawing
Fig. 3) of a sheet of lead (or lead alloy) "c" in metallic union on a comparatively
thin backing sheet "d" of a non-creeping metal such as Zink, Iron, Copper or Copper
alloy e. a combination, where every the smallest element of the lead sheet is held
in place by a corresponding element of the non-creeping backing sheet and thus
itself made non-creeping and to partake of the more rigid form of the backing
sheet and
2d. in the construction of boilers of such form, that the said compound sheets can
be easily applied as a lining in a position unalterable throughout.
The compound sheets I make by covering the backing sheets with lead in such
manner as to make it form metallic union with the backing sheet. The methods,
by which this may be done, are familiar to plumbers and consist briefly speaking in
melting (fusing) lead on to the clean (tinned) metallic surface under application of
heat in a suitable way-for the making of a sound coating of lead so as to form
metallic union requires, that the surface of the metal should be thoroughly clean
(metallic) it is for this reason generally first tinned--and also, in order that the
lead may "take" and get attached metallically to the surface, whereon it is to be
applied, that the said surface be heated to the fusing point of lead. As the backing
sheets, which I require to cover with lead, are comparatively thin (consequently do
not take much heating up) and may be treated in such sizes as make them easily
handled, it is easy to apply a thoroughly sound and reliable coating of lead (or lead
alloy) of any required thickness.
::
area of
As in the compound sheet here described every the smallest element of the lead
sheet is held in place by a corresponding element of the backing sheet, the "
expansion of the leadsheet (see Makins Specification) is reduced to nil. The
molecular strain in the lead sheet consequent upon the restriction of its naturally
greater tendency to expand by heat will be equally distributed and therefore' not be
detrimental.
As the backing sheets are comparatively thin, they may be first covered with lead
and the compound sheets then bent in the form required, or else the backing sheet
be bent in the form required' (at least approximately) before being covered with
lead.
The problem of applying the compound sheets in a position unalterable throughout
is one of so applying the backing sheets and can be solved with some degree of
success for any form of boiler by the aid of affixing screws or bolts with or without
strips but in a much more simple and fully efficient way in boilers constructed as a
series of segments (rings) formed as cones or as a succession of cones, joined together
with each other by means of tapjoints so arranged, that the inside plate edges face
in the same direction, in which the adjoining segments get narrower.
Butt joints, although they may be made use of, are not so suitable.
•
In Fig. 1. of the accompanying drawing is shown a spherical boiler constructed in
accordance with those principles (as a spherical segment may be considered as a
succession of cones). The parts constituting a segment may be joined with weld or
butt joint, but not with lap joints.
To line any one of the segments the compound sheets of corresponding form
and prepared in as large parts thereof as convenient (in 2 halves, when possible)

page_text: are introduced into the boilers through the manhole, and the backing sheets then
joined together in a substantial manner.
Before the last joint is made, the sheet should be sprung out so as to fit the
segment closely. The ring of compound sheets when fitted against the segment of
the boiler shell so as to abutt against the plate edges (at o) of the next wider
segment should overlap the segment a little at the narrow side, and the overlapping
portion should be knocked over the edge at "" (see Fig. 3), but if the segment,be
of the kind exemplified in Bẞy G., the lining ring should be made and applied so
as to overlap the segment a little at both sides, and the overlapping portions treated as
before-said.
The fit is afterwards, if necessary, perfected by beating with wooden mallets and
ultimately by applying water pressure, after all the segments have been lined and
the lead joints made in the usual way-a suitable number of small vent holes through
the boiler shell allowing air at the back of the lining to escape and thus making a
close fit possible.
Fig. 2 and Fig. 3, the latter of which shows in natural size a representative section
at the lap joint B, and the former of which includes a section of the two consecutive
lap joints A and B with the segment between the same, show clearly the position
of the compound sheet and tlie nature of the lead joint "1" between two segments of
the lining.
Considering the possibility of movement of the lining of a segment made as now
described it is evident from the nature and everywhere arched form of the compound
sheet, that it cannot bulge inwards, neither can it swerve round owing to friction,
being closely fitted against the boiler shell, (more especially if any of the component
parts of a segment of the boiler shell be joined with butt joint having inner strip, as
every such strip would present to the lining ring two abuttments in opposite
direction), moreover it is easy to find, that owing to either a conical form or
abuttments it is prevented effectually from moving sideways in either direction,
consequently the lining-ring is applied in a position unalterable throughout.
For the same or similar reasons the same applies to every segment forming part of
the boiler and consequently to the whole of the lining, and it may be added, that.
lead joints made between sheets, whose position is not subject to alteration, may be
expected to last as long as the lead on those sheets.
A so called cylindrical boiler I similarly construct as a series of lapjointed conical
rings and with conical or spherical ends as is usual. The inside edges of the plates
face in the direction, in which the adjoining rings get narrower.
The case is
altogether so analogous to the one described in re the spherical boiler as not to call
for special description.
If for the sake of greater convenience in introducing the lining sheets one of the
end-cones or part thereof be made detacheable and to this purpose finished with a
stout flange so, that it can be firmly bolted to a corresponding flange on the boiler,
the compound sheets meeting at such a joint must also be flanged and brought in
between the flanges named. Same applies in case of flanges necessitated by
man-holes or fittings generally.
Having now particularly described and ascertained the nature of my said Inven-
tion, and in what manner the same is to be performed, and having regard to
Makins Specification No. 5626 7th May 1885, I wish it to be distinctly understood,
that I do not claim compound sheets constructed as therein described or generally
such, where there is a mere metallic contact between the lead sheet and the sheet of
a firmer metal, with which it may be compounded, but what I do claim is :
1. The application-for lining boilers employed in treating wood or other fibrous
substances with certain acid solutions of compound sheets composed on one side of
a sheet of lead (or lead alloy) and on the other side of a comparatively thin sheet of
a metal more rigid of form such as Zink, Iron, Copper, or Copper alloy in metallic
union with each other so, that every the smallest element of the lead sheet is held by a
corresponding element of the more rigid backing sheet.

page_text: 2. Boilers of iron or steel for the application of the said compound sheets,
constructed partly or wholly as a series of segments (rings) formed as cones or as
a succession of cones and joined together with each other by means of lapjoint so, that
inside plate edges face in the same direction, in which the adjoining segments (rings)
get narrower.
3. The use of boilers constructed as stated in claim 2 for the application for
purposes stated in claim 1. of compound sheets others than those claimed by me in
that claim.