Improved Vacuum Drying Apparatus for Explosive Substances.
Year: 1890

page_text: Date of Application, 26th July, 1890-Accepted, 27th Sept., 1890
COMPLETE SPECIFICATION.
Improved Vacuum Drying Apparatus for Explosive Substances.
,٠٠
I, HERBERT JOHN HADDAN, of the firm of Herbert & Co., Patent Agents,
of 18 Buckingham Street, Strand, W.C., London, Civil Engineer, do hereby declare
the nature of this invention, a communication to me from abroad by Johann Heinrich
Voelkel of Gartenstrasse No. 42, Breslau, Germany, 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 apparatus for drying substances in closed spaces or
chambers under pressure less than that of the surrounding atmosphere or as it is
usually termed in vacuo, and the object of the invention is to construct such apparatus
so that it may be suitable for drying matters which are more or less explosive.
It is well known that when some explosive substances have reached a certain stage
or degree of dryness they are liable to explode and develop a more or less large
quantity of vapour and gases, and the purpose of the present improvements is to
prevent such explosion of the substance being dried, or of part of it, from causing
damage to the drying chamber or other parts of the apparatus, or injury to the
workinen attending to it.
Now, the improvement consists in constructing the drying chamber so that upon
the occurrence of an explosion disengaging more than sufficient gases to destroy the
vacuum, the said chamber will be opened or relieved automatically and so allow free
egress to gases etc., disengaged; and in arranging a space, spaces or expansion
chambers, from which the air is more or less exhausted, in communication with the
drying chamber so as to receive the said gases or a relative proportion of them and so
prevent the bursting of the drying chamber or breakage of other parts of the
apparatus.
These two appliances can be used separately or combined. Their united application
offers the special advantage that the whole of the substance is not involved in the
damage when a comparatively small portion explodes, since the gases disengaged,
unless sufficient to wholly destroy the vacuum, would not necessitate interruption of
the process by reason of the comparatively large increase of the space or chamber in
which the vacuum prevails. If, on the other hand sufficient matter should explode,
or should a general explosion occur sufficient to more than destroy the vacuum and
give an over pressure the apparatus will open for release of the gases etc., evolved.
The latter purpose is fulfilled by arranging in the wall of the drying or expansion
chamber in either or both where most convenient a sufficient number of holes or
safety branches, upon which are fitted closing lids made air tight with suitable rubber
or other packing rings. The lids press lightly only on the branches except during
the working of the process when the vacuum prevails in the chamber or chambers at
which time the excess of atmospheric pressure holds the lids in a firm and air tight
manner in place. As soon as overpressure prevails in the interior of, the chamber or
chambers by reason of an explosion of sufficient material, the lids open or are blown
off and allow the gases to escape from the openings. The lids are so arranged that
in flying off they do no damage, for this purpose their branches, may be arranged
so that they are not placed one immediately over the other, or the lids.may be
connected by hinges or their movements can be regulated in any other convenient
way.
The further arrangement by which the space to receive exploded gases in the
apparatus is increased may be provided for by connecting a suitably strong, closed
vessel by means of a pipe of large diameter, with the drying chamber, a valve or stop
cock being preferably provided in the said pipe so that the communication between
the said vessel and drying chamber may be opened or closed.. The air in the vessel

page_text: may be exhausted at the same time as that in the drying chamber or either imme-
diately upon or even after the commencement of that stage or period of the process of
drying which experience has shown to be liable to the danger of explosion. The
said vessel may also be fitted with one or more safety holes or branches with lids
thereon as before-described.
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The door or doors of the drying chamber by which access is had to the interior or
by which the matters to be dried are inserted or removed may be held closed lightly
by means of screws, bolts, weights or counterpoises, such doors will be held firmly
closed so long as the air pressure outside exceeds that inside the, drying chamber.
When such doors are fixed in place by screw-threaded bolts and hand-nuts, the latter
may be loosened after sufficient diminution of the interior pressure, so that being held
closed only by excess of exterior atmospheric pressure they will be loosened on
occurrence of an explosion of sufficient magnitude.
The improvements are shown in the accompanying drawings (Figs. 1 to 4) as
adapted to apparatus in which the substance to be dried is spread out on basins i
which stand upon boxes and to which the evaporating heat is supplied by conduction
from the latter which are heated by means of steam, hot water, hot air etc.
improvements may however be adapted in a similar way to any vacuum drying
apparatus. T is the door which closes air tight. ( is a condenser. the piping. Lis
The
the pipe branch connected with the vacuum chamber. P is the air pump.
For the purpose indicated the apparatus shown in Figs. 2 and 3 and in Fig. 4
possess at several places safety branches sss. dd are lids placed thereon and made
airtight with india rubber rings.
The farther arrangement is represented in the expansion vessel E. (Figs. 2 and 3.)
which is connected with the apparatus by the pipe R, R¹ with the valve and from
which the air is exhausted.
This vessel also can be provided with a safety branch or branches D with a lid or
lids made airtight with an india rubber ring or rings.
Now if a portion of the drying substance explodes the gases in the first place
detonate in the apparatus itself and in the expansion vessel E the vacuum being
diminished.
It is only upon greater or a general explosion that the safety lids fly open.
Fig. 4 shows an apparatus with a cylindrical form of vacuum body and safety
branches at both sides.
At the same time it shows a further modification in the carrying out of the
same invention.
The door of the apparatus and the lower lid D₁ close by a counterpoise but
only for the purpose of keeping them tightly shut during the exhausting of
the air.
As soon as the vacuum is created, the atmospheric pressure also presses the door
of the apparatus firmly to, upon a considerable internal overpressure the lower lid
and the door open automatically affording free passage for the explosion gases. In
Figures 1. and 3 on the other hand the door is shown as being pressed to by
hand cranks. As soon as after the creating of the vacuum the atmospheric pressure
presses the door sufficiently to the hand cranks can be released so that here again
the door flies open upon a considerable explosion and allows free passage for the
explosion gases.
According to the greater or less liability of the drying substance to explosion
the automatic means of opening here described will be adopted to a greater or
less extent.
Figs. 5 to 7 show a vacuum chamber of simplified style, Fig. 5 being a front
elevation Fig. 6 a sectional side view and Fig. 7 a sectional plan.
A is the drying chamber proper and E the space or chamber provided for
expansion, in this case the chambers A and E are made of equal cross section
and united to form one long chamber. S are the safety branches fitted with lids d
as shown furnished with rubber or other packing they are arranged in such
manner that the lids on being blown off are clear of each other. Ture the doors

page_text: furnished with packings held in positions by screws o and hand lever nuts x,
these nuts can be loosened or so adjusted that the doors may be held closed only
by the excess of exterior atmospheric pressure. are steam or hot water or hot
air boxes which carry trays for holding material or on which the material to be
dried can be placed. M is a steam hot water or hot air inlet with branches to
said boxes and N outlet for same. P Pare windows. The mode of construction
is also shown but in matters of detail may be varied.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1. In apparatus for the drying of explosive matters the arrangement of safety
branches with lids which open automatically as soon as an overpressure arises
through an explosion in the interior of the drying chamber.
2. In apparatus for the drying of explosive bodies the arrangement of separate
expansion vessels from which the air may be exhausted for the purpose of receiving
explosion gases in the event of the drying substance exploding in the interior of
the drying apparatus.
3. In apparatus for the drying of explosive substances the arrangement of lids
or of a door with counterpoise or the application of lids or doors pressed to during
the creation of the vacuum by means of hand cranks, but afterwards released,
which then remain pressed to by the atmospheric pressure but which open auto-
matically for the passage of gases upon the occurence of an explosion.
Dated this 26th day of Tul 1800
HERBERT & Co.,
18, Buckingham Street, Strand, London, W.C., Agents for the Applicant.