Improvements in Asbestos Filters.
Year: 1890

page_text: COMPLETE SPECIFICATION.
Improvements in Asbestos Filters.
1, FRIEDRICH BREYER of I Am Hof. No. 7 Vienna. Austria Engineer, do hereby
declare the nature of this invention and in what manner the sume is to be
performed to be particularly described and ascertained in and by the following
statement :-
This invention relates to filters, the filtering media of which are formed of very
finely divided asbestos, and it has for its object to arrange filtering plant for obtaining
sterilised water in any desired quantity in such manner that as soon as the filtering
layer is choked with deposit, it can be regenerated in the simplest possible manner,
without taking the apparatus to pieces.
For this purpose the filtering medium is placed upon the outer surfaces of the
porous sides of flat hollow bodies, which are enclosed in large numbers in a closed
vessel. The interior of the vessel is connected with a supply pipe for the water
to be purified, while the interiors of the several flat filtering bodies are connected
to a common water discharge pipe and a common air discharge pipe. The layer of
filtering medium is applied to the filtering bodies after these have been introduced
into the receptacle, by causing an asbestos emulsion to be forced through the water
supply passage into the vessel until a pressure gauge thereon indicates 1 atmos-
pheres over-pressure.
The fine asbestos for the asbestos emulsion is prepared by moistening asbestos,
and after allowing it to freeze, disintegrating it by grinding. When the filtering
layers that have become choked after long use require to be regenerated, the man-
holes of the receptacle are opened, and the asbestos layers are brushed off, in
order to deposit fresh layers of asbestos emulsion on the porous surfaces of the
bodies.
The porous hollow bodies upon which the asbestos layers are deposited are by
preference formed by covering in corrugated sheet metal with plane perforated
plates, the body so formed being then covered with a suitable woven fabric. I
will proceed to describe a filtering apparatus constructed in the before described
manner, for which purpose I will refer to the accompanying drawings.
Fig. 1 shews a flat hollow filtering body, with the covering fabric and perforated
plate partly removed, so as to shew the corrugated plate.
Fig. 2 shews a longitudinal section.
Fig. 3 a cross section on line a a Fig. 1.
Figs. 4 and 5 shew a plan and section of the plate for forming the discharge
branch.
Fig. 6 is a part section of the filtering body to a larger scale.
Fig. 7 and 8 are two vertical sections at right angles to each other, of a filtering
apparatus consisting of a number of filtering bodies enclosed in a receptacle.
Figs. 9 and 10 shew two vertical sections at right angles to each other, of a
filtering plant constructed according to this invention.
As shewn in Figs. 1 and 2, the trapez shaped plate a forming the skeleton of the
filtering body has vertical grooves a pressed into it, which project alternately on
opposite sides and thus form supporting ribs for the side walls of the body, formed
of the perforated flat plates as shewn at Fig. 6.
For the purpose of stiffening the plate a in the horizontal direction, the grooves a¹
are intersected at several points by flat parts a². The upper and lower edges of the
plate a, at a³ and a*, are formed trough shaped in a transverse direction, and have
in the middle a discharge spout, all the verticle channels a' being made to open into
the transverse channels a³ a. By fitting similar shaped sheet metal pieces a³ a on

page_text: the channels a³ a* there are formed at the upper and lower ends of a chambers with
discharge branches, of which the upper one serves for the escape of air while the
lower one serves for the discharge of the filtered liquid.
The plate a prepared as described, is enclosed between two perforated plates b, the
holes of which have a diameter of about 1 mm. and the edges of which are bent
over to a dish form corresponding with the depth of the channels a', and are provided
with flanges which are rivetted together as shewn. Over the metal body thus
formed is placed a strong closely woven fabric c. For this purpose two pieces of
fabric, cut to a size corresponding to the metal body, are sewn together at the two
longitudinal sides and at the upper end by a double lock stitch sewing machine;
the edges of the fabric are then ironed flat, and a strong tape is sewn with at
least three rows of stitches to each of the edges. The sack thus formed is then drawn
over the metal body and is sewn together at the open end with close overhead
stitching, the fabric being at the same time stretched as tight as possible.
The porous hollow body thus formed with discharge branches at the upper and
lower ends, already forms a filter by means of which coarser impurities can be
separated from liquids. For the purpose however of rendering it available for
separating microscopic impurities, and consequently for sterilizing liquids, the surface
must be covered with a layer of finely divided asbestos.
In order to prepare the woven fabric for the reception of such layer, the body is
first boiled in water for about one hour, then dried, and worked upon with wire
brushes until the surface of the fabric has a velvety touch, after which a coating of
asbestos emulsion, prepared as will be presently described, is applied by means of a
brush over the entire surface.
The coating must be uniform without leaving holes, and upon this is then
deposited the layer of asbestos by forcing the asbestos emulsion in the manner
previously described inwards through the outer surfaces of the bodies enclosed in the
receptacle until by the accumulation of the fibre a certain resistance is opposed to the
passage of the liquid.
Figs. 7 and 8 shew the cast iron battery casing d containing a certain number of
vertically mounted filtering bodies e, all the air discharge branches being made to
communicate wiha pipe common to all, and all discharge branches for the filtered
liquid communicating with another pipe g.
The pipe is connected by a pipe f passing through the receptacle with a discharge
pipe having a check valve f2, which branches off from the discharge pipe g for
liquid situated at the side of the lower end of the receptacle.
The rising pipe h, opening into the bottom of the receptacle, serves both for
forcing in the asbestos emulsion, and subsequently for the supply of the liquid to be
filtered.
For making the asbestos emulsion, woolly asbestos fibre, free from stones is taken
and is first boiled in water, then after cooling it is frozen either by natural or
artificial means.
The frozen mass is then reduced either by stampers or by disintegrators, then again
boiled, cooled and frozen. The product thus obtained is then ground so fine that a
small quantity placed in water forms an emulsion presenting no structural appearance
of the particles to the naked eye.
When using such emulsion for forming the filtering layers as described, the per-
centage of solid fibre contained therein must be accurately determined. According to
this percentage, it is then diluted to such an extent as to give to the square decimeter
of the filtering surface 0.3 gramme of asbestos.
The asbestos emulsion thus prepared is then introduced into a closed receptacle i
Figs. 9 and 10, from the bottom of which a pipe
being introduced between the two and a check valve
and the pipe h.
leads to the pipe h, a pump 22
being placed between the pump
The upper end of the vessel is also connected by a pipe, with shut off valve i³,
with the discharge pipe g' for filtered liquid, which pipe leads, from the branch g

page_text: the battery and is also connected with the collecting channel ; for the filtered liquid
by a pipe j', which has also a shut off valve j.
Before explaining the mode in which the asbestos layers, which are impermeable
for micro organisms, are formed on the filtering bodies, it may be further stated in
explanation that the rising pipe communicates at its lower end with a pipe k¹
having a shut off valve and leading to a mud channel k, and that the upper part of
the pipe .communicates on the one hand by a pipe m² with shut off valve m' with the
supply pipe m for the water to be filtered, and on the other hand with a hot air pipe.
with valve n¹.
12
The process for the formation of the filtering asbestos layers is as follows. The
asbestos emulsion charged into the vessel i is forced by pump through pipes and h
and receptacle d, then through the sides of the filtering bodies e, and pipes g g'i,
until the gauge on d shews that an over pressure of 14 atmospheres has been attained
in forcing the liquid through.
For this purpose the valve m' of the water supply, the mud valve 12, the hot air
valve n' and the valve for the filtered water are all closed, while the valves and are
opened for establishing a communication between d and i, after which the pump is
put in action. The air valve d' on the top of the vessel d is opened at the beginning of
the pumping and is closed as soon as asbestos emulsion begins to issue through it.
When the above mentioned pressure has been attained (which is necessary to obtain
a solid layer of asbestos on all porous parts of the filtering bodies e), the pump is
stopped, the valve 3 is closed, and the valve is opened in order to discharge the contents
of the battery vessel into the channel . In order to make sure that the asbestos layers
have the requisite density, they are first subject to an air pressure test. Experiments
have shown that asbestos layers are only suitable for sterilizing water by filtration, if
only air at from 1 to 1 atmospheres overpressure is enabled to pass through them. Con-
sequently after closing the valves k² and again, air is forced through pipe into the
battery vessel d; when the air pressure thus obtained begins to lift the discharge
valve the gauge must indicate 1 to 1 atmospheres over pressure, after which the
pump is stopped.
The pressure must then not sink more than about 15th atmospheres during 30
seconds. This air pressure test must only be effected while the asbestos layers are
still wet.
The next operation consists in sterilizing the asbestos layers, for which purpose the
valve at the top of the vessel d is opened, and air heated to a temperature of
about 150 C. is blown through for about half an hour through pipen and valve n; the
steam thus formed in the apparatus escapes through the valve f
The filter battery is now in condition for use, for which purpose valve m² and are
opened so as to admit water from m and discharge the filtered water into j. All the
other valves remain closed. Valve m' is so adjusted that the filtering takes place at
an overpressure of 1½ atmospheres. As will be readily understood from Figs. 9 and 10,
in order to enable the filtering to be carried on continuously, there must be a number
of filtering batteries, so that one or more can be put out of action for cleaning or
regenerating without interfering with the process. As soon as the swifting cocks
provided on the pipes indicate that too little water is passing through a battery, the
valves m' and thereof are closed, the manholes are opened and the accumulated
deposit is removed together with the uppermost asbestos layer, by means of wire
brushes; the removed matter is discharged through the valve k² into the mad
channel, after which the filter battery is regenerated in the above described manner.
As shewn at Figs. 9 and 10, a single emulsion tank i and one pump as also one hot
air pump connected to the pipe n can be made to serve for a number of batteries.
All the pipes leading from the batteries are in this case connected with a horizontal
pipe, which communicates with the emulsion tauki and has on both sides thereof
shut off valves ; and in the same way the pressure pipe of the pump is connected
to a horizontal pipe which communicates with the pipe h of each battery d and
which has shut off valves i on each side of the pressure pipe of the pump.

page_text: Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I declare that what I claim is :—
1. A hollow filtering body in which a corrugated metal plate with end chambers
having discharge branches is enclosed between two perforated flat sheets of metal
which serve as support to a filtering layer, such filter body being enclosed in a
casing charged with the liquid to be filtered in such a manner, that the upper air
discharge branch and lower liquid discharge branch open to the outside, substantially
as described.
2. In combination with a metal filter body, such as is referred to in the preceding
claim the use of a porous covering of textile material, substantially as described.
3. A filter consisting of a filter body constructed as set forth in the preceding
claims, upon the outer porous surface of which a layer of asbestos is deposited, sub-
stantially as described.
4. A filter consisting of a number of filter bodies in the form of hollow plates
with porous sides, which have an air discharge branch at top and a liquid discharge
branch at bottom, such branches being respectively connected to a main air dischargo
pipe and a main liquid discharge pipe, while all the filtering bodies are so enclosed in
a vessel containing the liquid to be filtered, in such a manner that the air discharge
and liquid discharge branches open to the outside, substantially as described.
5. A filtering apparatus consisting of a combination of filtering bodies, each of
which consists of a hollow metal plate with perforated sides, covered with woven
fabric on which is a layer of asbestos, and having an air discharge branch at top and
a liquid discharge branch at bottom, all such branches being connected respectively
to a main air discharge pipe and a main liquid discharge pipe, the filtering bodies
being so arranged within the receptacle that the said discharge branches all
pass to
the outside, while the receptacle communicates both with a supply pipe for the liquid
to be filtered, with a sludge channel, and through a pump with a tank for the asbestos
emulsion, the discharge pipe being capable of communicating either with the channel
for the filtered liquid or with the asbestos emulsion tank, substantially as described.
6. The described method of producing a layer of asbestos on the porous filtering
bedies that will prevent the passage of micro organism, wherein the filtering bodies
are enclosed in a receptacle, with their discharge branches for air and liquid passing
through the same, and asbestos emulsion is then forced into the receptacle until the
passage of liquid through the filtering layers can only be effected at a certain pressure.
7. The described method for testing the capacity of the filtering layers to resist the
passage of micro organisms, consisting in ascertaining the pressure required for
forcing gases through the layer.
8. The described method of producing finely divided asbestos fibre, consisting in
freezing wet asbestos, and then reducing the frozen material.
Dated this Sth day of April 1890.
ABEL & IMRA Y,
Agents for the Applicant.