Note: Descriptions are shown in the official language in which they were submitted.
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A~PARATUS FOR CONTINUOUSLY CIRCUL~TING A LIQUID.
BACKGROUND OF THE INVENTION.
The present invention relates to an apparatus
for continuously circulating a liquid and more
specifically for circulating this liquid between a
storage tank and a container in which a sampling or
control operation is to be carried out.
The main dificulty encountered in liquid
sampling apparatus, particularly for analysis purposes,
is to obtain a homogeneous and representative sample
of the liquid contained in the tank at the sampling
point. In most presently used systems, the liquid is
circulated be~ween the storage tank and the sampling
point, in order to ensure a good homogenization and
therefore a good representativeness. Another difficulty
to be solved is that of preventing deposits which could
form along the walls of the apparatus, because these
deposits may be dissolved by another liquid during a
subsequent control, thus falsi~ying the results of
the measurements. At present, systems called airlifts
are frequently used and in these the compressed air
is blown into a pipe connecting the storage tank to
the sampling point in order to facilitate the circulat-
ion of the liqu;d. Although such a system may well
~`~ 25 permit a good homogenization thereof, the presence of
air bubbles in the liquid can be prejudicial, particularly
in the case where sampling is carried out with the aid of
hollow needles on which is perforated a container or
jug in which a vacuum has previously been formed.
BRIEF SUMMARY OF THE INVENTION
The present invention relates to an apparatus
for continuously circulating a liquid, which obviates
the aforementioned disadvantages, but permitting not
only a good homogenization o~ the liquid and an
effective draining of the installation after sampling,
but which also prevents the presence of air ~ubbles
in the liquid at the sampling point.
The present invention therefore specifically
relates to an apparatus for continuously circulating a
liquid between a storage tankand a container or passage
pot in which the sampling or control is perormed,
wherein it comprises a compressed gas source, a supply
pipe connecting the tank to the lower part of a separator
positioned above the same, a duct connecting the lower
part of the separator to the lower part of the passage
pot,the lower par~ of the latter being at a higher
leel than the separator, a return pipe connecting the
upper part of the passage pot to the tank~ and a pipe,
equipped with a splash head, connecting the upper part
of the separator to a deviGe making it possible to
produce a pressure reduction.
The blowing of compressed air into the pipe
connecting thP tank to the separator facilitates the
rise of the liquid. The function o ~he device making
it possible to produce a pressure drop; which can be
a vacuum source or fan, is to eliminate gas present
in the liquid at the separator. Thus, ît is perectly
degassed liquid which is collected in the lower part of
the separator and it then progressively rises up to the
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passage pot.
According to a first variant of the in~ention,
the supply pipe is rQctilinear and is verticalLy
immersed in the storage tank. In this case, the com-
pressed gas source is connected to a pipe issuinginto the supply pipe at a point above the leveL of
the free surface of the liquid in the tank and the
device making it possible to produce a pressure drop
is a vacuum sourceO
According to another variant, the supply pipe
issues into-the lower part of the tank and has a
curved portion in this area. In this case, ~he pipe
connecting the compressed gas source to the supply
pipe issues into the latter at a point beneath the free
surace of the liquid in the tank, when the installation
is inoperative and the device making it possible to
produce a pressure drop is a fan.
Finally, according to another feature of the
apparatus according to the invention, it comprises an
overflow discharge pipe connecting the upper part of
the separator to the return pipe.
BRIEF DESCRIPTION OF THE DRAWINGS.
The invention is described in greater detail
hereinafter relative to non-limitativ~ embodiments and
the attached drawings, wherein show:
Fig 1 a diagrammatic view of a first constructional
variant of an apparatus according to the invention.
Fig 2 a diagrammatic view showing a second variant
thereof.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In Fig 1, it is possible to see a liquid l
contained in a tank 29 which can either be a storage
tank or a supply tank connected to a much larger
volume reservoir. A first pipe 4, called the supply-
pipe, connects the tank 2 to the lower part o a
container 6, called a separator, positioned above tank
2 and in which the separation of the liquid a~d the
compressed gas takes place. A perforated tube 9, placed
within separator 6, acts as a calming device for ~he
liquid in order to prevent agitation, which could be
prejudicial in passage pot 10, whilst two bubbling
rods 15 make it possible to check the presence of the
li~uid in the separator, as well as the level thereof.
The lower part of separator 6 is connected by a duct 8
to the lower part of the container 10~ called a passage
pot, in which the state of the liquid is checked. It
should be noted that the lower part of the passage pot
10 is at a higher level than the lower part o~ separator 6.
Passage pot 10 is equipped with a control device 12~
which either makes it possible to directly control the
state of the liquid within passage pot 10, or to carry
out a sampling process when the control is perfortned
in another installation. A return pipe 11, connected to
the upper part of the passage pot lO, connects the
latter to tank 2.
It is also possible to see a duct 14, equipped
with a splash head 16 and connecting the separator 6
to the vacuum source 17 connected to the upper part of
separator 6. Splash head 16 serves to perm;t the separation
of the last droplets, which may have been entrained
with the gas sucked in by the vacuum source 17. An
over10w discharge pipe 7 connects the upper part of
separator 6 to return pipe 11 and~consequentl~ to tank
20 The arrangement is such that the ~tarting point of
pipe 7 is at a higher level than the starting point of
return pipe 11. It is also possible to see a compressed
air pipe 3, which links supply pipe 4 with a compressed
air source S. In the ~iant of Fig 19 the supply pipe 4
is rectilinear and vertical and enters the upper part
of tank 2, whilst the compressed air pipe 3 issues into
pipe 4 at a point above the free surface of the liquid
in tank 2~
The apparatus according to the invention functions
in the following manner. When vacuum source 17 is put
into operation, there is a suction effect in supply
pipe 4. The liquid in tank 2 then rises along the
said pipe to a point below the connection point of the
compressed air pipe 3. At this moment, the compressed
air is blown into pipe 4 through pipe 3 and, due to the
fact that the installation is under vacuum~ the air
bubbles immediately rise in pipe 4, entraining therewith
the liquid contained in the tank. When the latter reaches
the lower part of separator 6 9 the air is discharged
through duct 14. As this produces a continuous suction
of liquid from tank 2 to separator 6, the level of the
liquid in the latter and therefore in pipe $ progressively
rises. Thus, as the air i.s removed from the liquid mass
at the separator, it is perfectly degassed liqu;d which
progressively enters from bottom to top pipe 8 and then
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passage pot 10. When the level of the liquid in the
latter reaches an adequate height, it drops down
again into tank 2 through return pipe 11. Thus, there
is a continuous circulation of liquid from tank 2 to
separator 6 through pipe 4 and then from the separator
to the passage pot through pipe 8 and finally from the
passage pot to the tank through return pipe 11. This
circulation makes it posssible to homogeniæe the liquid
level with the control device 12. In addition~ as a
result of the presence of separator 6 upstream of the
passage pot9 it is a gas-free liquid which passes
through the latter) whereby significantly improving the
representativeness of the checked samples and consequently
sampling is made easier. If 7 for any random reason~ e.g.
an accidental blocking of pipe 11, the liquid level in
separator 6 rises in a distur~ing manner, the overflow
discharge pipe 7, connected to the upper part thereof,
makes it possible to discharge the liquid towards return
pipe 11 and from there to tank 2. When the control or
2~ sampling operation is ended, the vacuum source is
stopped and the compressed air intake closed. At this
time, all the liquid contained in the installation drops
down again by gravity into tank 2. In particular, the
liquid contained in passage pot 10, drops again through
pipe 8 in the direction of the lower part of separator
6 and from there into tank 2 through pipe 4. Particularly
as a result of the slope of pipe 8, this arrangement
ensures an immediate and total drainage of the installat-
ion and cons-nderably reduces the risk of any deposits,
which could falsify subsequent measurements.
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In the variant of Fig 2~ it is possible to
see that the vacuum source 17 is replaced by a fan 18.
Furthermore, the supply pipe ~ no longer enters the
upper part of tank 2~ but instead lssues into the base
thereof. In this area, it has a curved portion 4a,
which is co~stantly filled with liquid up to a level
equal to that of the free surface o the liquid in the
tank. The compressed air supply pipe 3 issues into the
lower part o pipe 4 at a point which is beneath the
free surface of the liqllid~ when the installation is
inoperative. When compressed air is passed through
pipe 3, the air bubbles immediately entrain the liquid
along pipe 4. In this case, the ventilation ensured ~y
device 18 only serves to eliminate the air introduced
by pipe 3 in order to degas the liquid~ which collects
in the lower part o~ separator 6. ~hus, the liquid
rises along supply pipe 4 up to he lower part of
separa-tor 6, where the air is eliminated. It then rises
along pipe 8 according to the mechanism described
hereinbefore. When the installation is not operati.ng~
the liquid redescends in pipe 4 to a level corresponding
to that of the free surface of the liquid in tan~ 2.
The apparatus according to the invention has
numerous advantages, the most important of which is ~o
ensure the passage of a homogeneous and completely
degassed liquid to the sampling point. Moreover, when
the installation is not operating, it ensures a complete
and very effective draining, which obviates any risk
of deposits, which could falsify subsequent measurements.
Although such an apparatus can be used with
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particular interest in installations for taking
radioactive liquid samples, particularly those where
a hollow needle is used on which is pierced a jug in
which a ~acuum has previously been formed, it can also
be used in any random sampling installation in which a
liquid is circulated and in which it is desired that
said liquid is perfectly homogeneous and degassed.
