Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2 1 9~023
WO 96/10676 PCT/GB95/02314
SEPAR~TION DEVICE
This invention relates to a low maintenance separation
device intended for removing liquid-borne solids from the
carrier liquid by causing the liquid to enter a curved wall
chamber and form a vortex prior to exiting therefrom
normally under the influence of gravity. The rotational
flow characteristics created in the chamber result in a flow
velocity differential between liquid at the chamber wall and
that in the centre of chamber whereby the cont~m'n~nt solids
are accumulated for collection and separation from the
- liquid at the outlet of the chamber. Such devices are
generally known in the art and are commonly referred to as
hydrocyclones. In particular, though not exclusively, this
invention relates to hydrocyclones used in combined sewer
overflows.
A combined sewer is one where domestic sewage is
combined with other forms of waste water from roads, roofs,
land drains, etc. During periods of heavy rainfall the flow
through such a sewer increases dramatically and can exceed
the working capacity of any sewerage system or sewage
treatment plant situated downstream. As a consequence the
excess must be discharged without full treatment.
The problem of how to cleanse excess storm water has
been addressed in a number of ways. An early system
involved the use of a simple overflow weir. This was not
however particularly effective as it allowed a considerable
amount of solid matter to overflow and be discharged. The
addition of a mechanically raked screen was tried as a means
of reducing this emission.
In recent years, a method of separation using the
properties of vortex flow has been used with reasonable
success. In this method a high velocity stream of liquid,
containing solid matter, is introduced tangentially into a
cylindrical chamber with an outlet at its base. The
resultant bending of the inlet stream into a circular
W096/10676 2 1 9 9 0 2 3 PCT/GB9~07~14
cyclonic path produces a vortex which results in dynamic
separation of the components of the feed stream. Thus
polluting solids are discharged through the outlet before
being passed to a sewage treatment facility, while the
remaining liquid can be collected from the chamber and
discharged without treatment.
The advantages of a system that operates on this
principle are that it requires little maintenance and it can
be situated below ground. Tests however have shown that
while the system is efficient at removing settleable and
floating solids, it has difficulty in removing some types of
buoyant material. This material, termed neutral density
solids (NDS~, is composed of such items as condoms, the
backing of sanitary towels, hypodermic syringes, etc. These
solids are unfortunately the ones which create visible and
unsightly pollution, are in the most part non-biodegradable
and, if discharged in the vicinity of a recreational body of
water, can constitute a significant public health risk.
Also new legislation coming into force in the near future
will require that NDS above a certain two dimensional size
will have to be removed before overflow water can be
discharged.
It has been suggested that screens may be incorporated
into vortex separation equipment but it has been found that
these rapidly become blocked and ineffective. In addition,
with the separator unit commonly buried below ground, it is
extremely difficult to gain access in order to clear the
blockage. Therefore it is an object of the present
invention to obviate or mitigate at least some of the
aforementioned problems.
- According to the present invention there is provided a
hydrocyclone separator comprising a liquid vortex-forming
chamber provided with an inlet for supply of a solids-
contaminated liquid feed, and an outlet for gravity-assisted
outflow of liquids and solids, wherein the chamber is
21 99023
WO96/10676 PCT/GB95/02314
provided with a screen positioned in an upper portion of the
chamber, and arranged to interfere with raised liquid levels
so as to inhibit solids passage whilst permitting liquid
through-flow, the said screen having a surface which is at
least partially foraminated and of a concave shape.
A significant advantage is derived from the concave
shape of the screen in that as liquid level rises in the
chamber, e.g. during periods of high flow or overflow
conditions, the rotational velocity is increased by contact
- with the tapered surface, thereby providing an additional
scouring action which assists in clearing the foraminated
portion(s) of the screen. Furthermore whenever liquid
levels recede, the sloping surface of the screen will
encourage any solids trapped on the screen to drop off under
the influence of gravity. Likewise depending materials,
i.e. entrapped lengths of solids hanging from the screen
will tend to be caught in the receding swirling liquid flow
to be dragged free of the screen.
In one configuration, the screen has the form of an
inverted dish or shallow cone and the surface thereof has a
major portion which is foraminated whilst the minor portion
is continuous to direct or deflect flow. Baffles for
controlling or enhancing liquid flow across the screen may
also be provided on the screen surface or in close proximity
thereto. In one arrangement the foraminated surfaces are
set back from non-foraminated surfaces and the overall
surface configuration is arranged to optimise scouring flow
currents across the foraminated portions.
The concave screen surface may be manufactured from, or
coated with a non-, or low-stick material. A suitable
material of appropriate durability and non-stick
characteristics would be a fluorocarbon polymer resin such
as polytetrafluoroethylene (ptfe) such as that type known
generally by the Trade Mark TEFLON.
21 99023
WO96/10676 PCT/GB95/02314
It is also possible to design the screen surface to
discourage solids retention or adherence after high liquid
levels subside. This may be done by providing a plurality
of surface projections juxtaposed with respective apertures
in the screen surface which projections present a sloping
surface against the direction of flow to divert solids past
the adjacent aperture. Such projections may be discrete
deflector formations adjacent an aperture or may be a ridge
deflector aligned with a series of such apertures.
Conveniently the surface projection may be generally wedge-
shaped having a first surface forming a shallow incline
upwards from the screen surface and a second surface forming
a steep return thereafter. The aperture for permitting
liquid passage may be either immediately adjacent to the
steep return surface or may optionally be formed therein.
In either event, the momentum of solids carried in the
liquid passing rapidly over the projections should cause
these solids to by-pass the apertures and thereby obviate or
mitigate clogging of the foraminated portions of the screen.
Optionally, the screen may be provided with means for
clearing or dislodging solids, such means may be either
driven brushes, or water jet applicators, or a combination
thereof.
The brushes may be driven by means of a hydraulic or
electric motor, or by energy generated by the swirling
motion of fluid within the vortex chamber.
The separator may be provided with means to lower the
level of fluid contained within the vortex chamber during
sustained periods of high inlet flow-rate e.g. during and
after storm conditions. Said means may comprise at least
one siphon tube communicating between the vortex chamber and
the chamber outlet, or may take the form of a vortex breaker
intended to collapse the air core of the vortex and hence
increase the flow-rate of fluid through the chamber outlet.
It is the intention of such means to cause the sudden
WO96/10676 2 1 9 9 0 2 3 PCT/GB95/02314
lowering of the fluid level within the vortex chamber and
hence to cause solids trapped against the screen to fall
into the vortex chamber.
The screen may be provided with a chimney extending
vertically upwards, the purpose of which is, when elevated
fluid levels are present within the vortex chamber, to cause
the fluid level to rise yet further and subsequently prime
and then actuate the at least one siphon tube.
The screen may have a surface which is at least
partially foraminated. In a preferred embodiment there is
provided a frusto-conical screen where the non-foraminated
portions comprise a quadrant of said screen and a
circumferential band extending inwardly from said screens
outermost edge.
The interior of the vortex chamber may be provided with
baffle means and/or flow direction means to enhance the
vortex forming properties of the chamber and/or to direct
solid matter to the vicinity of the chamber outlet.
Preferably the vortex chamber is provided with baffles
around the tangential inlet which serve to direct inlet
fluid stream both downwards and onto the wall of the
chamber.
The chamber may also be provided with at least one
baffle which protrudes inwards from the wall of the chamber
and extends from the base of the chamber to screen atop the
chamber. In a preferred embodiment there is provided a
single baffle adjacent to the inlet.
The separator may be configured such that, in use, the
fluid level within the separator is maintained above the
base of the screen.
W096/10676 2 1 9 9 0 2 3 PCT/GBgS/02314
If the separator is furnished with an annular
collection chamber surrounding the vortex chamber, the fluid
level may be maintained above the base of the screen by the
provision of a weir surrounding the outlet from said annular
collection chamber. Alternatively, the separator may be
provided with a collection chamber, with communication
between said vortex chamber and said collection chamber
being permitted by virtue of an opening in the wall of the
vortex chamber, said opening being positioned above the base
of the screen.
In use, the separator may either be positioned so as to
interrupt the flow in a combined sewer or be provided in an
"off-line" position with provisions to enable it to be
brought "online" as and when it is needed.
Embodiments of the present invention will now be
described, by way of example only, with reference to the
accompanying drawings, in which is shown:
Figure 1. a side view of a conventional vortex
separator;
Figure 2. an overhead view of the separator
referred to in Figure 1;
Figure 3. a side view of a vortex separator in
accordance with the present invention;
Figure 4. an overhead view of the separator
referred to in Figure 3;
Figure 5. a side view of a separator in accordance
with the present invention and
incorporating a water jet system;
WO96/10676 2 1 9 9 0 2 3 PCTtGB95102314
Figure 6. a representation on an enlarged scale of
a possible configuration for at least a
portion of the screen;
Figure 7. a detailed view of the screen
perforations;
Figure 8. an alternative embodiment of the
construction of the screen perforations;
Figure 9. a side view of a hydro-mechanical
cleaning mechanism for use with a
separator in accordance with the present
invention.
Figure 10. a side view of a vortex separator in
accordance with an aspect of the present
invention;
Figure 11. a partial plan view of the vortex
separator of Figure 10;
Figure 12. a schematic side view of a vortex
separator equipped with water jet
apparatus and mechanical brushing
apparatus;
Figure 13. a side view of a vortex separator
equipped with a siphon tube;
Figure 14. a partial plan view of the vortex
separator of Figure 13;
Figs. 15A-15H. side and plan views of alternative
screen configurations;
Figs. 16A-16D. plan views of alternative vortex chamber
baffle configurations;
: 21 99023
WO96/10676 PCT/~b95l'~23l4
Figure 17. sectional view indicated by line A-A on
Figure 16B;
Figure 18. sectional view indicated by line B-B on
Figure 16B;
Figure 19. side view of a vortex separator in
accordance with an alternative
embodiment of the present invention;
Figure 20. plan view of the vortex separator of
Figure 19;
Figure 21. side view of a vortex separator in
accordance with an alternative
embodiment of the present invention; and
Figure 22. partial plan view of the vortex
separator of Figure 21.
Referring firstly to figures 1 and 2 there is shown a
separator 1 comprising a cylindrical outer casing 2
incorporating a sloping base 13, and a cylindrical inner
vessel 3 with a conical base 9. A circumferential lip 4
provided with an overflow portion (not shown) as part of the
circumference, extends from the outer surface of the inner
vessel 3 to the inner surface of the outer casing 2. This
has the effect of dividing the interior of the separator 1
into three distinct spaces: a vortex chamber 5, an annular
channel 6 formed between the inner vessel 3, the outer
casing 2 and the lip 4 , and an outlet chamber 7. The
latter is defined by the conical base 9, the lip 4, the
outer casing 2 and its sloping base 13. Communicatian
between the vortex chamber 5 and the outlet chamber 7 is
achieved by an aperture 8 situated at the centre of the
inner vessels conical base 9. The upper edge of the inner
vessel 3 defines a peripheral, circumferential weir 10.
Outlet chamber 7 is provided with orifice 11 to allow any
21 99023
WO96/10676 PCT/GB95/02314
matter present to be removed via channel 12. Tangential
inlet 14 is provided for introducing liquid into vortex
chamber 5. Outlet duct 17 permits the removal of liquid
present in the annular chamber 6.
In use, a liquid mixture of water and sewage is
introduced as a high velocity stream 15 into the vortex
chamber 5 through tangential inlet channel 14 located close
to the bottom of the chamber. The stream 15 impinges upon
the cylindrical inner wall of the inner vessel 3 with the
- result that a circular cyclonic stream 16, or vortex, is
created. Under normal operating conditions all the liquid
mixture entering the vortex chamber 5 through inlet 14 is
passed through aperture 8 and into the outlet chamber 7.
From there it is removed via outlet channel 12 for
appropriate treatment. However, when increased flow
conditions are experienced, i.e. during or immediately after
a storm, the volume of liquid entering the vortex chamber 5
exceeds that which can be removed for subsequent specialist
treatment. Accordingly liquid will begin to accumulate in
the vortex chamber 5 , its upper limit being defined by the
circumferential weir 10. As a result of the elevated flow
rate through tangential inlet 14 due to storm conditions,
the forces generated by the swirling motion of stream 16 are
sufficient to transport most types of solid matter through
aperture 8 into outlet chamber 7. It will be understood
that the mechanics of vortex flow produced by a high
velocity stream tangentially entering a cylindrical vessel
will be apparent to any appropriately skilled person with a
knowledge of hydrodynamics. Excess liquid not used to
transport solid matter through aperture 8 spills over weir
10 and into the annular channel 6 where it can be removed
via outlet duct 17. Arrows 18 and 18' indicate the movement
of liquid from the vortex chamber 5 to the annular channel
6.
Whilst the device shown in Figures 1 and 2 is
successful at removing most types of solid matter contained
2 1 99023
WO96/10676 PCT/GB95/02314
in domestic sewage it is ineffective at separating NDS.
These solids do not become trapped in the vortex 16 and are
transported over weir 10 and into channel 6. Referring now
to figures 3 and 4 there is shown a separator 19 operating
5 on the same principles described hereinbefore and adapted to
prevent NDS from passing between the vortex chamber 5 and
the annular channel 6. This is achieved by means of a
circular baffle 20 and a screen 21. The screen 21 is
concave with respect to the vortex chamber 5, abuts onto
the circumferential weir 10 and serves to enclose the vortex
chamber 5. The screen is provided with a plurality of
perforations 22 so as to allow water ejected from the vortex
chamber 5 to pass to the annular channel 6. The size of the
perforations 22 is such that neutral density material is
15 prevented from reaching the annular channel 6 and is
confined within the vortex chamber S. The screen 21 is
provided with an aperture 23 at its crown which acts as an
emergency overflow passage should the perforations 22 become
obstructed.
The circular baffle 20 is positioned within the vortex
chamber 5 and is provided with a central baffle 24. The
baffle 24 is aligned with the vortex chamber outlet aperture
8. The surface of the baffle 20 is contoured to promote the
25 movement of liquid from the inner surface of the screen 20
to the central baffle 24 and to increase the velocity of the
liquid coming into contact with the inner surface of screen
21. Arrows 25 and 25' indicate the direction of these
currents. This action is intended to scavenge any neutral
density material which may have become trapped against the
screen perforations 22, thus reducing the possibility of a
blockage being formed. The currents 25 and 25' are also
intended to transport the material removed from the screen
21 through the baffle 24 and into the vortex 16. Thus the
neutral density material is introduced into the centre of
the vortex 16, as opposed to its periphery when introduced
tangentially, and is conveyed through aperture 8 into the
outlet chamber 7.
WO96/10676 2 1 9 9 0 2 3 PCTtGBg5/02314
Once the elevated flow conditions have passed, i.e. the
extra storm water in the combined sewer has been disposed
of, the liquid level in the vortex chamber 5 recedes back
below that of the circumferential weir 10. As before all
the sewage/water mixture entering the vortex chamber 5 via
tangential inlet 14 is passed through aperture 8 and into
the outlet chamber 7. The screen 21 is shaped such that any
solid matter left in contact with it by the receding liquid
level will fall, under the influence of gravity, into the
- vortex chamber 5. The manufacture of the screen 21 from a
non-stick material or the presence of a non-stick coating on
its surface further enhances this self cleaning ability.
To aid the action of the scouring currents 25 and 25',
figure 5. illustrates an embodiment of the present invention
incorporating the possible use of a pressurised water jet
system. Nozzle units 26 and 26' are positioned outwith the
vortex chamber 5 and above the perforated sections of screen
21. Water jets 27 and 27' are directed by nozzles 26 and
26~ through the screen perforations 22. The action of these
jets is intended to dislodge any solid material adhering to
the inner surface of screen 21 which is resistant to the
scouring currents 25 and 25'.
Figure 6. shows a possible means of positioning the
perforations 22 upon the screen 21. The portion of the
screen 21 containing the perforations 22 is stepped back
from the main body 28. The action of scouring currents 25
across the stepped portion 28 produces eddy currents 29.
The flow disturbance produced by eddy currents 29 enhances
the ability of the scouring currents 25 to remove neutral
density matter in the vicinity of the perforations 22.
Figures 7. and 8. illustrate two possible embodiments
for the arrangement of screen perforations 22. Firstly
figure 7. shows a reciprocating saw-tooth surface profile
31 for the surface of the screen 21, with individual
- 21 99023
WO96110676 PCT/GB95102314
12
perforations 22 present in the shorter side of each tooth.
The action of scouring current 25 produces an eddy current
30 adjacent to each perforation 22. The recirculatory
motion imparted to the liquid adjacent to the perforations
22 discourages solid material from adhering to the screen
21. Figure 8. shows an alternative method of achieving the
aforementioned effect. The screen 21 is covered alternately
with perforations 22 and fin shaped projections 32. The
projections 32 protrude into the scouring currents 23 and
disturb the flow to discourage solid material from adhering
- to the screen 21.
It is possible that the screen 21 will need to be
physically cleaned on occasion. Figure 9 illustrates a
possible configuration for such a system adapted for use in
an underground separator. One or more high pressure water
jetting units 36 are positioned within the outer casing 2
and above the screen 21. The jetting units 36 may be built
into the separator 19 or inserted through holes in the
casing 39 when required. To aid the plurality of water jets
37 provided by units 36, a mechanical cleaning device may
also be incorporated. In alternative embodiments (not
shown), such mechanical devices may be used alone without
water jets. Drive unit 35 is connected via drive shaft 40
and articulated coupling 34 to cleaning brush 33. When
drive unit 35 is activated, drive shaft 40 rotates causing
brush 33 to move around the entirety of the outer surface of
the screen 21. The disturbance supplied by the brush 33 and
the water jets 37 is sufficient to remove stubborn material
from the screen 21. The drive unit 35, shaft 36 and brush
33 assembly may be removed through down shaft 38 for the
purposes of maintenance. The mechanical cleaning mechanism
may be powered by any suitable means including electricity
or solar or wind power. Smaller separators may incorporate
a manual system powered by hand. The action of the cleaning
mechanism may also be powered by hydraulic energy generated
by the rotating liquid within the device. The intervals at
which the screen 21 is physically cleaned may be
WO96110676 2 1 9 9 023 PCT/GB95,023,4
13
predetermined according to a set pattern or in response to
external stimuli. For example the drive unit 35 may
incorporate a control system which activates the cleaning
mechanism after a period of heavy rainfall. This could be
achieved by means of a liquid level detector within the
separator. Optionally the cleaning brush 33 may be
positioned within the vortex chamber 5 and hence facilitate
cleaning of the inner surface of the screen 21.
Referring now to Figures 10 and 11 there is shown a
separator 105 comprising a cylindrical outer casing 110, a
cylindrical inner vessel 115 with a conical base 120 and a
frusto-conical screen 125 mounted atop the cylindrical inner
vessel 115. The cylindrical inner vessel 115 and screen 125
serve to form a vortex chamber 130 while the cylindrical
outer casing 110 and the cylindrical inner vessel 115 define
an annular collection chamber 135. A collection chamber 140
is provided below the vortex chamber 130 with communication
between said chambers 130, 140 being permitted by means of
an aperture 145 in the conical base 120. The vortex chamber
130 is further provided with a tangentially disposed inlet
duct 150 , while the annular chamber 135 and the collection
chamber 140 are provided with outlet ducts 155 and 160
respectively.
In use, a liquid mixture of water and sewage is
introduced through the tangential inlet duct 150. The inlet
stream impinges upon the cylindrical wall of the vortex
chamber 130 with the result that a circular cyclonic stream
30 or vortex 165 is created. Under normal operating
conditions, i.e. except those experienced during and after
sustained periods of heavy rainfall, storms and the like,
- all the liquid mixture entering the vortex chamber 130 is
passed through the aperture 145 to the collection chamber
35 140, from where it is removed for appropriate cleansing
treatment. However, when increased inlet flow conditions
are experienced, i.e. during or immediately after a storm,
the volume of liquid entering the vortex chamber 30 exceeds
21 99023
WO96/10676 PCT/GB95/02314
14
that which can be removed for specialist treatment. Hence
the liquid level 168 within the vortex chamber 130 rises
above the edge 170 of the cylindrical inner vessel 115 and
excess fluid passes through perforations present in the
screen 125 and into the annular chamber 135. The screen 125
prevents matter such as neutral density solids (NDS)
reaching the annular chamber 135 and subsequently being
discharged without treatment.
The separator 105 may be provided with apparatus to
ensure the screen does not become blocked with solid and
semi-solid matter. The scouring action of the vortex 165
against the screen 125 discourages such matter from adhering
to the screen 125, however additional means may be required
to keep the screen 125 clear. Figure 12 shows schematic
representations of mechanical brushing 175 and water jet 180
apparatus adapted to prevent solid matter from adhering to
the screen 125. The brushing apparatus 175 may be powered by
either an electric or hydraulic motor 185, or by energy
20 generated by the swirling motion of fluid within the vortex
chamber.
During sustained periods of high inlet flow, i.e.
during and after prolonged storm conditions when the flow
25 velocity typically peaks in the region of 1 to 4 m/s, solid
matter may become trapped against the screen 125 despite
measures taken to avoid such an eventuality. It has been
found that a sudden drop in the liquid level 168 within the
vortex chamber 130 is advantageous in removing said solid
30 matter. The hydrodynamic pressure holding the solid matter
against the screen 125 is thus removed and said solid matter
falls from the screen 125 into the vortex chamber 130.
The sudden drop may be caused by a vortex breaker
35 device (not shown) which can collapse the air core 190 of
the vortex and increase the flow of liquid through the
vortex ch~mher aperture 145. Alternatively siphon tubes lg5
may be provided between the vortex chamber 130 and the
WO96110676 2 1 9 9 0 2 3
PCT/GB95/02314
collection chamber 140 as shown in Figures 13 and 14. In
use, the surface level 200 of the liquid within the siphon
tube 195 is e~ual to that within the vortex chamber 130.
= Should the liquid level 168 within the vortex chamber 130
rise high enough to prime the rising leg 205 of the siphon
tube 195, said siphon tube 195 will then proceed to vent
liquid from the vortex chamber 130 to the collection chamber
140. The separator 105 may be provided with as many tubes
as is necessary to achieve the required level drop within
10 the vortex chamber 130. The amount by which the level 168
will fall is governed by the inlet 210 to the siphon tube
195 which, in the example shown in Figure 13, is just below
the base 215 of the screen 125. The screen 125 may also be
provided with a chimney (not shown) extending centrally from
the top of the screen 125. The provision of the chimney
causes, during certain storm operating conditions, the rapid
rise of the liquid level 168 within the vortex chamber 130
and hence aid in the priming of the siphon tube 195.
The foraminated and non-foraminated portions of the
screen 125 may be arranged in a number of configurations to
aid the scouring action of the vortex 165. Figures 15A to
15H show various possible configurations for frusto-conical
screens 125 where the non-foraminated portion of the screen
25 125 is a circumferential band 220 or portion thereof 225, a
quadrant 230 of the screen 125 or a combination of any of
the above. A preferred embodiment is shown in Figures 15E
and 15F where the non-foraminated portion of screen
comprises a quadrant 230 of said screen 125 and a
circumferential band 220 extending inwards from said screens
outermost edge.
Baffle and flow direction means may be provided within
the vortex chamber 130 to aid in the formation the vortex
165 and to direct solid matter towards the centre of said
vortex. Said baffle means and flow direction means may be
positioned around the inlet duct 150 in order to concentrate
and/or direct the flow-stream entering the vortex chamber
21 99023
WO96/10676 PCT/GB95/02314
16
130. Baffles may also be provided around the inner surface
235 of the vortex chamber. Figures 16A to 16D show various
possible positions for baffles and flow directors within the
vortex chamber 130. Tests have shown that the configuration
shown in Figure 16B comprising an inlet extension 240 and a
wall baffle 245 to be successful in achieving the desired
results. Figures 17 and 18 show the sectional views
indicated by arrows A-A and B-B.
Referring to Figures 16B, 17 and 18 there is shown an
extension 240 of the inlet duct 150 which projects into the
vortex chamber 130 and which comprises a side wall 250 and
an upper wall 255. Said walls 250, 255 extend both from the
inner surface 125 and conical base 120 of the vortex chamber
130 and serve to reduce the cross sectional area of the
inlet duct 150. In an alternative embodiment, the extension
240 may serve to direct the inlet flow without reducing the
cross sectional area of the in let duct 150. The walls 250,
255 in reducing the cross sectional area of the inlet duct
150 direct the inlet flow both toward the base 120 and the
inner surface 235 of the vortex chamber 130. The wall baffle
245 extends from the conical base 120 of the vortex chamber
130 to the screen 125 atop said vortex chamber 130 and
comprises a concave leading edge 260 and a concave trailing
edge 265, the leading edge 260 having a radius of curvature
greater than that of the trailing edge 265. Baffles and flow
direction means provided within the separator may be
adjustable allowing their positions to be altered depending,
for example, on the inlet flow characteristics.
The separator devices 105 described hereinbefore
operate on the principal that under normal inlet flow
conditions all the liquid, solid and semi-solid matter
entering the vortex chamber 130 is conveyed through the
vortex chamber aperture 145, while the screen 125 is only
employed under operating conditions experienced, for
example, during and after a storm. Figures 19 to 22 show
21 99023
WO96/10676 PCT/GB95/02314
17
two possible embodiments in which the liquid level is
maintained above the base of the screen.
Figures l9 and 20 show a separator 300 substantially as
5 described hereinbefore comprising a vortex chamber 330 with
a frusto conical screen 325, an annular chamber 335, a
collection chamber 340, a tangential inlet duct 350 and
outlet ducts 355, 360 from the annular and collection
chambers 335, 340. The annular chamber outlet 355 is
shrouded by a weir 365, the upper lip 370 of which is higher
than the base 315 of the screen 325, and hence the liquid
level 368 with the vortex chamber 330 must exceed the level
of the lip 370 before fluid can pass to the annular chamber
outlet 355.
Figures 21 and 22 represent an alternative embodiment
wherein there is shown a separator 400 without an annular
collection chamber. The wall 410 of the vortex chamber 430
extend above the base 415 of the screen 425 and there is
20 provided an overflow box 470 which abuts the vortex chamber
430. An opening 475 is provided in the wall 410 of the
vortex chamber 430 which permits liquid to flow from the
vortex chamber 430 into the overflow box 470. Once again
the lower lip 465 of the opening 475 is above the base 415
25 of the screen 425 and thus the liquid within the vortex
chamber 430 is maintained at an elevated level. The
advantages of maintaining the fluid level above the base of
the screen include a greater screen area in contact with
liquid within the vortex chamber 430 at lower flow rates,
and automatic backwash when storm flow abates.
It should be understood that the embodiments of the
invention described hereinbefore are given by way of example
only, and these are intended to illustrate not limit the
35 scope of the invention. Those appropriately skilled in this
art will appreciate that the invention herein disclosed
provides a simple and relatively easily constructed solution
to long-standing problems experienced in this art.
