Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: CLARIFIER COVER
FIELD OF THE INVENTION
This invention pertains to flexible covers for clarifiers, and more
particularly, the present invention pertains to the sealing of a flexible
cover
over a clarifies for maintaining the content of the clarifies in a sealed
environment.
BACKGROUND OF THE INVENTION
A typical industrial clarification installation comprises a plurality of
reservoirs or holding tanks to be filled with mill effluent. Clarification is
normally effected by alternatively agitating and letting the effluent settle,
and lifting floating scum from the surface of the effluent or scooping
sediments at the bottom of the reservoir. These holding tanks are generally
equipped with mechanical equipment that must be accessible for
inspection, maintenance or for repair.
The clarification process is often accompanied by a fermenting
action and a generation of odorous bio-gases, and/or the release of volatile
organic carbons. For environmental reasons, these gases must be collected
and treated. Therefore, a clarification reservoir, or clarifies, is preferably
covered and sealed to contain the gases. Also, a clarifies preferably has a
piping system to transport the gases to a gas treatment plant.
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When a removable flexible cover is installed over a clarifier, the
installation must resist wind forces that tend to flap portions of the cover
and stretch it laterally. Also, the attachment of a flexible cover must be
sufficiently strong to permit one or more workers to walk on the flexible
cover to fix it if the need arises.
A clarifier having a removable flexible cover mountable thereon
must also provide for a certain level of safety when the cover is removed.
During maintenance activities for example, it is common to find power
tools, welding machines, acetylene torch carts and maintenance wagons
along the perimeter of the clarifier. It is therefore important to prevent
workers and equipment from sliding into the reservoir.
Examples of various systems available for covering a reservoir are
described in the following documents:
US Patent 3,195,310 issued on July 20, 1965 to C.E. Schroeder;
US Patent 4,324,370 issued on Apr. 13, 1982 to W. Guard et al.;
German Patent DE 2,938,496 published on April 24, 1980;
French Patent FR 2,668,195 published in April 24, 1992.
Although the flexible covers of the prior art deserve undeniable
merits, it is believed that these systems do not meet all the requirements for
a flexible clarifier cover which is securely mountable, removable and safe.
It is believed that there continues to be a need for a new removable flexible
cover which may be positively sealed, which can support workers walking
thereon and which provides for a safe working environment.
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SUMMARY OF THE INVENTION
In the present invention, however, there is provided a removable
clarifier cover which has safety features incorporated therein, which is
particularly efficient for sealing a clarifier in a manner to resist wind
stresses and to support workers walking thereon.
In a first aspect of the present invention, there is provided a
removable cover for retaining off gases inside a clarifier having first,
second, third and fourth walls. The cover comprises a flexible sheet laid
across the clarifier and having first, second, third and fourth margins.
There are also provided means for retaining and sealing the first margin to
the first wall, and means for pulling and releasably sealing the second, third
and fourth margins to the second, third and fourth walls respectively. The
means for retaining and sealing the first margin to the first wall comprise
a first structural angle extending along the first wall and having a leg
member aligned upwardly. The means for pulling and releasably sealing
the second, third and fourth margins comprise spaced-apart pullers
mounted inside second, third and fourth structural angles extending along
the second, third and fourth walls respectively and each structural angle has
a leg member aligned upwardly.
In this aspect of the present invention the first, second, third and
fourth walls, and the flexible sheet are usable for containing off gases
inside the reservoir and the first, second, third and fourth structural angles
constitute kick plates enclosing the clarifier for enhancing the safety of
workers working around the clarifier.
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In another aspect of the present invention, the clarifier cover
comprises a plurality of spaced-apart trusses mounted across the clarifier
and the flexible sheet is laid over the spaced-apart trusses. In this aspect
of
the invention, the flexible sheet is selectively rolled-up over the spaced-
apart trusses for accessing equipment inside the reservoir.
In accordance with another aspect of the present invention, the
means for pulling and releasably sealing the second, third and fourth
margins against the second, third and fourth walls respectively also
comprise cables affixed to the second, third and fourth margins of the
flexible sheet and individually attached to a respective pulley. Each of the
pulleys has a cable deflector bar extending substantially at a same level as
a plane of mounting of the pulley. These pulleys are advantageous for
pulling the margins of the flexible sheet against the mounting surface of
each pulley for facilitating the sealing of the flexible sheet against the
second, third and fourth walls.
In accordance with yet another feature of the present invention,
there is provided a removable cover for retaining off gases inside a clarifier
having first and second opposite side walls, and a pair of opposite end
walls. A plurality of spaced-apart trusses are mounted across the first and
second side walls. The trusses comprise first and second outmost trusses
each having an arched plated structure attached thereto, and a series of
intermediate trusses disposed between the first and second outmost trusses.
The flexible sheet is laid over the spaced-apart trusses and the outmost
trusses. The flexible sheet has first and second longitudinal margins and
first and second transversal edges. The clarifier cover further has means
for retaining and sealing the first longitudinal margin to the first side
wall;
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means for pulling and releasably sealing the second longitudinal margin to
the second side wall, and means for pulling the flexible sheet across the
trusses and for releasably sealing the first and second transversal edges to
the first and second outmost trusses respectively. The means for pulling
and releasably sealing the second longitudinal margin against the second
side wall further comprise a pipe affixed to the second longitudinal margin,
a first series of pullers mounted to the second wall and a resilient pad
extending under and adjacent the first series of pulleys. Each pulley has
means for pulling the pipe and the second longitudinal margin downward
against the resilient pad for sealing the second longitudinal margin against
the second side wall.
The means for pulling the flexible sheet across the trusses and for
releasably sealing the first and second transversal edges against the first
and second outmost trusses respectively comprise grommets along the first
1 S and second transversal edges of the flexible sheet. Cables extend through
the grommets. Second and third series of pulleys are affixed to the first and
second outmost trusses respectively. The pulleys have means for pulling
the cables and the first and second transversal edges against the first and
second outmost trusses respectively for sealing these transversal edges
against the outmost trusses.
The first, second and third series of pulleys have ratchet-type
mechanisms that axe easily worked for selectively releasing the flexible
sheet for opening the clarifier and exposing the equipment inside the
clarifier.
Other advantages and novel features of the present invention will
become apparent from the following detailed description.
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BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of this invention and several variant
elements are illustrated in the accompanying drawings, in which like
numerals denote like parts throughout the several views, and in which:
FIG. 1 is a perspective view of a clarification installation showing a
clarifier having a pair of covers according to the preferred
embodiment of the present invention mounted thereon end-to-end;
FIG. 2 is a cross-section view of the clarifier illustrated in FIG.1 as seen
along line 2-2 in FIG.1;
FIG. 3 is an enlarged partial view of the attachment side of the clarifier
cover taken from the left side of the cross-section view in FIG. 2;
FIG. 4 is an enlarged partial view of the openable side of the clarifier
cover taken from the right side of the cross-section view in FIG. 2;
FIG. 5 is a partial perspective view of a preferred truss member supporting
the flexible sheet over a clarifier;
FIG. 6 is a partial perspective view of one corner of the clarifier cover,
taken along the openable side thereof
FIG. 6A is an enlarged partial view of the pipe extending along the
openable side of the flexible sheet and illustrating a keyhole-like
slot in this pipe, as seen in detail circle 6A in FIG. 6;
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FIG. 7 is a front, top and side perspective view of the preferred puller for
retaining the clarifies cover in a sealed condition;
FIG. 8 is an enlarged partial cross-section view of the openable side of the
clarifies cover as seen along line 8-8 in FIG. 6;
FIG. 9 is an enlarged partial cross-section view along an edge of the
clarifies cover, showing a first preferred sealing arrangement of the
flexible sheet over the outmost truss of the clarifies cover, as seen
along line 9-9 in FIG. 6;
FIG.10 is a schematic illustration of a first preferred sealing arrangement,
as seen generally along line 10 in FIG. 9, for sealing the transversal
edge of the cover;
FIG. 11 is an enlarged partial cross-section view along an edge of the
clarifies cover, showing a second preferred sealing arrangement of
the flexible sheet over the outmost truss of the clarifies cover, as
seen along a similar location as for the view defined by line 9-9 in
FIG. 6;
FIG. 12 is a schematic illustration of the second preferred sealing
arrangement, as seen generally along line 12 in FIG.11;
FIG. 13 is a plan view of a triangular cover segment for covering an
opening in a circular clarifies;
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FIG. 14 is a cross-section view of the triangular segment, as seen along
line 14-14 in FIG. 13.
FIG.15 is a plan view of a non-rectangular clarifier covered by a plurality
of clarifier covers according to the present invention;
FIG.16 is an elevation view of the non-rectangular clarifier shown in FIG.
15;
FIG. 17 is a cross-section view of the openable side of a clarifier cover
showing a variant puller mounted along the openable side;
FIG.18 is a cross-section view of the attachment side of a clarifier cover
showing a variant arrangement for sealing the attachment side of
the flexible sheet to the peripheral walkway;
FIG.19 is an end view of the openable side of a clarifier cover showing a
variant installation for stretching and sealing the flexible sheet along
1 S one of the outmost trusses;
FIG. 20 is an end view of the attachment side of a clarifier cover showing
additional details of the variant installation shown in FIG. 19;
FIG. 21 is a cross-section view of the outmost truss as seen along line 21-
21 in FIG. 20;
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FIG. 22 is a plan view of a suspended clarifies cover comprising some of
the novel elements used in the clarifies cover according to the
preferred embodiment of the present invention;
FIG. 23 is a cross-section view of the suspended cover as seen along line
23 in FIG. 22.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
While this invention is susceptible of embodiments in many
different forms, there is shown in the drawings and will be described in
details herein a specific embodiment, with the understanding that the
present disclosure is to be considered as an example of the principles of the
invention and is not intended to limit the invention to the embodiment
illustrated and described. A number of variant elements are also
presented herein to illustrate various manners of construction, installation
and operation of the present invention as applied to various clarifies
configurations.
A clarification installation showing juxtaposed reservoirs 20 each
being covered by a pair of clarifies covers 22 according to a preferred
embodiment of the present invention is illustrated in FIG.1. In a typical
clarification installation, each reservoir or clarifies 20 is divided in two
or
more sections by one or more intermediate walkways 24. In a preferred
installation, each section is covered by a clarifies cover 22 according to the
preferred embodiment of the present invention and is openable
individually. Both covers 22 are symmetrical and jointly seal the entire
reservoir 20. Peripheral walkways 26 are also provided along the perimeter
of each reservoir 20.
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In the preferred installation, a suction pipe 30 and valve 32 are
connected to the intermediate walkway 24, to draw bio-gases from under
the covers 22 and to convey the bio-gases through a main suction pipe 34
leading to a bio-gas treatment plant 36.
Referring now to FIGS. 2-S, the structure of the clarifier cover 22
according to the preferred embodiment is illustrated therein. The reservoir
20 illustrated therein has concrete perimeter walls 40, 42 each having a T-
like configuration and forming the peripheral walkways 26.
The clarifier cover 22 comprises a series of trusses 44 that are
removably anchored to the opposite side walls 40, 42 of the reservoir. The
trusses 44 are made of a single arched aluminum pipe having an outside
diameter of between about 1-1/2 inches (38 mm) to 2 inches (50 mm) for
installation in clarifiers having a width of about between 14 to 20 feet (4.3
to 6 m). The spacing between adjacent trusses is about 4 to 6 feet (1.2 to
1.8 m).
These trusses 44 are covered by a flexible gas-impermeable fabric
sheet 46 which is referred to herein as the flexible sheet. This preferred
flexible sheet is a fibre-reinforced nylon-based sheet having stretch
resistance properties to resist shrinking or sagging and sufficient tensile
strength to support several workers walking thereon between the trusses.
The flexible sheet is preferably coated with polyvinyl chloride or
polypropylene to resist a variety of toxic fumes and has properties to resist
deterioration by ultraviolet sun rays. The preferred flexible sheet is pliable
and also has fire retardant properties.
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The clarifies cover 22 has an attachment side 50 to which the
flexible sheet 46 is permanently affixed and an openable side 52, opposite
the attachment side 50. The flexible sheet 46 is affixed to the attachment
side 50 for being clamped down to the peripheral walkway 26 under a first
structural angle 54 extending along the attachment side 50.
The flexible sheet 46 has a hem 56 along the openable side 52 ofthe
clarifies cover, and an aluminum pipe 58 is mounted inside the hem 56 and
extends the full length of the clarifies cover 22. The pipe 58 has an outside
diameter of about 2- 3 inches (51-76 mm).
There is provided along the openable side 52, an elongated resilient
pad 60 made of a resilient material such as soft rubber for example. A
series of pulleys 70 is installed along the openable side 52, inside a second
structural angle 72 attached to the openable side, for pulling the pipe 58
against the resilient pad 60 and for efficiently sealing the flexible sheet 46
to the openable side 52.
Each truss 44 has right-angled brackets 80, one at each end thereof.
Each angle bracket 80 has a slot 82 in its lower vertical segment and one
or more holes 84 in its upper horizontal segment. In the preferred
installation, the rim wall 86 of each reservoir 20 has protruding anchor
bolts 88 which coincide in size and locations with the placement of the
trusses 44, such that each truss is attachable to, or removable from a
respective anchor bolt 88, by working the bolt and by lifting the truss 44
out of the bolt 88.
The takeoff pipe 30 is preferably connected to the upper portion of
the walkway 24. A valve 32 is also preferably mounted on the takeoff pipe
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30 to isolate one reservoir 20 from the main suction pipe 34, for doing
inspection, maintenance or repair work on that reservoir without affecting
the operation of other reservoirs in a same clarification installation.
Referring back to. FIG. 1, the outmost truss of a clarifies cover 22
is enclosed on one side thereof by an arched plated structure 90 extending
to and sealed against the peripheral walkway 26. The opposite outmost
truss is mounted to the arched plated structure 92 between two clarifies
covers and constitutes, with the arched plated structure 92, the intermediate
walkway 24. The arched plated structures 90, 92 may have one or more
louvers or portholes therein (not shown) to admit air under the clarifies
cover 22, or to allow visual inspection of the reservoir.
Refernng back to FIG. 2 the clarifies cover is openable by rolling
the flexible sheet 46 onto the pipe 58 and along the trusses 44 as
illustrated.
The preferred pipe 58 has a square or hexagonal boss 96 at each end. One
of these bosses 96 is partly illustrated in FIGS. 4 and 6. A socket wrench,
a hand wheel 98 or similar tool may be mounted to these bosses 96 for
facilitating the winding of the flexible sheet onto the pipe 58. When a pair
of hand wheels 98 are used, one of which is shown in FIG. 2, two workers,
one standing on an intermediate walkway 24 and the other one standing on
the arched plated structure 90 for example, can roll up the flexible sheet 46
with ease.
An elongated tray 100 is defined by the first structural angle 54 for
receiving and holding the flexible sheet 46 in a rolled-up form. A series of
gussets 102 are welded inside this first structural angle 54 for forming a
cradle for retaining the rolled-up flexible sheet above the anchor bolts 104.
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When inspection or repair work needs to be done inside the reservoir
20, the flexible sheet 46 is easily removed as described and illustrated, and
a number of trusses 44 may be removed and stacked side by side at one end
of the reservoir 20 for example, thereby providing unobstructed access to
the equipment inside the reservoir.
Referring now to FIG. 6, there is illustrated therein one comer of
the clarifier cover 22 according to the preferred embodiment. An important
feature of the clarifier cover according to the preferred embodiment is that
there are provided kick plates enclosing each cover. T'he kick plates are
made of the first and second structural angles 54 and 72 and two arched
structural angles 110,112 mounted over the arched plated structures 90 and
92 respectively. As illustrated, the structural angles are installed with one
leg member extending upwardly and the other leg member, referred to
hereinafter as the sole portion, laid against the surface of the walkways 26
or the plated structures 90, 92. The height of the kick plates, or the
dimension of the uprising leg member, is preferably at least about four
inches ( 10 cm).
The kick plates, or structural angles 54, 72, 110 and 112 are
advantageous for preventing a worker from slipping and falling into the
reservoir, or dropping a power tool or maintenance equipment in the
reservoir when effecting maintenance work around the reservoir.
For further increasing the safety of workers working around the
clarifier, there are provided handrails 120 mounted along the clarifier
cover. These handrails 120 are mounted into a series of sockets 122
affixed to the structural angles. The handrails 120 are removable from the
sockets for doing maintenance work inside the clarifier.
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Another important aspect of the clarifier cover according to the
preferred embodiment is the use of pullets 70 for sealing the flexible sheet
46 to the outmost trusses 44 and to the openable side 52 of the clarifier
cover. The preferred pullet 70 has a frame 130, a main shaft 132 mounted
inside the frame 130. A ratchet wheel 134 is affixed to the main shaft 132
outside the frame. A pawl 136 is also mounted to the outside of the frame
130 and interferes with the movement of the ratchet wheel 134 for
maintaining a tension on a cable wound around the main shaft 132. The
main shaft 132 also has a square or hexagonal stem 138 protruding outside
the frame 130 on the opposite side of the frame relative to the ratchet wheel
134 and the pawl 136. The square or hexagonal stem 138 has dimensions
for engagement with a socket wrench for rotation by a socket wrench. The
main shaft 132 also has a slot 140 there along and a pin 142 extending
across the slot for retaining a cable 144 to the shaft.
The preferred pullet 70 also has a pair of flanges 146, for attachment
to the sole portion 148 of one of the structural angles 72, 110, 112, as
illustrated in FIGS. 8 and 9 in particular. The pullets 70 which are
mounted along the openable side 52 of the cover are preferably held by
anchor bolts 150 extending through the flanges 14b, through the sole
portion 148 and through the resilient pad 60, for holding the pad 60 down
against the surface of the walkway 26. When the pullet 70 is mounted to
the arched plated structure 90 or 92, the pullet 70 is retained to the arched
plated structure by means of machine bolts 152 extending through the
flanges 146, through the sole portion 148 of the structural angle 110 or 112,
and through the axched plate structure 90 or 92.
The preferred pulley 70 also has a deflector bar 156 mounted to the
frame, below the flanges 146. The deflector bar 156 is particularly
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advantageous for changing the direction of force of the pullet for pulling
the flexible sheet downward as illustrated and described hereinafter, to
better seal the clarifies cover 22.
The sealing of the clarifies cover 22 along the openable side 52 is
effected by pulling the pipe 58 downward against the resilient pad 60.
This is effected using several pullets mounted along the structural angle 72,
each having a cable 144 and a knob 158 crimped on the end of that cable
144. The knobs 158 are inserted into keyhole-like slots 160 which are
illustrated in FIGS. 6 and 6A.
The cables 144 are pulled from under the deflector bars 156 and into
the pullets 70, for pulling the pipe 58 downward against the resilient pad
60 and for pulling the longitudinal margin of the flexible sheet 46 along the
trusses 44 and across the reservoir. The pipe 58 is preferably held to the
hem 56 by means of a plurality of fasteners 162 extending through the
longitudinal margin of the flexible sheet and through the wall of the pipe
58. The preferred spacing between the pullets 70 along the openable side
52 is between 24 inches and 72 inches (0.6 to 1.8 m) for common clarifies
installations.
The releasing ofthe pullets 70 for opening the clarifies cover is done
by working the hexagon stem 138 and the pawl 136 as is customary with
common ratchet-type winches.
The sealing of the clarifies cover 22 along both outmost trusses 44
is effected with another series of pulleys 70 spaced apart along the arched
structural angles 110 and 112 as illustrated in FIGS. 6 and 9. The flexible
sheet 46 has grommets 170 along each transversal edge thereof and a cable
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loop 172 extending through each grommet. The locations of the grommets
170 correspond to the locations of the pulleys 70 along the structural angles
110,112. Each cable loop 172 is engaged under the deflector bar 156 and
into the main shaft 132 of each pulley 70. As illustrated in FIG. 9, the
deflector bar 156 is generally closer to the mounting structure 90 as is the
upper segment 174 of each truss 44. Hence, the edge of the flexible sheet
46 is pulled downward by each cable loop 172, as indicated by arrow 176
in FIGS. 9 and 10. In the first preferred arrangement, the cable loops 172
are parts of a continuous cable 178 extending along the transversal edge of
the flexible sheet 46 and through all grommets 170. The cable 178 has
straight segments 180 extending between adjacent loops 172. Therefore,
when one loop 172 is pulled into a pulley 70, the tension of the cable is
applied to the respective grommet 170 in a downward direction 176 as
indicated previously, and also in a circumferential direction as indicated by
arrows 182.
These compound forces 176,182 are advantageous for pulling the
flexible sheet 46 against the trusses 44 and for preventing the flexible sheet
from slipping across the trusses 44 in conditions of strong wind for
example, or when one or more workers walk over the flexible sheet for any
reason. The circumferential tension 182 of the cable 178 causes the arc
defined by the straight segments 180 to have a smaller radius than the
radius of the upper segment 174 of the outmost truss 44. This feature is
advantageous for preventing the slipping of the flexible sheet across and
over the outmost truss 44 in a variety of stress conditions.
Referring now to FIGS. 11 and 12, there is illustrated therein a
second preferred arrangement for sealing the edges of the flexible sheet 46
against the outmost truss 44. In this second preferred arrangement, the kick
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plate along the arched plated structures 90 or 92 is made of a curved flat
bar 190 affixed to a curved structural channel 192, the flanges of which
face downward. The web portion of the channel 192 has a series of
slots 194 therein, the locations and spacing of which correspond to the
locations and spacing ofthe grommets 196 along the transversal edge ofthe
flexible sheet 46. The flexible sheet is lashed to the channel 192 by means
of a cable 198 extending inside the channel and through the slots 194 and
grommets 196.
The preferred cable 198 has a series of preformed loops 200 there
along. Each loop 200 is defined by a clip 202. The length 'L' of each loop
200 is a same as a spacing 'L' between two adjacent grommets 196. This
characteristic is advantageous for lashing the transversal edge of the
flexible sheet to the channel 192 by inserting each loop through a grommet
and into an adjacent loop, as illustrated in FIG.12. In this second preferred
installation, both ends of the cable 198 are attached to a respective puller
70 one of which is shown in FIG.12. Upon tightening of the puller 70, the
cable 198 is stretched around the circumference of the arched plated
structure 90 or 92 as illustrated by arrows 204 to further seal the
transversal
edge of the flexible sheet against the outmost truss 44.
While a rectangular clarifier cover has been illustrated and
described, it will be appreciated that the principles and structural
arrangements of the present invention are not limited to rectangular
clarifiers, but are also applicable to clarifiers having circular or polygonal
perimeters.
For example, FIGS. 13 and 14 illustrate partial details of a
triangular cover segment 210 for covering an opening in a circular clarifier.
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The cover segment 210 consists of a flexible gas-impermeable fabric sheet
with grommets along the sides thereof. The circular clarifies of interest
herein has a rigid cover with one or more triangular openings, through
which inspection and repair work inside the clarifies is carried out. The
circular clarifies structure is not illustrated in details herein for being
apparent from the previous disclosure. In this circular clarifies, each
triangular opening is cover-able by a cover segment 210, and is openable
by rolling the cover segment 210 on a flexible pipe 212, in a similar manner
as previously described for the rectangular clarifies. The cover is openable
entirely as previously described for the rectangular clarifies, or partly as
illustrated herein with portions of the cover segment 210 being securely
affixed to the clarifies structure.
The cover segment 210 is partly of entirely held against the frame
214 of the clarifies by several pullers 70 mounted inside structural angles
21b also as previously described and aligned along one or both sides of the
triangular opening. The angles 216 are attached to the rigid portions of the
clarifies cover (not shown), and constitute kick plates along both sides of
the triangular opening.
In this particular installation, the flexible pipe 212 is preferably
made of several straight sections linked to each other by flexible torque-
transmitting joints 218. The flexible pipe 212 is thereby workable between
a straight mode for rolling the cover segment thereon, and a curved mode
to better seal the cover segment Z10 against a circular clarifies wall 220.
Although the preferred flexible pipe 212 is illustrated herein with joints
218, it will be appreciated that it may be made of a single section of
flexible plastic material for example.
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Another series of pullers 70 is mounted to the outside surface of the
clarifier wall 220 and is used to retain the flexible pipe 212 and the cover
segment 210 in a closed mode. The structural angle 222 retaining the
pullers 70 to the clarifier wall constitutes a guard rail for preventing
damage to the cover segment 210 and to the flexible pipe 212 by equipment
such as lawn mowers moving near the clarifier wall.
When the triangular cover segment is partly openable, the fixed
portion 224 is permanently anchored to the clarifier structure by means of
clamp bars 226 for example along both sides thereof. An intermediary
tubular bar 228 is preferably affixed to the fixed portion 224 and held tight
by two pullers 70 mounted to the clarifier structure 214.
For convenience, the triangular cover 210 segment may also be
retained to a channel and flat bar structure 230, such as described herein as
the second preferred arrangement and illustrated in FIGS.11 and 12. In
this case, the edge of the triangular segment is affixed to the channel and
flat bar structure 230 by a lashed rope 232 as previously described and
illustrated.
Another example of a clarifier having a non-rectangular shape is
presented in FIGS.15 and 16. In this arrangement, the clarifies 250 has a
octagonal shape and is covered by two rectangular covers 252 and four
trapezoidal covers 254 separated by walkways 256, one of which 256'
extends generally along a diameter of the clarifies. Each of the covers 252,
254 has an openable side adjoining the diametrical walkway 256'. Each of
the covers 252, 254 is opened by rolling the flexible sheet 260 toward the
outside of the clarifies in a same manner as previously described.
Similarly, the edges of the flexible sheets are sealed along the attachment
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sides and against the upper segments of the outmost trusses of each cover
in a similar manner as previously described.
It should be noted that the trusses 262 of the trapezoidal covers 254
have a same profile but different lengths. Each of these trusses 262 has a
low end along the diametrical walkway 256' and a high end along one of
the outside walls 264 of the clarifier. The high ends of these trusses define
a series of juxtaposed vertical trapezoidal planes which are covered and
sealed by end plates 266. Each of the outmost trusses is also covered and
sealed by end plates 268.
The openable side 52 of each cover is sealed against the diametrical
walkway 256' using the resilient pad 60 and pulleys 70 as previously
described, or using alternate pulleys as will be described hereinafter.
It will be appreciated that the pulleys 70 as illustrated in the
preferred embodiment of the present invention are advantageous but not
essential to the proper operation of the cover. The illustration in FIG. 17
presents an alternate pulley arrangement 270 which is also effective in
sealing the flexible sheet 46 to the peripheral walkway 26. In this alternate
pulley arrangement 270, a hook member 272 is mounted on a threaded stem
274 anchored to the walkway 26. The hook member 272 is adjustable
vertically along the threaded stem 274 by means of a nut 276 and washer.
The hook member 272 engages with the aluminum pipe 58 through an
opening (not shown) in the hem 56. The nut 276 is tightened to pull the
hook member 276 and the aluminum pipe 58 downward to seal the flexible
sheet 46 against the structural angle 278.
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When the structural angle 278 consists several short segments each
anchoring a single truss 44, a continuous S-shaped sealing plate 280 is
preferably attached to the structural angle segments and made to extend
along the entire length of the openable side 52 This S-shaped sealing plate
280 has a lower curved lip 282 sealed against the surface of the walkway
26, and an upper curved lip 284 covering the upper edges of the structural
angle segments 278. This upper curved lip 284 constitutes the sealing edge
against which the openable margin of the flexible sheet 46 is pulled tight
by the hook members 272.
When the structural angle 278 consists several short segments each
anchoring a single truss 44, another continuous S-shaped sealing plate 280
is also used along the attachment side 50 of the cover as illustrated in FIG.
18. The sealing plate 280 is attached to the structural angle segments 278
by bolts 288. In this arrangement, the attachment margin of the flexible
sheet 46 is affixed to the walkway 26 under a clamp bar 290 bolted to the
walkway by anchor bolts 292. These S-shaped sealing plates 280 constitute
kick plates along both sides of the clarifier for enhancing the security of
workers around the clarifier.
Referring now to FIGS. 19-21 a variant installation for stretching
and sealing the flexible sheet against one of the outmost trusses is
illustrated therein. In this variant installation, a rope 300 is threaded into
a hem 302 along the lateral margin of the flexible sheet 46 and is kept taut
by a puller 70 affixed to the structural angle 278, with the deflector bar 156
thereof set below the top surface of the truss 44.
On the attachment side 50 of the cover, the rope 300 is guided under
a peg 304 affixed to the end plate 306 on the outmost truss. The peg 304
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is substantially a same distance from the upper segment of the truss 44 as
is the deflector bar 156 on the pulley 70. The rope 300 is anchored to the
structural angle 278 on the attachment side 50 of the cover.
The rope is pulled tight by the pulley 70, to retain the hem 302 at a
radius which is smaller than the radius of the upper segment of the truss 44,
whereby the hem 302 is effectively retained against movement across the
truss 44.
In this variant installation, one or more clips 308 are affixed to the
end plate 306 along the arched segment defined by the hem 302, and the
rope 300 is inserted under each clip 308. It has been found a few clips
along the rope are very effective in preventing any slippage of the flexible
sheet 46 over the outmost truss 44, and for enhancing the safety of workers
who may have to walk over the cover.
Referring particularly to FIG. 20, the clamp bar 290 on the
attachment side 50 of the cover may be replaced by a structural angle 310
to obtain substantially the same function, while providing an additional
kick plate along the cover.
In FIGS. 22 and 23, there is illustrated a suspended rectangular
cover comprising a sheet of gas-impermeable, flexible, high strength fabric
such as the aforesaid flexible sheet 46 which is stretched across and affixed
to all four sides of a reservoir 320 using clamp bars 290 as previously
described herein. This type of cover is more economical and versatile than
those already described. These covers are typically used to capture odorous
vapours from the reservoir contents, to block sunlight thus reducing algae
growth or chlorine loss, to protect against debris, and to reduce heat loss in
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the reservoir contents. In this type of installation, there is no truss or
other
cross member to support inwardly-directed reaction loads on the walls of
the reservoir. The walls of these reservoirs are susceptible of being
damaged by inwardly-directed point loadings.
In the suspended cover described herein, however, the flexible sheet
46 may be floating at the surface of the reservoir or suspended loosely from
its edges. The flexible sheet is not tensioned across the reservoir opening
like a trampoline. It is designed to deflect or sag loosely in the middle.
This deflection allows the cover to support snow loads while keeping the
fabric tension within safe working limits of the material. One or more
weight lines 322 are mounted over the cover to cause one or more
depressions in the cover surface to collect rainwater or melting snow. One
or more drain holes 324 extend through the flexible sheet 46, along the
weight lines to automatically evacuate rain and snow-melt water from the
surface of the cover into the reservoir.
The weight line 322 also tensions the flexible sheet 46 to reduce
wind flutter and to prolong the life of the cover fabric. The weight line 322
is secured in its position on the cover by ropes or straps which are tied to
anchors at the cover perimeter. The weight line 322 can be removed and
reinstalled by operators without standing on the cover.
An array of cables 326 is mounted under the flexible sheet 46. Each
cable has one end affixed to an anchor 328 on one side or one end of the
reservoir 320 and the other end is mounted in a pulley 70 or winch on the
other side or the other end of the reservoir. The winches 70 allow operators
to vary the cables' lengths and tensions. In normal use, the cables 326 are
set to sag loosely below the flexible sheet 46 as illustrated in FIG. 23, such
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that the cover is not supported on the cables. When the cover needs to be
opened, the cables 326 are pulled tight to support the flexible sheet 46. The
flexible sheet 46 can then be released from its clamp bars 290 and can be
partially rolled up from one side ar from one end of the reservoir. The
array of cables 326 is also pulled tight to install a new flexible sheet 46 in
a new installation, or to replaced an aging cover.
As soon as the flexible sheet is clamped down to the walls 330 of the
reservoir, the cables 326 are lengthened and left to hang loosely under the
flexible sheet. The major advantage of this installation is that in normal
conditions, the cables do not apply point loading or concentrated side load
on the walls of the reservoir which could eventually lead to damage to these
walls. The loads applied to the walls of the reservoir by the flexible sheet
are evenly distributed and therefore not detrimental to the structural
integrity of the reservoir.
Although the above description refers to industrial clarifier
installations, it will be appreciated that the principles of the present
invention can be applied to other water and wastewater reservoirs and tanks
such as: chlorine contact basins; raw water storage tanks; reclaimed water
storage tanks, sand filters, aeration basins; digesters; trickling filters;
sludge
thickeners; equalization basins; etc. It will also be appreciated that the
feature of one embodiment may be used in another.
In view of the above, it will be appreciated that many changes and
modifications may be made to the illustrated and described embodiments
without departing from the essence of this invention. Therefore, the above
description and illustrations should not be construed as limiting the scope
of the invention which is defined by the appended claims.
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