Note: Descriptions are shown in the official language in which they were submitted.
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A VIBRATORY SEPARATOR
The present invention relates to a vibratory
separator, and particularly, but not exclusively, to a
shale shaker, to a basket and to a screen assembly
therefore.
Vibratory separators have been employed for many
years to separate particles in a wide array of industrial
applications. One common application for vibratory
separators is in drilling operations to separate
particles suspended in drilling fluids, such as that
known as drilling mud. Screens are mounted generally
horizontally in a basket or frame on a vibrating
mechanism or shaker that imparts a desired motion to the
screen. Material from which particles are to be separated
is poured onto a back end of the vibrating screens,
usually from a pan mounted above the screen. The material
generally flows toward the front end of the screen. Large
particles are unable to move through the screen and hence
remain on top of the screen and move towards the front of
the screen where they are collected. The smaller
particles and fluid flows through the screen and collects
in a tank, receptacle or pan beneath the screen.
Typically the screen is resiliently suspended or
mounted upon a support in a basket or frame, the basket
being caused to vibrate by a vibrating mechanism, such as
a an unbalanced weight on a rotating shaft connected to
the basket or frame. The screen is vibrated by vibratory
equipment to create a flow of trapped solids on top
surfaces of the screen for removal and disposal of
solids. The fineness or coarseness of the mesh of a
screen may vary depending upon mud flow rate and the size
of the solids to be removed.
The need for solids control in drilling mud used in
hydrocarbon well drilling is well known in the prior art.
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Drilling mud, typically a mixture of clay and water and
various additives, is pumped down through a hollow drill
string, (pipe, drill collar, bit, etc.) into a well being
drilled and exits through holes in a drillbit. The mud
picks up cuttings, such as rock and other solids from the
well and carries them upwardly away from the bit and out
of the well in a space between the well walls and the
drill string. At the top of the well, the solids-laden
mud is discharged over a shale shaker, a device which
typically has a screen or a series of screens arranged in
tiered or flat disposition with respect to each other.
The prior art discloses a wide variety of vibrating
screens, devices which use them, shale shakers, and
screens for shale shakers. The screens catch and remove
solids from the mud as the mud passes through them. If
drilled solids and/or debris are not removed from the mud
used during the drilling operation, recirculation of the
drilled solids can create weight, viscosity, and gel
problems in the mud, as well as increasing wear on mud
pumps and other mechanical equipment used for drilling.
In many cases it is difficult if impossible to mount
or hang a screen in a vibratory separator or shale shaker
so that the lateral plane of its surface is perfectly
horizontal.
Material to be separated generally comprises various
sized particles in a fluid. It is generally advantageous
to remove the fluid as quickly as possible, so that the
vibratory separator in order to reduce the weight of
material to be separated and to speed up separation of
the particles therefrom. It is also advantageous to
increase the screening area in a given size vibratory
shaker.
In accordance with the present invention, there is
provided a vibratory separator comprising a basket having
screening apparatus mounted therein, the screening
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apparatus having at least a first portion and a second
portion, the first portion lower in the basket than the
second portion.
The present invention also provides a basket and a
screen apparatus of the vibratory separator of the
invention.
The present invention also provides a method for
screening material comprising the steps of introducing
material to be screened into a basket of a vibratory
separator, said material landing on a screen having a
first portion and a second portion, the first portion at
a lower height in the basket than the second portion.
For a better understanding of the present invention,
reference will now be made, by way of example, to the
accompanying drawings, in which:
Figure 1 is an end view of a prior art screen
connected to mounting brackets of a shale shaker;
Figure 2 is a perspective view of a prior art shale
shaker;
Figure 3 is a perspective view of a prior art basket
with a screen mounted therein;
Figure 4A is a side cross-sectional view of a shale
shaker with a screen arranged therein in accordance
with the present invention;
Figure 4B is an end view of the shale shaker of
Figure 4A;
Figure 5A is a side cross-section view of a shale
shaker and screen arranged therein in accordance
with the present invention;
Figure 5B is an end view of the shale shaker of
Figure 5A;
Figure 6 to 10 are side cross-sectional views of
shale shakers and screens in accordance with the
present invention;
Figure 11A is a side cross-sectional view of a shale
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shaker in accordance with the present invention; and
Figure 11B is an end view of a part of Figure 11A.
Figure 1 shows a screen S having left and right
sides. Each side is provided with hook shaped strips. The
screen S is hooked via the hook shaped strips to hooked
bolts which are arranged on each side of a basket (not
shown) of a shale shaker (not shown). The screen S may be
tensioned over formers (not shown) spaced along the
interior of the basket. The centre of the screen bulges
upwardly from the longitudinal edges of the screen as
shown in Fig. 1 (an "over slung" screen as described in
U.S. Patent 4,820,407), in which case the screen is said
to be "crowned" or "over slung", or the centre bulges
downward in which case the screen is said to be "under
slung". A screen that is "crowned" or "over slung" (Fig.
1), causes solids to tend to congregate at the screen's
longitudinal edges; if a screen is "under slung", solids
tend to congregate at its centre.
Figure 2 shows a typical prior art shale shaker
system A with a screen B (comprising screening cloth or
mesh as desired) mounted on a vibratable "basket" C. The
screen B may be any screen disclosed herein or have any
combination of any feature or features of any screen or
screen part disclosed herein; and any such screen may be
used with any appropriate shaker or screening apparatus.
The basket C is mounted on springs I (only two shown; two
are on the opposite side) which are supported from a
frame D. The basket C is vibrated by a motor E and
interconnected vibrating apparatus F which is mounted on
the basket C for vibrating the basket and the screens.
Elevator apparatus G provides for raising and lowering of
the exit end of the basket C. The screen B is any prior
art screen, screens, and/or screen assembly.
Figure 3 shows a prior art basket J with a screen K
mounted therein with a typical prior art "crown"
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disposition with a middle crown portion L. Typical
mounting rails or channels M are used with typical
mounting devices N to releasably secure the screen K in
the basket J.
Referring to Figures 4A and 4B, there is shown a
shale shaker 10 in accordance with the present invention.
The shale shaker 10 has a basket 12 for retaining
screens. Vibrating apparatus 14 is connected to the
basket 12. Material to be treated by the shale shaker 10
is introduced into a first end 16 of the basket 12 above
a screen 30 releasably secured within the basket 12 by
any suitable known screen securement device and/or
structure. Item 18 is a back plate or rear weir.
The screen 30 has a central portion 31 which is
higher than either screen end 32, 33. A pool 22 of
material to be treated is above the screen end 31 and
enclosed by sides 13, 15 and end 16 of the basket 12.
Fluid 24 (e.g. but not limited to drilling fluid
separated from drilled solids, cuttings and debris)
separated from the material to be treated falls from the
screen 30 into a receptacle or pan 26, and onward through
a pipe system for further processing. Alternatively, the
basket 12 may be bottomless, such that fluid and small
particles fall into a separate receiver or funnel and
onward through a pipe system to be processed further
before being re-used. The larger particles separated from
the fluid and smaller particles, exit from the end 33 of
the screen 30 into a skip (not shown) or the like.
It is within the scope of this invention to adjust
the height of the screen ends 32, 33 as desired and
thereby to adjust the size and depth of the pool 22.
This also permits adjustment of the location of the edge
of the pool in relation to the discharge end of the
screen so that solids can have a longer distance to move
on the screen (while liquid escapes and moves through the
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screen) once they have left the pool. The screen(s) of
baskets according to the present invention may be mounted
to the basket in any known manner with any known screen
mounting apparatus or device. In certain aspects a
reverse hook strip tensioning system may be used at
either end of the screen (which may be at the first end
16 and discharge end of the basket) and, in one aspect,
tension may be applied to a "live" end of the screen with
the system at the basket's discharge end. In one
particular aspect at the "live" end a normally open
spring actuator is used which is selectively actuated to
a closed position to tension and secure the screen. Such
an actuator may be manually actuated or operated with
appropriate hydraulic and/or pneumatic systems.
Figures 5A and 5B show a shale shaker 40 according
to the present invention with a screen mounting basket
42, vibrating apparatus 44 connected to the basket 42.
Material is introduced into a first end 46 of the basket
42 above a screen 50 releasably secured within the basket
42.
The screen 50 has a central portion 51 which is
higher than either screen end 52, 53. A pool 59 of
material to be treated is above the screen end 51 and
enclosed by sides 43, 45 and end 46 of the basket 42. A
flat screen 60 is located with part thereof beneath the
end 53 of the screen 50 so that solids flow onto the
screen 60 from the screen 50 for further separation of
fluid from solids. Fluid 54 (e.g. but not limited to
drilling fluid separated from drilled solids, cuttings
and debris) separated from the material to be treated
falls from the screen 50 into a receptacle or pan 56 or
may have an open bottom having a separate receiver
arranged therebelow, having no physical connection
thereto. Separated materials on the screen top exit from
the end 53 of the screen 50.
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Figures 6 and 8A - 9C show various screens according
to the present invention, each in a screen mounting
basket 62 of a shale shaker vibrated by vibrating
apparatus 64. Figure 7 shows a basket 63.
In the apparatus of Figure 6, two screens 70, 71 are
mounted one above the other, each with central portions
70a, 71a respectively which are above screen ends 70b,
70c and 71b, 71c, respectively. Optionally either screen
may be deleted or may be substantially horizontal viewed
from the sides and ends. A pool 61 is above the screen
end 70b. The upper screen 70 and lower screen 71 may
comprise screening material of the same mesh size or the
upper screen may comprise screening material of a larger
mesh size. The upper screen may be a scalping screen. The
screens may be spaced by approximately 10cm.
In Figure 7 the apparatus has a screen 72 (like
screen 50, Figure 5A) with a middle portion 72a and an
end 72c from which separated materials fall onto a lower
screen 73 which itself is curved rather than flat (as is
the screen 60, Figure 5A). As shown the lower screen 73
is convex (viewed from the side); but it is within the
scope of this invention for the lower screen 73 to be
concave as viewed from the side. A pool 69 of material to
be treated is above an end 72b of the screen 72. A solid
partion, known as a flow back pan, as shown and described
in PCT Publication No. WO 96/33792 may be arranged
between the upper and the lower screen. The flow back pan
is preferably solid and inhibits material and fluid
falling through the upper screen 72 to land on the upper
surface of the lower screen 73. Alternatively, a simple
barrier, as shown in Figure 7, is arranged at the leading
end of the lower screen to inhibit large particles from
dropping into the receptacle, receiver or sump for the
fluid and smaller particles.
As shown schematically in Figure 7, the "crown" or
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height of the screen 72 may be selectively adjusted by an
inflatable bladder 163 with an appropriate inflation
system 162 controlled by a system 160 with a
control/monitor system 161. Alternatively crown height
may be manually adjusted and screens thus adjusted held
in place by any suitable means, including, but not
limited to: nuts and bolts; support blocks, beams, or
members; and/or recesses or grooves in side walls, with
or without one or more screen projections or screen frame
projections therein.
In the apparatus of Figure 8A a screen 80 has a
first end 81 which is lower than the remaining screen
portion 82. The remaining screen portion 82 is
substantially flat. A pool 65 of material to be treated
is above the end 81. Solids on the screen top exit from a
screen end 83.
In the apparatus of Figure 8B a screen 84 has a
first substantially flat end 85 and a downwardly angled
exit end 87 which is lower than the end 85 and central
screen portion 86. In the apparatus of Figure 8C a screen
90 has a first end 91 and a second end 93 both of which
are lower than a central scr&en portion 92. A pool 66 of
material to be treated is above the end 91. Solids on the
screen top exit from the screen end 93.
In the apparatus of Figure 9A a screen 95 has a
first screen portion 96 which is lower than the remaining
screen portions 97, 98. The first screen portion 96 is
substantially flat, although may be slanted and may be
concave or convex. The remaining screen portions 97,98
are substantially flat and are arranged at a higher level
than the first screen portion 96. The remaining screen
portions 97,98 may be slanted and may be concave or
convex. A connecting portion 99 is arranged between the
first screen portion 96 and a leading end of the
remaining screen portions 97, 98. The connecting portion
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99 is substantially vertically arranged and may be either
solid or perforated, and made of screen, mesh, or any
suitable material. A pool 67 of material to be treated is
above the end 96. Larger particles exit from a screen end
97.
In the apparatus of Figure 9B a screen 100 has a
first end 101 and a central portion 109 which are higher
than a screen exit end 104. A connecting portion 105 is
like the portion 99, Figure 9A.
In Figure 9C a screen 110 has a first end 111 lower
than a central screen portion 112. A pool 68 of material
is above the end 111. Solids exit from a screen end 113
which is also lower than the central portion 112.
Connecting portions 114, 115 are like the portion 99,
Figure 9A.
Any screen or screen portion in any screen disclosed
herein may be any known screen for a vibratory shaker,
including, but not limited to, known two- and three-
dimensional screens and screen assemblies. Any screen
disclosed herein with portions at different levels may
include a separate screen or screens for each portion,
the multiple screens mounted adjacent each other in a
basket.
In certain embodiments of the present invention a
long single screen, initially flat, is bent to produce
the "reverse crown" shape (e.g. the shape of the screen
in Figure 4A, viewed from the side or of Figures 8A - 8C)
and is secured in a basket.
Figure 10 shows a basket 120 for a vibratory shaker
such as a shale shaker (e.g. but not limited to
apparatuses as shown in Figure 2) with ends and side
walls which may be like those of any basket described
herein. Material to be treated is introduced at a first
end 121 of the basket 20 where it forms a pool 122 above
part of a screen 123 according to the present invention.
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(The screen 123 may be like the screens 31, 50, or 72
described above and with any suitable layer or layers of
screening material and/or mesh, either two- or three-
dimensional bonded together and/or mechanically connected
together - as may be any screen or screen assembly
herein). Fluid (e.g. but not limited to drilling fluid)
separated from the pool 122 flows down into a collection
receptacle 124. Fluid that exits the pool 122 in material
on the screen top can move through the screen 123 and
flow down to contact another screen 130 (which may be
like any screen disclosed herein, including, but not
limited to screens 60, 73, 87 or 93. Fluid separated by
the screen 130 flows down into the collection receptacle
124.
A rear barrier or weir 131 contains one end of the
pool 122. A barrier 132 (solid or made of screening
material) may be used with the screen 130. As shown the
barrier 132 may lie below the end of the pool 122 nearest
the discharge end 125 of the screen 123. However, the
barrier 132 may be positioned further under the poo]. 122
(to the left in Figure 10) or closer to the discharge end
125 (to the right in Figure 10). Also the screen 130 may
extend across the entire length of the basket 120 or any
part thereof. Instead of a barrier 131, a screen may be
used.
Figure 11A shows a vibratory separator or shale
shaker 140 according to the present invention with a
basket 150 according to the present invention (e.g., but
not limited to like the apparatus of Figure 4A; and like
numerals indicate like parts and items). The sides of the
shaker 140 incorporate side screens 142 (one side shown
in Figure 11A) adjacent the pool 22. Either or both side
screens 142 may be deleted. The side screen opposite the
side screen 142 in Figure 11A is the same as the side
screen 142 shown. Optionally, the basket 150 has an end
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opening 152 and an end screen 154 adjacent the pool 22.
The end screen and side screens may be like any described
in pending PCT Publication No. WO 02/40186. Such an end
screen and/or side screen(s) may be used with any basket
disclosed herein. The screens may be two dimensional, or
three dimensional.
In a typical prior art apparatus, a pool formed on
the top of the screen has a "horseshoe" or U-shape with
side pool portions along side edges of a screen and with
the central raised part of the screen above the pool, or
with the pool on a central screen portion relatively
shallow compared to the pool at the screen's sides and
end. A pool in a system according to the present
invention (e.g., but not limited to any of the pools in
Figures 4A - 11A) extends from one side of the basket to
the other with a uniform depth at any particular distance
from the basket input end.
