Note: Descriptions are shown in the official language in which they were submitted.
CA 02820204 2013-08-06
Mobile Dry Material Storage
Background
The present invention relates to the handling, storing, and distribution of
bulk dry
materials, such as sand.
There are many applications in which it is necessary to store large amounts of
bulk dry
material at a site. The following description gives the background of the
invention in the context
of one such application¨the handling, storage and distribution of silica sand
used as a proppant
at a gas or oil well site in carrying out the process known as hydraulic
fracturing, or "ftacking."
It should be understood, however, that the invention is not so limited.
The conventional prior art approach to storing sand at a well site is to place
storage
trailers horizontally on the ground and load and unload the sand using
pneumatics.
Disadvantageously, this requires a large footprint on the site, which has an
impact on site lease
costs and has environmental impacts as well. Other problems with this approach
include
inefficient use of trucking equipment, increased complexity of operations at
the well site and,
ultimately, lower downhole production due to proppant damage.
If, in order to ameliorate these problems, only a few storage trailers are
used on site, then
other issues arise. For example, having low sand capacity at the well site
causes logistical
problems and increases incremental costs associated with truck and rail
demurrage. The loading
and unloading of. the sand is inefficient. And pneumatic filling changes the
particles of silica
sand from their generally spherical shape to irregular/broken shapes. This
results in less negative
space, i.e., less space between the sand particles, which leads to lower well
conductivity, i.e.
lower rates of extraction of the oil or other material being drilled for,
Pneumatic pumping also
creates an unhealthy dust.
A known alternative to the horizontal storage approach, which addresses at
least some of
the above problems¨such as site footprint¨is to store the sand vertically in
free-standing silo
units that can be trucked to the well site and then stood on end. The silo
units are filled with sand
from the top and the sand can then be gravity-drained or discharged from each
silo unit through a
chute extending from the side of the silo unit. Use of such free-standing silo
units ameliorates
some of the problems associated with the use of horizontal storage trailers.
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Summary of the Invention
We have recognized, however, that further improvements are desirable and,
indeed,
possible. In particular, we have come to recognize that a particularly
disadvantageous aspect of
the prior art silo units arises from the fact that each unit brought to the
site is a discrete system.
This means that the silo units must be individually filled pneumatically,
giving rise to the above-
noted problems inherent in that approach. Another problem is that it can take
quite a lot of
time¨anywhere from 35 minutes to 60 minutes or longer¨to fill the silo units.
Having to
transfer filling and unloading equipment from one silo unit to another is
itself time-consuming.
Moreover, the free-standing nature of the silo units requires that there be
enough space between
the units to allow for trucks and other equipment to load and unload the sand,
which wastes
space at the site.
A system embodying the principles of the invention improves over the prior art
in a
number of aspects. The system includes a plurality of elongate storage
bins¨illustratively
having a generally rectangular cross-section--that can be trucked to a site
horizontally and then
lifted and positioned vertically onto a base structure, or "skid," that holds
the bins upright in at
least one line¨illustratively touching, or at least very close to, one
another. A downward-facing
end of each bin has a discharge outlet that can be controllably opened and
closed to allow sand or
other product in the bins to be discharged downwards due to gravity onto a
conveyor.
Particular embodiments of the bins include legs or other bin-support structure
surrounding the discharge outlet. The bins are supported on the legs or other
bin-support
structure when positioned on the skid. Since the legs and, illustratively,
reinforcing cross
members surround the discharge outlet, the discharge outlet is protected from
accidental damage
when a bin is being raised or lowered or otherwise moved about when the system
is being
assembled or disassembled
In preferred embodiments, a bottom conveyor is disposed within the skid in
such a way
that the dispensed material falls from the bins onto the bottom conveyor. The
bottom conveyor is
arranged to convey the material thus dispensed to one end of the skid from
which the conveyed
material can be, for example, loaded onto a blender, transfer belt or truck
via a stinger. In
particular embodiments, the bottom conveyor runs down the center of the skid
and the bins are
supported in two lines with their discharge outlets positioned over the bottom
conveyor.
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Also in preferred embodiments, the system further includes a vertical
elevator, such as a
high-capacity bucket elevator, installable on an end portion of the skid. The
elevator lifts
material to be stored to the level above the top of the positioned bins. Such
embodiments
illustratively further include a top conveyor system positionable on the bins
and arranged to
receive material discharged at the top of the elevator and to distribute the
material into each bin
via a filling inlet in the upper end of each bin.
The invention provides many benefits over the prior art. Vertical, instead of
horizontal,
placement on the site gives rise to a much smaller footprint. This reduces
site congestion and
increases the volume of material that can be stored within a given site area.
The reduced
footprint saves time and money on site preparation and reclamation. Since in
preferred
embodiments the material is transported on conveyor belts at every point in
the
delivery/storage/dispensing process, there is virtually no damage to sand
grains or other material
that might otherwise be damaged during handling, as is the case for pneumatic
handling. The fact
that a greater amount of material can be stored on site within a given
footprint as compared to
prior art approaches reduces standby time as one waits for trucks to arrive to
deliver material or
to haul it away. The fact that the bins are fillable using a vertical
conveying mechanism such as a
bucket elevator means that belly dump trailers can be used to disperse their
product onto a drive-
over conveyor system at ground level that feeds the material into the
elevator, allowing for very
efficient loading of the material into the bins and, in particular, allows for
the drive-over
conveyor system and the bins to be filled simultaneously. Indeed, we have
observed at least a
three-fold reduction in the time required to unload and store material brought
to the site. Unlike
the prior art use of individual horizontal or vertical bins, the present
system allows delivering
trucks to disperse the material at a single point of discharge, rather than
having to back up to the
individual units, which reduces site congestion, speeds delivery and storage
of the delivered
material, and enhances site safety. Less manpower than prior art approaches is
required to
receive, store and dispense the material. Indeed, the system can be readily
operated by two
workers. And we have observed that something like 30% fewer trucks may be
required to
move a given amount of material within a given amount of time as compared to
the horizontal
storage approach¨the percentage depending on the particular maximum allowable
vehicle
weight limits imposed by various jurisdictions.
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Drawings
FIG. 1 is a perspective view of an illustrative system ("the system")
embodying the
principles of the present invention, the system as shown having been assembled
and ready to
receive and store sand or other material and to thereafter discharge same;
FIG. 2 is a side view the system;
FIG. 3 is a top view of the system;
FIG. 4 is a side view of an illustrative embodiment of one of the bins of the
system;
FIG. 5 is a perspective view of the system in the process of being assembled
or
disassembled and shows details of the skid onto which the bins and elevator
are mounted;
FIG. 6 depicts the process of one of the bins being lifted (or lowered) by a
pair of cranes
as part of the process of assembling (or disassembling) the system;
FIG. 7 is an end view of an illustrative implementation of the skid in its
installed
configuration;
FIG. 8 is an end view of the skid showing how it can be configured to fold up
for
transport; and
FIG. 9 is a perspective view of an illustrative top conveyor system that can
be used to
distribute and dispense the material to be stored into the bins.
Detailed Description of an Illustrative Embodiment
Reference is first made to FIGS. 1-5 depicting various views of an
illustrative system 10
embodying the principles of the present invention, the system having been
assembled and ready
to receive and store sand or other material and to thereafter discharge same.
System 10 includes a plurality of elongate storage bins 20 which are
substantially
rectangular in cross-second over the majority of their length so as to
comprise an elongate box in
which sand or other material can be stored. Bins 20 are positioned vertically
upright on a base
structure, or "skid," 50 in at least one line¨illustratively touching, or at
least very close to, one
another. In this embodiment, there are 12 bins arranged in two lines of 6 bins
each. Each bin 20
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has a discharge end 201 through which product in the bins can be discharged
downwardly via
gravity feed. Discharge end 201 includes a discharge outlet 209 that can be
closed and opened
(via a mechanism not shown) to controllably dispense sand or other material
stored in the bin as
desired.
Each of bins 20 includes legs 251 or other bin-support structure surrounding
the
discharge end 201. Legs 251 are interconnected by cross-members 204. The bins
are supported
on the legs put into position on skid 50, as described in further detail
hereinbelow. Legs 251
extend from the storage portion further than discharge outlet 209 extends
therefrom, so that the
legs protect the discharge outlet from damage during movement of the storage
bin¨particularly
when it is being moved between horizontal and vertical orientations.
Each of bins 20 is configured as a trailer brought to the site by a tractor
210 in a tractor-
trailer configuration. The trailer is illustratively a single-axle trailer but
could be, for example, a
double-axle trailer in other embodiments. Each bin has a wheel-and-axle
assembly 202
supporting the bin at one end and a stand 203 that is lowered to support the
bin upon its being
disconnected from tractor 210. Each bin has a conventional coupling device
that allows it to be
coupled to tractor 210 when being hauled .
A variable-speed bottom conveyor 501 is disposed within the skid in such a way
that
when one or more of the bin discharge outlets 209 are opened and material in
the bins is allowed
to flow downward out of the bins via gravity feed, the dispensed material
falls onto that
conveyor. Conveyor 501 illustratively runs down the center of the skid,
parallel to the lines of
bins. The material thus dispensed from the bins is conveyed by conveyor 501 to
one end of the
skid from which the conveyed material can be loaded onto trucks via a truck-
loading stinger
system 70, which illustratively comprises conveyor 71 and stinger 72 disposed
at approximately
right angles to one another. The outline of the truck into which the material
is thus loaded is
shown in dashed outline FIG. 3 and designated at 231.
An elevator system 30, comprising a bucket elevator 32 integral with its
supporting
structure 31 is mounted on skid 50 at the other end of skid 50 from where
bottom conveyor 501
discharges its load. Material delivered to the site for storage by a truck is
dispersed into a drive-
over conveyor system 61 of an overall loading system 60. The outline of such a
truck is shown in
FIG. 3 and designated at 221. Drive-over conveyor system 61 is at ground
level, allowing truck
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221 to belly-dump its load into the drive-over conveyor system. Loading system
60 further
includes a conveyor 62 that conveys the material from drive-over conveyor
system 61 into
elevator 32, which lifts the material to a level above the top of the bins 20.
When the material reaches the top of elevator 32, it is transferred to a
covered top
conveyor system 40 mounted atop the bins. Top conveyor system 40
illustratively includes two
conveyors 41 and 42 which carry the material along the top of the assembled
bins. As described
in further detail in connection with FIG. 9, top conveyor system 40 is
operable to direct the
material into the various bins 20 through filling inlets 207 disposed within
the top end wall of the
various bins. Also in the top end wall of each bin is an inspection hatch 208.
Top conveyor
system 40 is a covered structure, the covering being provided to protect the
conveyed material
from rain or other contamination as it moves along conveyors 41 and 42.
Also installed on the top of bins 20 is a safety railing 49.
Details of an illustrative embodiment of skid 50 can be seen in FIGS. 5-7. In
order to best
illustrate the various features of skid 50, FIG. 5 only shows two of the bins
20, and the ones that
it shows are those installed at the opposite end of the skid from the
elevator. As noted below,
when the system is assembled, it is envisioned that the two bins shown would
actually be the last
two bins mounted onto the skid.
Skid 50 has a horizontal base that includes pair of outer beams 520 and two
pairs of inner
beams 531 and 532, respectively. Each outer beam 520 is connected to a
respective one of
beams 531 via cross-members indicated generally 524. Each one of beams 531 is
connected to a
respective one of beams 532 via a set of hinges 541. Beams 532 are connected
to each other via
cross-members 533. It is thus seen that the base comprises a central elongate
frame 53
comprising beams 532 and 533 and two elongate outer frames 54 and 55 each
comprising one of
beams 520, one of beams 531 and their respective cross-members 524.. Bottom
conveyor 501
extends along the length of skid 50 within the footprint of the central frame
53.
Standing on each of beams 520 is a row of seven upwards extending generally
linear
outer stanchions 503 aligned with corresponding stanchions 503 on the other
one of beams 520.
Aligned with each aligned pair of outer stanchions is a respective one of
seven upwards
extending U-shaped inner stanchions 505, each comprising a pair of legs and a
cross-member.
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Stanchions 503 and 505 extend upward by, illustratively, 3 feet from the beams
on which they
stand.
Tapered leg positioners 510 mounted atop stanchions 503 and 505 are sized and
positioned to receive legs 251 of bins 20, legs 251 being hollow at least at
their free ends (i.e. the
ends on which they stand) and having a generally square cross-section. When
legs 251 are in
place, each leg stands on one of stanchions 503 and 505, with a corresponding
one of leg
positioners 510 extending up into that leg. Holes (not shown) in each leg
align with holes (not
shown) in the corresponding leg positioner and a pin can be inserted through
the aligned holes to
secure the legs in place.
Each of the four outermost stanchions 503¨i.e. the stanchions 503 at the
extreme ends of
each of the two rows thereof¨ supports a single one of legs 251 and thus has
only a single one
of leg positioners 510. Each of the ten inner stanchions 503 (5 in each row of
same) supports two
legs 251 and thus has two leg positioners 510. Each of the two outermost U-
shaped stanchions
505 supports two of the legs 251 and thus has two leg positioners 510. Each of
the five inner
ones of U-shaped stanchions 505 supports four legs 251 and thus has four leg
positioners 510.
Advantageously, skid 50 is foldable to facilitate its being trucked to the
site. To this end,
the connection of each of beams 531 to the corresponding beam 532 is by way of
hinges 541,
allowing skid 50 to be folded up as seen in FIG. 8, with the two outer frames
being rotated into a
generally perpendicular orientation relative to the central frame. Eyebolts or
the like (not shown)
- bolted or otherwise affixed at strategic locations on skid 50¨are provided
as anchor points
for load binders 544 that are used during transit to hold skid 50 in the
folded position as shown in
FIG. 8. Also during transit, load binders or other similar means 545 are
connected between
anchor points (not shown) on corresponding pairs of stanchions 503. Bottom
conveyor 501 can
be permanently installed within skid 50, or could be a separate element that
is installed within
skid 50 at the assembly site.
FIG. 9 shows top conveyor system 40 without its protective cover. System 40
includes a
framework 47, conveyors 41 and 42, and chutes 46. Each of chutes 46 has a
filling inlet that sits
underneath tracks 43 on which conveyor 42 travels, and each of chutes 46 has a
flanged
discharge outlet that fits into a respective one of, bin filling inlets 207.
As indicated by the
designation "sand path," material lifted by elevator 32 gets discharged onto
the leftmost end of
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upper conveyor 41, from which it travels from left to right to a discharge end
of conveyor 41 and
drops onto conveyor 42. The conveying belt of conveyor 42 is controllable to
convey the
material thereon either left-to-right or right-to-left. Moreover, the entirety
of conveyor 42 is
controllable to move along tracks 43 either left-to-right or right-to-left.
These capabilities of conveyor 42 allow all of the bins to be filled. In
particular with the
belt of conveyor 42 traveling left-to-right, as is depicted by the sand path
shown, the right-hand
end of conveyor 42¨one of two discharge ends¨is positioned at one of a number
of positions
along tracks 43 so as to be successively positioned over the six right-most
ones of chutes,
allowing the conveyed material to drop into each of those six chutes and thus
into the six right-
most bins. When the belt of conveyor 42 is caused to travel right-to-left, the
sand or other
material is conveyed along conveyor 42 underneath conveyor 41. The left -hand
end of
conveyor 42¨its other discharge end¨is moved to various positions along tracks
43 so as to be
successively positioned over the six left-most ones of chutes, allowing the
conveyed material to
drop into each of those six chutes and thus into the six left-most bins. In
the embodiment shown,
it will be desirable to turn off the conveyor belts when conveyor 42 is being
moved to its various
positions so that none of the conveyed material will drop into the open spaces
between the
chutes.
As an alternative, the filling inlets of the chutes can be widened so as to
touch each other
and/or all the open space below conveyor 42 can be closed up, so that none of
the conveyed
material can drop anywhere other than into one of the chutes. Such a
configuration would allow
conveyor 42 to be moved from one of its positions to the next without having
to stop the
conveyor belts between repositionings of conveyor 42.
Advantageously, a 12-bin system such as that just shown and described can be
assembled
in about 6 ¨ 8 hours and disassembly requires approximately that same amount
of time.
An illustrative order of system assembly process is as follows:
a) Skid 50 is brought onto the site in its folded configuration (FIG. 8) on
truck bed and a
crane places it on a concrete pad, rig mats or other support at ground level.
Each storage
bin ¨configured as trailer¨is hauled onto the site via a tractor 210 and
disengaged
therefrom. The other elements of the system are also brought to the site,
these including
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the bucket elevator system 30, the top conveyor system 40, the safety railings
49, a
control station (not shown) for operating the various moving elements, as well
as other
components (generator, cables, etc.) that will be apparent to those skilled in
the art.
b) The skid is opened from its folded configuration into its installed
configuration (FIG. 7)
and bottom conveyor 501 is then installed in its proper place within the skid
if conveyor
501 arrived on site as a separate unit.
c) Lifting equipment, such as one or more cranes, are used to position the
bucket elevator on
the skid.
d) The lifting equipment, such as the pair of cranes 215 and 216 as shown in
FIG. 6, elevate
the bins and the bin legs are positioned on their respective leg positioners
510 and
secured with pins inserted through holes in the legs and the positioners. One
of the two
bins nearest the elevator is the first to be put in place. Then the other bin
nearest the
elevator is put in place. The remaining bins are similarly put in place next
to those
already installed. As each bin is put in place, an associated section of the
safety railing 49
is also installed.
e) The crane(s) lift the top conveyor system 40 onto the top of the structure
thus assembled
with the discharge outlets of the chutes 46 fitting into the bin inlets 207.
f) Various other components, such as the control station, an electrical
generator and its
cables and so forth are installed at appropriate/convenient places and points
of time
during the assembly process. The loading and unloading systems 60 and 70 are
also
brought to the site and put in position to make the system ready for
operation. The control
station is advantageously installed in a location that provides an operator
with a good
view of the discharge stinger 70.
Disassembly may be conducted in essentially the reverse order. A different
order of assembly
and/or disassembly may be used, as may be found desirable.
Some illustrative physical dimensions, capacities and parameters are as
follows:
a) Bin dimensions: 50' (length) x 8.5' (width) x 10.5' (height)
b) Skid dimensions (system footprint) 22' x 58'
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c) System height: 65'
d) Storage capacity: ¨1,956 tons (1,774 metric tonnes) @ 100 pounds per cubic
foot density
e) Fill rate: 200 tons/hour
0 Fill time: 10 hours of actual filling
g) Fill time: 13 hours start to finish
g) Blender feed rate: 0 ¨ 20 tons/minute.
The foregoing presents a particular embodiment of a system embodying the
principles of the
invention. Those skilled in the art will be able to devise alternatives and
variations which, even
if not explicitly disclosed herein, embody those principles and are thus
within the invention's
spirit and scope.
