Note: Descriptions are shown in the official language in which they were submitted.
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BOREHOLE RESIDENT ELECTRONIC DEVICE
Field of the Invention
The present invention relates in general to borehole resident electronic
devices used in blasting
operations and to a method of reducing or preventing failure of such devices
during blasting
operations.
Background of the Invention
Large scale mining operations form an important part of modern day society.
Often critical to
mining operations, be it surface or subsurface, is the use of explosives in
blasting operations to
expose and gain access to the product being mined.
The use of explosives in mining operations has and will continue to present
high-level safety
concerns for mine operators.
Modern day mining operations continue to demand an ever-increasing degree of
control over
and performance from blasting operations.
With factors such as safety. control, efficiency and performance in mind,
considerable research
has been applied over the years in developing electronic devices to facilitate
mining.
Electronic detonation systems for explosives used in blasting operations are
now common
place. Electronic-based monitors are also commonly used in blasting
operations, for example
in the form blast movement monitors to track movement in the mining body after
being
subjected to a blasting operation.
Such electronic devices are typically loaded across multiple boreholes of
given blasting
operation. For example, electronic explosives initiators and/or electronic
blast movement
monitor devices may he loaded into multiple boreholes drilled into a blast
site for a given
blasting operation.
The electronic devices may be operated through wired or wireless means.
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While such electronic devices offer numerous advantages, they remain to this
day prone to
failure given the harsh conditions they must endure.
For example, while electronic explosives initiators will ultimately be
destroyed in an explosion
they initiate, such devices are commonly used to initiate a sequenced series
of explosive events
in which a blast wave, part of which constitutes a shockwave, propagating from
an explosion
initiated earlier in the sequence reaches the location of an initiator that
has yet to electronically
initiate its explosion within the sequence or be electronically signalled to
initiate its explosion
within another loaded sequence in the area. Electronic blast movement monitors
are intended
to endure/survive the blasting operations to track movement in the mine site
after the blasting
operation has been completed.
It is therefore important such electronic devices remain functional upon being
subjected to a
shockwave generated remote from the device during a blasting operation.
Electronic components of electronic devices are known to be adversely affected
upon being
subjected to a shockwave generated during the blasting operation. For example,
electronic
devices exposed to so-called "shock-stop" (i.e., the harsh conditions produced
by a shockwave)
can undergo partial or total failure. As those skilled in the art will
appreciate, any type of
malfunction of electronic devices used in association with blasting operations
can cause
significant economic and/or safety concerns.
Despite attempts to develop such borehole resident electronic devices that are
more resistant to
failure due to shock-stop effects, it remains a problem in the art to this
day.
Accordingly, there remains an opportunity to develop borehole resident
electronic devices used
in blasting operations that exhibit improved shock-stop resistance relative to
the electronic
devices currently used in practice.
Summary of the Invention
The present invention provides a borehole resident electronic device for use
in a blasting
operation, the device comprising a container in which is located one or more
electronic
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components, the container having a wall structure comprising a fibre-
reinforced composite
thermoset resin layer positioned to shield the one or more electronic
components from an
explosive shockwave generated during the blasting operation and remote from
the device,
wherein the fibre is in a form selected from unidirectional fibre, woven
fibre, wound fibre,
nonwoven fibre, and combinations thereof.
The present invention also provides a method of shielding one or more
electronic components
of a borehole resident electronic device from an explosive shockwave in a
blasting operation,
the method comprising deploying the device into a borehole of the blasting
operation, wherein
the device comprises a container in which is located the one or more
electronic components,
the container having a wall structure comprising a fibre-reinforced composite
thermoset resin
layer positioned to shield the one or more electronic components from an
explosive shockwave
generated during the blasting operation and remote from the device, and
wherein the fibre is in
a form selected from unidirectional fibre, woven fibre, wound fibre, nonwoven
fibre, and
combinations thereof.
It has now been found borehole resident electronic devices used in blasting
operations can
exhibit improved shock-stop resistance by locating its shockwave sensitive
electronic
componentry within a container having a wall structure comprising a fibre-
reinforced
composite thermoset resin layer positioned such that it shields the electronic
componentry from
the shockwave. Without wishing to be limited by theory, the container having a
wall structure
comprising a fibre-reinforced composite thermoset has been found to dissipate
the force of the
shockwave and also be substantially more resistant to distortion/deformation
upon being
subjected to an explosive shockwave (relative to conventional containers used
in the art).
thereby reducing or preventing damage to the electronic componentry during a
blasting
operation.
The fibre in the reinforced composite thermoset resin layer is in a form
selected from
unidirectional fibre, woven fibre, wound fibre, nonwoven fibre, and
combinations thereof. The
combination of thermoset resin and the fibre form/arrangement has been found
to be
particularly effective at protecting the integrity of electronic components
subjected to an
explosive shockwave. The enhanced shielding effect from the explosive
shockwave afforded
by the thermoset resin layer can advantageously prevent premature failure of
the electronic
componentry and hence the electronic function of the device itself.
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The present invention also provides a method of performing a blasting
operation, the method
comprising deploying a borehole resident electronic device into a borehole of
the blasting
operation, wherein the device comprises a container in which is located one or
more electronic
components, the container having a wall structure comprising a fibre-
reinforced composite
thermoset resin layer positioned to shield the one or more electronic
components from an
explosive shockwave generated during the blasting operation and remote from
the device, and
wherein the fibre is in a form selected from unidirectional fibre, woven
fibre, wound fibre,
nonwoven fibre, and combinations thereof.
In one embodiment, one or more voids are located between the fibre-reinforced
composite
thermoset resin layer and the one or more electronic components.
In a further embodiment, the one or more electronic components are partially
or fully embedded
within a polymer.
In another embodiment, the borehole resident electronic device is in the form
of an explosives
initiator.
In a further embodiment, the borehole resident electronic device is in the
form of a monitor
device.
Examples of monitor devices include those that measure or monitor movement,
temperature,
pressure, and/or magnetic field.
In another embodiment, the borehole resident electronic device is in the form
of a
communications device.
Examples of communications devices also include those capable of relaying or
transmitting
voice, text or data to a remote electronic device.
Additional embodiments and/or aspects of the invention are discussed in more
detail below.
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Brief description of the drawings
Embodiments of the invention are herein described with reference to the
following non-limiting
drawings in which:
Figure 1 illustrates a borehole resident electronic device in the form of a
blast movement
monitor in accordance with the invention;
Figure 2 illustrates a borehole resident electronic device in the form of an
explosives initiator
in accordance with the invention;
Figure 3 illustrates the test rig used in Example 2 where (1) represents the
booster charge, (2a)
and (2b) represent the assembled test samples (with (2a) being comparative and
(2b) being of
the invention), (3) represents an electronic circuit board, (4) represents an
antenna, (5)
represents pressure gauges, (6) shows a representative direction of the
explosives shockwave
derived from booster (1), (7) shows the test rig suspension system, (8)
represents water and (9)
represents air.
Figure 4 shows damage to the antennas of sample (2a) from Example 2;
Figure 5 illustrates a schematic representation of the deformation of the
polycarbonate
casing/sleeve of sample 2a showing: (1) the electronic circuit board, (2) the
antenna, (3) the
original shape of the polycarbonate casing/sleeve, (4) the proposed
deformation shape of the
polycarbonate casing/sleeve due to dynamic pressure (Force) from the
shockwave, (5) the
region of major cracking of the polycarbonate casing/sleeve due to
deformation, and (6) the
impact region on electronic components by the deformed polycarbonate
casing/sleeve;
Figure 6 illustrates results from Example 3 of pressure testing a comparative
polycarbonate
container and a pultruded container of the present invention;
Figure 7 illustrates a schematic of the test set up to measure the internal
pressures in a FWC
sleeve exposed to an explosives shockwave, where (1) represents a booster
charge, (2a)
represents a pressure gauge inside a FWC sleeve (3), (2b) represents a
pressure gauge(s)
attached externally to the FWC sleeve (3), (4) represents aluminium end caps,
(5) represents a
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pressure gauge wire. (6) represents a suspension system, (7) represents water
and (8) represents
air.
Detailed description of the invention
The present invention relates to borehole resident electronic devices for use
in blasting
operations.
By being an "electronic device" is meant the device comprises electronic
componentry
configured to operate one or more features of the device.
By the device being "borehole resident" is meant the device is suitable for
and intended to be
used in a borehole that has been created as part of a blasting operation. In
other words, the
electronic device is one that has been manufactured for use in a borehole
created as part of a
blasting operation. The electronic device therefore has the required
characteristics for being
resident in a borehole of a given blasting operation.
For avoidance of any doubt, by being "borehole resident" it is not meant the
electronic device
per se is limited by way of actually residing in a borehole. Rather the
electronic device is to be
designed and manufactured for and intended to be used in a borehole of a
blasting operation.
The borehole resident electronic device may therefore also be described as
being an electronic
device manufactured for use in a borehole of a blasting operation.
Provided the electronic device can be resident in a borehole and play some
role in a blasting
operation, there is no particular limitation on the specific form and function
of the device.
As the present invention advantageously provides a means for shielding
electronic
componentry from the detrimental effects of an explosive shockwave generated
in a blasting
operation, the specific form and function of the electronic device in a
blasting operation is not
of primary importance.
Examples of suitable borehole resident electronic devices include, but are not
limited to, an
explosives initiator, a monitor device or communications device.
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In one embodiment, the borehole resident electronic device is in the form of
an explosives
initiator.
In another embodiment, the borehole resident electronic device is in the form
of a monitor
device.
In a further embodiment, the borehole resident electronic device is in the
form of a
communications device.
Examples of suitable monitor devices include those for measuring blast
movement of an ore
body, temperature, pressure, magnetic field and combinations thereof. Examples
of suitable
monitor devices also include those for tracking an ore body through a mining
operation.
In one embodiment, the borehole resident electronic device is in the form of a
blast movement
monitor.
In another embodiment, the borehole resident electronic device is in the form
of an ore body
tracking monitor.
Examples of suitable communications devices include the aforementioned monitor
devices and
also devices for transmitting or relaying voice, text or other forms of data.
In the form of an explosives initiator, the borehole resident electronic
device will be capable of
receiving an electronic signal to initiate detonation of an explosives
material that forms part of
the device. Such a device will generally comprise relevant electronic
componentry together
with a primary and possibly also a secondary explosives material. The incoming
electronic
signal triggers detonation of the primary explosive material that can in turn
promote detonation
of the secondary explosive material if present. The function of the explosives
initiator is to
trigger detonation of the primary explosives material, or primary and
secondary explosives
material, which in turn triggers detonation of a tertiary explosives material
that typically resides
together with the initiator device within the borehole. The tertiary
explosives material is
provided in much larger quantities than the initiator-type explosive materials
(primary and
secondary) and will generally be responsible for the main explosive force
output of the blasting
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operation.
Primary, secondary and tertiary explosive materials are well known to those
skilled in the art.
Examples of the primary explosives include, but are not limited to, lead
azide, mercury
fulminate, lead styphnate and diazodinitrophenol.
Examples of the secondary explosives include, but are not limited to,
pentaerythritol tetranitrate
(PETN) and 2, 4, 6-trinotrotoluene (TNT).
Examples of the tertiary explosives include, but are not limited to, ammonium
nitrate ¨based
systems such as ammonium nitrate/fuel oil (ANFO) and ammonium nitrate
emulsions.
Explosive material associated with a borehole resident electronic device in
the form of an
initiator will typically be located within a separate container that is
connected to and in
communication with the one or more electronic components being shielded by the
fibre-
reinforced composite thermoset resin layer in accordance with the invention.
Although not necessarily a requirement, primary or primary and secondary
explosives
associated with the initiator may also be located in the same container with
the one or more
electronic components being shielded by the fibre reinforced composite
thermoset resin layer
in accordance with the invention.
In the form of a monitor or communications device, the borehole resident
electronic device will
be capable of monitoring a particular parameter and/or receiving and/or
sending data including
communications data. The device will comprise appropriate electronic
components to
undertake those tasks.
Irrespective of its practical function, the device in accordance with the
invention comprises a
container in which is located one or more electronic components. Those one or
more electronic
components facilitate one or more functions of the device. The specific nature
of and function
of the one or more electronic components are not particularly relevant in the
context of the
present application in the sense they can represent any type of electronic
component that
facilitates a desired function of the device. Rather, an important feature of
the one or more
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electronic components located in the container in the context of the present
invention is that
they are of a type that can be adversely affected upon being exposed to an
explosive shockwave
and consequently warrant shielding from that shockwave. Most if not all
electronic components
used in such borehole resident electronic devices can be adversely affected
upon being exposed
to an explosive shockwave, prompting the need for the present invention.
The container used in accordance with the present invention is advantageously
resistant to
distortion/deformation upon being subjected to an explosive shockwave.
Accordingly, in
addition to dissipating force of the explosive shockwave on the one or more
electronic
components located therein, the container itself exhibits improved resistance
to undergoing
distortion/deformation upon being exposed to the explosives shockwave and
thereby further
protects the integrity of the one or more electronic components contained
therein.
Those skilled in the art will be able to select and configure suitable
electronic components for
use in a given electronic device as applied in the present invention.
Examples of common electronic components that would be expected to be located
within the
container in the present invention include, but are not limited to, resistors,
capacitors,
microprocessors, antennas, batteries, inductors, sensors such as pressure
sensors, temperature
sensors, magnetic field sensors and accelerometers, circuit boards and
connectors.
Blasting operations contemplated herein are intended to embrace those well-
known in the art,
including surface (open cut) and subsurface (underground) blasting operations.
There is no particular limitation on the shape or size of the container used
in the present
invention. The shape and size of the container will usually be dictated by the
nature of
electronic components required by the device.
For example, the container may have a circular or rectangular cross-sectional
shape. The
container may be spherical or elongated.
To function as a container, it will generally be spherical or have an
elongated dimension so as
to provide depth within the container to locate the one or more electronic
components.
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In one embodiment, the container has a tubular shape with a circular or
rectangular cross-
section.
In another embodiment, the container is spherical.
Where the container has an elongated dimension, for example in the form of a
tubular shape,
the longest dimension or length of the container can, for example, range from
about 50 rum to
about 500 mm. The width of such a container can, for example, range from about
10 mm to
about 100 mm.
Where the container has a spherical shape, it may have, for example, a
diameter ranging from
about 50 mm to about 500 mm.
The container may form all or only part of the electronic device. For example,
the container
housing the one or more electronic components may form only part of the
electronic device
with other features of the device (e.g. non-electronic components) being
associated with the
container but not located therein.
The device may contain one or more electronic components located outside the
container.
However, in that case such electronic components will typically be of a type
that are not
adversely affected by an explosive shockwave.
In one embodiment, all electronic components of the device having potential to
be adversely
affected by an explosive shockvvave are located in the container.
The container used in accordance with the invention has a wall structure
comprising a fibre-
reinforced composite thermoset resin layer. By being a container it will of
course have a wall
structure that defines the container body. For example, the container may be
defined by a
tubular or spherical wall structure and thereby have a tubular or spherical
shape, respectively.
The container is a "container" in the sense it has located within its confines
the one or more
electronic components. In that context, the "container" need not necessarily
have a shape and
configuration suitable for holding or retaining a liquid within it. For
example, as discussed
herein a container in accordance with the invention may be in the form of a
tube open at both
ends that functions as a sheath, sleeve or casing within which the one or more
electronic
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components are contained.
The container can be pre-formed prior to the one or more electronic components
being located
therein. In that case the container will generally be provided with at least
one opening through
which the one or more electronic components may be passed so as to be housed
within the
container. For example, as in a container having a tubular wall structure open
at one end, or
perhaps a container having a spherical wall structure having one opening
therein. The container
may also have two openings, for example, located at opposite ends of the
container in the form
of a tube. In that case, the container may be described as being an open-ended
tube. In use and
after the electronic components have been located therein, the container will
typically have all
such openings sealed.
Alternatively, the container may be formed or created around the one or more
electronic
components. In that case, it will be appreciated the so formed container may
be described as
not having any openings per se through which the one or more electronic
components are
passed so as to become housed therein. In such an embodiment, the one or more
electronic
components may be first located in a sub container around which of the
container in accordance
with the present invention is formed. Such an embodiment advantageously does
away with the
need to seal an opening through which the one or more electronic components
are passed so as
to become located within the container. That in turn can further increase the
structural integrity
of the container and eliminate the chance of defects in sealing the container.
In one embodiment, the one or more electronic components are located in a sub
container and
the container having the fibre reinforced composite thermosetting resin layer
is formed around
the sub container. In a further embodiment, the step of forming the container
having the fibre
reinforced composite thermosetting resin layer around the sub container fully
encapsulates the
sub container.
In another embodiment, the container has a tubular wall structure open at one
or both ends. In
that case, upon the one or more electronic components being located within the
container
through an opening, one or both of the open ends may be sealed, for example
with sealing caps.
An open end of the container may be sealed with the same or different material
from which the
container itself is made. Where some part of the container is sealed with a
material different
from which the container itself is made, that different material may be of a
type that can also
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shield the electronic components from the explosive shockwave. For example,
that different
material may be a different polymer or a metal.
Suitable metals might include, but are not limited to, aluminium, copper,
brass, bronze, steel
and stainless steel.
It should be acknowledged certain metals can exhibit properties suitable to
effectively shield
electronic components from an explosive shockwave.
However, while making the container as described herein entirely from such
metals may prove
effective at shielding the electronic components from an explosive shockwave,
those skilled in
the art will appreciate such metal containers can block the transmission of
electromagnetic
waves, thereby limiting communication for wireless transmitting or receiving
systems
In the context of explosives initiators, metal-based containers can also
present safety concerns
in that they will give rise to dangerous high-energy shrapnel. Certain metals
can also react with
reagents commonly used in explosives operations, for example tertiary
explosive such as
ammonium nitrate, to form highly sensitised and hazardous explosive products.
In addition, such metal-based containers are highly thermally conductive and
prone to
transferring heat from the surrounding borehole environment (e.g. from a high-
temperature
mine site or heated tertiary explosive in which the electronic device is
deployed) to the
electronic components contained therein and adversely affect their
performance.
Manufacturing such containers entirely from metal therefore has numerous
shortcomings.
The containers used in accordance with the present invention not only exhibit
advantageous
properties derived from using polymer in their construction (e.g. having high
transparency to
electromagnetic waves, relatively low thermal conductivity and good chemical
resistance), but
the specific form of fibre-reinforced composite thermoset resin used imparts
shockwave
resistance properties more closely aligned with that of metal containers. The
containers used in
accordance with the present invention therefore can advantageously derive
shock stop
resistance properties approaching or exceeding metals but without many of the
shortcomings
of using metals.
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Having said that, as previously mentioned the containers used in accordance
with the invention
may nevertheless comprise at least some metal components, for example metal
and caps,
provided the function of the electronic components is not adversely affected.
In one embodiment, the container has a tubular wall structure sealed at one
end and open at the
other end. In that case, after the one or more electronic components are
located within the
container, the open end of the tubular wall structure may be sealed. It may be
sealed with the
same or different material from which the container is made.
Where the container has a tubular wall structure open at both ends of the
tube, the container
may simply be used in that form as an outer sheath. That outer sheath may be
placed over and
thereby contain a second or sub-container in which is located the one or more
electronic
components. In such an embodiment the container used in accordance with the
invention has
an open-ended tubular wall structure that functions as a sheath or sleeve and
contains therein a
second container in which the one or more electronic components are located.
In other words,
the container defined in accordance with the invention may itself have located
therein a second
container (sub-container) within which is located the one or more electronic
components.
The one or more electronic components may therefore be located within a sub-
container that
itself is located within the container having a wall structure comprising a
fibre-reinforced
composite thermoset resin layer. Similarly, the container having a wall
structure comprising a
fibre-reinforced composite thermoset resin layer may itself he located in a
super-container or
have an overlaying material (e.g. polymer coating or layer) applied thereto.
To assist with describing of the form of the borehole resident electronic
device according to the
present invention, reference is made to Figure 1. In that case, the electronic
device is
represented in the form of a blast movement monitor or tracker (10). The blast
movement
monitor or tracker (10) comprises a container (20) in which is to be located
the relevant one or
more electronic components (30). The container (20) has a tubular wall
structure sealed at one
end (20a) and open at the other end (20b). The tubular wall structure of the
container (20)
comprises a fibre-reinforced composite thermoset resin layer in which the
fibre is in the form
of unidirectional fibre (not shown). Sub-container (40) is inserted into the
open end (20b). Sub-
container (40) also has a tubular wall structure that is open at least at one
end (40a). The one
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or more electronic components (30) are inserted into the open end (40a). By
sliding parts in
the direction (60), the one or more electronic components (30) is located in
sub-container (40),
which in turn is located in the container (20). Container (20) thereby has the
one or more
electronic components (30) located therein. The open ends (20b) and (40a) are
then sealed with
cap (50) to afford a borehole resident electronic device in accordance with
the invention. The
fibre-reinforced composite thermoset resin layer of the container (20)
functions to shield the
electronic components (30) contained therein from an explosive shockwave
generated remote
from the device.
To assist with describing the form of the borehole resident electronic device
according to the
present invention, reference is made to Figure 2. In that case, the electronic
device is represented
in the form of explosive initiators (10). The explosive initiators (10)
comprise a container (20)
in which is located relevant one or more electronic components (not shown).
The container (20)
has a tubular wall structure with one sealed end (20a) and one open end (20b)
(shown on only
one initiator for clarity). The tubular wall structure of the container (20)
comprises a fibre-
reinforced composite thermoset resin layer in which the fibre is in the form
of wound fibre (not
shown). The container (20) is placed over and thereby contains the electronic
components of
the explosive initiator. The container (20) may be described as functioning as
a sheath or sleeve
that fits over the electronic components. The explosive initiators (10)
include a component (30)
that contains primary and secondary explosives material and which is joined to
the container
(20) at its opened end (20b). The fibre-reinforced composite thermoset resin
layer of the
container (20) functions to shield the electronic components contained therein
from an
explosive shockwave generated remote from the device.
By the wall structure comprising a "fibre-reinforced composite thermoset resin
layer" is meant
the wall has a fibre-reinforced composite thermoset resin composition that
defines a layer
within its structure. That layer may define the entire thickness of the wall
structure or part
thereof. Generally, the fibre-reinforced composite thermoset resin layer will
have a thickness
ranging from about 1 mm to about 10 mm, for example from about 4mm to about 8
mm.
The wall structure of the container may contain one or more layers other than
the fibre-
reinforced composite thermoset resin layer. For example, the wall structure
may comprise a
thermoplastic polymer layer such that it is positioned in between the fibre-
reinforced composite
thermoset resin layer and the one or more electronic components.
Alternatively, the wall
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structure may comprise a thermoplastic polymer layer such as that of the fibre-
reinforced
composite thermoset resin layer is positioned in between the thermoplastic
polymer layer and
the one or more electronic components. The wall structure might also comprise
a thermoset
resin layer absent reinforcement fibre in substitution for the aforementioned
thermoplastic
polymer layer.
There is no particular limitation on the type of thermoset resin that may be
used in forming the
layer.
In one embodiment, the thermoset resin is selected from epoxy, melamine
formaldehyde,
polyester, urea formaldehyde, vinyl ester, phenolic, cyanate esters,
polyimide, maleimide
resins, and combinations thereof.
The thermoset resin forms part of a fibre-reinforced composite. In other
words, the thermoset
resin provides for a polymer matrix throughout which the fibre is located and
gives rise to the
reinforced composite material.
Provided the fibre can present in the composite in a form required in
accordance with the present
invention (discussed below) there is no particular limitation on the material
from which it is
made. For example, the fibre may comprise ceramic, metal, metal oxide, metal
carbide, glass,
polymer or carbon material.
If the fibre to be used in the composite is a polymer fibre, to form a true
composite that polymer
will of course be of a different composition to the thermoset polymer matrix
throughout which
it is located.
In one embodiment, the fibre is glass fibre.
Fibre used in accordance with the invention will generally have a circular
cross-section with a
diameter ranging from about 0.5 pm to about 40 pm, or about 0.5 !MI_ to about
30 p.m, or about
0.8 pm to about 25 i.tm.
The wall structure of the container will define a perimeter and the fibre-
reinforced composite
thermoset resin layer will generally be present along the entire perimeter.
For example, where
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the wall structure is tubular having a circular cross-section, the fibre-
reinforced composite
thermoset resin layer will generally be present around the entire
circumference of that circular
cross-section.
An important feature of the present invention is that the fibre-reinforced
composite thermoset
resin layer is positioned as part of the container to shield the one or more
electronic components
from an explosive shockwave generated during the blasting operation and remote
from the
device. By the resin layer being "positioned to shield" the one or more
electronic components
from the explosive shockwave is meant the resin layer will be located in
between the one or
more electronic components and the general direction of an incoming explosive
shockwave. In
that way, the resin layer serves to protect the one or more electronic
components from the
explosive shockwave.
It will be appreciated the device may itself be an explosives initiator that
generates its own
explosive shockwave and the device will consequently be destroyed in the
process. The
relevant explosive shockwave in accordance with the invention will therefore
be one generated
remote from the device itself.
For example, the electronic device in accordance with the present invention
may represent one
of many explosives initiators used in a blasting operation that provides for a
sequenced
explosives event whereby individual or groups of individual explosives
initiators are shielded
from an explosive shockwave generated remote by other explosives initiators
that form part of
the sequenced explosives event.
Alternatively, an electronic device in accordance with the present invention
may be in a form,
for example a monitoring or communications device, that is not intended to be
destroyed during
the blasting operation. In that case, it remains equally important the
electronic device be
protected from the adverse effects of the explosive shockwave generated in the
blasting
operation.
The fibre-reinforced composite thermoset resin layer has been found to improve
the shock stop
resistance of the borehole resident electronic devices by shielding its
electronic components
from the explosive shockwave. Depending upon the configuration of the
container comprising
the resin layer, the degree of shielding of the electronic components may
vary. Generally, the
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fibre-reinforced composite thermoset resin layer shields at least 50%, 60%,
70%, 80%, 90%,
or 95% of the surface area defined by the one or more electronic components
from the explosive
shockwave originating remote from the device.
An important feature of the fibre-reinforced composite thermoset resin layer
in shielding the
one or more electronic components from the explosive shockwave is that the
fibre embedded
in the resin layer is in a form selected from unidirectional fibre, woven
fibre, wound fibre,
nonwoven fibre, and combinations thereof.
Without wishing to be limited by theory, it is believed the particular form of
fibre used as part
of the fibre-reinforced composite thermoset resin layer imparts to the device
an excellent ability
to shield the one or more electronic components located in the container from
high pressures
imparted by the explosive shockwave. The fibre reinforced composite resin
layer also imparts
excellent structural integrity thereby presenting increased
deformation/distortion resistance to
the container. Those combined properties have been found to protect and
prevent failure of the
device.
In one embodiment, the fibre-reinforced composite thermoset resin layer
shields the one or
more electronic components from an explosive shockwave that exerts on the
device a pressure
ranging from greater than about 200 bar, or greater than about 300 bar, or
greater than about
400 bar, or greater than about 500 bar, or greater than about 600 bar, or
greater than about 700
bar, or greater than about 800 bar, or greater than about 900 bar, or greater
than about 1000 bar,
or greater than about 1100 bar.
In another embodiment, the fibre-reinforced composite thermoset resin layer
shields the one or
more electronic components from an explosive shockwave that exerts on the
device a pressure
ranging from about 200 to about 1100 bar, or about 300 bar to about 1100 bar,
or about 400 bar
to about 1100 bar, or about 500 bar to about 1000 bar, or about 600 bar to
about 1000 bar, or
about 700 bar to about 1000 bar, or about 800 bar to about 1000 bar, or about
900 bar to about
1000 bar.
Containers suitable for use in accordance with the invention (i.e. those
having a wall structure
comprising a fibre-reinforced composite thermoset resin layer in which the
fibre is in a form
selected from unidirectional fibre, woven fibre, wound fibre, nonwoven fibre,
and combinations
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thereof) can be prepared using techniques well-known to those skilled in the
art.
In one embodiment, the fibre used is the form selected from unidirectional
fibre or wound fibre.
For example, fibre-reinforced composite thermoset resin layers having
unidirectional fibre may
be manufactured using a technique known as pultrusion.
Fibre-reinforced composite thermoset resin layers having a woven or nonwoven
fibre may be
manufactured using so called prepregs.
In one embodiment, the fibre used is wound fibre.
Fibre-reinforced composite thermoset resin layers having wound fibre may be
manufactured
using rotating mandrels around which the fibre (also referred to as a roving
or filament) is laid
down. The fibres can be laid down on the rotating mandrel in a desired pattern
or angle to the
rotational axis. Generally, the fibres will be laid down on the rotating
mandrel at an angle
ranging from about 20 to about 90 to the rotational axis.
In one embodiment, the wall structure is elongated and comprises a wound fibre-
reinforced
composite thermoset resin layer in which the wound fibre has an angle ranging
from about 20'
to about 90 or about 30 to about 90 , or about 40 to about 90 , or about 50
to about 90 , or
about 60 to about 90 , or about 70 to about 90 , or about 80 to about 90 ,
or about 90 ,
relative to the axis of elongation.
It is common for wound fibre reinforced composites to include wound fibre
having a
combination of different fibre angles, relative to the access of elongation.
Containers having a wall structure comprising a wound fibre-reinforced
composite thermoset
resin layer have been found to exhibit superior ability to shield the one or
more electronic
components located in the container from high pressures imparted by the
explosive shockwave.
The containers will be manufactured having a suitable size and shape to
accommodate the one
or more electronic components to be located therein. The containers may also
be designed so
as to be coupled to other components that form part of the electronic device.
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Such other components will typically not have a requirement to be shielded
from the explosive
shockwave.
The one or more electronic components may be located within the container such
that one or
more voids are positioned between the fibre-reinforced composite thermoset
resin layer and the
one or more electronic components. In that context, reference to one or more
"voids" is
intended to mean a solid or liquid free space that may be in vacuum or
comprise or a gas, for
example, air, nitrogen, or argon. By positioning one or more voids in between
the electronic
components and the thermoset resin layer of the container it is believed the
shock-stop
resistance afforded by the container can be enhanced. In particular, it is
believed the presence
of such a void reduces propagation of any shockwave passing through the resin
layer and
impacting the electronic components.
In one embodiment, one or more voids are positioned between the fibre-
reinforced composite
thermoset resin layer and the one or more electronic components.
In one embodiment, the one or more voids are filled with a gas.
In a further embodiment, the one or more voids are under vacuum.
In some embodiments, it may also be desirable for the one or more electronic
components to
he coated with or embedded fully or partially in polymer. For example, the one
or more
electronic components located in the container may be so-called "potted".
Examples of
polymers that may coat or embed the one or more electronic components include
polydimethylsiloxane, polyurethane, epoxy resin and melamine resin.
In one embodiment, the one or more electronic components are partially or
fully coated by or
embedded within polymer.
In some embodiments, the one or more electronic components are not partially
or fully coated
by or embedded within polymer.
Where present, the one or more voids may define a distance between the wall
structure of the
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container and the one or more electronic components of at least 0.1 mm.
Generally, the one or
more voids, when present, will define a distance between the wall structure of
the container and
the one or more electronic components of about 0.1 mm to about 10 mm.
The borehole resident electronic devices in accordance with the invention may
be wired or
wireless devices. Where the devices are wireless they will of course comprise
electronic
components that enable the device to wirelessly communicate with a second
remote electronic
device. To facilitate such wireless communication the container may comprise
an aerial or
antenna connected to the one or more electronic components.
The containers used in accordance with the invention can advantageously be
readily fitted with
conventional aerials/antennas.
In one embodiment, the wall structure comprises an aerial or antenna that is
in communication
with the one or more electronic components.
In a similar vein, the containers used in accordance with the invention may
comprise
electrically-conductive wires that can be used to heat the containcr and
assist with regulating
the temperature of the one or more electronic components contained therein.
That heating effect
can be powered by a battery contained in the electronic device and find
application in
environments where the borehole temperature in which the device is deployed is
sufficiently
low to interfere with the function of the electronic components.
In a further embodiment, the wall structure comprises electrically conducting
wire.
In another embodiment, the electrically conducting wire is connected to a
power source and
promotes heating of the container.
The electrically conducting wire may be metallic or polymeric.
The present invention also provides a method of shielding one or more
electronic components
of a borehole resident electronic device from an explosive shockvvave in a
blasting operation.
The method comprising deploying the device into a borehole of the blasting
operation.
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By "shielding" the one or more electronic components is meant at least
protecting them from
the adverse effects of an explosive shockwave. As described herein, the
container in which the
one or more electronic components are located functions to provide that
protection. However,
the container may also serve to protect or shield the one or more electronic
components from
other potentially adverse factors such as the harsh environmental conditions
often presented in
borehole of a blasting operation. Such harsh environmental conditions in
include temperature
extremes and exposure to petroleum products such as diesel and oil, corrosive,
acidic, and basic
conditions.
Shielding the one or more electronic components as described in herein can
advantageously
reduce or prevent premature failure of the one or more electronic components.
By "premature"
failure is intended mean failure of the device absent using a container of the
type in accordance
with the invention. In particular, the type of electronic devices relevant to
the present invention
are intended to perform a particular task or function. Absent the container
used in accordance
with the present invention that task or function may not occur due to one or
more electronic
components in the device failing as a result of being exposed to an explosive
shockwave.
Having failed upon exposure to an explosive shockwave, those one or more
electronic
components will be considered to have undergone premature failure (i.e., they
have not been
able to function as intended). The method in accordance with the present
invention can reduce
or prevent the occurrence of such premature failure through use of the
borehole resident
electronic device as described herein.
Those skilled in the art will be familiar with the process of drilling
boreholes as part of a blasting
operation and the deployment therein of products to effect the blasting
operation or facilitate it
in some way. Such products include the borehole resident electronic devices
described herein,
which may be used in combination with tertiary explosive in a case where the
electronic device
is an explosives initiator.
Producing the boreholes and deployment of such borehole resident electronic
devices can
advantageously be performed in accordance with the invention using techniques
well known to
those skilled in the art.
The present invention also provides a method of performing a blasting
operation, the method
comprising deploying a borehole resident electronic device into a borehole of
the blasting
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operation, wherein the device comprises a container in which is located one or
more electronic
components, the container having a wall structure comprising a fibre-
reinforced composite
thermoset resin layer positioned to shield the one or more electronic
components from an
explosive shockwave generated during the blasting operation and remote from
the device, and
wherein the fibre is in a form selected from unidirectional fibre, woven
fibre, wound fibre,
nonwoven fibre, and combinations thereof.
The present invention further provides use of a borehole resident electronic
device in a blasting
operation, the device comprising a container in which is located one or more
electronic
components, the container having a wall structure comprising a fibre-
reinforced composite
thermoset resin layer positioned to shield the one or more electronic
components from an
explosive shockwave generated during the blasting operation and remote from
the device,
wherein the fibre is in a form selected from unidirectional fibre, woven
fibre, wound fibre,
nonwoven fibre, and combinations thereof.
The present invention also provides use of a borehole resident electronic
device located in
borehole of a blasting operation, the device comprising a container in which
is located one or
more electronic components, the container having a wall structure comprising a
fibre-reinforced
composite thermoset resin layer positioned to shield the one or more
electronic components
from an explosive shockwave generated during the blasting operation and remote
from the
device, wherein the fibre is in a form selected from unidirectional fibre,
woven fibre, wound
fibre, nonwoven fibre, and combinations thereof.
The present invention will hereinafter be described with reference to the
following non-limiting
examples.
EXAMPLES
Example 1
To determine the ability of different configurations to survive damage a trial
was carried out
using an impact tester where a 10Kg weight was dropped from a height of lm
onto a
polycarbonate (comparative), pultruded and fibre wound composite (FWC) sample
container
(made using epoxy resin and glass fibre), all having a wall thickness of -3mm.
The
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polycarbonate sample underwent significant deformation, in some instances
cracking of the
part and a large impression from the impact head of the machine was left in
the sample. The
pultruded sample showed cracking along the length of the tube where the glass
fibre had
delaminated. Only the FWC sample showed negligible damage from the test with
some minor
delamination at the impact point and no loss of integrity of the sample.
Example 2
To compare the performance between polycarbonate (comparative) and FWC
protective
sleeves (where the fibres are wound around the radial direction of a central
core at different
angles) an assembly similar to the structure shown in Figure 1 was tested with
the sleeve (40)
being either made from polycarbonate (comparative) or FWC (of the invention).
The test rig used is described with reference to Figure 3. A 150-gram charge
identified as a
booster (1), pressure gauges (5), the assembled test samples (2a and 2b)
(comprising electronic
circuit board (3) and antenna (4)) were suspended by wooden rod (7), all
spaced at known
distances. The test assembly was lowered into water (8) below an air interface
(9). The
electronic board (3) and antenna (4) were orientated so they faced toward the
shockwave
generated from the detonation of the booster (1).
Sample 2a represents a comparative polycarbonate sleeve system and sample 2b
represents a
FWC sleeve system of the invention, apart from those differences in the
sleeves, the test
samples were the same. The samples were sealed so that the internal atmosphere
was air (9) to
prevent ingress of water (8) which may adversely affect the electronics.
Pressure gauges (5) were placed throughout the test rig to obtain a pressure
profile with distance
and when compared to a calibration chart the actual pressures on the test
samples (2a and 2b)
could he calculated. The test samples (2a and 2h) were placed equidistance on
either side of the
charge (booster) (1) to experience the same pressure profile and allow direct
comparison. The
location of the pressure gauges (5) throughout the experiment is arbitrary
(other than known
distance from the donor charge) and did not affect the result. In Figure 3 the
pressure gauges
(5) are shown on one side of the test set up only, but any number could have
been placed on
either side.
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In Figure 3 the shockwave force (6) is represented for clarity only as going
in one direction
toward sample 2a. It will be appreciated the shockwave from (1) will actually
radiate out in all
directions out from the donor charge (1). Both test samples 2a and 2b received
the same
shockwave force.
The tests were completed a number of times.
On completion of the test, some of the comparative 2a samples exhibited clear
damage to larger
components such as antennas and batteries (see Figure 4). Damage to the
antennas, which
included complete fracture, tended to be located at the extreme edges of the
electronic
components located closest to the wall of the inner casing. After being
subjected to the
explosives shockwave the electronic circuit board of comparative 2a also
failed to function.
Test samples 2b using the FWC in accordance with the invention did not exhibit
any damage
after being subjected to the explosives shockwave and remained fully
functional as per their
intended design.
The electronic componentry of samples 2a and 2b were also contained (in
addition to the
polycarbonate sleeve and FWC sleeve) within an inner polycarbonate casing, not
shown in
Figure 1. For test sample 2a, which used the comparative polycarbonate sleeve,
damage was
also observed to its inner polycarbonate casing. That damage consisted of
longitudinal cracks
along the length of the casing at 900 to the direction of the generated force
(6) as well as several
other large cracks randomly around the comparative sample. It is believed such
longitudinal
cracks are associated with a point of flexure of the inner and outer
polycarbonate
casings/sleeves. As the casings/sleeves of the comparative test sample is
compressed down by
the shockwave it is also forced outwards at 90 to the point shockwave impact
(see Error!
Reference source not found. 5). That extension exceeds the mechanical
properties of the
polycarbonate casing/sleeve causing it to fail in the form of crack stress
relief. Figure 5
illustrates a schematic representation of the deformation of the polycarbonate
casing/sleeve of
sample 2a showing: (1) the electronic circuit board, (2) the antenna, (3) the
original shape of
the polycarbonate casing/sleeve, (4) the proposed deformation shape of the
polycarbonate
casing/sleeve due to dynamic pressure from shockwave, (5) the region of major
cracking of the
polycarbonate casing/sleeve due to deformation, and (6) the impact region on
antenna by the
deformed polycarbonate casing.
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No damage to the inner polycarbonate casing or electronic componentry was
observed for
sample 2a that was shielded/protected from the shockwave buy the FWC sleeve.
Example 3
In a series of trials for the development of the products shown in Figure 2, a
system comprising
of an outer polycarbonate casing, either a polycarbonate (comparative) or a
pultruded inner
sleeve, and an inner polycarbonate casing, in which was housed the electronics
for the control
system, was tested at pressures between 200 and 1200 bar (without the
explosive booster
labelled (30) in Figure 2). Following exposure to the explosives shockwave,
the samples were
examined for integrity of the casings/sleeves and damage to the electronics
board and
components. A sample was considered to pass if the total system appeared
undamaged. The
sample with the pultruded sleeve passed the test at pressures nearly double
than could be
sustained by the comparative system using the polycarbonate sleeve (see Figure
6).
Example 4
To determine the effect of a FWC sleeve (of the invention) to reduce the
incident pressure
experienced by the electronics contained therein a test using the set up shown
in Figure 7 was
performed. A pressure gauge (2a) was placed centrally inside the FWC sleeve
(3). To prevent
water ingress during the experiment the FWC sleeve (3) was sealed using
aluminium end caps
(4) which were glued onto the ends of the FWC sleeve (3). The top end cap (4)
had a hole
drilled through it to allow the pressure gauge wire (5) to pass through and
this hole was sealed
with epoxy resin to prevent water ingress during the experiment. The internal
environment
within the sleeve during the test was air (8). A second pressure gauge (2b)
was attached to the
outside wall of the FWC sleeve (3) to measure the incident pressure delivered
by the charge
booster (1). The booster (1) and FWC sleeve (3) assembly were suspended from
wooden rods
(6) and suspended in water (7) beneath an air interface (8). Suspension in
water ensured direct
coupling of the shockwave and the sample. By measuring the distance between
the charge
booster (1) and the pressure sensor (2b) attached to the outside wall of the
FWC sleeve (3) and
the use of calibration curves the incident pressure can be calculated. Based
on the measured
signal from the pressure gauge (2a) inside the FWC sleeve assembly (3 and 4)
and use of the
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calibration curve the pressure exerted on the internal sensor (2(a)) can be
calculated. The
expected pressure that the internal sensor (2a) should experience based on its
distance from the
donor charge (1) if the protective FWC sleeve (3) had not been in place can
also be calculated
using the known distance and calibration curve.
Six samples were tested in the Figure 7 set up. Based on previous calibration
curves the
expected pressures and the measured pressures without and with the FWC sleeve
in place could
be determined. As shown Table 1 there is a significant drop in measured
pressure for all 6
samples compared to the calculated expected pressure if the FWC sleeve had not
been present.
Table 1: Pressure data
Thctanc¨\\1
\\I
.\\\\ --\\\bir1.\\\ \\\\
gica(Jtdoke.
gi
150 6.07M 608
N/A
Free Field)
..t.RG gauge
157 57/ 581
N/A
(Free. Field)
MF'Ci D R X C. 1 108 19 861
1137
D R X 021 12 19927
*iii#GP R X miiii6$
8
. =
RiD:RXC 4 113 24 819 1066
FGD:RXC 6 130 34 : 711 892
That data demonstrates the effectiveness of the fibre-reinforced composite
thermoset resin layer
used in accordance with the invention to shield/protect electronic components
from an
explosive shockwave.
The reference in this specification to any prior publication (or information
derived from it), or
to any matter which is known, is not, and should not be taken as an
acknowledgment or
admission or any form of suggestion that that prior publication (or
information derived from it)
or known matter forms part of the common general knowledge in the field of
endeavour to
which this specification relates.
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Throughout this specification and the claims which follow, unless the context
requires
otherwise, the word "comprise", and variations such as ''comprises" and
"comprising", will be
understood to imply the inclusion of a stated integer or step or group of
integers or steps but
not the exclusion of any other integer or step or group of integers or steps.
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