Note: Descriptions are shown in the official language in which they were submitted.
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NS-488
CONDUIT LINER WITH WEAR-RESISTANT ELEMENTS
Inventors: Soon Won Moon, Stefano Chiovelli
Assignee: Syncrude Canada Ltd. In Trust for the Owners of the Syncrude Project
File No. 53707.478
Field of the Invention
[0001] The present invention relates to conduits having a liner with
protective wear-resistant
elements, and in particular, hard material segments embedded in and backed by
an elastomer.
Background
[0002] Mining products are frequently transported as slurries, which causes
considerable wear
within pipes. Large rubber hoses with rubber liners have comparatively much
better wear
properties, primarily due to the energy-dampening capability of the rubber
liner through
elastic deformation. In the same way, elastomer-lined pipes also provide good
wear
performance in many high wear locations.
[0003] However, when the impact energy of the solid slurry particles exceeds
the elastic
capability of the liner, permanent damage may result in the form of gouging or
tearing of the
liner. Thus, the size of solid particles, speed of the slurry flow, and flow
characteristics are
parameters which affect the application window of rubber hoses or elastomer-
lined pipes. In
particular, the speed of the slurry flow is sometimes a critical factor
limiting the usage of
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rubber hose or elastomer-lined pipes. If a particular location is subject to
high slurry flow
speed, an impingement point may exist, and the liner may fail due to localized
damage at the
impingement point.
[0004] It is known to use wear-resistant material such as tungsten carbide
overlaid pipe in
such cases, however such material is prohibitively expensive.
Summary Of The Invention
[0005] In one aspect, the invention may comprise a conduit, such as a pipe or
a hose defining
an inner bore, having an elastomeric liner comprising at least one, and
preferably a plurality of
embedded hard material segments, embedded in and backed by the elastomeric
liner, and
exposed to the inner bore.
[0006] In one embodiment, the conduit elastomeric liner comprises a rubber or
apolyurethane.
The hard material segment may comprise tungsten carbide, or sintered tungsten
carbide, a
cermet, or a ceramic material. The hard material segments may comprise a three-
dimensional
shape comprising tiles, blocks, cylinders, spheres, or ovoids. The hard
material segments may
have a two-dimensional shape which faces the conduit bore comprising squares,
rectangles,
circles, ovals, hexagons or other polygons, or combinations thereof
[0007] In one embodiment, the hard material segments are tiles, which may be
rectangular,
and which may be parallel to or angled away from a plane which is parallel to
a central axis of
a conduit which is straight, or a plane tangential to the central axis of a
conduit which is
curved.
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Brief Description of the Drawings
[0008] The following drawings form part of the specification and are included
to further
demonstrate certain embodiments or various aspects of the invention. In some
instances,
embodiments of the invention can be best understood by referring to the
accompanying
drawings in combination with the detailed description presented herein. The
description and
accompanying drawings may highlight a certain specific example, or a certain
aspect of the
invention. However, one skilled in the art will understand that portions of
the example or
aspect may be used in combination with other examples or aspects of the
invention.
[0009] Figure 1 is a cross-sectional view of one embodiment of a hose of the
present
invention.
[0010] Figure 2A is a cross-sectional view in the liner along a longitudinal
plane of one
embodiment while Figure 2B is a schematic view of the inner bore of the same
embodiment.
[0011] Figure 3A is a cross-sectional view in the liner along a longitudinal
plane of one
embodiment while Figure 3B is a schematic view of the inner bore of the same
embodiment.
[0012] Figure 4A is a schematic view of the inner bore of one embodiment
showing
hexagonal tiles while Figure 4B is a schematic view of the inner bore of an
alternative
embodiment of hexagonal tiles.
[0013] Figure 5A is a schematic view of the inner bore of one embodiment
showing
rectangular tiles axially staggered. Figure 5B is a schematic view of the
inner bore of an
alternative embodiment showing rectangular tiles longitudinally staggered.
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[0014] Figure 6 is a cross-sectional view of one embodiment, showing a
simulated impact by
a rock.
[0015] Figure 7 is a cross-sectional view of an alternative embodiment,
showing embedded
tiles which are angled.
[0016] Figure 8 is a view of the embodiment of Figure 7, with rubber wear.
[0017] Figure 9 is a cross-sectional view of an alternative embodiment, where
the tiles are
angled at a shallower angle than shown in Figure 7, and with rubber wear.
[0018] Figure 10 is a schematic representation of chemical bonding between an
elastomer and
a wear-resistant material, with a primer layer and an adhesive layer.
Detailed Description
[0019] As used herein, the recited terms have the following meanings. All
other terms and
phrases used in this specification have their ordinary meanings as one of
skill in the art would
understand.
[0020] To the extent that the following description is of a specific
embodiment or a particular
use of the invention, it is intended to be illustrative only, and not limiting
of the claimed
invention. The following description is intended to cover all alternatives,
modifications and
equivalents that are included in the spirit and scope of the invention, as
defined in the
appended claims. References in the specification to one embodiment", "an
embodiment",
etc., indicate that the embodiment described may include a particular aspect,
feature, structure,
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or characteristic, but not every embodiment necessarily includes that aspect,
feature, structure,
or characteristic. Moreover, such phrases may, but do not necessarily, refer
to the same
embodiment referred to in other portions of the specification. Further, when a
particular
aspect, feature, structure, or characteristic is described or claimed in
connection with an
embodiment, it is within the knowledge of one skilled in the art to affect or
connect such
aspect, feature, structure, or characteristic with other embodiments, whether
or not explicitly
described.
[0021] The present invention comprises a conduit having an elastomeric liner
comprising at
least one hard material segment embedded in and backed by the elastomeric
liner and exposed
to the conduit inner bore, and preferably a plurality of hard material
segments. The embedded
segments provide additional wear resistance, however, the primary role of the
segments is to
protect the elastomeric liner underneath. The hard material segments are
positioned over the
elastomeric liner at high impact / impingement locations so that the
elastomeric liner
underneath the segments are protected from high energy impacts. Elastomers
backing the
hard material segments may provide an energy dampening function, thereby
reducing the net
impact energy directly imparted onto the hard material segments. In this
sense, embodiments
of the present invention are distinct from overlay coatings of a wear-
resistant material. The
hard material of this invention should be segmented so that impact energy can
be effectively
transferred to the elastomer behind the segment.
[0022] The conduit may be a pipe having a rigid outer layer, or a hose. As
shown
schematically in Figure 1, in one embodiment, a hose (10) comprises an
elastomeric liner
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(12), a reinforcing layer (14) such as a fabric reinforcing layer to provide
mechanical strength
to the hose, and an outer elastomeric layer (16). In elastomer-lined pipes,
the liner may have a
monolayer or a multilayered construction.
[0023] As used herein, a "hard material" is any material known to have greater
mechanical
strength than the underlying elastomer and good abrasion resistance. Such
material may
include, without limitation, metallic materials, ceramic or non-ceramic
carbides such as
chromium carbide, tungsten carbide, or a cermet such as sintered tungsten
carbide. Sintered
tungsten carbide, also known as cemented carbide, is a composite material
comprising
tungsten carbide powder mixed with a binder metal such as cobalt or nickel,
compacted in a
die and then sintered at a very high temperature. Wear-resistant materials may
also include
various ceramic materials such as alumina or a nitride such as silicon
nitride. As used herein,
a ceramic material is an inorganic, non-metallic, oxide, nitride or carbide
material, which may
or may not be crystalline. Suitable hard materials are well known in the art
and are readily
commercially available.
[0024] As used herein, an elastomer is a polymer having the property of
elasticity, whereby
the polymer deforms in response to the application of stress, and
substantially recovers its
original form when the stress is removed. Elastomers typically have a low
Young's modulus
and a high yield strain, as is well known in the art. Suitable elastomers
include, without
limitation, natural ot synthetic rubbers, polyurethanes, thermoplastic
polymers, and other
thelmoset polymers.
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,
[0025] In one embodiment, the liner (12) is embedded with a plurality of wear-
resistant
segments (20). The segments (20) may be present throughout the entire conduit,
or localized
in high wear locations. The segments are preferably separated by gaps (18)
which are filled
by the elastomer.
[0026] The segments (20) may have a three-dimensional shape including, without
limitation,
tiles, blocks, cylinders, spheres, or ovoids. The segments may have a two-
dimensional shape
which faces the conduit bore including, without limitation, squares,
rectangles, circles, ovals,
hexagons or other polygons, or combinations thereof. The hard material
segments should be
thick enough to resist the expected bending stress under impact conditions.
[0027] For example, in one embodiment, the segments (20) are tiles as shown in
Figure 1.
The tiles may be flat or curved according to the curvature of the conduit
bore. In another
embodiment, the segments (20) are spherical, as shown in Figures 2A and 2B. In
another
embodiment, the segments (20) are cylindrical, embedded in an upright
orientation, as is
shown in Figures 3A and 3B. Alternatively, cylindrical segments (20) may be
embedded
longitudinally. In another embodiment, the segments (20) may be tiles which
have a
hexagonal two-dimensional shape, as shown in Figures 4A and 4B. In Figure 4B,
the
segments are spaced much closer together, reducing the surface area of
elastomer which is
exposed to the fluid flowing in the bore In another alternative, the segments
(20) comprise
tiles having a rectangular two-dimensional shapes. The rectangular segments
may be
staggered in at least one direction, for example, axially (Figure 5A) or
longitudinally (Figure
5B).
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[0028] As may be apparent, there are numerous options as to the shape and
configuration of
the segments (20), and the above exemplary description of alternatives should
not be
considered limiting of the claimed invention.
[0029] The segments (20) present a wear-resistant hard face to the material
flowing in the
conduit bore, while being backed by and surrounded by a resilient elastomer
material. In one
embodiment, the segments are substantially level with the surrounding
elastomer in order to
present a smooth bore for the fluid flowing in the conduit. The elastomer gaps
(18) between
segments provide some energy dampening capacity in the longitudinal direction.
The
elastomer backing (12) absorbs a significant amount of impact energy from
larger slurry
particles, thereby reducing the risk of fracture damage of the segments.
[0030] In embodiments of the invention, the elastomeric liner (12) provides an
energy
dampening function to mitigate the impact damage on the hard material segments
(20).
Accordingly, the thickness of the wear-resistant segments and the elastomeric
liner backing
may be configured to minimize the propensity of the segments to crack in
response to particle
impact. The shape and size of the hard material segment; the degree of energy
absorbing
capability of the elastomer; and the environmental conditions such as solid
particle size,
impact velocity, temperature, etc. may also be factors to consider.
[0031] In one embodiment, the thickness of hard material segments is in the
range of about 5
to about 50 mm, while the thickness of the elastomer backing may be in the
range of of about
mm to about 100 mm. The elastomer backing must be thick enough, having regard
to its
energy dampening capacity, to adequately cushion impacts to the hard material
segments. In
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one embodiment, the ratio of the hard material segment thickness to the
elastomer backing
thickness may be about 1:1 to about 1:4.
[0032] In one particular embodiment, the segments comprise planar tungsten
carbide tiles (30)
having a thickness of about 13 mm, while the elastomer comprises a rubber
layer having a
thickness of about 38 mm. The tiles are spaced apart by gaps (18) which are
about 13 mm
wide.
[0033] Simulations using finite element analysis indicate that impact stress
on the segments
(20) may be decreased by up to about 80% because of the elastomer backing
layer. Figure 6
shows a schematic of one simulation configuration. The test conditions shown
in Figure 6
considered the simulated impact of a rock (R) which impacts a tungsten carbide
tile (20) at an
angle of 45 .
[0034] In an alternative embodiment, the wear-resistant segments may be planar
tiles (30)
which are embedded in the elastomeric liner at an angle, preferably angled
towards the
direction of flow within the conduit such that rocks that impact the tiles are
likely to do so at a
direct angle, as opposed to an oblique angle. Specifically, as shown in Figure
7, the tiles (30)
may be angled at an angle a, which may be range from about 5 to about 90 ,
and preferably
between about 10 and 45 , and more preferably between about 20 and 30 . This
angle a is
measured from a plane which is parallel to a central axis of a conduit which
is straight, or a
plane tangential to the central axis of a conduit which is curved. If angle a
is 0 , then the tile
is parallel to the central axis, or a plane tangential to the central axis.
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[0035] In one embodiment as shown in Figure 7, less of the surface area of the
inner bore is a
hard material wear-resistant surface, but may have a greater impact absorption
capability. The
elastomer surface may then wear away, exposing more of the tiles (30), such
that the tiles may
protrude slightly from elastomer liner (12), as shown schematically in Figure
8. Simulation
testing has shown that while maximum principal stresses caused by rock impacts
increase
when the elastomer wears away, the peak stresses are still below the level
which would cause
fracture of tungsten carbide tiles of sufficient thickness. Maximum principal
stresses in the
hard material tiles may be reduced by increasing tile thickness.
[0036] Maximum principal stresses in the elastomer may be decreased by
increasing the hard
material tile thickness. The angle a does not appear to have a significant
effect on elastomer
maximum principal stress.
[0037] The interface adhesion strength between the hard material segments and
the elastomer
layer must be greater than the forces which would tend to separate the two. In
a preferred
embodiment, the interface adhesion between the two includes chemical bonding.
Without
chemical bonding, cured elastomer adheres to the metal surface by means of
physical interlock
at the microscopic level. It is common practice when using adhesives to bond
polymers and
metal to deliberately increase the surface roughness of the metal component to
promote this
microscopic interlock. Chemical bonding provides adhesion at the molecular
bond level, and
may work well even with polished surfaces. Instead of microscopic material
shear provided
by the mechanical interlock of surface roughness, adhesion is created via
atomic forces. For
this reason, such bonds can exceed the shear resistance of the elastomer
itself. If one were to
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forcibly separate the bonded components so described, the bond surface would
be covered
with a thin layer of the elastomer. Such destructive testing is commonly
employed in the
manufacture of elastomeric-metal composites. Examples of such are well
described in the
American Society for Testing and Materials (ASTM) publication: ASTM D429 ¨ 14,
Standard
Test Methods for Rubber Property¨Adhesion to Rigid Substrates.
[0038] Chemical bonding may be exemplified by, but is not limited to, the type
of vulcanized
bond commonly used in vibration isolation components, automotive tires,
conveyor belts, and
other rubber-metal composites known in other arts.
[0039] In one embodiment, a bonding agent is used, and may comprise a single
coat material
placed between the hard material and the elastomer. The bonding mechanisms of
the
multiphase systems involved in making elastomer to hard material bonds are
complex and the
chemistry of the reactions involved may not be totally disclosed or understood
in the art.
Descriptions of such bonds may be found in the prior art, such as US Patent
6,632,319
assigned to Bridgestone Corporation, and US Patent 5,268,404 assigned to Lord
Corporation,
the entire contents of which are incorporated herein by reference, where
permitted.
[0040) Therefore, in one embodiment, and depending on the specific elastomer
and hard
material, an additional primer coat may be applied to the hard material, and a
cover coat is
applied thereon which adheres between the elastomer and the primer. Such a two-
coat primer
and bonding agent system is shown schematically in Figure 10.
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[0041] A primer layer (40) and adhesive layer (41) is shown between the hard
material (10)
and the elastomer (11). Prior to curing, chemical agents in the primer layer
(40) diffuse into
the substrate material (10, 12) by chemisorption as illustrated by arrows
(42). Chemical
agents in the adhesive layer 41 diffuse into the elastomer layer (11) as
illustrated by arrows
(43). In addition, chemical agents inter-diffuse between the primer and
adhesive layers (40,
41) as shown by arrows (44).
[0042] Upon curing, crosslinks (45) form between the polymer chains in the
elastomer.
Internal crosslinks are formed between the polymer chains of the adhesive
layer (41) as
depicted by (46). And similarly, internal crosslinks (47) are formed between
the polymer
chains of the primer layer (40).
[0043] Crossbridging reactions then form chemical bonds or linkages (48, 49,
50) between the
respective layers which have been assisted by the chemisorption, and inter-
diffusion as
described above.
[0044] Those skilled in the art are aware that creating an effective chemical
bond between an
elastomer and a hard material requires suitable surface preparation. Any
contamination of the
surfaces at any interface will reduce the bond strength. For example, to
prepare a metal
surface, all traces of oil, grease or solid lubricant must be completely
removed from the metal
surface. Degreasing and shot blast, and wet blast followed by a phosphate
conversion methods
are suitable.
Definitions and Interpretation
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[0045] The singular forms "a," "an," and "the" include plural reference unless
the context
clearly dictates otherwise. It is further noted that the claims may be drafted
to exclude any
optional element. As such, this statement is intended to serve as antecedent
basis for the use
of exclusive terminology, such as "solely," "only," and the like, in
connection with the
recitation of claim elements or use of a "negative" limitation. The terms
"preferably,"
"preferred," "prefer," "optionally," "may," and similar terms are used to
indicate that an item,
condition or step being referred to is an optional (not required) feature of
the invention.
[0046] The term "and/or" means any one of the items, any combination of the
items, or all of
the items with which this term is associated. The phrase "one or more" is
readily understood
by one of skill in the art, particularly when read in context of its usage.
[0047] As will be understood by one skilled in the art, for any and all
purposes, particularly in
terms of providing a written description, all ranges recited herein also
encompass any and all
possible sub-ranges and combinations of sub-ranges thereof, as well as the
individual values
making up the range, particularly integer values. A recited range of values
includes each
specific value, integer, decimal, or identity within the range. Any listed
range can be easily
recognized as sufficiently describing and enabling the same range being broken
down into at
least equal halves, thirds, quarters, fifths, or tenths. As a non-limiting
example, each range
discussed herein can be readily broken down into a lower third, middle third
and upper third,
etc.
[0048] As will also be understood by one skilled in the art, all language such
as "up to", "at
least", "greater than", "less than", "more than", "or more", and the like,
include the number
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recited and such terms refer to ranges that can be subsequently broken down
into sub-ranges
as discussed above. In the same manner, all ratios recited herein also include
all sub-ratios
falling within the broader ratio. Accordingly, specific values recited for
radicals, substituents,
and ranges, are for illustration only; they do not exclude other defined
values or other values
within defined ranges for radicals and substituents.
[0049] One skilled in the art will also readily recognize that where members
are grouped
together in a common manner, such as in a Markush group, the invention
encompasses not
only the entire group listed as a whole, but each member of the group
individually and all
possible subgroups of the main group. Additionally, for all purposes, the
invention
encompasses not only the main group, but also the main group absent one or
more of the
group members. The invention therefore envisages the explicit exclusion of any
one or more
of members of a recited group. Accordingly, provisos may apply to any of the
disclosed
categories or embodiments whereby any one or more of the recited elements,
species, or
embodiments, may be excluded from such categories or embodiments, for example,
as used in
an explicit negative limitation.
[0050] As will be apparent to those skilled in the art, various modifications,
adaptations and
variations of the foregoing specific disclosure can be made without departing
from the scope
of the invention claimed herein. The various features and elements of the
invention described
herein may be combined in a manner different than the specific examples
described or
claimed herein without departing from the scope of the invention. In other
words, any
element or feature may be combined with any other element or feature in
different
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embodiments, unless there is an obvious or inherent incompatibility between
the two, or it is
specifically excluded.
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