Note: Descriptions are shown in the official language in which they were submitted.
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SHELL LINER ASSEMBLY FOR ORE GRINDING MIL1S
;3ACKGROUND OF THE INVENTION
The invention relates generally to apparatus for
comminuting ore, and is specifically directed to an im-
proved liner assembly for an ore grinding mill used incommercial mining operations.
Grinding mills of -this type may employ rods or
balls to assist in the comminuting process as the mill is
rotated, or the ore may be self-grinding in large auto-
matic mills. An example of the latter type mill consists
of a large cylindrical drum mounted on bearings for rota
tion about a substantially horizontal axis and dri~en by a
powerful motor through conventional reduction gearing. The 1
axial ends of the drum are open, and -the material to be ;~
comminuted is continuously fed into the mill at one end
with the comminuted product continuously emerging from the
other end.
From the economic standpoint, it is important to
keep any t~pe of ore grinding mill in operation as con-
tinuously as possible, keeping the do~ltime for main-ten~
ance or repair to a minimum. However, many ores ~e.g.,
taconite) are extremely hard and highly abrasive, and in
order to maintain continuous operation o~ the grinding
mill it is necessary to provide a liner ~or the drum which
is highly abrasion resis-tant, and also tough enough to
withstand the continuous impact of the ore ~ragments.
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Due -to size and weigh-t considerations, liner
assemblies for ore grinding mills of this type are typi-
cally segmented; i.e., they comprise a plurality of
separa-te components that are individually secured to the
drum of shell o~ the mill. My earlier U.S. Pate~-t No.
4,018,393* is directed to liner segments which are formed
with sockets of a special shape and disposed at predeter-
mined intervals, and which are held within the cylindrical
shell ~y bolts having heads received in the soc~ets and
threaded shanks passing through the liner segments and the
mill shell to receive nu-ts at the outer surface. Th~
sockets and heads are shaped to provide continuous flat
contact areas of substantial size regardless of variations
in center dis-tances of holes axially along the shell.
This particular approach to securing the se~nent
and liners to the shell has represented a significant im-
provement due to previous difficulties in obtaining regis-
tration of bolt holes in the segments and shell, and
continuous flush engagemen-t of contiguous surfaces. How-
ever, as was recognized in my later issued U. S. Patent~o. 4,046,326,** the structural configuration of liner
se~nents is necessarily complex, and does not lend itself
to fabrication from materials which are highly abrasion
resistan-t. Examples of ideal materials for this use are
martensitic white iron or martensitic steel, both of which
are extremely abrasion resistant. However, since mater-
ials such as these undergo a significant volume change as
thëy pass from the austenitic stage to martensitic form,
it is extremely difficult to form from such materials an
article o:~ significant size or complex configuration since
the transformation from martensite, as the result of rapid
cooling, may crack the article and render it useless in an
ore crushing operation. Thus, prior to the invention
disclosed and claimed in U. S. Patent No. 4,046,326
segmented liners were usually made from a "tough" material
which o~fered relatively good resistance to impact, al-
* Issued 18 Aprll, 1977 to Minneapolis Electric Steel Castings
CompanyO
** Issued 6 September, 1977 to -2-
Minneapolls Electric Steet Castings Company
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though its resistance to abrasion was somewhat lower~ My later
patent was, therefore directed to a liner assembly in which the
primary structure of each liner segment is made from a ~Itough~
material, coupled with the use of one or more inserts formed
from highly abras;on resistant material in a manner such that
the insert or inserts represent primary exposure to the ore
ragments but are always retained, even if they break due to
brittleness. This is accomplished through the formation of an
opening extending entirely through the liner assembly, and which
has tapered sides converging toward the exposed surface. The
inserts axe of conforming shape and size, having similar con-
verging sides which engage and wedge against those oE the
segment opening. The inserts are placed into the segment
opening Erom its back or unexposed side, projecting through to
the exposed surface but being retained in this posikion by th~
wedging action. As the liner segment is bolted to the shell,
the inserts are positively and rigidly retained, capable of com-
minuting the ore, but incapable of escape~ With such an
assembly, the inserts can be made in fairly simple con-
figurations, to overcome the fabrication problem mentionedabove, and thus enabling the benefits of abrasion resistant
materials.
Copending Canadian application Serial No. 333,432 and
applicant's copending Canadian patent application Serial No.
351,103 are both directed to an improved liner assembly for ore
grinding mills which simplifies replacement of the assembly
while at the same time preserving the substantial benefit
derived from the use of the abrasion-resistant inserts. These
improved assemblies comprise a plurality of holder segments
formed from tough, impact-resistant material which are Eastened
directly to the shell in a conventional mannex. The assemblies
further comprise a second plurality of liner segments formed
from abrasion-resistant material which "cap" the holder segments
and are uniquely connected directly thereto without any mounting
connection to the shell itself.
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In the liner assemblies disclosed in Serial Nos.
333,432 and 351,103, provision is made for protecting the means
Eor fastening the abrasion resistant caps to the holder segments
from ore fragments so that, even if the liner is substantially
worn, there is less diEficulty in removing the abrasion
resistant caps.
Provision is also made in these liner assemblies for
protecting the means for fastening the holder segments ko the
shell from damage by ore fragments, which permits easier
replacement of the holder segments as this becomes necessary.
More specifically, the holder segments are provided with trans-
verse mounting openings through which bolts extend, projecting
outwardly of the shell to receive the threaded nuts. These
mounted openings are positioned so that the abrasion resiskant
wear caps protectively overlie the mounting openings of the
holder segments as well as the mounting bolts which khey
receive.
However, in the liner assemblies of bokh Serial Nos.
333,432 and 351,103, the holder segmenks are exposed in part to
ore fragmenks and wear during the comminution process. 5ince
the holder segmenks are formed from material having a lesser
resistance ko abrasion than khat of khe wear caps, wear occurs
in these exposed areas and replacement eventually becomes
necessary, albeit less frequently than the rake of replacemenk
of the wear caps.
The invenkion of this application is thus directed to
an improved liner assembly for ore grinding mills of khe
segmented type comprising a plurality of holder segments and a
plurality of wear segmenks, the holder and wear segments being
uniquely configured so that the former is prokectively covered
by the latter substantially in its entirety. Stated otherwise,
khe holder segments are substantially unexposed ko the ore com-
minution process, and, to the extent that wear of the liner is
properly moni~ored; the holder segmenks do not become worn at
all. ~;
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An additional advantage is that the wear seg-
ments, in protectively overl~ing the holder segments, also
protectively overlie the means for mounting the holder
segments to the shell, so that replacement of the holder
segments, when this e~entua:Lly becomes necessary, is
simplified because there is no damage to the holder seg-
ment or its mounting means during the comminution process.
~ his composite approach to the segmented liner
assembly is significant and advan-tageous for several
reasons. First, the lower or holder segment can be formed
from material which does not have high resistance to
abrasion or high impact resistance. Because it is not
exposed, its sole function is to support the upper or wear
element. To the extent that it does not become e~posed to
the comminution process, which is accomplished by careful
monitoring of the wear of the upper segments, the lower or
holder segments will last through several replacements of
the wear segments.
The fact that the holder segments can be made
f~om material of lesser wear characteristics is a signifi-
cant advantage both with respect to weight and economy.
The material of the upper wear segments preferably exhib~
its ~igh resistance to abrasion, examples of which are
martensitic white iron or steel. These materials are not
only much heavier, but also significantly more costly.
Conse~uently, the substitution of a lesser material in
this inventive structural combination does not impair
performance, but effects both a reduction i.n weight and in
cost.
As pointed out above, it is difficult to cast
articles from abrasion res:istant material which are of
significant size or complex configuration. Further, it is
difficult to manufacture such products with any degree of
close tolerance, and obviously, a product which is highly
i abrasion resistant does not lend itself to machining.
However, it is important for the holder and wear segment~
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to fit together reasonably well so that forces of impact aredistributed and withstood uniformly. This is particularly dif-
ficult where the area oE interface hetween the holder and wear
segments is significant in size. In view of this, the pre-
Eerred embodiment of the inventive liner assembly includes a
layer of rubberized fabric or the functional equivalent
thereof. The resilient nature of this layer covers imperfec-
tions in the castings and is therefore a significant advantage
to the foundry In addition, the layer assists in distributing
forces of impact, and it is easily replaceable. Lastly, it
serves as a visual indicator to the mill operator that replace-
ment of the wear segments is necessary when the layer can be
seen.
The interconnection between the holder and wear
segments is also unique through the provision of a ~lurality of
luys or bosses projectincl downward from the wear segments, and
similarly configured recesses in the holder segments. These
bosses ~roject through the entire thicknesc of the holder
segment and approach contact with the drum surface itself.
Mounting openings are formed transversely through the wear
segments in the center of the bosses. Because of this struc-
tural configuration, the head of each mounting bolt used to
secure the wear segments ~o the shell are oriented much more
closely to the inner shell surface, which means that the wear
segment can be worn down to a greater degree without damaging
the mounting bolts and loosening the wear segments~. This also
leads to greater time between liner assembly changes and econo-
mic savings in the overall operation.
In one broad form, the invention resides in a liner
assembly for the cylindrical shell of an ore grinding machine,
which comprises first and second liner segments of predeter-
mined si%e and configuration. Each of the first liner segments
defines a bottom mounting surface constructed for mounting
engagement with the inner surface of the cylindrical shell and
a top mounting surface, and each includes a plurality of
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mounting openings formed transversely therethrough. Each of
the second liner segments defines a bottom mounting surface
constructed for mounting engagement with the top mounting sur-
face of an associated first liner segment, and further defines
a top grinding surface for comminuting the oreO The liner
assembly further comprises first connecting means comprising a
plurality of mounting bolts extending through the mounting
openings for mounting ~he first liner segments directly to the
cylindrical shell of the ore grinding machine independently of
the second liner segments, and second connecting means for
mounting each of the second liner segments on an associated one
of the first liner segments, the second connecting means con-
structed and arranged to permit removal of a second liner
segment from the associated first liner segment without
removing the associated first liner segment from the cylindri-
cal shell. The first and second liner segments are so con
structed that the first liner segments, the mounting openings
and mounting bolts are protectively covered by the second liner
segments in assembled relation and virtually unexposed to the
ore comminution process.
In another broad form, the invention resides in a
liner assembly or the cylindrical shell of an ore grinding
machine which comprises a plurality of first liner segments of
predetermined size and configuration, each defining a bottom
mounting surface constructed for mounting engagement with the
inner surface of the cylindrical shell, and each further
defining a top mounting surface. The first liner segments are
disposed in close proximity to each other with minimum space
therebetween so that the plurality of first liner segments
covers virtually the entirety of the cylindrical shell. The
liner assembly further comprises a plurality of second liner
segments of predetermined size and configuration, each defining
a bottom mounting surface constructed for mounting engagement
with the top mounting surface of an associated first liner
segment, each second liner segment fur~her defining a top
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grinding surface for comminuting ore. The second liner
segments are disposed in close proximity to each other with
minimum space therebe-tween, and are siæed relative to the first
liner segments so that, in assembled relation, the first liner
segments are substantially covered by the second liner segments
and virtually unexposed to the ore comminution process to pre~
vent the first liner segments from becoming worn. The liner
assembly further comprises first connecting means for releas-
ably mounting a portion of the first liner segments to the
cylindrical shell independently of the second liner segments,
and second connecting means for releasably mounting each of the
second liner segments on an associated one of the first liner
segments to permit removal thereof without removing the asso-
ciated first liner segments from the c~lindrical shell. The
first and second liner segments are so constructed that the
second liner segments completely and protectively cover the
first connecting means with the liner assembly in assembled
relation.
In a third broad form, the invention resides in a
liner assembly for the cylindrical shell of an ore grinding
machine, which comprises a plurality of first and second liner
segments of predetermined size and configuration. Each of the
first liner segments defines a bottom mounting surface
constructed for mounting engagement with the inner surface of
the cylindrical shell, and further defines a top mounting s~r-
face. Each of the second liner segments deines a bottom
mounting surface constructed for mounting engagement with the
top mounting surface of an associated first liner segment, and
further defines a top grinding surface for comminuting the ore~
Each of the second liner segments further comprises a plurality
of bosses extending downward from the bottom mounting surface
thereof, and a mounting opening extending through the segment
from the grinding surface ~o the center of each boss. Each
first liner segment further comprises a mounting opening
extending transversely therethrough~ each mounting opening
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disposed to receive one of the bosses in conforming shape
thereto. Each mounting opening of the second liner segment is
countersunk within the associated boss, whereby mounting bolts
may be used to secure the first and second liner segments to
the shell with the heads thereof substantially recessed from
the grinding surface. The second liner segments are sized
relative to the first liner segments so that, in assembled
relation, the first liner segments are substantially covered by
the second liner segments and virtually unexposed to the ore
comminution process to prevent the first liner segments Erom
becoming worn.
Additional features and advantages will be appreciated
from the accompanying drawings and specification.
Brief Description of the Drawings
Figure 1 is a fragmentary plan view of a seg-
mented liner assembly for an ore grinding mill according
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to the invention, and viewed radially outward Erom within the
mill;
Figure 2 is a fragmentary sectional view of the liner
assembly taken along the line 2-2 of Figure l;
Figure 3 is an enlarge~ fragmentary transverse sec-
tional view of the liner assembly taken along the line 3-3 of
Figure l;
Figure 4 is an exploded perspec~ive view of the liner
assembly components as viewed from the front side and one end
thereof; and
Figure 5 is a perspective view of a wear segment com-
ponent of the liner assembly viewed from the bottom and one end
thereof.
Descr~ption of the Preferred Embodiment
Figures 1-5 disclose a segmented liner assembly
according to the invention and adapted for use with a cylindri-
cal drum or shell 11 of an ore grinding machine. The ore
grinding machine may be of the type disclosed in U.S. Patent No.
4,046,326, issued 6 September, 1977 to Minneapolis ~lectric
Steel Castings Company, in which the hollow cylindrical drum or
shell 11 is constructed and arranged for rotation about a
substantially horizontal axis. The drum or shell 11 is substan-
tially closed by axial end walls with the exception of central
axial openings through which the ore is respectively supplied ~;-
and discharged. `
With specific reference to Figure 3, the liner
assembly comprises a plurality of holder segments 12 fastened
directly to the shell 11 by ~irst fastening means 13, and a
plurality of wear segments 14 which are secured to the shell 11 ;~by second fastening means 15. As shown in Figures 1, 2 and 4
both the holder segments 12 and wear segments 14 are elon~ated
in shape, but in the preEerred embodiment five holder segments
12 are provided for two of the wear segments 14. These relative ~-lengths are chosen as a matter of convenience in manufacture and
installation, and other relative lengths, including equivalent
lengths, will function as well.
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As shown in Figure 1, the segments 12, 14 are arranged
in a plurality of rows which are substantially parallel with the
axis of rotation of the shell 11, the rows being disposed in
close proximity to substantially cover the inner cylindrical
surface of shell 11~ The shell 11 is rotated in the direction
indicated in Figure 3, and since the liner assembly defines a
plurality of axially extending ridges, ore fragments are carried
upward with rotation of the drum and then tumble downward in a
comminuting manner
With reference to Figures 2 and 4, it will be seen
that two structural configurations of the holder segments 12 are
provided, and these different configurations bear the reference
numerals 12 and 12', respectively. This is necessary because
five of the holder segments are provided for two of the wear
segments, and also due to the spacing of mounting openings
within the holder segments 14, as will be described below. The
sole structural difference between the holder segments 12, 12'
resides in the type oE mounting openings, as is particularly
apparent in Figure 4, and also as described below.
With reference to Figure 4, each of the holder
segments 12, 12' defines a slightly arcuate or convex mounting -~
surface 16 which conEorms to the inner cylindrical surface of
the shell llo The top surface of the holder segments 12, 12',
which bears the reference numeral 17, is also convex, but as
best shown in Figure 3, the radius of curvature of the surface
17 is somewhat less than the surface 16, and the curvature
itself is therefore more pronounced. Each o:E the holder
segments defines identical flat sides 18 which, as shown in
Figure 3, substantially lie on radii of the shell 11, and iden-
tical flat ends 19, which are substantially mutually parallel.
With reference to Figures 1-4, each of the holder
segments 12 includes two different mounting openings
21, 22 which are disposed along the longitucinal axis
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thereof in predetermined spaced relation. Each of the
holder segments 12' includes two mounting openings 21,
also spaced along the segment longitudinal axis.
The spacing of the mounting openings 21, 22
within the holder segmen-ts 12, 12' is determined as a
function of the sp~cing between the circumferential rows
of mounting openings formed in the cylindrical shell 11,
which bear reference numeral 23 in Figures 2 and 3.
Typically, these circumferential rows of mounting openings
23 are spaced -twelve inches apart in a cylindrical shell
11 having a length of ten feet and a diameter of ~eet.
Accordingly, the spacing between the mounting openings 21,
22 within the holder segments 12, 12' is uniform, and this
spacial dis-tance is the same between any mounting opening
21, 22 and the mounting opening in the next adjacent
holder segment 12 or 12l.
As viewed in the top plan of Figure 1 and the
perspective view of Figure 4, each of -the mounting open-
ings 22 is oblong in configuration at the convex surface
17. As viewed in the longitudinal sectional view of
Figure 2, each of the mounting openings 22 defines a first
pair of angular side walls that incline or converge from
the top surface 17 to the bottom surface 16. As viewed in
the transverse sectional view of Figure 3, each of the
mounting openings 22 defines a second pair of flat, ~.
mutually parallel side walls.
As constructed, the mounting openings 22 are
adapted to receive -the fastening means 13, each of which
specifically comprises a threaded bolt 24 having a gener-
ally oblong head with one pair of tapered sides whichround into a pair of parallel sides. This configuration
enables the bolt 14 -to center ltself within the mounting
opening 22, and to clamp the holder segment 12 against the
inner surface of drum 11 by the wedging rela-tion between
the bolt head and mounting opening 22. This is specifi-
cally accomplished by a lock nut 25 which threads onto the
bol-ts 24 externally of the shell 11, as shown in Figure 3.
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With reference to Figures 1-3, each of the mounting
openings 21 is substantially larger than the mounting openings
22. Each mounting opening 21 extends entirely through the
holder segment 12 and takes the shape of an inverted frustum of
a cone.
As configured, each of the mounting openings 21 is
adapted to receive one o a plurality of frustoconical hosses 26
which project downwardly from the bottom surface 27 of wear `
segments 14. As best shown in Figures 2 and 3, the bosses 26
are slightly smaller than the mounting openings 21, and the
resulting spacing therebetween avoids any problem of abnormal
tolerance. Because of potential difficulties in obtaining
registration of the bosses 26 within the mounting openings 21
relative to the shell mounting openings 23, it is preferred that
this fit be loose enough to permit ad~ustable movement.
The bottom surface 27 oE each of the wear segments 14
otherwise generally conforms to the top surface 17 of holder
segments 12, and is thus convex as viewed in the transverse sec-
tional view of Figure 30
Each of the wear segments 14 is also formed with iden-
tical Elat sides 28 which are coplanar with the sides 18 of
holder segments 12 when assemble~ (Figure 3)~ As shown in
Figure 1, each of the wear segments 14 is formed with identical
flat ends 29 which are substantially mutually parallelO
The top or grinding surface of each of the wear
segments 14 is symmetrical in transverse section (Figure 3),
comprising a pair of opposed concave surfaces 31 that curve
upward from the sides 28 to a top flat surface 32. With the
wear segments mounted in end-to-end relation within an axial -~
row, the top surEaces 32 together de~ine an axial ridye which
runs virtually the entire length of the sbell or drum 11. Since
the holder segments are also disposed in side-by-side relation,
as shown in Fiyure 1, it will be seen that the plurality of
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axial ridges are disposed circumEerentially around the inner
surface of the drum, with alternating recesses or valleys as
defined by the concave surfaces 31.
This ridged inner surface causes the ore fragments to
be carried upward as the drum 11 rotates, and comminution .
results from the tumbling action as the fragments fall back on
one another.
As best understood from Figure 3, rotation of the drum
11 in one direction causes wear of the wear segments 14 on one
side more than the other. The symmetrical cross section of the
wear segmens 14 means that the drum 11 may be rotated in the
opposite direction to obtain maximum wear time, and it also per-
mits the wear segments 14 to be mounted in either end~~o end
directionO
Mounting is accomplished by a plurality o~ mounting
openings 33, which are disposed in alignment with the bosses 26
and extend entirely through the wear segment 14 from the top
surface 32 to the bottom of the bosses 26. As shown in Figures
2 and 3, mounting openings 33 are substantially the same as
mounting openings 22 of the holder segments 12, with the excep-
tion that they are countersunk a much greater distance than the
mounting openings 22. ~ :
The fastening means 15 are identical to the fastening
means 13, comprising a bolt 34 having a tapered head and lock
nut 35 that threads onto the projecting bolt externally of the
shell 11. The depth of the countersink of mounting opening 33
enables the head of bolt 34 to be deeply recessed from the top
surEace 32. Consequently, substantially the entire thickness of
the wear segments 14, excluding the projecting dimension of the
bosses 26, may be worn away without exposing the bolt 34 to
wear, thus opt.imizing wear life of the wear segments 14.
The mounting openings 33 and bosses 26 are spaced
along the longitudinal axis of wear segments 14 for registration
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with the mounting openings 21 and ~3, respectively. The struc~
tural configuration not only enables the wear segments 14 to
wear longer~ but also assists significantly in obtaining align-
ment of the wear segments on the underlying holder segments 12,
1~' during installation of the liner assembly.
Installation is acilitated by the integral casting of
a large ear 36 tFigure 3), projecting fr~m each of the concave
surfaces 31 at the longitudinal midpoint of the wear segments
14. The ears 36 are formed with large apertures 37, permitting
the wear segments 14 to be lifted into place.
In the preferred embodiment, a layer 38 of rubberized
fabric is disposed between the holder segments 12 and wear
segments 14 so that these components fit snugly together without
the need for close tolerance casting or machining. The rub-
berized fabric layer 38 causes impact forces to be distributed
evenly over the entire convex surface of the holder segments 12;
12'.
The layer 38 is rectangular in shape, conforming in
size to the undersurface 27 of wear segment 14. Apertures 39
are punched through the layer 38 to register with the mounting
openings 21.
In addition to the convenience which the layer 38
offers to the foundry by covering imperfections in the casting,
the rubberized fabric layer also provides a visual indication
that operators of the apparatus can see as the wear segments 14
wear down. As soon as the rubberized fabric 38 may be seen, the
wear segments 14 should be replaced.
The preEerred material from which the layer 38 is made
is rubberized fabric, although other materials could be used so
long as the layer 38 is adaptive or resilient.
In installation of the inventive liner assembly, the
holder se~ments 12 are first mounted by placement of the
segments relative to the mountillg openings 23 in axial rows.
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Although holder segments 12 have but a single mounting opening
22, they are retained in place by the engayement of adjacent
ends 19. The same holds true for the holder segments 121, which
are held temporarily in place by the adjacent holder segments 12
unt.il the wear segments 14 are placed in position and bolted by
the fastening means 15. The rubberiæed fab.ric ].ayer 38 is
placed over the holder segments 12 before the wear segments 14
are introduced, and they are replaced with the wear segments 14
when necessary.
Because the holder segments 12, 12' are covered
substantially in their entirety by the wear segments 14 and rub-
berized fabric layers 38, wear is much less significant, and it ~.
is intended that the holder segments 12, 12' remain in place and
be reused for several changes of the wear segments 14. This
effects a significant saving because installation of the entire
assembly is avoided, coupled with the fact that the cost of the
holder segments 12, 12' may be significantly less than the wear
segments 14 because a softer, less expensive material may be .
used.
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