Note: Descriptions are shown in the official language in which they were submitted.
CA 02522723 2005-10-18
WO 2004/096476 PCT/CA2004/000599
APPARATUS AND METHOD FOR THERMAL DE-BURRING
OF SLOTTED WELL LINERS
FIELD OF THE INVENTION
The present invention relates to apparatus and methods for removing burrs from
internal
surfaces of tubular goods, and in particular for removing burrs from internal
surfaces of slotted
pipe used as liners in oil and gas wells.
BACKGROUND OF THE INVENTION
In the production of oil or gas from an subsurface formation, steel liner
pipes with
multiple longitudinal slots ("slotted liners") are commonly installed in both
vertical and
horizontal wells to allow oil or gas present in the formation to enter the
wells, whereupon the oil
or gas can then be pumped or otherwise lifted to the surface for processing.
The slots must be
narrow enough to prevent significant amounts of formation materials from
entering and clogging
up the well and associated equipment such as pumps. For wells installed in
formations
containing fne-grained materials, liner slot width may need to be as narrow as
0.04 inches (1.0
millimeter) or even considerably less. The slots must be long enough and
numerous enough to
allow for effective flow into the liner, without reducing the liner's
structural strength below safe
levels. The liner's structural strength (especially its flexural strength) is
particularly important
for horizontal wells, in which the liner must retain sufficient strength to be
bent through
transition sections between vertical and horizontal wellbores without fracture
or excessive
plastic deformation.
The slots may be of any convenient length, but they are typically in the range
of 3 to 4
inches (75 to 100 millimeters) long. They are usually arrayed at uniform
spacing about the
circumference of the pipe, at radial intervals as low as 5 degrees. They are
commonly cut into
the liner sidewall using narrow circular slitting blades. One known method
uses a "gang mill"
fitted with multiple slitting blades radially oriented on planes passing
through the longitudinal
axis of the liner. As the liner is moved longitudinally relative to the gang
mill, the blades are
deployed so as to cut slots of desired length through the liner sidewall.
1
CA 02522723 2005-10-18
WO 2004/096476 PCT/CA2004/000599
Rather than making perfectly clean cuts, the slitting blades tend to leave
jagged burrs or
tendril-like "wickers" where the slots intercept the interior surface of the
liner. These burrs and
wickers are undesirable for a variety of reasons, so the production of slotted
liners typically
includes steps to remove them, but known methods of doing so are not entirely
satisfactory. One
common method is to run a device commonly called a "stinger" through the
slotted liner. The
stinger has multiple rotating blades disposed such that they will essentially
scrape the interior
perimeter of the liner as the stinger passes through. The intent is that the
rotating blades will cut
off the wickers, which can then be removed from the liner by compressed air or
other means.
However, this method has proved to be only partially effective, because the
scraping
blades tend to bend the burrs and wickers and push them back across or into
the slots, causing a
direct reduction in the open slot area available for passage of oil into the
liner. This problem is
particularly evident for slot widths of 0.04 inches (1 mm) and less. The
effective slot area tends
to become further reduced when the liner is placed in service, because foreign
materials entering
the slots build up on the bent-back wickers, causing the slots to become
partially or totally
plugged.
Other mechanical methods, such as honing or burnishing, have been used in an
attempt
to polish the wickers down. However, these methods have similar drawbacks, in
that they tend
to simply brush some or all of the wicker metal back into the slots.
When using known de-burring methods having such significant drawbacks, it may
be
necessary to allow for slot plugging by providing a greater amount of slotting
than might
otherwise be required. It has been observed that slot plugging can reduce the
effective
permeability of a slotted liner by as much as 40% to 60%, so in order to
obtain a desired
permeability, liners may have to have a slotted area up to or more than twice
as large as the area
theoretically required for a given application. Such extra slotting obviously
increases liner
fabrication cost. It also decreases the structural strength of the liner,
possibly entailing the use of
liners with greater wall thickness, thus increasing the total cost of the
slotted liner even further.
In addition to the foregoing problems, wickers or any other material left
inside slotted
liners can damage or interfere with expensive down-hole tools used in well-
servicing operations.
A possible alternative approach to wicker and burr removal would be thermal de-
burring;
i.e., exposing the wickers and burrs to a high-temperature flame. It is well
known that burrs of
steel or other materials can be burned off and effectively incinerated if
subjected to a sufficiently
2
CA 02522723 2005-10-18
WO 2004/096476 PCT/CA2004/000599
hot flame. This would facilitate very effective removal of burrs from a
slotted liner, as it would
be fairly simple to remove the residue from the process (i.e., oxides) using
compressed air, high-
pressure water blasting, or other conventional means.
For the type of steel commonly used for slotted liners, effective use of this
method would
require heating the burrs to temperatures in the range of 6000° F
(3316° C). At the same time,
though, care would have to be taken to ensure that the temperature of the main
body of the liner
does not become excessive, in order to prevent undesirable metallurgical
changes in the parent
metal. This would not be overly difficult if the high-temperature flame could
be effectively
focused or concentrated on the burrs and not on the main body of the liner,
because the much
larger mass of the liner (i.e., compared to the mass of the burrs) would allow
efficient dissipation
of the heat applied to the burrs through conduction, without excessive
temperature build-up in
the parent material. However, it is virtually impossible to direct a flame
toward burrs inside a
steel liner without exposing the main body of the liner to the flame.
Furthermore, the inventor
has observed that when conventional flame sources such as acetylene torches
are used in an
attempt to heat burrs inside a slotted liner to temperatures sufficient to
achieve vaporization, the
flame must dwell upon the burrs for so long that excessive localized heating
of the parent metal
is unavoidable. The prior art appears to disclose no solution to this problem.
For the foregoing reasons, there is a need for wicker-removal and de-burring
apparatus
and methods that can remove burrs and wickers from slotted metal liners with
substantially
greater effectiveness than known apparatus and methods. In particular, there
is a need for such
apparatus and methods that can remove burrs and wickers by exposure to an
oxidizing flame,
without raising the temperature of the adjacent parent metal so high as to
cause metallurgical
changes or other undesirable effects. The present invention is directed to
these needs.
BRIEF SUMMARY OF THE INVENTION
In general terms, the present invention is a method and apparatus whereby
burrs inside a
slotted metal liner may be exposed to a gas flame hot enough as to effectively
oxidize or
incinerate the burrs, without inducing undesirable temperature levels in the
parent material. This
is accomplished by providing a torch head having multiple gas torch nozzles
disposed around
the circumferential perimeter of the torch head, such that when the torch head
is passed through
a slotted liner, the flames are directed toward the interior surface of the
liner. The apparatus is
3
CA 02522723 2005-10-18
WO 2004/096476 PCT/CA2004/000599
adapted to deliver a substantially stoichiometrically-balanced fuel mixture
(i.e., a combustion
gas and an oxidizing gas) to the nozzles, so as to produce substantially
neutral-burning flames at
the nozzles. It has been determined, through testing, that the temperature of
a neutral-burning
flame will increase considerably in the presence of oxygen. In accordance with
the present
invention, therefore, provision is made for introducing an auxiliary oxidizing
gas - preferably
pure oxygen -- near the nozzle outlets, thus increasing the flame velocity and
intensity, and in
turn causing a significant increase in flame temperature.
The temperature of the torch flames produced according to the present
invention is thus
considerably higher than it would be without the introduction of auxiliary
oxidizing gas. It has
been found that when the torch head, having a suitable number of nozzles and
having auxiliary
oxidizing gas introduced around the torch flames, is passed through a slotted
liner at an
appropriate rate of travel, the flame intensity is sufficient to incinerate a
high percentage of burrs
and wickers from the liner, without excessive temperature rise in the parent
metal. The
appropriate torch head travel speed will depend on a variety of factors,
including liner diameter
and wall thickness, feed pressures of the fuel mixture components and the
auxiliary oxygen, the
number of nozzles on the torch head, and the distance from the nozzle outlets
to the inner
surface of the liner.
Accordingly, in one aspect the present invention is a de-burring apparatus,
for removing
burrs from interior surfaces of a slotted metal liner, said apparatus
comprising:
(a) a torch carrier body having a front end and a rear end;
(b) a torch head connected to the torch carrier body at the front end thereof,
said
torch head having a longitudinal axis and a circumferential lateral surface,
said
torch head having formed therewithin:
b.1 a fuel plenum, for receiving a fuel mixture comprising a combustion
gas and a primary oxidizing gas;
b.2 an auxiliary plenum, for receiving and conveying an auxiliary
oxidizing gas from a source of auxiliary oxidizing gas;
b.3 a plurality of fuel channels, each fuel channel having an outer end and an
inner end, and each fuel channel at its inner end being in fluid
communication with the fuel plenum; and
4
CA 02522723 2005-10-18
WO 2004/096476 PCT/CA2004/000599
b.4 a plurality of nozzle ports, each nozzle port extending inward from the
circumferential lateral surface of the torch head and having an inner wall
surface, and each nozzle port being in fluid communication with a
corresponding one of the fuel channels; and
(c) a plurality of torch nozzles, each nozzle having an outer end, an inner
end, and a
side surface, an inner end, and each nozzle having a fuel passage extending
through the nozzle between said inner and outer ends;
said apparatus being characterized by:
(d) each nozzle being retainingly installed within a corresponding nozzle port
and
defining an interstitial space between the side surface of the nozzle and the
inner
wall surface of the nozzle port, said interstitial space having an outer end
in
proximity to the outer end of the nozzle;
(e) the outer end of each nozzle extending close to or beyond the
circumferential
surface of the torch head;
(f) the inner end of each nozzle being sealingly engaged with the fuel channel
associated with the corresponding nozzle port, such that the outer end of the
fuel
passage of each nozzle is in fluid communication with the fuel plenum; and
(g) each interstitial space being in fluid communication with the auxiliary
plenum,
and intercepting the circumferential surface of the torch head, such that
auxiliary
oxidizing gas can flow from the auxiliary plenum into the interstitial spaces
and
exit at the outer end thereof.
In another aspect, the invention is a method of removing burrs from interior
surfaces of a
slotted metal liner, said method comprising the steps of
(a) introducing a fuel mixture comprising a combustion gas and a primary
oxidizing
gas into the fuel plenum of the torch head of a de-burring apparatus
substantially
as described immediately above, such that the fuel mixture flows into the fuel
passages of the torch nozzles of the torch head;
5
CA 02522723 2005-10-18
WO 2004/096476 PCT/CA2004/000599
(b) igniting the fuel mixture exiting the fuel passages of the torch nozzles
to create
torch flames;
(c) introducing an auxiliary oxidizing gas into the auxiliary plenum of tl~e
torch head,
such that the auxiliary oxidizing gas flows out of the interstitial spaces
around the
torch nozzles;
(d) regulating the respective flowing pressures of the fuel mixture and
auxiliary
oxidizing gas so that the torch flames are of a temperature sufficient to
substantially incinerate metal burrs present on the interior surface of the
slotted
liner; and
(e) passing the torch head through the slotted liner at an appropriate speed
such that
the torch flames are directed toward the interior surface of the slotted liner
so as
to substantially incinerate the metal burrs.
In a further aspect, the invention is a method of removing burrs from interior
surfaces of
a slotted metal liner, said method comprising the steps of:
(a) providing a torch head having one or more torch nozzles;
(b) delivering a fuel mixture comprising a combustion gas and a primary
oxidizing
gas to the one or more torch nozzles;
(c) igniting the fuel mixture exiting the one or more torch nozzles, thus
creating one
or more torch flames;
(d) introducing an auxiliary oxidizing gas in the immediate vicinity of each
torch
flame so as to raise the flame temperature to a level sufficient to
substantially
incinerate metal burrs present on the interior surface of the slotted liner;
and
(e) passing the torch head through the slotted liner at an appropriate speed
such that
the torch flames are directed toward the interior surface of the slotted liner
so as
to substantially incinerate the metal burrs.
6
CA 02522723 2005-10-18
WO 2004/096476 PCT/CA2004/000599
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described with reference to the
accompanying
figures, in which numerical references denote like parts, and in which:
FIGURE 1 is a perspective view of a typical slotted liner for use in oil or
gas
wells.
FIGURE 2 is a perspective view of the torch head and torch carrier body of a
first embodiment of the apparatus.
FIGURE 3 is a cross-sectional side view of the torch head and torch carrier
body
of a second embodiment of the apparatus.
FIGURE 4a is a perspective view showing the torch head, flame shield, and
centralizer means of one embodiment of the apparatus.
FIGURE 4b is a cross-sectional perspective view of the torch head, flame
shield,
and centralizer means illustrated in Figure 4a.
FIGURE 5 is a cross-sectional view of the torch head of an embodiment of the
invention in which the torch nozzles are oriented substantially
perpendicularly
relative to the axis of the torch head.
FIGURE 6 is a cross-sectional view of the torch head of an embodiment of the
invention in which the torch nozzles are oriented with a forward cant.
7
CA 02522723 2005-10-18
WO 2004/096476 PCT/CA2004/000599
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure 1 illustrates a slotted liner 100 of the general type that may be de-
burred using the
present invention may be used. The slots 102 in the slotted liner 100 shown in
Figure 1 are
oriented parallel to the longitudinal axis of the liner 100, but in other
variations of slotted liner
100 the slots 102 may be oriented transversely or obliquely relative to the
axis of the liner 100.
However, the functioning of the present invention is not dependent upon or
affected in any
substantial way by the orientation of the slots 102 in the liner 100 being de-
burred.
As illustrated in the Figures, the de-burring apparatus 10 of the present
invention
includes a torch carrier body 12 having a front end 14 and a rear end 16. The
torch carrier body
12 is adapted to accommodate conduits 18a, 18b, and 18c for conveying,
respectively, a
combustion gas, a primary oxidizing gas, and an auxiliary oxidizing gas from
respective sources.
Where the same type of gas is used for both the primary and auxiliary
oxidizing gases, a
common source may be used. A torch head 20, having a longitudinal axis A and a
circumferential lateral surface 22, is connected to the torch carrier body 12
at the front end 14
thereof. The torch head 20 has multiple gas torch nozzles 50 disposed
(preferably, but not
necessarily, at uniform spacing) around the circumferential lateral surface 22
of the torch head
20, such that when the torch head 20 is passed through the interior of a
slotted liner 100, flames
from the torch nozzles 50 will be directed toward the interior surface of the
liner 100 and,
therefore, toward any burrs or wickers that may be present in the vicinity of
the slots 102 in the
liner 100.
As particularly illustrated in Figures 5 and 6, the torch head 20 is formed so
as to define a
fuel plenum 30 for receiving a fuel mixture comprising a combustion gas and a
primary
oxidizing gas. The fuel plenum 30 may receive combustion gas and oxidizing gas
conduits 18a
and 18b, with these gases being combined within the fuel plenum 30, or the
combustion gas and
oxidizing gas may be combined in a separate mixing chamber (not shown) and
then delivered to
the fuel plenum 30.
In addition, the torch head 20 defines an auxiliary plenum 32, which is in
fluid
communication with the auxiliary oxidizing gas conduit 18c, as illustrated in
Figure 6. In the
particular embodiment illustrated in Figure 6, the auxiliary oxidizing gas
conduit 18c, although
not fully shown, passes through the fuel plenum 30 and discharges auxiliary
oxidizing gas into
the auxiliary plenum 32 at point X.
8
CA 02522723 2005-10-18
WO 2004/096476 PCT/CA2004/000599
The torch head 20 also defines a plurality of fuel channels 34, each of which
has an outer
end 34a, plus an inner end which is in fluid communication with the fuel
plenum 30. Each fuel
channel 34 is in fluid communication with a corresponding nozzle port 40
formed in the torch
head 20. Each nozzle port 40 intercepts the circumferential lateral surface 22
of the torch head
20 and having an inner wall surface 42 (which will typically, but not
necessarily, be cylindrical).
Each nozzle port 40 is adapted to receive and retain a torch nozzle 50, with
clearance space
between the nozzle 50 and the inner wall surface (or surfaces) 42 of the
nozzle port 40. Each
nozzle 50 has a side surface 52 (typically cylindrical), an inner end SOa, and
an outer end SOb,
plus a fuel passage extending through the nozzle 50 from inner end SOa to
outer end SOb. The
length of the nozzles 50 is selected such that the outer ends SOa thereof will
extend close to or
beyond the circumferential surface 22 of the torch head 20 when the nozzles 50
are installed in
their corresponding nozzle ports 40. Accordingly, when a nozzle 50 is
installed in its
corresponding nozzle port 40, with its inner end SOa in sealing engagement
with the
corresponding fuel channel 34, a fuel mixture can flow from the fuel plenum 30
into the fuel
channel 34 and into fuel passage 54 of the nozzle 50, exiting therefrom at the
outer end SOb of
the nozzle 50, at which point the fuel mixture may be ignited to create a
torch flame.
The nozzles 50 may be of any suitable construction having central longitudinal
fuel
passages 54 for conveying the fuel mixture from a fuel plenum 30. In one
embodiment, the
nozzles 50 are conventional "MIG tips"; i.e., wire-feeder tips of a type
commonly used in the
metal-inert gas welding process. It has been found that acceleration of the
fuel mixture as it
exits the fuel passages 54 of the nozzles 50 facilitates establishment of a
stable, neutral flame, by
inducing a certain amount of backpressure and increasing the flame velocity.
Accordingly, in
one embodiment of the apparatus of the invention, the fuel passages 54 of the
nozzles 50 have a
narrowing or constriction near the external ends thereof, so as to accelerate
the fuel mixture as it
exits the nozzles 50.
The installation of a nozzle 50 into a corresponding nozzle port 40 will
result in the
formation of an interstitial space 44 between the side surface 52 nozzle 50
and the inner wall
surface (or surfaces) 42 of the nozzle port 40. The interstitial space 44 will
have an outer end 45
in proximity to the outer end SOa of the nozzle 50. The nozzle 50 will
typically be of cylindrical
cross-section, and as previously mentioned, the nozzle port 40 will typically
have a cylindrical
inner wall surface 42, so the interstitial space 44 will typically and
preferably be of annular
cross-section. However, this characteristic is not essential to the present
invention. What is
essential is that the interstitial space 44 intercepts or is otherwise in
fluid communication with
9
CA 02522723 2005-10-18
WO 2004/096476 PCT/CA2004/000599
the auxiliary plenum 32, such that auxiliary oxidizing gas can flow from the
auxiliary plenum 32
into the interstitial space 44, and will exit from the outer end 45 thereof.
Regardless, though, of
the dimensional characteristics of the interstitial space 44 at other points
along its length, it will
be preferable for the exit width W of the interstitial space 44 (i.e., at its
outer end 45) to be
substantially uniform, for reasons explained below.
It can be readily seen that when a fuel mixture exiting from the fuel passage
54 of the
nozzle 50 has been ignited to create a torch flame, the auxiliary oxidizing
gas exiting the
interstitial space 44 will effectively create a curtain or shroud of auxiliary
oxidizing gas
substantially enveloping the torch flame. This flow of auxiliary oxidizing gas
in the vicinity of
the torch flame substantially increases flame velocity, intensity, and
temperature. As mentioned,
it is preferable for the exit width W of the interstitial space 44 to be
uniform, thus promoting
uniform flow of auxiliary oxygen around the flame and correspondingly uniform
resultant
effects on the flame.
The nozzle ports 40 may be configured such that the axes of the torch nozzles
50
intersect the longitudinal axis A of the torch head 20 (i.e., in radial
fashion), and also at right
angles to axis A, as may be seen in Figure 5. It has been observed, however,
that torch flame
effectiveness may be enhanced by tilting the flames forward. This has the
beneficial effect of
increasing the temperature of portions of the liner 100 immediately ahead of
the torch head 20,
thus decreasing the amount of heat that needs to be transferred to the burrs
and wickers when the
torch flames come into direct contact with them. The tilt of the flames also
induces a forward-
moving pressure wave inside the liner 100 that assists in blowing debris from
incinerated burrs
and wickers out of the liner 100.
Accordingly, in the preferred embodiment of the apparatus, one or more of the
torch
nozzles 50 (and their corresponding nozzle ports 40) have a forward cant, so
that the flames
from these nozzles 50 will be directed both radially outward and toward the
front of the torch
head 20, as illustrated in Figures 3, 4b, and 6. The forward cant angle may be
selected to suit
particular applications. By way of example, Figures 4b and 6 illustrate a
15° forward cant.
However, beneficial results have also been obtained using cant angles of
30°, 45°, and 60°, in
torch heads 20 for use with liners having of nominal diameters of 3.5", 4.5",
and 5.5" (89 mm,
114 mm, and 140 mm) respectively.
CA 02522723 2005-10-18
WO 2004/096476 PCT/CA2004/000599
It is not essential for the torch nozzles 50 to be installed in a radial
configuration relative
to the longitudinal axis A of the torch head 20. In one alternative embodiment
(not shown), one
or more of the nozzle axes are oriented at oblique angles to axis A, such that
the torch flames
exit the torch head 20 in "pinwheel" fashion, thus creating a swirling effect
to the flames as the
torch head 20 moves through the liner 100. In a variation of this alternative
embodiment, one or
more nozzles 50 have a forward cant as well as an oblique orientation relative
to axis A.
The combustion gas may be any combustible gas having suitable heat-producing
characteristics, and acetylene is one example. However, particularly
beneficial results have been
observed when using a mixture of MAPP gas (i.e., methylacetylene-propadiene)
and oxygen.
While acetylene produces a higher flame temperature, it has been found that a
MAPP gas flame
is more stable than an acetylene flame. Propane or natural gas, which also
produce suitably
stable flames, could also be used, but their heating values are lower than for
MAPP gas, making
the latter more desirable to optimize burr removal rates. The fuel mixture
preferably will be
substantially stoichiometrically balanced, so as to produce substantially
neutral-burning flames.
The auxiliary oxidizing gas may comprise air. However, particularly beneficial
results
have been achieved using substantially pure oxygen as the auxiliary oxidizing
gas.
As previously mentioned, it has been found that when a torch head 20 in
accordance with
the present invention, having a suitable number of nozzles 50, is passed
through a slotted liner
100 at an appropriate rate of travel, the flame intensity is sufficient to
incinerate a high
percentage of burrs and wickers from the interior of the liner 100, without
excessive temperature
rise in the parent metal. The appropriate torch head travel speed will depend
on a variety of
factors, including liner diameter and wall thickness, feed pressures of the
fuel mixture
components and the auxiliary oxygen, the number of nozzles 50 on the torch
head 20, and the
distance from the nozzle outlets to the inner surface of the liner 100.
As only one representative example, it has been found that a travel speed in
the range of
4.0 to 4.5 feet (1.2 to 1.4 meters) per minute is effective for de-burring a
nominal 7-inch
diameter steel liner (i.e., 7.75" or 197 mm outer diameter; and 6.35" or 161
mm inner diameter)
using a torch head 20 having 48 radially-disposed nozzles 50 burning a MAPP
gas mixture fed
at approximately 20 pounds per square inch (138 kiloPascals), with auxiliary
oxygen fed at
approximately 50 psi (345 kPa), and with the radial distance between the
nozzle outlets and the
inner cylindrical surface 104 of the liner 100 being approximately 0.5 inches
(13 mm).
11
CA 02522723 2005-10-18
WO 2004/096476 PCT/CA2004/000599
The apparatus 10 of the invention preferably includes fuel mixture control
means and
auxiliary oxidizing gas control means, for regulating the flowing pressure of
the fuel mixture and
the oxidizing gas respectively. It will be readily appreciated by persons
skilled in the art that
various known means for controlling or regulating the pressure of a flowing
gas may be easily
adapted for use as the fuel mixture control means and auxiliary oxidizing gas
control means.
In the preferred embodiment, the torch head 20 will also have a flame shield
70, which
may be provided in the form of a collar or flange mounted rearward of the
nozzles 50 and
extending radially outward from the torch head 20, but stopping just short of
the inner surface
104 of the liner 100 such that it does not impede passage of the torch head 20
through the liner
100. The flame shield 70 serves two primary functions, the first of which is
to shield from the
flames those portions of the liner 100 which the torch head 20 has already
passed by, thus
further minimizing the temperature increase in the parent metal of the liner
100. The second
function or effect of the flame shield 70 is to concentrate the torch flames
in a region
immediately adjacent to the nozzles 50, by preventing the flames from
deflecting back over the
region previously exposed to the flames, thus optimizing heat transfer to the
burrs present inside
the liner 100.
In the preferred embodiment, the apparatus 10 of the invention will include
centralizes
means 60, for ensuring that the longitudinal axis A of the torch head 20 is
substantially aligned
with the axis of the liner 100 through which the torch head 20 passes when the
apparatus is in
use, thus ensuring that all of the nozzles 50 are approximately equidistant
from the inner surface
104 of the liner 100, so as to facilitate substantially consistent heat
transfer from the nozzles 50
to the liner 100 and any burrs or wickers present at or near the inner surface
104 of the liner 100.
As particularly illustrated in Figures 4a and 4b, the centralizes means 60 may
include a plurality
of rub bars 62 disposed radially about the perimeter of the torch carrier body
12, each rub bar 62
being mounted to a bracket 64 hingingly connected to the of the torch carrier
body 12, and each
bracket 64 having biasing means (such as a spring) for urging the rub bars 62
radially outward so
as to ride against the inner surface 104 of the liner 100 as the torch head 20
passes through.
Other effective centralizing means will be readily apparent to persons skilled
in the art of the
invention. For example, the rub bars may include (or be replaced by) rollers
that will roll against
the inner surface 104 of the liner 100.
Just as the liner 100 needs to be protected from excessive heat build-up, the
temperature
of the torch head 20 also should be kept within an acceptable range, to
prevent metallurgical
12
CA 02522723 2005-10-18
WO 2004/096476 PCT/CA2004/000599
changes or other undesirable effects. Accordingly, in the preferred
embodiment, the apparatus
of the invention include torch head cooling means. Although the torch head 20
may be
effectively cooled using a gaseous coolant such as air, in the preferred
embodiment the torch
head 20 is cooled by circulation of a liquid coolant (which could comprise
water or ethylene
5 glycol) through one or more coolant circulation chambers 24 formed within
the torch head 20,
analogous in principle to the coolant circulation chambers in a liquid-cooled
automotive engine.
The coolant circulation chambers 24 for the preferred embodiment of the
invention may be
located and configured within the torch head 20 in any convenient fashion, in
accordance with
principles and methods well known in the art.
10 In the preferred embodiment, the torch head 20 is fabricated at least in
part from steel. In
an alternative embodiment, the torch head 20 is fabricated at least in part
from a metal (such as
titanium) that can withstand higher temperatures than steel without
undesirable metallurgical or
other effects, thus reducing the cooling load on the torch head cooling means,
or even
eliminating the need or desirability for torch head cooling means.
The torch head 20 may be fabricated in a number of sections that are
subsequently
assembled by bolting or other suitable means. One example of this method of
fabricating and
assembling the torch head 20 is illustrated in Figure 4b; however, other
arrangements may be
possible. Individual sections of the torch head 20 may be machined from solid
stock, or may be
made as castings for machining as necessary to fashion required structural
features. Casting
methods may also be available which enable the entire torch head 20 to be a
single casting, to be
machined as necessary.
In the preferred embodiment of apparatus and method of the invention, the
torch head 20
is movable through the liner 100 being de-burred. In alternative embodiments,
however, the
liner 100 may be moved over a stationary torch head 20. Suitable motive means
for moving the
torch head 20 through the liner 100, or for moving the liner 100 over a
stationary torch head 20,
will be readily devisable by persons skilled in the art. The motive means may
include a
extension member attached to the rear end 16 of the torch carrier body 12, or
integral with the
torch carrier body 12, and of a suitable length to facilitate insertion of the
torch head 20 into the
liner 100 for substantially its full length. In one embodiment of the
apparatus, the motive means
includes a pull rod/cable assembly connected to a hydraulic motor, for
inserting the torch head
20 into the liner 100 and retracting it therefrom. Other types of motors and
components may be
used for the motive means without departing from the present invention.
13
CA 02522723 2005-10-18
WO 2004/096476 PCT/CA2004/000599
Preferably, the motive means includes torch head speed control means for
regulating the
rate at which the torch head 20 travels through the liner 100. As will be
appreciated by persons
skilled in the art of the invention, suitable speed control means may be
readily provided by use
or adaptation of known technology. To provide one example, torch head speed
control may be
provided by use of a variable-speed motor as a component of the motive means.
It has been observed that the temperature at the outer surface of the liner
100 in the
vicinity of the zone being exposed to the torch flames can be a good indicator
of the flames'
effectiveness in removing burrs and wickers for a given torch head speed;
i.e., whether the burrs
and wickers are being exposed to the flames long enough for removal. For
example, in one
tested assembly, a measured liner temperature of about 250° F
(121° C) would indicate that the
torch head speed was too fast, and that burr removal was less than optimally
effective. This
would in turn indicate that the torch head speed should be increased. At the
other end of the
scale, a measured liner temperature of about 350° F (177° C)
would indicate that the torch head
speed was too high. These approximate temperature limits, for purposes of
monitoring flame
effectiveness and for regulating torch head speed, may differ depending on
various factors
including the number of torch nozzles, liner dimensions, and torch flame
characteristics.
In view of the foregoing observations, the preferred embodiment of the
apparatus of the
present invention includes means for monitoring the temperature of the parent
metal of liner 100
in the general vicinity of the torch nozzles 50 as they pass through the liner
100. In a
particularly preferred embodiment, the temperature-monitoring means is coupled
to the motive
means, using suitable known control technology, such that the torch head
travel speed is
automatically regulated in response to detected variations in parent metal
temperature. As well
as providing an indication of torch flame effectiveness as discussed above,
the temperature-
monitoring means may also be advantageous to alert the operator of the
apparatus in the event
that the parent metal temperature approaches or exceeds a selected maximum
value above which
undesirable effects could result, in which case appropriate remedial or
preventive steps can be
initiated.
When the torch head 20 is moving through the slotted liner 100 at an
appropriate speed,
the temperature rise in the parent metal of the liner 100 should not to
temperatures high enough
to cause undesirable metallurgical or other effects. However, it has been
observed that the
parent metal temperature tends to be higher at the crown of the liner 100 than
at lower locations,
and this can result in longitudinal bowing of the liner 100 as it cools down.
To mitigate or
14
CA 02522723 2005-10-18
WO 2004/096476 PCT/CA2004/000599
prevent this undesirable condition, the preferred embodiment of the method of
the invention
includes the additional step of rotating the liner relative to the torch head
20, thus promoting
uniform temperature rise in the parent metal around the circumference of the
liner 100. As a
result, the liner 100 will cool more uniformly and will therefore be less
prone to longitudinal
distortion. Suitable means for rotating the liner 100 will be readily apparent
to persons skilled in
the art, including but not limited to the use of suitably shaped rollers to
cradle the liner 100, with
one or more of the rollers being a drive roller that can be actuated to rotate
the liner 100.
It will be readily appreciated by those skilled in the art that various
modifications of the
present invention may be devised without departing from the essential concept
of the invention,
and all such modifications are intended to be included in the scope of the
claims appended
hereto.
In this patent document, the word "comprising" is used in its non-limiting
sense to mean
that items following that word are included, but items not specifically
mentioned are not
excluded. A reference to an element by the indefinite article "a" does not
exclude the possibility
that more than one of the element is present, unless the context clearly
requires that there be only
one such element.
