U.S. patent application number 11/990870 was filed with the patent office on 2009-08-13 for removal of magnetic particles from a fluid.
Invention is credited to Martin McKenzie.
Application Number | 20090200220 11/990870 |
Document ID | / |
Family ID | 37192604 |
Filed Date | 2009-08-13 |
United States Patent
Application |
20090200220 |
Kind Code |
A1 |
McKenzie; Martin |
August 13, 2009 |
Removal of magnetic particles from a fluid
Abstract
An apparatus (10) for removing magnetic particles from a mud
slurry is disclosed. The apparatus (10) includes one or more
endless belts or chains (12) enclosed almost wholly within a pipe
(22a). A motor (28) drives the chain (22) around the pipe (22a).
When the pipe (22a) is located within a mud slurry, magnetic
particles in the mud slurry are drawn to the pipe (22a) and carried
along the outside and away from the slurry until a collar (29) is
reached. Once so separated the particles can be collected for
disposal. The chain (12) comprises a series of units linked
together. Each unit includes a magnet (50) with pole pieces (51a,
51b) at either pole to direct magnetic flux. Wear discs (52a, 52b)
prevent the magnets (50) and pole pieces (51a, 51b) from abrasion
as they are drawn through the pipe (22a). Units can be included in
the chain (12) which units do not include a magnet, thereby
providing a break in the field, allowing particles to fall away
from the collar region.
Inventors: |
McKenzie; Martin; (Ellon
Aberdeenshire, GB) |
Correspondence
Address: |
Thomas M. Galgano
20 W. Park Avenue, Suite 204
Long Beach
NY
11561
US
|
Family ID: |
37192604 |
Appl. No.: |
11/990870 |
Filed: |
August 22, 2006 |
PCT Filed: |
August 22, 2006 |
PCT NO: |
PCT/GB2006/003148 |
371 Date: |
March 20, 2009 |
Current U.S.
Class: |
210/222 |
Current CPC
Class: |
B03C 1/286 20130101;
B03C 1/20 20130101; B03C 2201/18 20130101; B03C 2201/20 20130101;
B01D 35/06 20130101 |
Class at
Publication: |
210/222 |
International
Class: |
B03C 1/28 20060101
B03C001/28 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 24, 2005 |
GB |
0517252.3 |
Jul 21, 2006 |
GB |
0614493.5 |
Claims
1. An apparatus for removing magnetic particles from a liquid or
slurry; said apparatus comprising; an endless belt of chain,
including along its length, a plurality of magnetic field
generation units to attract magnetic particles; an enclosing means
preventing contact of magnetic particles with said magnetic field
generation units; drive means to circulate said endless belt within
the said enclosing means; and collection means to collect the
particles.
2. An apparatus according to claim 1, wherein said magnetic field
generation unit comprises at least one permanent magnet.
3. An apparatus according to claim 2, wherein said magnetic field
generation unit comprises at least one pole piece to direct the
magnetic field of said magnets.
4. An apparatus according to claim 1, wherein said magnetic field
generation unit includes at least one wear disc (52a) to reduce
wear on a magnet or a pole piece.
5. An apparatus according to claim 2, wherein said magnet includes
a hole along its axis.
6. An apparatus according to claim 1, wherein said endless belt or
chain comprises a plurality of units linked together.
7. An apparatus according to claim 6, wherein said endless belt or
chain includes at least one unit not including a magnet.
8. An apparatus according to claim 1, wherein said apparatus
includes a plurality of enclosing means, arranged in an array each
enclosing means enclosing said endless belt.
9. An apparatus according to claim 8, wherein the relative
positions of said enclosing means can be adjusted.
10. An apparatus according to claim 1, wherein said enclosing means
is mounted to mounting means.
11. An apparatus according to claim 1, wherein said enclosing means
is formed of steel.
12. A device for removing magnetic particles from a liquid or
slurry, the device comprising; an elongate magnetic field
generator; a casing separating said generator from a liquid or
slurry; the magnetic field passing through said casing causing
magnetic particles in a slurry to be attracted to said device and
be retained on said casing; and means for removing the attracted
particles from the field generated by said generator, enabling the
particles to be removed from said device (70).
13. A device according to claim 12, wherein said device comprises a
helical cleaning means, rotatable about the axis of said magnetic
field generator, the inner surface of said cleaning means engaging
said casing and rotation of said cleaning means moving the
attracted particles from the field generated by said generator.
14. A device according to claim 12, wherein said device includes a
cleaning barrier, engaging said casing said barrier being movable
between a first and second position, the motion causing particles
to move out of the field generated by said generator.
15. A device according to claim 12, wherein said magnetic field
generator comprises a stack of magnets alternating polarity along
the length of the generator.
16. A device according to claim 12, wherein the magnetic poles are
orientated along the length of the axis of said magnetic field
generator.
17. A device according to claim 12, wherein the poles are
orientated perpendicularly to the axis of said magnetic field
generator.
18. An array for removing magnetic particles from a liquid or
slurry, the device comprising; at least one magnet, said magnet
being housed within a casing; said housing being attached to a
framework, which framework being locatable on a fluid-carrying
channel, and such that said casing is at least partially immersed
in the fluid.
19. (canceled)
20. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention relates to apparatus for removing
magnetic particles from a fluid. The apparatus finds particular
application in the oil and gas industry in relation to separating
iron-containing swarf from free-flowing or viscous liquid mud.
BACKGROUND TO THE INVENTION
[0002] Oil and gas wells usually have their bore holes lined with
steel pipes, referred to normally as casing. In mature wells, when
oil or gas production drops below economic production levels, it is
often useful to utilise at least part of said bore hole. In order
to be able to do this one alternative is to remove the casing
completely. However, it is more cost effective to simply drill the
pipeline out, or at least to drill a window in the pipeline. The
window can then be used to allow a drilling assembly to exit the
bore hole and reach a new part of the reservoir.
[0003] Such a method obviously produces large quantities of steel
swarf derived primarily from the pipeline. The swarf is mixed
during the drilling process with large quantities of mud either
from the bore hole or from its introduction as a lubricant.
Typically the mud/swarf mixture will comprise a sufficient quantity
of water to enable the mixture to flow.
[0004] Due to the high steel content of the mud when it exits the
bore hole and its potential hazard, in part due to the sharpness of
the metal slithers it contains, disposal or re-use of the mud can
be problematic. One method of decontamination is simply to remove
excess water from the mixture and then separate the larger swarf
pieces by hand. This is obviously a time consuming and potentially
dangerous mode of separation.
[0005] It is an object of the present invention to provide an
improved apparatus to separate the solid magnetic or magnatisable
particles from a fluid system and in particular, apparatus which
can be applied in the oil and gas industry.
SUMMARY OF THE INVENTION
[0006] According to a first aspect of the invention there is
provided an apparatus for removing magnetic particles from a liquid
or slurry; the apparatus comprising; [0007] an endless belt or
chain, including along its length, a plurality of magnetic field
generation units to attract magnetic particles; [0008] an enclosing
means preventing contact of magnetic particles with the magnetic
field generators; [0009] drive means to circulate the endless belt
within the enclosing means; [0010] collection means to collect the
particles.
[0011] The apparatus provides a simple and efficient method to
separate the magnetic particles from the slurry allowing the
magnetic particles to be disposed of more easily or to be
reused.
[0012] Preferably, one or more magnetic field generation units
comprises one or more permanent magnets, which do not therefore
require an electricity supply to function. The units further
preferably comprise one or more pole pieces to direct the magnetic
field of the magnets. Optionally the units include one or more wear
discs to reduce wear on the magnets or pole pieces. Advantageously,
the or each magnet includes a hole along its axis to enable linkage
means to be attached to the unit.
[0013] Preferably the endless belt or chain consists of a plurality
of units linked together. Particularly preferably the chain
includes one or more units not including a magnet. The gap in the
magnetic field resulting in the lack of magnet allows swarf to be
more easily removed from the apparatus.
[0014] The apparatus preferably includes one or more enclosing
means arranged in an array each enclosing means associated with an
endless belt. By combining a plurality of enclosing means a larger
flow of mud can be subjected to swarf removal.
[0015] The relative positions of enclosing means can optionally be
adjusted, thereby allowing channels of different shapes to be used
to allow mud flow. Advantageously, the or each enclosing means is
mounted to mounting means. Further advantageously, the enclosing
means is formed of steel.
[0016] According to a second aspect of the invention there is
provided a device for removing magnetic particles from a liquid or
slurry, the device comprising;
an elongate magnetic field generator; a casing separating the
generator from a liquid or slurry; the magnetic field passing
through the casing causing magnetic particles to be attracted to
the device and be retained on the casing; means for removing the
attracted particles from the field generated by the generator,
enabling the particles to be removed from the device.
[0017] Preferably, the device comprises a helical cleaning means,
rotatable about the axis of the magnetic field generator, the inner
surface of the cleaning means engaging the casing and rotation of
the cleaning means moving the attracted particles from the field
generated by the generator.
[0018] Alternatively, the device preferably includes a cleaning
barrier, engaging the casing around the generator, the barrier
being moveable between a first and second position, the motion
pushing the particles out of the field generated by the generator.
The particulars can thereby easily be removed from the device.
[0019] Advantageously, the magnetic generator comprises a stack of
magnets alternating polarity along the length of the generator.
[0020] Optionally, the magnetic poles are orientated along the
length of the axis of the field generator. The magnetic field
generated levels to push away from the device which is of
assistance when moving particles. Alternatively, the poles are
orientated perpendicularly to the axis of the field generator. The
magnetic field assists motion of the particles along the axis of
the device.
[0021] According to a third aspect of the invention there is
provided an array for removing magnetic particles from a liquid or
slurry, the device comprising;
one or more magnets, said the or each magnet being housed within a
casing; the housing being attached to a framework, which framework
being locatable on a fluid-carrying channel, and such that the or
each casing is at least partially immersed in the fluid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The invention will now be described with respect to the
accompanying drawings which show by way of example only,
embodiments of swarf removing apparatus. In the drawings;
[0023] FIG. 1a is a side view of a first embodiment of swarf
removing apparatus;
[0024] FIG. 1b is an end view of the first apparatus shown in FIG.
1a;
[0025] FIG. 2 is an illustrative side view of the embodiment of
FIGS. 1a and 1b;
[0026] FIGS. 3a, 3b are side views illustrative of a first
configuration of the embodiment of FIG. 1;
[0027] FIGS. 4a, 4b are side views illustrative of a second
configuration of the embodiment of FIG. 1;
[0028] FIGS. 5a to 5e are diagrams of magnetic elements and means
of joining the elements together;
[0029] FIGS. 6a, 6b are detailed side and end views of drive means
for use in the apparatus;
[0030] FIG. 7 shows two configurations of the second embodiment of
swarf removing apparatus;
[0031] FIGS. 8a to 8d show in use configurations of the apparatus
of FIG. 7;
[0032] FIG. 9 shows a further example of the second embodiment of
swarf removing apparatus;
[0033] FIG. 10 shows an array of swarf removing apparatus according
to the second embodiment;
[0034] FIGS. 11A, 11B show two orientations for magnets within the
second embodiment; and
[0035] FIG. 12 shows further apparatus for use in the embodiment of
FIG. 1;
DETAILED DESCRIPTION OF THE INVENTION
[0036] Referring initially to FIGS. 1 and 2, these show an overview
of an apparatus combining two embodiments of the invention for use
as a swarf remover, removing swarf from a mud slurry. In FIG. 1,
swarf is to be removed from mud flowing from right to left across
the figure. The apparatus shown comprises two distinct sections
which act together to remove the maximum percentage of swarf.
[0037] In the first section, the mud is passed around a series of
steel pipes 11 of an apparatus 10 through which pipes 11 an endless
chain of magnets, moving in the opposite direction to the flow of
the mud, is circulated. In the second section, the mud passes a
series of static magnets 13 the magnets 13 remove any swarf not
caught in the first section.
[0038] FIG. 2 is a schematic representation of the apparatus 10,
showing a series of magnets 21, linked together into an endless
chain drawn through a steel pipe 22a. Motive force for the movement
of the magnets 21 is provided by the rotating driver 23. Swarf
attracted towards the magnets 21 is held against the outside of the
steel pipe 22a and drawn with the magnets 21 along the pipe 22a.
Eventually, the swarf is prevented from moving further along the
pipe 22a by a collar 24 located across the pipe 22a. As the magnets
21 continue through the pipe therefore, the magnetic force holding
the swarf against the pipe 22a is removed and the swarf drops into
a collection chute 25.
[0039] The apparatus 10 is shown in more detail in FIG. 1 and
comprises a series of magnets 21 linked together to form a chain
12. The chain 12 is drawn through the pipe 22a by a drive means 26
mounted to a support frame 27. Motive force to the drive means 26
is provided by a motor 28, driving a shaft 29--mounted on bearings
30--onto which a drive gear 31 is mounted. The drive gear 31
comprises a series of paddles or projections 32 to engage the chain
12 of magnets conveying the chain 12 through the pipe 22a.
[0040] In FIG. 1b, an apparatus is shown having four magnetic
chains and pipes 22a-d mounted alongside each other to enable the
width of the channel 33 carrying the mud to be subjected to the
magnetic fields generated. The whole volume of the mud is therefore
subject to magnetic fields to remove the metal swarf. As can be
seen from FIG. 1b, the drive gears associated with the chains are
mounted about a common shaft. Moreover, the swarf collected from
each pipe is collected into the common chute 25.
[0041] The above arrangement allows the apparatus to be used in mud
channels of differing cross-sectional shape. This is illustrated in
FIGS. 3 and 4. In FIGS. 3a, 3b the channel 33 is of rectangular
cross-section and the steel pipes 34a to d are lined up with one
another much that the lowest point of each pipe 34a to d is at
substantially the same distance from the channel 33 as its
neighbour. In FIGS. 4a, 4b the channel 43 is deeper on one side. By
tilting the drive means associated with certain of the pipes 44a to
d, the pipes can be lowered further into the channel so that swarf
does not slip underneath the pipe. The side view of the pipes in
FIG. 4a shows the non-overlapping configuration of the pipes.
[0042] It will be obvious to the skilled man, that through this
means, channels of different cross-sectional shape to the above
exemplified can be dealt with by the apparatus.
[0043] Turning to the magnetic chain, this is shown in more detail
in FIGS. 5a to d. The basic unit for the chain is shown in FIGS. 5a
to c and comprises a magnet with means for linking this to
neighbouring magnets.
[0044] The basic magnetic unit comprises a substantially
cylindrical magnetic element or magnet 50 formed of a transition
metal magnet having a cylindrical hole along its axis. Pole pieces
51a, 51b are affixed to the end of the magnet 50. The pole pieces
51a, 51b are formed of soft iron and act to direct magnetic flux
out of the pipe to facilitate attraction of swarf in the mud flow.
Wear discs 52a, 52b which are resistant to wear are secured to each
pole piece 51a, 51b. As can be seen from the Figures, the diameter
of the wear discs 52a, 52b greater than that of the magnet 50 and
the pole pieces 51 to ensure that the wear discs 52a, 52b wear away
sacrificially. The elements 50, 51 and 52 can be quickly removed
and replaced with a similar unit when necessary.
[0045] In order to enable the magnets to be secured to one another,
the unit is provided at a first end with a female clevis 57 and at
a second end with a corresponding male clevis 58. To ensure that
the basic unit remains together, a stud 53 is fixed across the
assembly passing through the holes in the magnet 50, pole pieces
51a, 51b and wear discs 52a, 52b. A screw or bolt is passed through
the holes 54, 55 in each clevis 57, 58 and through the stud 53.
[0046] In order to link adjacent magnets therefore, the clevis of
each neighbouring magnetic unit is aligned, with opposite poles
adjacent to each other, and secured to one another, allowing the
units to pivot relative to one another. Sufficient units are linked
together eventually to form an endless chain which passes through
and is enclosed almost completely, by the steel pipe.
[0047] In use it has been found that care needs to be taken to
provide breaks in the magnetic field, to allow the swarf to be
released from the pipe, to enable the outside of the pipe 22 around
the region of the collar 24 to be kept free of swarf. One solution
to this problem is to replace the magnet in alternate links with a
dummy, non-magnetic element 56. As the chain moves through the pipe
therefore, the region around the collar 24 is periodically subject
to magnetic fields which are not strong enough to retain the swarf,
allowing the swarf to drop into the collection chute 25. It will be
apparent that the weakening of the field can be achieved in a
number of ways. For example, in similar fashion to the embodiment
described above, every third, fourth etc magnet can be excluded.
Alternatively or additionally, the distance between magnets can be
increased.
[0048] Although it has been found advantageous to include gaps in
the field it is not essential, and the amount of swarf in the
collar region can be allowed to build up until its own weight
causes a proportion of the mass built up to fall into the
chute.
[0049] FIG. 5e shows an alternative, more flexible linkage means 59
between adjacent magnets, allowing curvature of the chain in two
places.
[0050] A drive mechanism for the chain including the magnet units
of FIGS. 5a to 5d is shown in FIGS. 6a, 6b which illustrate a drive
head assembly. A drive wheel 60 is mounted to a rotatable shaft 61.
The magnet is held between the teeth 62 of the drive wheel 60 and
as the wheel 60 rotates therefore, the endless chain of magnets is
drawn around the pipe 22. Loosening of the nut 63 allows the
assembly to be rotated about the shaft 61 in order to change the
orientation of the steel pipe 22 in the manner described above.
Once the pipe 22 is in the required orientation, the nut 63 can be
tightened. Tensioning of the chain of magnets can be achieved
through the use of tensioning adjuster 64. This effectively moves
the drive gear to make the overall length of the path followed by
the chain longer or shorter.
[0051] In use therefore, the supporting frame is located above the
channel through which the mud contained in the swarf is to flow.
The drive mechanism and the steel pipes through which the magnetic
chains are drawn, are located on the support frame such that the
base of the steel pipes guiding the chain are close to the bottom
of the channel and spaced apart sufficient that the space between
the pipes is small enough for the entire width of the mud in the
channel to be subjected to a magnetic field. If necessary, a pipe
can be tilted to enable the pipe layout to conform to the shape of
the channel. Moreover, the pipes are aligned such that the movement
of the chain within the pipe is opposed to the flow of the mud in
the section of pipe below the mud surface.
[0052] The drive meal's is then activated, circulating the magnetic
chain within the pipe. The mud is allowed to flow within the
channel. As the mud flows past the pipes, metal swarf is attracted
to the pipe and, due to the chain circulation, is carried out of
the mud along the outside of the pipe until it engages the collar
24. As a magnetic element 50 of the chain together with the swarf
particles attracted by that element 50 circulates beyond the collar
24, the magnetic field retaining the swarf particles drops and the
swarf particles fall from the pipe into a collection chute. Using
the above apparatus, and a typical swarf-containing mud,
approximately 800-1000 gallons of mud have been processed at a rate
of yield of 1 ton/hour of swarf.
[0053] The second section of the apparatus shown in FIG. 1 is shown
in FIG. 7. In FIG. 7, a rod 70 comprises an outer tubular steel
case 71 closed at its in use lower end to prevent penetration of
water into the tubular case 71. Slideably mounted within the case
71, a cylindrical magnet 72 is capable of moving from a lower in
use position (left-hand view) to a raised cleaning position
(right-hand view). The magnet 72 comprises alternatively rare-earth
type magnets 77 and soft iron pole pieces 78, again to force lines
of flux outside the case 71. In this section, the magnets 77 are
orientated in N-N, S-S relationship with neighbouring magnets. As
can be seen from FIG. 7, the height of the magnet is approximately
half that of the case 71. A shaft-rod 73 is mounted at its first
end to the upper end of the magnet 72 and passes through the upper,
open end of the case 71. A seal is maintained at the open end to
prevent water ingress. The second end of the shaft 73 comprises a
handle 74 to operate the rod 70.
[0054] The rod 70 further includes a swarf stop 75 in the form of
an annulus mounted about the outside of the case 71 and at the
height of the top of the magnet 72, when the magnet 72 is in its
lower position. A support 76 enables the rod 70 to be held in
position in the channel by a suitable frame.
[0055] In use therefore, the rod or series of rods 70 is positioned
in the channel. The magnet 72 is lowered within the case 71 by
operation of the swarf-rod 73. The flow of mud within the channel
is commenced and as the mud flows around the rod 70, swarf in the
mud is attracted to the case 71 and held there by the magnet 72.
When sufficient swarf has been collected, the rod 70 is lifted out
of the mud stream. The handle 74 is used to pull the magnet 72 from
one end of the case 71 to the other. As this occurs, the
accumulated swarf is pulled along the case until it reaches the
stop 75. Eventually, as all of the magnet 72 is withdrawn above the
level of the stop 75, the swarf drops off, preferably into a
suitable collection vessel.
[0056] FIGS. 8a to 8d show an alternative embodiment comprising a
series of rods 80, secured to a framework 81. The rods 80 comprise
an outer casing, formed of steel. The casing houses a series of
magnets, fixed in position, and separated by pole pieces as
described above. The magnets can be orientated, with respect to a
neighbouring magnet in a N-S, N-N or S-S configuration. The
framework 89 is designed specifically for the channel 82 in which
the mud flows, and is such that the rods 80 follow the contours of
the channel 82. In use, once the rods 80 have accumulated
sufficient swarf, the framework 81 is lifted out of the channel 82
and the swarf removed, usually by hand. The framework 81 can then
be replaced in the channel.
[0057] A further embodiment of the rods shown in FIG. 7 is shown in
FIG. 9. The rod 100 is designed to be self cleaning which again
minimises operator time which needs to be devoted to maintenance.
The rod 100 comprises a central shaft 101 which contains a series
of magnets assembled together in the same fashion as those in the
embodiment of FIG. 7. The rod 100 further comprises a helix 102
wound about the shaft 101: the inner surface of the helix 102 being
in contiguous relationship with the surface of the shaft 101. The
helix 102 is rotatably mounted and its motion about the shaft 101
is driven by the motor 103 which drives the helix 102 in the
direction indicated; the helix therefore functions in the same
fashion as a conventional auger.
[0058] As will be envisaged therefore any swarf attracted to the
magnets in the shaft 101 will be pushed by the helix 102 up the
shaft 101 towards the motor 103. Eventually as the swarf reaches
the upper half of the shaft 101, the magnetic attraction exerted by
the magnets in the shaft 101 on the swarf reduces eventually until
the force is insufficient to retain the swarf and it falls from the
rod 100. The rod 100 is orientated at around 45.degree. to the
horizontal to ensure that when the swarf is released from the rod
it does not fall back down the rod 100, but instead falls into a
collection element (not illustrated).
[0059] In FIG. 10, an array of rods 110 shown in FIG. 9 is shown.
The array comprises four rods 110 (which are according to the rod
100 described above) mounted together and deployed in a vertical
orientation in a channel (not illustrated) through which mud from
which swarf is to be removed is flowing. The array has a further
rod 104 which is also of the same type as 100, which is orientated
horizontally. The rod 104 is so positioned that the magnetic
elements of the rod 110 are sufficiently close to the non-magnetic
regions of the vertically orientated rods 100 to remove any swarf
from these regions of the vertically orientated rods 100.
[0060] In use therefore, swarf removed from the mud flow by the
rods 110 is conveyed by the helices 102 up the shaft 101 of the rod
110. The swarf is eventually conveyed into the non-magnetic region
of the rods 110. Here the swarf is attracted to the magnetic region
of the rod 104. From here, the swarf is conveyed along the rod 104
by the helix 102 in the direction of the motor 105. Swarf is
conveyed to the non-magnetic region of the rod 104 from which it
falls under gravity and can be collected in a suitable
container.
[0061] FIGS. 11A, 11B describe two orientations for magnets
contained within rods. In FIG. 11A, the magnet 120 has a north pole
running along one side of the length of an internal core 121 of the
rod 122. As can be seen from the sectional drawing of this rod, the
resultant magnetic flux extends away from the rod and is symmetric
across the plane running from the north pole to the south pole. In
the arrangement shown in FIG. 11B, the magnets 125 are arranged in
a stacked fashion giving a series of alternate poles 126. As can be
seen from the section taken through the stack of magnets shown
under the main drawing of the rod. In this particular arrangement
the magnetic flux assists in movement of swarf along the rod, as
flux lines connect adjacent magnets.
[0062] In a further embodiment of the invention, as shown in FIG.
1a, the two above embodiments can be used co-operatively with one
another. In this embodiment, apparatus including an endless chain
described above is used upstream of the rods, the rods being used
effectively to collect the swarf missed by the chain apparatus.
[0063] FIG. 12 shows a further embodiment of an apparatus including
an endless chain, the apparatus being designed particularly for use
where space for the chain to turn is limited and the path described
by the chain includes regions of high curvature. In addition to the
features described above, the apparatus includes a gearing
mechanism 130 to assist the motor (FIGS. 1, 28) to circulate the
chain and to ensure that the tension within the chain remains
suitable.
[0064] In an alternative embodiment, not illustrated, the swarf can
be removed from the steel pipe by a brush means. Such a brush means
is particularly suited for use where the magnetic field generated
by the magnetic chain is fairly continuous, and at least sufficient
to hold the swarf against the pipe in the region of the collar.
[0065] It will be appreciated that the embodiment of FIGS. 7-11
employing the static magnets and the embodiment incorporating the
moving magnets can be used independently of one another. In some
situations the more portable static magnet arrangement is more
easily deployed and serviced, whereas in other the moving magnet
arrangement will be more suitable.
[0066] It will of course be understood that the invention is not
limited to the specific details described herein, which are given
by way of example only, and that various modifications and
alterations are possible with the scope of the appended claims.
* * * * *