Note: Descriptions are shown in the official language in which they were submitted.
CA 02658718 2009-03-17
TUBE STUB REMOVAL APPARATUS AND METHOD
[0001] Field and Background of Invention
[0002] The present invention relates generally to the field of tube
extraction, and
more particularly to an improved apparatus and method of removing tubes and/or
tube
stubs from structures comprising multiple tubes, such as boilers, condensers,
evaporators, drums, and the like.
[0003] A typical heat exchanger comprises a pair of parallel tube sheets,
a
plurality of baffle plates, and a plurality of heat exchanger tubes. The tube
sheets are
located at the ends of the heat exchanger. The baffle plates are positioned
between the
tube sheets and generally parallel thereto. The tubes extend between the tube
sheets
and through the baffle plates and are supported by the tube sheets. The tube
sheets
ancl baffle plates have a series of aligned holes formed therein, and the
tubes are
inserted through these holes and then expanded in the areas of the tube sheets
into
fluid-tight pressure contact therewith.
[0004] In the course of normal preventative maintenance and/or repair it
may be
necessary to remove and replace one or more tubes from the structure. This
process
generally begins by cutting the tubes to form a tube stubs protruding several
inches
from the tube sheet. The expanded fluid tight pressure contact ends of the
tube stubs
are then withdrawn from the sheet by forced or deformation.
[0005] Various tools are known for removing tube stub, such as wedges
that
mechanically deform the tube stub, collapsing the tube inward upon itself.
Anvils and
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hammers are also readily used to mechanically force collapsed and uncollapsed
tubes
out a tube sheet hole or bores.
[0006] Additional prior art tube stub removal devices include:
[0007] U.S. Pat. No. 4,355,450 to Miller discloses a tube extracting
mechanism
having a wedge with expandable circumferential gripping teeth.
[0008] U.S. Pat. No. 3,791,011 to Keys shows a tube pulling device with
longitudinally fixed radially expanding gripping means which engages the tube
wall for
withdrawal of the tube from the tube sheet.
[0009] U.S. Pat. No. 3,507,028 to StellateIla shows a hydraulic tube puller
with
radial expansion of an inner end portion of a tube gripping member into the
tube wall.
[00010] The primary problem with all these prior art structures is the
imposition of
expansion force on the tube precisely at the point where it is engaged with
the tube
sheet which can damage the metal between adjacent holes and cause the holes in
the
tube sheet to enlarge and not properly grip a new tube when it is expanded.
Moreover,
the prior art devices require multiple devices, increasing the likelihood of
breakage of
the removal devices, and resulting in an increase of down-time of the
structure for
repairs.
[00011] U.S. 11/762,104, discloses
a recent
innovation that overcomes many problems encountered during traditional tube
stub
removal. U.S. 11/762,104 teaches a method of tube stub removal wherein a metal
tube
stub is heated then subsequently elongated and circumferentially contracted
for the
purpose of readily removing a tube from a tube sheet. While a beneficial
method over
prior art, the method of 11/762,104 requires multiple operators thereby
increasing tube
removal costs and down time related to tube removal. Accordingly, a need
exists for an
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improved method of tube stub removal that require only a single operator and
overcome
deficiencies of the prior art.
[00012] The present invention improves upon the method of tube stub
removal
disclosed in U.S. 11/762,104, and provides a novel apparatus that allows a
single
operator to readily remove a tube stub from a tube sheet without damaging the
tube
sheet, in addition to the additional advantages as discussed herein.
[00013] Summary of Invention
[00014] It is an object of the present invention to provide an apparatus
and method
of tube extraction that is easy to use and does not cause damage to the tube
sheet
upon tube withdrawal.
[00015] A further object of the invention is to provide an apparatus and
method of
tube extraction enabling a single technician to quickly and effectively remove
tubes
having belled ends from a tube sheet.
[00016] A further object of the invention is to provide an apparatus and
method of
tube extraction enabling a single technician to quickly and effectively remove
ribbed
tubes from a tube sheet.
[00017] A further object of the invention is to provide an apparatus and
method of
tube extraction enabling a single technician to quickly and effectively remove
ribbed
tubes having belled ends from a tube sheet.
[00018] Accordingly, the present invention introduces a tube pulling
apparatus
comprising an induction heating coil attached to a inner ram, a outer ram
concentrically
surround the inner ram, and a sheath concentrically surrounding the outer ram.
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[00019] The present invention further introduces a method of tube
extraction
comprising providing a tube pulling apparatus comprising an inner ram attached
to an
induction heating coil, and a outer tube ram concentrically surrounding the
inner ram;
placing the apparatus over a tube stub, attaching the outer ram to the tube
stub,
lowering the induction heating coil into the tube stub, heating the tube stub
with the
induction heating coil, and removing the heated tube stub from the tube drum
with the
outer ram.
[00020] The various features of novelty which characterize the invention
are
pointed out with particularity in the claims annexed to and forming a part of
this
disclosure. For a better understanding of the invention, its operating
advantages and
specific objects attained by its uses, reference is made to the accompanying
drawings
and descriptive matter in which a preferred embodiment of the invention is
illustrated.
[00021] Brief Description of the Drawings
[00022] In the drawings:
[00023] FIG. 1 is a graphical representation of a tube sheet and tube
stubs;
[00024] FIG. 2 is a graphical representation of a tube removal apparatus
positioned over a tube stub;
[00025] FIG. 3 is a cross sectional view of a tube removal device of the
present
invention positioned over a tube stub;
[00026] FIG. 4 is a graphical representation of an elongated tube;
[00027] FIG. 5 is a graphical representation of an elongated tube broken
between
the bell and the rings.
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[00028] FIG. 6 is a graphical representation of an inner ram according to
the
present invention;
[00029] FIG. 7 is a graphical representation of an alternative embodiment
of an
inner ram according to the present invention.
[00030] FIG. 8 is a graphical representation of an outer ram according to
the
present invention;
[00031] FIG. 9 is a graphical representation of an alternative embodiment
of an
outer ram according to the present invention.
[00032] FIG. 10 is a graphical representation of an sheath according to
the present
invention;
[00033] FIG. 11 is a graphical representation of an alternative embodiment
of a
sheath according to the present invention.
[00034] FIG. 12 is a cross sectional view of a tube stub pulling apparatus
using the
sheath of Fig. 10;
[00035] Fig 13 is FIG. 12 is a cross sectional view of a tube stub pulling
apparatus
using the sheath of Fig. 11;
[00036] Description of the Preferred Embodiments
[00037] Referring now to the drawings, in which like reference numerals
are used
to refer to the same or similar elements, FIG. 1 is a graphical representation
of a type of
tube sheet known as a tube drum 10. Tube drum 10 contains at least one tube or
tube
stub 15, and in many cases a plurality thereof. Tubes 15 generally extended
through
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the wall of the tube drum 10, such that a portion of the tube 15 is
circumferentially
surrounded by the tube drum 10. The tube end extending in the tube drum 10 may
be
belled 11 (Fig. 4, 5) as a means to secure and seal the tube 15 to the tube
drum 10.
Ribs 14 (Fig 4, 5) may also be present on the tube 15 for similar purposes.
[00038] Referring
now to Fig 3. a cross sectional view of a tube removal apparatus
27 according to the present invention is show. The apparatus 27 comprises
three
distinct concentrically arranged elements, an inner ram 18, and outer ram 24,
and a
sheath 32.
[00039] In a
first step, tube stub removal is accomplished by placing the apparatus
27 over the tube stub 22, such that inner ram 18 is capable of descending into
tube stub
15 and the outer ram 24 circumferentially surrounds tube stub 15. As would be
appreciated by the skilled artisan, the diameters of both the inner ram 18 and
outer ram
24 can be readily adjusted to accommodate any tube stub diameter.
[00040] In a
subsequent step, the inner ram 18 is lowered into, and subsequently
removed from, the inner circumference of tube stub 22. The lower portion of
inner ram
18 comprises an induction heating coil 42 such as the coil described in U.S.
Patent
6,778,057. Heat
provide by the induction heating coil
42 rapidly elevates the temperature of the tube stub from the inside out,
softening the
tubes metallic structure, making it more docile.
[00041] In
another step, the outer ram 24 is attached to a portion of the tube stub
15. Subsequent to induction heating outer ram 24 provides and a tensile force
that
elongates and removes the softened tube stub from the tube drum, or
sufficiently
removes the tube stub in a manner that allows an apparatus 27 operator to
complete
removal by hand.
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[00042]
Fig.'s 6 and 7 are graphical representation of inner ram 18 embodiments
according to the present invention. Movement of inner ram may be controlled
electronically or hydraulically via inner ram rod 29 (Fig. 6) or manually via
heating
control arms 36, 37 (Fig. 7). Alternatively, movement of inner ram 18 can be
controlled
electronically by a combination of electronical, hydraulic or manual means.
[00043]
Inner ram 18 may also be fitted with cooling fluid inlet 51 and outlet 52 to
mitigate overheating. In one embodiment optional cooling channels 58 within
inner ram
18 cool the inner ram 18 in addition to provide a cooling fluid to the coil.
In another
embodiment a stream of air is provide through the cooling channel.
[00044]
Fig.'s 8 and 9 are graphical representation of outer ram 24 embodiments
according to the present invention. Movement of outer ram may be controlled
electronically or hydraulically via an outer ram rod 37. Alternatively,
multiple outer ram
rods may control movement of out ram.
[00045]
During tube stub removal, outer ram 24 is attached to tube stub 15.
Attachment can occur via one or more clamps 6, or the additional step of
creating one
or more holes or orifices 8 in the tube stub 15 and placing a rod (not shown)
though
similar holes or orifices 47 in the outer ram 24.
[00046]
Operation of the outer ram 24 provides tensile force to the heated tube
stub, while sheath 32 provide supports for the apparatus 27 against the tube
drum 10
during operation of outer ram 24.
In a preferred embodiment, the elongation
circumferentially reduces a portion of the tube diameter 17, allowing easy
removal of the
tube 15 from the tube drum 100 without damaging the tube drum 100. In an
alternative
embodiment heating may be localized around the belled 11, Fig 5, and/or ribbed
14
section of tube 15, such that the elongation step tears the tube into two
pieces. In this
embodiment one piece of the torn tube is removed from the inside of the tube
drum 10,
and one piece from the outside of the tube drum 10.
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[00047] Fig.'s 10 and 11 are graphical representation of sheath 32
embodiments
according to the present invention. Sheath 32 provides structural support for
the inner
ram 18 and outer ram 24. Handles 70, 71 allow an operator to control the
apparatus
and may be equipped with buttons (not shown) to control the movement of inner
ram 18
and outer ram 24. Lines 60 provide hydraulic fluid and/or electric current to
the
apparatus 27, depending on the embodiment. In some embodiments sheath 32
includes one or more a channel 63 (Fig. 10) wherein inner ram 18 control arms
36, 37
and/or a rod connecting the tube stub 15 to outer ram 24 pass there through.
In other
embodiments (Fig. 11) no channel is necessary. Cross sectional views of tube
stub
apparatus 27 embodiments utilizing Fig.'s 10 and 11 sheath's 32 are shown in
Fig.'s 12
and 13.
[00048] While specific embodiments of the invention have been shown and
described in detail to illustrate the application of the principles of the
invention, it will be
understood that the invention may be embodied otherwise without departing from
such
principles.
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