Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
ISOLATION KNIFE GATE VALVE
TECHNICAL FIELD
[0001] Isolation knife gate valves.
BACKGROUND
[0002] Isolation knife gate valves (Isolation KGV) typically seal
either using a
perimeter seal that extends around the perimeter of the gate ending at a
packing seal or
using a face seal that seals against the face of the gate. A face seal
generally can only seal
effectively in one direction of flow. Bidirectional sealing can be achieved by
face seals
on both sides of a gate, but this creates a pocket beneath the gate that is
not exposed to
much flow but is accessible to fluid passing through the valve when the valve
is open.
This pocket can collect debris which can eventually impede the closing of the
isolation
KGV. A perimeter seal ending at a packing seal provides bidirectional sealing
without
such a pocket, but it is difficult to provide fully leak-tight sealing with
only a perimeter
and packing seal particularly in valves that are large in size or under high
pressures or
especially both. Valves used in oilsands and mining, for example, can be
upwards of 36
inches in diameter.
[0003] It is also desired for a KGV to have a strong uni-body
construction and for
the seals to be replaceable.
SUMMARY
[0004] An isolation knife gate valve has a valve housing including
first and
second pipe couplings for connecting to respective pipes, the valve housing
defining an
opening and a gate slot extending in a first direction away from the opening.
A gate is
movable within the gate slot opposite to the first direction to a closed
position in which
the gate obstructs the opening and in the first direction to one or more open
positions, the
gate having first and second faces. First and second face seal elements are
removably
attachable to the valve housing and when installed positioned interior to the
couplings to
seal against the first and second faces of the gate.
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Date Regue/Date Received 2023-02-09
[0005] In various embodiments, there may be included any one or more
of the
following features: The valve housing may be a uni-body valve housing. The
isolation
knife gate valve may also include a perimeter seal mounted within the gate
slot for
sealing against the gate when the gate is in the closed position. The
perimeter seal may
also define first and second side surfaces, the first and second face seal
elements when
installed including respective first and second flexible seal elements
extending around the
opening, each of the first and second flexible seal elements having respective
first
portions respectively sealing against the first and second side sealing
surfaces of the
perimeter seal, the first and second flexible seal elements also having
respective second
portions sealing respectively against the first and second faces of the gate
when the gate
is in the closed position. The first and second flexible seal elements may
each comprise
an 0-ring. When the isolation knife gate valve is in an operating fully open
position, a
portion of the first and second faces of the gate may remain in contact with
the first and
second flexible seal elements. The first and second face seal elements may
also be
configured to seal against the gate with a metal-to-metal seal. The perimeter
seal may
have a T-shaped cross section defining a thin portion of the perimeter seal
and a bar of
the perimeter seal, the thin portion contacting the gate and defining the
first and second
side surfaces. The perimeter seal may have a stiffening member extending
lengthwise
through the perimeter seal, the stiffening member being located substantially
at a junction
of the T-shaped cross section. The bar of the perimeter seal may be mounted in
a groove
in the valve housing, the first and second face seal elements overlapping
edges of the
groove to constrain the perimeter seal within the groove. Regardless of
whether the
perimeter seal has a T-shaped cross section, the perimeter seal may include a
stiffening
member extending lengthwise within the perimeter seal. The perimeter seal may
have end
portions extending along the gate slot away from the opening, the end portions
sealing
against respective sides of the gate. The end portions may extend to a
transverse seal
sealing against the faces of the gate within the gate slot. The valve housing
may be
configured to allow the gate and the transverse seal to be removable from the
gate slot
away from the opening, and to allow the perimeter seal to be removable from
the gate
slot away from the opening when the gate and the transverse seal are removed.
Regardless of whether a perimeter seal is present, the first and second face
seal elements
when installed may include respective first and second flexible seals elements
extending
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Date Regue/Date Received 2023-02-09
around the opening. The first and second flexible seal elements may each
comprise an 0-
ring. When the isolation knife gate valve is in an operating fully open
position, a portion
of the first and second faces of the gate may remain in contact with the first
and second
flexible seal elements. The first and second face seal elements may also be
configured to
seal against the gate with a metal-to-metal seal. The first and second face
seal elements
may comprise bore liners. The bore liners may be configured to be flush with
an internal
diameter of the respective pipes. The first and second face seal elements may
be
configured to be bolted to the valve housing.
[0006] There is also provided a method of service of an isolation
knife gate valve
as described above. One or more of the first and second face seal elements is
removed
and repaired or replaced. The repaired or replaced one or more of the first
and second
face seal elements is then attached in installed position interior to the
couplings.
[0007] There is also provided a method of service of the isolation
knife as
described above having a transverse seal and perimeter seal. The gate and the
transverse
seal are removed along the gate slot away from the opening. The first and
second seal
elements are also removed. The perimeter seal is then also removed along the
gate slot
away from the opening and repaired or replaced. The repaired or replaced
perimeter seal
is installed along the gate slot toward the opening. The gate, the transverse
seal, and the
first and second face seal elements or replacements are then reinstalled.
[0008] These and other aspects of the device and method are set out in
the claims.
BRIEF DESCRIPTION OF THE FIGURES
[0009] Embodiments will now be described with reference to the
figures, in
which like reference characters denote like elements, by way of example, and
in which:
[0010] Fig. 1 is an isometric view of an example isolation knife gate
valve.
[0011] Fig. 2 is a front view of the isolation knife gate valve of
Fig. 1.
[0012] Fig. 3 is a cutaway isometric view of the isolation knife gate
valve of Fig.
1.
[0013] Fig. 4 is a side view of the isolation knife gate valve of Fig.
1.
[0014] Fig. 5 is an isometric exploded view of the isolation knife
gate valve of
Fig. 1, with a yoke not shown.
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Date Regue/Date Received 2023-02-09
[0015] Fig. 6 is another isometric exploded view of the isolation
knife gate valve
of Fig. 1, also not showing the yoke.
[0016] Fig. 7 is a closeup of a portion of the cutaway isometric view
of Fig. 3.
[0017] Fig. 8 is a side cutaway view of substantially the same portion
of the valve
shown in Fig. 7.
[0018] Fig. 9 is a closeup of a top portion of the view of Fig. 8.
[0019] Fig. 10 is a closeup of a bottom portion of the view of Fig. 8.
[0020] Fig. 11 is an isometric view of a valve body of the valve of
Fig. 1.
[0021] Fig. 12 is a cutaway isometric view of the valve body of Fig.
11.
[0022] Fig. 13 is another cutaway isometric view of the valve body of
Fig. 11.
[0023] Fig. 14 is closeup side cutaway view of the valve of Fig. 1,
with the gate
cross-hatched and shown in a closed position.
[0024] Fig. 15 is closeup side cutaway view of the valve of Fig. 1,
with the gate
cross-hatched and shown in an operating fully open position.
[0025] Fig. 16 is a front view of the valve of Fig. 1 with the body
and a face seal
element omitted to better show a transverse seal and perimeter seal.
[0026] Fig. 17 is an isometric view of the valve of Fig. 1 with the
same
components omitted as in Fig. 16.
DETAILED DESCRIPTION
[0027] Immaterial modifications may be made to the embodiments
described here
without departing from what is covered by the claims.
[0028] An isolation knife gate valve (isolation KGV) 20 is shown in
Fig. 1. The
KGV includes a housing 22 which may be for example a uni-body housing. The
housing
22 defines an opening 24 and a gate slot 26, better shown in Fig. 13,
extending away
from the opening. This direction of the gate slot away from the opening is
shown as an
upward direction, and installing the valve in this orientation may have
advantages for
example in teims of protection of valve components, described below, and in
preventing
pooling within the gate slot. For convenience, this direction is referred to
as upward in
this description, but the valve need not have any predetermined direction of
orientation,
and "upward" in this disclosure should be considered to be referring to the
direction in
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Date Regue/Date Received 2023-02-09
which the valve gate opens regardless of actual orientation and not limiting
the valve to
that orientation. A gate 28 is movable within the gate slot 26 between a
closed position
where the gate 28 obstructs the opening 24, as shown in Fig. 1 and in Fig 14,
and upward
to one or more open positions, for example as shown in Fig. 15. A valve yoke
30 attached
to the uni-body housing 22 may include any suitable actuation mechanism 70 or
manual
control to open and close the valve.
[0029] Fig. 2 shows an end view of the valve 20 of Fig. 1 and Fig. 3
shows a
cutaway view. Fig. 4 shows a side profile.
[0030] Figs. 5 and 6 show isometric exploded views of the valve of
Fig. 1. As
shown in these figures, face seal elements 32 and 34 are attachable to the
housing 22. The
face seal elements may be positioned interior to couplings 60 and 62 for
connecting the
valve to pipes. A perimeter seal 36 is also provided to seal around a
perimeter of the
gate 28. The face seal elements 32 and 34 may include flexible seals 38 and 40
to seal
against the gate. In addition to or instead of the flexible seals, they may
also provide a
metal-to-metal seal as upstream pressure against the gate may push the gate
against the
downstream face seal element 32 or 34. In the embodiment shown, the flexible
seals 38
and 40 are 0-rings. The face seal elements 32 and 34 may have a rotational
symmetry
allowing the face seal elements 32 and 34 to be rotated and reinstalled. This
allows
possibly uneven wear on portions of the face seal elements 32 and 34, such as
the flexible
seals 38 and 40, to be evened out. The flexible seal elements, depending on
the
embodiment, may also be replaced easily when the face seal elements 32 and 34
are
removed from the housing 22. For example, where a flexible seal element is an
0-ring, it
may be installed in a groove 80 (shown in Figs. 9 and 10) in the corresponding
face seal-
element and removed from the groove 80 and a replacement installed in the
conventional
manner or inserting and removing 0-rings from grooves. It would also be
possible to
rotate the 0-rings within the face seal elements 32 and 34 by removing and re-
installing
the 0-rings but it is considered easier to rotate each of the face seal
elements 32 and 34 as
a whole. The face seal elements 32 and 34 may be installed and removed for
example
using bolts 42 inserted into bolt through-holes 44 to threaded bolt receiving
holes 46 in
the housing 22. The bolts 42 are not shown in Figs. 5 and 6, but are shown
most clearly
in Figs. 7-10.
Date Regue/Date Received 2023-02-09
[0031] The face seal elements 32 and 34 may also act as bore liners.
In the
embodiment shown, the face seal elements 32 and 34 comprise separate bore
liner
components 50 and attachment components 48. The bore liner portion or
component 50
may comprise metal sealing surfaces 58 and flexible sealing elements 38, 40.
The bore
liner may be shaped, for example, to be flush with an internal diameter of the
pipes to
which the valve is to be connected, in order to streamline flow. Further
seals, e.g. further
0-rings (not shown), may be located in cavities 86 between the face seal
elements 32, 34
and the housing 22 in order to prevent leakage from the gate slot 26 through
gaps
between the face seal elements and the housing. The use of removable face seal
elements
32 and 34 as well as the flexible seal element 38 and 40 embedded into these
elements
allows independent material selection between perimeter seal, 0-rings and face
seal
elements as well as operation at higher pressures. The face seal elements 32
and 34 may
each provide a metal surface 58 that adds structural stability to the gate as
the gate is
pushed against them and can provide an additional face seal against the gate
38 and 40,
particularly when it comes to abrasive services such as oilsands tailings. The
flexible
seal elements may be positioned, e.g. embedded at sufficient depth within the
face seal
elements 32 and 34, and be sufficiently flexible, so as to not prevent contact
between the
metal surface 58 and the gate 28 at typical operating pressures.
[0032] Fig. 7 is a closeup cutaway view of a lower part of the valve
20. Fig. 8 is a
corresponding side cutaway view and Figs. 9 and 10 are further closeups of
portions at
the top and bottom respectively of the opening 24. The face seal elements 32
and 34 in
these closeups can be seen in this embodiment to each be formed of an outer
attachment
component 48 through which the bolts 42 are placed and an inner bore liner
component
50 which mounts the 0-ring 38 and seals against the perimeter seal 36 and gate
28. As
can be seen in these figures, in this embodiment the perimeter seal 36 has a T-
shaped
cross section. The inner rings 50 of the face seal elements 32 and 34 bear
against side
surfaces 72, 74 of the perimeter seal, which are in this embodiment on the
thin portion 52
of the T, and lie on top of the 'bar' 54 of the T holding the perimeter seal
36 in place
when the face seal elements 32 and 34 are installed. The perimeter seal 36 may
be formed
for example of urethane. The perimeter seal may also be stiffened by an
internal
stiffening member 56 enclosed by and extending lengthwise within the perimeter
seal.
Where the perimeter seal 36 has a T-shaped cross section, the stiffening
member may be
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Date Regue/Date Received 2023-02-09
located substantially at a junction of the T. The stiffening member 56 may be,
for
example, a steel rod.
[0033] As can be best seen in Fig. 10, the flexible seal elements 38
and 40 may
contact the perimeter seal 36 at a lower portion of the valve. When the gate
28 is in the
closed position, the gate may push down on the perimeter seal 36 to radially
compress the
perimeter seal 36. The amount by which the gate 28 compresses the perimeter
seal 36
may be selected via configuration of the actuation mechanism 70 or other
control element
controlling the movement of the gate. In an example where the perimeter seal
extends up
vertical sides of the gate slot, the stroke of the gate 28 may be set to
compress the
perimeter seal by an amount equal to an interference fit installation of the
gate with the
perimeter seal at the sides, thus evenly compressing the perimeter seal when
the gate is in
the closed position. For example, if the gate is 50" wide, the width left
after the perimeter
seal 36 is installed and before the gate 28 is installed may be 49.75" which
creates 0.125"
of interference fit per side. The same 0.125" of interference (compression)
may be
applied to the bottom of the U-shape of the perimeter seal 36 when the gate 28
full closes
on top of the perimeter seal 36. The 0-rings 38, 40 may be placed below this
compression set to avoid an unnecessary extrusion gap for the 0-ring when the
gate is
closed under pressure. Dashed line 84 shows an exemplary height of a bottom
tip of the
gate 28 when the gate is in a fully closed position. This compression of the
perimeter seal
36 may cause the perimeter seal 36 to further axially press against the face
seals
including the flexible seals 38 and 40 and metal surfaces 58 of the face seal
elements. As
shown in Fig. 9, at an upper portion of the valve, the flexible seal elements
38 and 40
may directly contact the face of the gate. The portion of the flexible seal
elements 38 and
40 in contact with the perimeter seal may be more than half of the
circumference of these
elements.
[0034] The perimeter seal alone could provide seal/shutoff capability,
as could
the flexible seals, e.g. 0-rings, alone with adjustment of the gate so it
closes further down
to contact the entire 0-rings, as could the metal/metal seat of the gate to
the bore liners.
However, the combination of these seals together provides better performance
than the
separate seals and also provides longer life and wear resistance. Valves using
the
perimeter seal without the face seal elements and 0-rings have been found to
allow a
slight leakage to drip down on the side of the gate opposite to the pressure
from the gate
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Date Regue/Date Received 2023-02-09
slot area. With the addition of the 0-rings, this slight leakage is prevented.
Substantially
zero leakage sealing may be provided, for example compliant with the API 598
standard
or ASME B16.34 standard. These standards may be met even at high pressures,
for
example, at 825 PSI seat test pressure for an ANSI 300 pressure class valve.
The 0-ring
covers the entire flow port in combination with the perimeter seal, and the
perimeter seal
protects the portion of the 0-ring at the bottom of the valve from contact
with flow of
fluid through the opening 24. An upper portion may be exposed but is subject
to less flow
than the lower portion in normal use. In addition, these replaceable
components may
protect the valve body from damage. The valve gate and perimeter seal may in
use have
substantially the same thickness in contact with the 0-rings so that there is
no gap as the
0-rings transition between contact with the valve gate and contact with the
perimeter
seal. The perimeter seal, including the thin part of the T-profile if present
may have a
natural thickness larger than that of the gate, but be compressed to
substantially match the
gate's thickness by compression by the face seal elements and the 0-rings.
[0035] The housing 22 may be a tmi-body housing. The term "nni-body"
in uni-
body housing 22 is used to indicate that the housing 22 is foirned of a
strong, non-
disassemblable construction. A uni-body construction may include multiple
portions
welded together or a single casting. In an example, the uni-body housing is
formed by
fillet welds on multiple sections of plates to form an integral one-piece
construction valve
body from the multiple plates welded together. The example valve shown in the
figures is
formed with integral, full penetration welds. This uni-body construction helps
to obtain a
high level of strength to withstand possible high internal pressures as well
as bending
loads transferred from the pipes. The valve shown in Fig. 1 includes couplings
60 and 62
for connecting to pipes (not shown) on each side, where the couplings 60 and
62, here in
the form of flanges, are included in the uni-body housing 22. Figs. 11-13 show
the nni-
body housing 22 in more detail. Fig. 11 is an isometric view of the uni-body
housing 22
and Figs. 12 and 13 are cutaway isometric views. In these views the gate slot
26 can be
seen to extend slightly downward past the opening to define a groove 64 to
accommodate
a portion of the perimeter seal 36. Alternatively, the face seal elements 32
and 34 could
be shaped to accommodate the full profile of the perimeter seal. As can be
seen, the gate
slot provides a passage for smooth movement of the perimeter seal downward
into
position via the gate slot.
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Date Regue/Date Received 2023-02-09
[0036] Also shown in Figs. 12 and 13 is a pocket 66 for accommodating
a
transverse seal 82 (shown in Fig. 3) to prevent leakage from the valve into
the open air
above the valve. The transverse seal may be, for example, a packing seal.
Where a
packing seal is used, a packing follower 68 may be used to compress the
packing. The
transverse seal may comprise components extending sideways across each face of
the
gate between the ends of the perimeter seal. Where the perimeter seal has a T-
shaped
cross section, the transverse seal components may contact the side surfaces
72, 74 of the
thin part of the T-shaped cross section. These side surfaces are shown in Fig.
10 at the
bottom of the valve but may continue throughout the length of the perimeter
seal. As can
be seen in Figs. 12 and 13, in the embodiment shown the gate slot has a
substantially
uniform thickness and the perimeter seal is placed around the perimeter of the
gate slot
without any overhanging portions being present from the gate slot itself The
absence of
obstructions within the gate slot enables simple installation of the perimeter
seal by
inserting the perimeter seal in from the top before the face seal elements are
installed.
The gate and transverse seal (e.g. packing ropes) can be installed by
inserting them after
the perimeter seal is in place. The face seals may be installed after the gate
in order to
avoid impacting the gate on the 0-rings, but the opposite order is also
possible. Where
the transverse seal is a packing seal, it is installed after the gate. There
is no order
requirement as between installation of the face seals and transverse seal. The
perimeter
seal can be removed by reversing this procedure and replaced by repeating the
install
procedure. It is not necessary for the gate slot to be of uniform thickness,
as the valve
gate does not need to be in contact with the gate slot surfaces directly. The
gate slot can
be positioned and oriented by contact with the perimeter seal 36, with a
packing follower
68 above the packing seal (or by contact with the transverse seal itself), and
with the face
seal elements 32 and 34 and flexible seal elements 38 and 40.
[0037] The transverse seal and the face seal elements may be shaped to
secure the
perimeter seal in place when installed. For example, in an embodiment in which
the
perimeter seal has a T-shaped profile as shown, they may be shaped to match
the thin
portion of the T-profile of the perimeter seal. Along the vertical sides of
the gate slot
between the opening and the transverse seal, there may be gaps between the
thin portion
of the T-profile of the perimeter seal and the gate slot. These gaps may be
filled with a
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Date Regue/Date Received 2023-02-09
filler material (not shown), for example thermoplastic sheet material, but it
has been
found that the valve operates successfully with this filler material omitted.
[0038] Further details of the transverse seal 82 and its interaction
with the
perimeter seal 36 in this embodiment can be seen in Figs. 16-17. The valve
body 22 and
one of the face seal elements 32 are omitted from Figs 16-17 to show the
transverse seal
82 and perimeter seal 36 in greater clarity. In the embodiment shown, the
transverse seal
82 is a packing seal formed of multiple rows 88 of rope packing. The rope
packing may
be installed after the urethane seat 36 and gate 28, and squeezed in place one
row at a
time. The gate 28 may be sized so that the packing seal remains fully in
contact with it
throughout its range of travel between the open position shown in Fig. 15 and
closed
position shown in Fig. 14. The rope packing may have ends cut to fit the T-
shaped profile
of the urethane seat. The multiple rows are selected to ensure atmosphere
leakage from
the top packing is prevented.
[00391 Figs. 1-13 show the gate 28 in the closed position or with the
gate 28
removed from the gate slot 26 entirely. Figs. 14 and 15 are closeup side
cutaway views of
a portion of the valve with the gate 28 in a closed position in Fig. 14 and in
an operating
fully open position in Fig. 15. For clarity, the gate 28 is shown with cross
hatching. In an
example, in the operating fully open position a bottom tip 76 of the gate 28
may
substantially correspond in position to a top 78 of a flow port defined by the
bore liners
32, 34. In some embodiments the bottom of the gate 28 overlaps top portions of
the
flexible seals 38 and 40 in the operating fully open position. As the gate is
in noimal
operation always in contact with the top portions of the flexible seals in
these
embodiments, potential wear is avoided that might otherwise be caused by the
gate
impacting perpendicularly on or pinching the flexible seals 38 and 40 or
impacting on the
face seal elements 32 and 34 in normal operation of the valve. The gate may
also be
configured to be positioned in use to partially open positions (not shown)
between the
fully closed position shown in Fig. 14 and the fully open position shown in
Fig. 15.
[00401 In the claims, the word "comprising" is used in its inclusive
sense and
does not exclude other elements being present. The indefinite articles "a" and
"an" before
a claim feature do not exclude more than one of the feature being present.
Each one of
the individual features described here may be used in one or more embodiments
and is
Date Regue/Date Received 2023-02-09
not, by virtue only of being described here, to be construed as essential to
all
embodiments as defined by the claims.
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Date Regue/Date Received 2023-02-09
