U.S. patent application number 11/340994 was filed with the patent office on 2007-07-26 for flow restricting devices in pumps.
Invention is credited to David Jeffrey Janocko.
Application Number | 20070172367 11/340994 |
Document ID | / |
Family ID | 38285746 |
Filed Date | 2007-07-26 |
United States Patent
Application |
20070172367 |
Kind Code |
A1 |
Janocko; David Jeffrey |
July 26, 2007 |
Flow restricting devices in pumps
Abstract
Restriction of flow along a shaft by interposing a split ring in
the annulus between the shaft and housing. When the ends of the
split ring are separated, the effective diameter of the ring is
increased and a clearance between the ID of the split ring and the
shaft is maintained permitting flow. When the ends are released and
allowed to come together the split ring closes the annular gap and
restricts the flow. Also contemplated is the restriction of flow
along a shaft by interposing an axially movable sleeve in the
annulus between the shaft and housing. Flow through the annulus
between the movable sleeve and the shaft is resisted by the
clearance or features such as labyrinths, to thereby create a
differential pressure from one end of the sleeve to the other.
Inventors: |
Janocko; David Jeffrey;
(Pittsburgh, PA) |
Correspondence
Address: |
REED SMITH LLP
P.O. BOX 488
PITTSBURGH
PA
15230-0488
US
|
Family ID: |
38285746 |
Appl. No.: |
11/340994 |
Filed: |
January 26, 2006 |
Current U.S.
Class: |
417/423.11 |
Current CPC
Class: |
F04D 29/106 20130101;
F16J 15/164 20130101; F04D 15/00 20130101; F04D 29/126
20130101 |
Class at
Publication: |
417/423.11 |
International
Class: |
F04B 17/00 20060101
F04B017/00 |
Claims
1. In a structure comprising a shaft member and a support structure
through which the shaft member extends, an arrangement for
restricting fluid flow along the shaft member relative to the
support structure in at least one annular space defined between the
shaft member and the support structure, said fluid flow restricting
arrangement comprising: a discontinuous ring member disposed about
the shaft member; said discontinuous ring member having two ends;
said discontinuous ring member being actuable between: a first
condition, wherein said ends are spaced apart over a first
distance; and a second condition, wherein said ends are spaced
apart over a second distance, the second distance being less than
the first distance; wherein, in said first condition, a greater
flow path for fluid is afforded, in the at least one annular space
defined between the shaft member and the support structure, than in
said second condition.
2. The fluid flow restricting arrangement according to claim 1,
wherein, in both said first and second conditions of said
discontinuous ring member, sufficient clearance is provided for
displacement of the shaft member with respect to the support
structure.
3. The fluid flow restricting arrangement according to claim 1,
wherein, in said second condition, said ends of said discontinuous
ring member converge to restrict fluid flow in the at least one
annular space defined between the shaft member and the support
structure.
4. The fluid flow restricting arrangement according to claim 1,
wherein said discontinuous ring member is in elastic deformation
while in said first condition, thereby promoting actuation from
said first condition to said second condition.
5. The fluid flow restricting arrangement according to claim 1,
further comprising an arrangement for promoting actuation of said
discontinuous ring member from said first condition to said second
condition.
6. The fluid flow restricting arrangement according to claim 5,
wherein said arrangement for promoting actuation comprises a spacer
element disposed between said ends of said discontinuous ring
member when said discontinuous ring member is in said first
condition.
7. The fluid flow restricting arrangement according to claim 6,
wherein said spacer element is adapted to be materially compromised
in response to at least one ambient condition and thereby promote
convergence of said ends of said discontinuous ring member towards
said second condition.
8. The fluid flow restricting arrangement according to claim 7,
wherein the at least one ambient condition includes at least one
of: a temperature change and a change in fluid chemistry.
9. The fluid flow restricting arrangement according to claim 7,
wherein said spacer element comprises a metal alloy or a
thermoplastic polymer.
10. The fluid flow restricting arrangement according to claim 5,
wherein said arrangement for promoting actuation comprises a
mechanical actuator configured for holding said ends of said
discontinuous ring member apart in said first condition and for
facilitating convergence of said ends of said discontinuous ring
member towards said second condition.
11. The fluid flow restricting arrangement according to claim 1,
further comprising an annular chamber for housing said
discontinuous ring member, said annular chamber being sufficiently
sized to accommodate both said first and second conditions of said
discontinuous ring member.
12. The fluid flow restricting arrangement according to claim 1,
wherein said discontinuous ring member has a generally right
triangular cross sectional shape.
13. The fluid flow restricting arrangement according to claim 12,
wherein said discontinuous ring member comprises a first side
oriented substantially in parallel to a longitudinal axis of the
shaft member and a second side oriented substantially in a radial
direction with respect to a longitudinal axis of the shaft
member.
14. The fluid flow restricting arrangement according to claim 13,
wherein: said discontinuous ring member comprises a third side,
extending between said first and second sides, oriented
substantially at a non-right acute angle with respect to a
longitudinal direction of the shaft member; and said annular
chamber comprises a conical surface for interfacing with said third
side of said discontinuous ring member.
15. The fluid flow restricting arrangement according to claim 11,
wherein said discontinuous ring member has a generally rectilinear
cross sectional shape.
16. The fluid flow restricting arrangement according to claim 1,
further comprising an arrangement for biasing said discontinuous
ring member in a predetermined direction substantially in parallel
to a longitudinal axis of the shaft member.
17. In a structure comprising a shaft member and a support
structure through which the shaft member extends, an arrangement
for restricting fluid flow along the shaft member relative to the
support structure in at least one annular space defined between the
shaft member and the support structure, said fluid flow restricting
arrangement comprising: a sleeve member disposed about the shaft
member; said sleeve member being displaceable, in a direction
generally parallel to a longitudinal axis of the shaft member,
between a first position and a second position; wherein, in said
first position, a greater flow path for fluid is afforded, in the
at least one annular space defined between the shaft member and the
support structure, than in said second position.
18. The fluid flow restricting arrangement according to claim 17,
wherein said sleeve member is generally cylindrical in shape.
19. The fluid flow restricting arrangement according to claim 17,
wherein said sleeve member generally maintains an annular clearance
with respect to the support structure in both said first and second
positions.
20. The fluid flow restricting arrangement according to claim 19,
further comprising an arrangement for sealing the annular clearance
of said sleeve member with respect to the support structure.
21. The fluid flow restricting arrangement according to claim 20,
wherein said sealing arrangement comprises an O-ring.
22. The fluid flow restricting arrangement according to claim 17,
wherein: the shaft member comprises a fixed supplementary member
configured for limiting further displacement of said sleeve member
when said sleeve member is in said second position; and the fixed
supplementary member and said sleeve member combine to restrict
fluid flow in the at least one annular space defined between the
shaft member and the support structure when said sleeve member is
in said second position.
23. The fluid flow restricting arrangement according to claim 22,
wherein the fixed supplementary member comprises a cylindrical
appurtenance fixed to the shaft member which increases an effective
diameter of the shaft member.
24. The fluid flow restricting arrangement according to claim 17,
wherein said sleeve member is configured to displace from said
first position to said second position in response to a
predetermined flow rate or flow condition.
25. The fluid flow restricting arrangement according to claim 17,
wherein said sleeve member further comprises internal deformations
disposed adjacent the shaft member, said internal deformations
being adapted to increase fluid flow resistance during displacement
of said sleeve member between said first and second positions.
26. The fluid flow restricting arrangement according to claim 25,
wherein said internal deformations comprise circumferential grooves
recessed into at least one surface of said sleeve member which
faces the shaft member.
27. The fluid flow restricting arrangement according to claim 17,
further comprising: a discontinuous ring member disposed about the
shaft member; said discontinuous ring member having two ends; said
discontinuous ring member being actuable between: a first
condition, wherein said ends are spaced apart over a first
distance; and a second condition, wherein said ends are spaced
apart over a second distance, the second distance being less than
the first distance; wherein, in said first condition, a greater
flow path for fluid is afforded, in the at least one annular space
defined between the shaft member and the support structure, than in
said second condition.
28. The fluid flow restricting arrangement according to claim 27,
wherein: said sleeve member comprises an internal surface which
faces the shaft member; said sleeve member further comprises an
annular chamber recessed into said internal surface of said sleeve
member; and said discontinuous ring member is disposed in said
annular chamber recessed into said internal surface of said sleeve
member.
29. The fluid flow restricting arrangement according to claim 28,
wherein: said discontinuous ring member assumes said first
condition at least when said sleeve member is in said first
position; and said discontinuous ring member assumes said second
condition at least when said sleeve member is in said second
position.
30. A rotary pump comprising: a motor; a shaft member extending
from said motor; an impeller attached to a free end of said shaft
member; a housing which encloses a major portion of said shaft
member; said housing comprising a seal housing which circumscribes
at least a portion of said shaft member, said seal housing
including at least one sealing element for restricting fluid flow
along said shaft member; said motor being configured for rotating
said shaft in a manner to drive said impeller; and an arrangement
for restricting fluid flow along the shaft relative to the seal
housing in at least one annular space defined between said shaft
member and said seal housing; said fluid flow restricting
arrangement comprising a discontinuous ring member disposed about
said shaft member; said discontinuous ring member having two ends;
said discontinuous ring member being actuable between: a first
condition, wherein said ends are spaced apart over a first
distance; and a second condition, wherein said ends are spaced
apart over a second distance, the second distance being less than
the first distance; wherein, in said first condition, a greater
flow path for fluid is afforded, in the at least one annular space
defined between said shaft member and said seal housing, than in
said second condition.
31. The rotary pump according to claim 29, wherein said rotary pump
comprises a chemical processing pump.
32. The rotary pump according to claim 30, wherein said
discontinuous ring member is in elastic deformation while in said
first condition, thereby promoting actuation from said first
condition to said second condition.
33. The rotary pump according to claim 30, further comprising an
arrangement for promoting actuation of said discontinuous ring
member from said first condition to said second condition.
34. The rotary pump according to claim 33, wherein said arrangement
for promoting actuation comprises a spacer element disposed between
said ends of said discontinuous ring member when said discontinuous
ring member is in said first condition.
35. The rotary pump according to claim 33, wherein said arrangement
for promoting actuation comprises a mechanical actuator configured
for holding said ends of said discontinuous ring member apart in
said first condition and for facilitating convergence of said ends
of said discontinuous ring member towards said second
condition.
36. A rotary pump comprising: a motor; a shaft member extending
from said motor; an impeller attached to a free end of said shaft
member; a housing which encloses a major portion of said shaft
member; said housing comprising a seal housing which circumscribes
at least a portion of said shaft member, said seal housing
including at least one sealing element for restricting fluid flow
along said shaft member; said motor being configured for rotating
said shaft in a manner to drive said impeller; and an arrangement
for restricting fluid flow along the shaft relative to the seal
housing in at least one annular space defined between said shaft
member and said seal housing; said fluid flow restricting
arrangement comprising a sleeve member disposed about said shaft;
said sleeve member being displaceable, in a direction generally
parallel to a longitudinal axis of said shaft member, between a
first position and a second position; wherein, in the first
position, a greater flow path for fluid is afforded, in the at
least one annular space defined between said shaft member and said
seal housing, than in said second position.
37. The rotary pump according to claim 36, wherein said rotary pump
comprises a chemical processing pump.
38. The rotary pump according to claim 36, wherein said sleeve
member is generally cylindrical in shape.
39. The fluid flow restricting arrangement according to claim 36,
wherein: said shaft member comprises a fixed supplementary member
configured for limiting further displacement of said sleeve member
when said sleeve member is in said second position; and said fixed
supplementary member and said sleeve member combine to restrict
fluid flow in the at least one annular space defined between said
shaft member and said seal housing when said sleeve member is in
said second position.
40. The fluid flow restricting arrangement according to claim 36,
further comprising: a discontinuous ring member disposed about said
shaft member; said discontinuous ring member having two ends; said
discontinuous ring member being actuable between: a first
condition, wherein said ends are spaced apart over a first
distance; and a second condition, wherein said ends are spaced
apart over a second distance, the second distance being less than
the first distance; wherein, in said first condition, a greater
flow path for fluid is afforded, in the at least one annular space
defined between said shaft member and said seal housing, than in
said second condition.
Description
FIELD OF THE INVENTION
[0001] The present invention generally relates to rotary pumps,
such as chemical processing pumps or nuclear reactor coolant pumps,
and constituent components therefor, such as flow restricting
devices.
BACKGROUND OF THE INVENTION
[0002] In pressurized water nuclear power plants, a reactor coolant
system is used to transport heat from the reactor core to steam
generators for the production of steam. The steam is then used to
drive a turbine generator. The reactor coolant system includes a
plurality of separate cooling loops, each connected to the reactor
core and containing a steam generator and a rotary coolant pump.
Other venues also present situations where containment of a process
fluid is critical, such as in the case of rotary chemical
processing pumps.
[0003] A rotary pump such as a reactor coolant pump or chemical
processing pump typically is a centrifugal pump designed to move
large volumes of process fluid (e.g., reactor coolant) at high
temperatures and pressures. Such a pump normally includes
hydraulic, shaft seal and motor sections. A hydraulic section
usually includes an impeller mounted at an end of a pump shaft
which is operable within the pump casing to pump process fluid. A
motor section includes a motor which is coupled to drive the pump
shaft. A middle shaft seal section usually includes tandem sealing
assemblies located concentric to, and near the top end of, the pump
shaft. Such sealing assemblies normally are configured for allowing
but minimal process fluid leakage along the pump shaft during
normal operating condition. Representative examples of known pump
shaft sealing assemblies, at least in the context of reactor
coolant pumps, may be found in the following U.S. patents: MacCrum
(U.S. Pat. No. 3,522,948), Singleton (U.S. Pat. No. 3,529,838),
Villasor (U.S. Pat. No. 3,632,117), Andrews et al (U.S. Pat. No.
3,720,222) and Boes (U.S. Pat. No. 4,275,891).
[0004] Pump shaft sealing assemblies, as such, must normally be
capable of containing a high system pressure without excessive
leakage. Tandem arrangements of sealing assemblies, for instance,
serve to break down the pressure in stages. Pump sealing assemblies
in fact may act as controlled-leakage seals which, in operation,
allow a minimal amount of controlled leakage at each stage while
preventing excessive leakage of process fluid (e.g., reactor
coolant) from the primary fluid system to respective seal leakoff
ports. This applies in many scenarios where containment of excess
leakage is critical. In the case of nuclear reactor coolant pumps,
since pump sealing assemblies can be prone to failure, e.g. in
response to unmitigated high temperatures of reactor coolant, any
resultant excessive leakage rates could lead to reactor coolant
uncovering of a reactor core, and subsequent core damage.
[0005] While U.S. Pat. No. 5,171,024 (Janocko) discloses a shutdown
seal arrangement for preventing and arresting excess fluid leakage
along a pump shaft, a need has been recognized in connection with
providing an even more effective arrangement, whether in the
context of nuclear reactor coolant pumps or other contexts such as
chemical processing pumps.
SUMMARY OF THE INVENTION
[0006] There is broadly contemplated herein, in accordance with at
least one embodiment of the present invention, a split ring
arrangement, disposed about a shaft, that actuates in response to a
fluid leak. In a first condition, ends of the split ring
arrangement are spaced apart, whereby a flow path for fluid is
provided and clearance is provided for a normally moving shaft. In
a second condition, these ends of the split ring arrangement
converge such that a flow path for fluid is blocked or restricted.
Pressure loadings may be employed to hold the split ring
arrangement in this second, "closed" position. As an advantageous
alternative, a meltable spacer can be initially positioned between
ends of the split ring, and melt at a prescribed temperature to
actuate a closing of the ring.
[0007] In accordance with at least one further embodiment of the
present invention, a sliding sleeve is provided about a shaft.
Responsive to a pressure drop (e.g., pursuant to high fluid flow
rates, a phase change or choked flow), the sleeve may slide in a
direction parallel to the longitudinal axis of the shaft to a
position in which fluid flow about the shaft is restricted or
blocked.
[0008] In accordance with at least one additional embodiment of the
present invention, the split ring and sliding sleeve arrangements,
as described above, may be provided together in the context of a
single pump.
[0009] In summary, there is broadly contemplated herein, in
accordance with at least one presently preferred embodiment of the
present invention, in a structure comprising a shaft member and a
support structure through which the shaft member extends, an
arrangement for restricting fluid flow along the shaft member
relative to the support structure in at least one annular space
defined between the shaft member and the support structure, the
fluid flow restricting arrangement comprising: a discontinuous ring
member disposed about the shaft member; the discontinuous ring
member having two ends; the discontinuous ring member being
actuable between: a first condition, wherein the ends are spaced
apart over a first distance; and a second condition, wherein the
ends are spaced apart over a second distance, the second distance
being less than the first distance; wherein, in the first
condition, a greater flow path for fluid is afforded, in the at
least one annular space defined between the shaft member and the
support structure, than in the second condition.
[0010] Additionally, there is broadly contemplated herein, in
accordance with at least one presently preferred embodiment of the
present invention, in a structure comprising a shaft member and a
support structure through which the shaft member extends, an
arrangement for restricting fluid flow along the shaft member
relative to the support structure in at least one annular space
defined between the shaft member and the support structure, the
fluid flow restricting arrangement comprising: a sleeve member
disposed about the shaft member; the sleeve member being
displaceable, in a direction generally parallel to a longitudinal
axis of the shaft member, between a first position and a second
position; wherein, in the first position, a greater flow path for
fluid is afforded, in the at least one annular space defined
between the shaft member and the support structure, than in the
second position.
[0011] Further, there is broadly contemplated herein, in accordance
with at least one presently preferred embodiment of the present
invention, a rotary pump comprising: a motor; a shaft member
extending from the motor; an impeller attached to a free end of the
shaft member; a housing which encloses a major portion of the shaft
member; the housing comprising a seal housing which circumscribes
at least a portion of the shaft member, the seal housing including
at least one sealing element for restricting fluid flow along the
shaft member; the motor being configured for rotating the shaft in
a manner to drive the impeller; and an arrangement for restricting
fluid flow along the shaft relative to the seal housing in at least
one annular space defined between the shaft member and the seal
housing; the fluid flow restricting arrangement comprising a
discontinuous ring member disposed about the shaft member; the
discontinuous ring member having two ends; the discontinuous ring
member being actuable between: a first condition, wherein the ends
are spaced apart over a first distance; and a second condition,
wherein the ends are spaced apart over a second distance, the
second distance being less than the first distance; wherein, in the
first condition, a greater flow path for fluid is afforded, in the
at least one annular space defined between the shaft member and the
seal housing, than in the second condition.
[0012] Also, there is broadly contemplated herein, in accordance
with at least one presently preferred embodiment of the present
invention, a rotary pump comprising: a motor; a shaft member
extending from the motor; an impeller attached to a free end of the
shaft member; a housing which encloses a major portion of the shaft
member; the housing comprising a seal housing which circumscribes
at least a portion of the shaft member, the seal housing including
at least one sealing element for restricting fluid flow along the
shaft member; the motor being configured for rotating the shaft in
a manner to drive the impeller; and an arrangement for restricting
fluid flow along the shaft relative to the seal housing in at least
one annular space defined between the shaft member and the seal
housing; the fluid flow restricting arrangement comprising a sleeve
member disposed about the shaft; the sleeve member being
displaceable, in a direction generally parallel to a longitudinal
axis of the shaft member, between a first position and a second
position; wherein, in the first position, a greater flow path for
fluid is afforded, in the at least one annular space defined
between the shaft member and the seal housing, than in the second
position.
[0013] The novel features which are considered characteristic of
the present invention are set forth herebelow. The invention
itself, however, both as to its construction and its method of
operation, together with additional objects and advantages thereof,
will be best understood from the following description of the
specific embodiments when read and understood in connection with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The present invention and its presently preferred
embodiments will be better understood by way of reference to the
detailed disclosure herebelow and to the accompanying drawings,
wherein:
[0015] FIG. 1. illustrates, in a partial cross sectional view, a
centrifugal pump employing a split ring arrangement.
[0016] FIG. 2 provides a close-up of a split ring and surrounding
components in the pump of FIG. 1.
[0017] FIG. 3A illustrates schematically an elevational view of a
first split ring arrangement about a shaft, and deployed in a first
position.
[0018] FIG. 3B illustrates the split ring from FIG. 3A in plan
view.
[0019] FIG. 3C is essentially the same view as FIG. 3A but showing
the split ring arrangement deployed in a second position.
[0020] FIG. 3D illustrates the split ring from FIG. 3C in plan
view.
[0021] FIG. 4A illustrates schematically an elevational view of a
second split ring arrangement about a shaft, and deployed in a
first position.
[0022] FIG. 4B illustrates the split ring from FIG. 4A in plan
view.
[0023] FIG. 4C is essentially the same view as FIG. 4A but showing
the split ring arrangement deployed in a second position.
[0024] FIG. 4D illustrates the split ring from FIG. 4C in plan
view.
[0025] FIG. 5 illustrates, in a partial cross sectional view, a
centrifugal pump employing a sliding sleeve arrangement.
[0026] FIG. 6 provides a close-up of a sliding sleeve arrangement
and surrounding components in the pump of FIG. 5, with the sliding
sleeve arrangement in an actuated position.
[0027] FIG. 7A illustrates schematically an elevational view of a
first sliding sleeve arrangement about a shaft, and deployed in a
first position.
[0028] FIG. 7B is essentially the same view as FIG. 7A but showing
the sliding sleeve arrangement deployed in a second position.
[0029] FIG. 8A illustrates schematically an elevational view of a
second sliding sleeve arrangement about a shaft, further including
a split ring, and deployed in a first position.
[0030] FIG. 8B is essentially the same view as FIG. 8A but showing
the sliding sleeve arrangement deployed in a second position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] Referring to FIG. 1, a pump 10 generally includes a main
pump housing 12. While, in the embodiment shown, housing 12 forms a
large portion of an external housing for pump 10, it retracts
inwardly to further form an internal seal housing 12a. An impeller
housing 14 is also bolted to the main pump housing 12 and houses an
impeller 16. Pump 10 can be representative of a wide variety of
rotary pumps, including general centrifugal pumps, nuclear reactor
coolant pumps and chemical processing pumps (e.g., as commonly used
in the chemical processing industry). Pump 10 may be oriented in
any direction appropriate for the application at hand, e.g., a
generally horizontal direction or (in the case of a reactor coolant
pump) in a generally vertical direction.
[0032] The pump 10 includes a pump shaft 18 extending centrally
with respect to the pump housing 12 and being sealingly and
rotatably mounted within the seal housing 12a. Pump shaft 18, at
one end thereof, is connected to impeller 16 (e.g., via a cap 20 as
shown), while, at another end, is connected to an electric motor
22. When the motor 22 rotates the shaft 18, the impeller 16 causes
pressurized reactor coolant to flow through the general reactor
coolant system. At the same time, this pressurized coolant applies
an upwardly directed, hydrostatic load upon the shaft 18.
[0033] In order that the pump shaft 18 might rotate freely within
the seal housing 12a while maintaining a high pressure boundary
between the pump high pressure region (i.e., the chambers
associated with impeller 16 and extending to the right therefrom
with respect to FIG. 1) and a region (indicated at 24) ambient to
the seal housing 12a, sealing assemblies are preferably provided,
including a mechanical face seal. The general layout and function
of conventional sealing assemblies can be more fully understood
from Janocko, supra. In accordance with at least one presently
preferred embodiment of the present invention, there is broadly
contemplated a split ring 26 which serves to limit fluid flow
between shaft 18 and housing 12a under given conditions, as will be
better appreciated in the discussion herebelow.
[0034] Ring 26 is preferably split (or cut) along a cutting plane
at a point along the circumference of ring 26, or presents even a
non-planar end treatment as discussed further below. Preferably,
ring 26 is configured such that the free ends thereof, absent any
intervening structure or any appreciable opposing forces, come into
contact when in a "relaxed" or "free" state. As such, ring 26 is
further preferably configured such that when these free ends are
separated such that a gap between the ends develops and then
increases, the ring 26 thereby deforms elastically and the
effective diameter of the ring increases. (Thus, conversely,
decreasing the gap in the ring 26 to the point that the ends
contact allows the effective diameter of the ring to decrease.) It
will be appreciated from the discussion herebelow that a split ring
26, in accordance with at least one embodiment of the present
invention, may advantageously have its ends spaced apart in a
first, initial condition, whereby elastic properties of the ring 26
itself can promote (with or without assistance of another closing
force) convergence of the ends towards a second, "closed"
condition. To better appreciate the functioning of a split ring 26
in the context of FIG. 1, reference can also be made to FIG. 2
(which is a close-up view of split ring 26 and surrounding
components of pump 10).
[0035] While the ends of split ring 26 indeed can be cut along a
simple cutting plane that is parallel to a central (longitudinal)
axis defining the ring, other types of "end treatment" are of
course possible. As known in the art of piston rings (and even
other rings), a split ring 26 may have a "mitred" or diagonal
planar cut to define the free ends or even more elaborate end
treatments are possible. For instance, a "notched" type of end
treatment may be employed where a protrusion at one end may mate
with a recess or notch at the other end. In general, various end
treatments may be employed to reduce leakage at the junction of the
ends while accommodating variations in the circumference of the
shaft or split ring due to manufacturing tolerances, thermal
expansion or loading. (As such, split ring 26, in a particularly
preferred embodiment of the present invention, includes a "mitred"
end treatment, where ends of split ring 26 meet at a mitred or
diagonal interface, wherein these ends can slide against one
another, in response to small displacements from, e.g., thermal
expansion, without essentially compromising the capability of the
ring to protect against leakage.)
[0036] As shown, the split ring 26 is positioned between shaft 18
(or an integral portion thereof) and seal housing 12a, in chamber
suitable for accommodating ring 26. This chamber is preferably
sized, in particular, to readily accommodate both the initial and
closed conditions of ring 26. As such, in the aforementioned first
or "initial" condition of ring 26, a gap is maintained between the
ends of the split ring 26 such that the split ring 26 contacts only
the housing 12a. This allows for the normal relative motion between
the housing 12a and the shaft 18. The sizing of ring 26 is also
preferably such that when the gap between the ends of the split
ring 26 is allowed to close (as further described below), the split
ring 26 constricts around shaft 18, closing the annular gap between
the inner diameter of the split ring 26 and the outer diameter of
the shaft 18.
[0037] Because the gap between ends of the split ring 26 is more or
less artificially created, a suitable arrangement is preferably
employed to hold the ends apart in the first, initial condition of
ring 26. One such arrangement may preferably be embodied by a
spacer composed of a material which, when exposed to certain
conditions in the fluid such as temperature or fluid chemistry or
other conditions, reacts with the fluid to dissolve, change state,
or otherwise be materially compromised (see below regarding FIG.
3B). Upon such exposure, ends of the split ring 26 would thereby be
released, allowing the ring 26 to constrict around the shaft 18.
Actuation of the spacer could thus be automatic. Such a spacer
could be formed, e.g., from a metal alloy or thermoplastic polymer
with a melting temperature in a desired actuation range (though
chemical compatibility of the spacer material with the ambient
fluid would of course be important).
[0038] Alternatively, a mechanical actuator could be provided, a
mechanical actuator could be provided to initially hold the split
ring 26 in the first, "initial" condition and then permit split
ring 26 to constrict around the shaft 18 into the second, "closed"
condition. Such a mechanical actuator could employ a type of
automatic response to a change in the condition of the fluid and
mechanically release the ends of the split ring 26 and thus promote
constriction about shaft 18 (see below regarding FIGS. 4A and
4B).
[0039] To bias ring 26 within its surrounding annular chamber in a
direction towards the motor 22 and away from impeller 16 (i.e., in
a direction of potential leakage flow or in a direction from high
pressure within the pump housing to a lower external pressure
outside the pump), there can be provided a number of springs 28a
oriented in parallel to the central axis of pump 10 as shown.
Additional springs 28b, oriented in a radial direction with respect
to the central axis of pump 10, could assist in promoting closure
of the ring 26 by supplementing the normal elastic tendency of the
ring 26 towards "closure", or a convergence of the ends of the
ring, once an "actuator" (e.g., meltable or mechanical) serves to
"release" the spaced-apart ends of ring 26.
[0040] Various cross-sectional shapes for a split ring 126 are
conceivable, two of which are shown in FIGS. 3A-4D. FIGS. 3A-3D
illustrate a first such arrangement, namely a shape which
approximates a right triangle. As shown, ring 126 may be disposed
within a chamber defined by shaft 118 and housing 112a. Biasing
springs 128a may also be provided to bias the ring 126 in an upward
direction with respect to FIGS. 3A and 3C, or in a direction
towards a motor and away from an impeller. FIGS. 3A and 3B
particularly show ring 126 in a first, initial position, where ends
of the ring 126 are spaced apart, while FIGS. 3C and 3D show ring
126 in a second, closed position, where ends of the ring 126 are
together. Dotted lines in FIG. 3B, indicated at 129, illustrate the
prospective location of a meltable or consumable spacer as
described heretofore.
[0041] In the cross-sectional shape of a right triangle as shown in
FIGS. 3A and 3C, the legs of the "triangle" forming the right angle
could preferably be aligned in parallel to axial and radial
directions, respectively, of shaft 118; the inner diameter of the
split ring 126 would thereby be approximately parallel to the
surface of shaft 118. The angled conical surface formed by the
hypotenuse of the right triangle of the section of the split ring
could thus interface with a similarly beveled conical surface
integral to housing 112a (or with an appurtenance of housing
112a).
[0042] In the embodiment illustrated in FIGS. 3A-3D, the split ring
126 and the seating surface of housing 112a are oriented such that
a pressure differential resulting from any restriction of flow by
the imposition of the split ring 126 would tend to hydrostatically
load the split ring 126 against the conical surface in housing
112a. The axial loads applied to the conical interface between the
split ring 126 and the housing 112a would result in a radial
reaction component acting on the split ring 126, which would also
tend to force the split ring 126 radially inward toward the shaft
118, further tending to close the annular gap between the inner
diameter of the split ring 126 and the shaft 118, and also thereby
tending to close the circumferential gap between the ends of the
split ring 126.
[0043] With split ring 126 being held open by a mechanical actuator
or spacer, the split ring 126 could preferably be held against the
conical seating surface of the housing by springs or by another
suitable arrangement. This would restrict any motion of the split
ring 126 until such a time that the actuator or spacer released the
ends of the split ring 126 and the split ring 126 was allowed to
constrict. As the split ring 126 constricts because of the
effective change in the diameter of its conical surface, it would
tend to move axially toward the conical surface of the seating
surface in the housing 112a to maintain contact between the conical
interfaces. The springs or alternate arrangement would continue to
load the split ring 126 against the conical seating surface of the
housing 112a. This continued contact would tend to limit flow
between the split ring 126 and housing 112a.
[0044] A triangular cross-sectional shape of the split ring 126 is
of course only one possible realization. For instance, rather than
the beveled conical surfaces resulting from the triangular shape,
the split ring 126 may have flat or spherical surfaces of interface
with housing 112a which may provide other desirable benefits, such
as automatic allowance for misalignment or radial offset of the
inner circular shaft member to the outer housing member. FIGS.
4A-4D, for their part, illustrate a split ring 126 with an
essentially rectangular cross-section. Essentially in parallel with
FIGS. 3A-3D, FIGS. 4A and 4B show a split ring 126 in a first,
initial position while FIGS. 4C and 4D show a split ring 226 in a
second, closed position. Components that are essentially similar to
those in FIGS. 3A-3D bear reference numerals advanced by 100.
[0045] In the embodiment illustrated in FIGS. 4A-4D, the annular
chamber containing ring 226 is essentially rectilinear in
cross-section as well, and thus there is essentially a "flat"
interface between ring 226 (at an upper portion thereof) and
housing 212a (or an interface which runs perpendicular with respect
to the common central longitudinal axis of shaft 218 and housing
212a.
[0046] FIGS. 4A and 4B illustrate a mechanical actuator 231 as an
alternative to the meltable/consumable spacer 129 shown in FIG. 3B.
A mechanical actuator 231 could function analogously to a
meltable/consumable spacer, i.e., act to promote closure of ring
226 in response to given conditions. As such, mechanical actuator
231 could be embodied by any of a very wide variety of
arrangements. For instance, a spring-loaded retractable plunger
could hold the ends of ring 226 apart and, in response to
temperature change or other type of change in the ambient fluid,
could release the ends of ring 226 which would then converge and
close of their own accord. In accordance with such an arrangement,
the plunger could be actuated by an electromotive device (e.g.,
solenoid or motor) that responds to an external electrical signal
transmitted when a predetermined condition is met. Alternatively, a
plunger arrangement could include differing hydrostatic areas that
are in communication with different parts or chambers of the pump
such that a plunger would retract when certain pressure conditions
in the pump prevail.
[0047] A hybrid arrangement is even conceivable, where a
spring-loaded plunger itself contains a meltable/consumable member
or spacer which, when it melts or is physically compromised in
response to temperature, permits the plunger to retract and thus
promote convergence of the ends of ring 226. In accordance with
such an arrangement, the meltable/consumable material could
actually be contained away from the process fluid (e.g., within a
chamber associated with the plunger spring[s]) and be configured
for responding to temperature only.
[0048] It should be clearly understood that the meltable/consumable
spacer 129 of FIG. 3B and the mechanical actuator 231 of FIGS. 4A
and 4B are essentially interchangeable and can be employed with
essentially any split ring arrangement, and thus need not be
associated solely with those specific split ring arrangements and
geometries shown in the respective drawings.
[0049] In the context of all conceivable embodiments, the split
ring is preferably sized such that, when released and permitted to
contract around the shaft, the inner diameter of the split ring
contacts or comes in close proximity to the surface of the shaft,
thereby closing or rendering very small the circumferential gap
between the inner diameter of split ring and outer diameter of
shaft. This will thus have the effect of generally limiting the
flow of fluid through the annulus between the shaft and the
surrounding housing.
[0050] It will further be appreciated that by limiting fluid flow
in the second "constricted" condition, the split ring also creates
a differential pressure across the contact surfaces between the
split ring and the shaft as well as the contact surfaces between
the split ring and the housing and that by carefully controlling
the locations of these contact surfaces, the locations of pressure
drops can be controlled. These contact surfaces and their
associated pressure drops would thus define hydrostatic areas to be
acted on by the various pressures to generate forces acting on the
split ring, which can be utilized to augment the "seating" forces
for split ring and the forces acting to further constrict the split
ring, and can preferentially control deformations of the split
ring.
[0051] A split ring as described heretofore may also incorporate
deformable elements to enhance the seating of the contact surfaces
between the split ring and inner and outer members and/or between
the ends of the split across the circumference of the ring.
[0052] The disclosure now turns to a discussion of "sliding sleeve"
arrangements for limiting fluid flow through an annulus between a
shaft 318 and a housing 312a, as depicted illustratively yet
non-restrictively in FIGS. 5-8B. As such, FIG. 5 illustrates, in a
partial cross sectional view, a pump 310 employing a sliding sleeve
arrangement. (Again, pump 310 can be representative of a wide
variety of rotary pumps, including general centrifugal pumps,
nuclear reactor coolant pumps and chemical processing pumps.) FIG.
6 is essentially a close-up view taken from FIG. 5, but showing the
sliding sleeve in an actuated position (i.e., having slid in a
direction towards the motor). Various pump components illustrated
in FIGS. 5 and 6 are similar to those shown in FIGS. 1 and 2, and
corresponding reference numerals are thus advanced by 300. As the
discussion presently continues, simultaneous reference may be made
to both FIGS. 5 and 6 to better understand and appreciate the
sliding sleeve arrangement at hand.
[0053] Preferably provided is a cylindrical sleeve 330 of specific
cross section which is disposed around shaft 318, between shaft 318
and housing 312a, and is free to move in a direction essentially
parallel to a longitudinal axis of shaft 318. The inner diameter
surface of the cylindrical sleeve 330 preferably does not contact
the surface of the shaft 318, but does maintain a small annular
clearance. The outer surface of the cylindrical sleeve 330 is
preferably mounted in a close clearance fit with the housing 312a,
which permits the cylindrical sleeve 330 to move along the
direction of its own central axis.
[0054] The close clearance fit between the cylindrical sleeve 330
and the housing 312a may be sealed with an elastomer sealing
element (e.g., O-ring) 332 which seals the joint through
compression or contact with the two members while still allowing a
sliding fit and relative motion. Alternate suitable arrangements
for minimizing leakage across this sliding fit, such as a piston
ring, of course may be used.
[0055] One end or face of the cylindrical sleeve 330 is preferably
designed to interface with a fixed sleeve or appurtenance 334
having a diameter larger than--and mounted to--the shaft 318, such
that as the cylindrical sleeve 330 moves axially in one direction,
the end or face of the cylindrical sleeve 330 approaches the face
of the appurtenance or fixed sleeve 334 on the shaft 318. Normally,
since motions between the shaft 318 and housing 312a tend to be
large, the cylindrical sleeve 330 is held in a position such that
its face maintains a significant clearance with respect to the face
of the appurtenance 334 fixed to the shaft 318. Under certain
conditions, when normal relative motions are stopped or reduced and
when it becomes desirable to limit flow of the fluid between the
shaft 318 and the housing 312a, the cylindrical sleeve 330 can be
moved toward the appurtenance 334 on the shaft 318 such that their
ends come in contact and thereby restrict any flow of the fluid
between the shaft 318 and the housing 312a.
[0056] The specific geometry of the contacting surfaces of the
cylindrical sleeve 330 and the sleeve or appurtenance 334 fixed to
the shaft 318 may be varied to optimize the restriction of flow
when in contact. The geometry of the section of the movable
cylindrical sleeve 330, the location and dimensions of its sliding
fit with the housing 312a and the location and dimensions of the
contacting surfaces can all be used to optimize the hydrostatic
pressure forces of the fluid such that the balance of forces tend
to maintain the contact between face of the movable sleeve 330 and
the face of the appurtenance 334 fixed to the shaft 318, once
contact is achieved.
[0057] Particularly advantageous is the fact that the motive force,
which causes the cylindrical sleeve 330 to move axially toward the
fixed appurtenance 334 of the shaft 318, closes the gap between the
face of the cylindrical sleeve 330 and the face of the appurtenance
334 to the shaft 318, and promotes initial contact of the faces in
restricting the flow, is obtained by designing the cylindrical
sleeve 330 to utilize certain changes in the conditions of the
fluid which alter the pressure forces acting on the cylindrical
sleeve 330 and cause the sleeve to move in the direction of the
fluid flow.
[0058] Flow passing along the annulus defined by the shaft 318 and
the inner diameter of the cylindrical sleeve 330 will tend to meet
resistance to flow due to the friction at the fluid interfaces and
the fluid viscosity as described by standard laws of fluid
dynamics. This resistance to flow will create a pressure
differential between the inlet side of the annulus and the outlet
side. This differential pressure acting on the hydrostatic areas of
the cylindrical sleeve 330, as defined by the region defined
between the inner diameter of the circular sleeve 330 and its outer
sliding fit diameter, will create a force imbalance which will tend
to increase the acting forces toward the direction of flow. When
flow through the annulus is at normal low volumetric rates, the
differential pressure across the annulus is small and the force
developed would normally be insufficient to overcome the body
forces and friction forces acting on the cylindrical sleeve 330,
and thus move the cylindrical sleeve 330 along its sliding fit.
However, when the volumetric flow rate in the annulus increases
either due to an increase in the mass flow rate or a phase change
of the fluid from liquid to gas, the differential pressure across
the annulus will increase and when the hydrostatic pressure forces
exceed the body and friction forces, the cylindrical sleeve 330
will tend to move in the direction of flow. To provide additional
stability of the sleeve 330 at low volumetric flow rates, the
sleeve 330 may be additionally loaded by a spring which counteracts
the forces generated by normal flow; or, the sleeve 330 may be
locked in place by a suitable alternate device so that the sleeve
330 will not move until a desired flow rate or condition is
reached.
[0059] FIGS. 7A-8B illustrate sliding sleeve arrangements
schematically but in somewhat more detail. Accordingly, FIG. 7A
illustrates schematically an elevational view of a first sliding
sleeve arrangement about a shaft, and deployed in a first, initial
position, while FIG. 7B is essentially the same view as FIG. 7A but
showing the sliding sleeve arrangement deployed in a second,
"advanced" position (i.e., in a position closer to the pump motor).
On the other hand, FIG. 8A illustrates schematically an elevational
view of a second sliding sleeve arrangement about a shaft, and
deployed in the first, initial position, while FIG. 8B is
essentially the same view as FIG. 8A but showing the sliding sleeve
arrangement deployed in the second, "advanced" position.
[0060] As shown, the geometry or surface of the inner diameter of
the cylindrical sleeve 430 may incorporate features which tend to
increase the resistance to flow or increase the differential
pressure along the annulus.
[0061] These may, e.g., involve a series of circumferential grooves
(indicated at 436) disposed along all or a portion of the length of
the surfaces, forming a labyrinth seal or pressure breakdown
device. These may offer a resistance to flow that, depending on,
e.g., the mass flow rate, absolute pressures, temperatures and
nature of the fluid, a phase change or flashing from liquid to
vapor, may occur at some position along the length of the annulus.
As choking of the flow occurs, the result could be a more
significant pressure differential between the inlet and outlet of
the seal, generating larger forces to move the cylindrical sleeve
430.
[0062] FIGS. 7A-8B each illustrate an O-ring 432/532 similar to
that indicated at 432 in FIGS. 5 and 6.
[0063] In accordance with an additional embodiment of the present
invention, a given "split ring" arrangement and a given "sliding
sleeve" arrangement, substantially as described and contemplated
hereinabove, could be combined in the context of a single pump. As
such, one of these flow restricting arrangements could be disposed
about a shaft and within a seal housing in one location and the
other could be disposed about the shaft and within the seal housing
at another location; the relative locations could be chosen with a
view to maximizing the attendant advantages of each flow
restricting arrangement at particular locations along the
shaft.
[0064] FIGS. 8A and 8B illustrate a very interesting and
advantageous alternative in which a split ring 526, which is
configured (and functions) substantially as described heretofore,
is mounted in a groove in the inner diameter of the cylindrical
sleeve 530 and which is disposed along with the cylindrical sleeve
around the outer diameter of the shaft 518. The concentric ring
would split or cut radially across its circumference in one
location as discussed heretofore. With the sleeve 530 in the first,
initial position as shown in FIG. 8A, ring 526 itself is in a
first, initial position as described heretofore (i.e., where ends
of the split ring are spaced apart). On the other hand, with the
sleeve 530 in the second, "advanced" position as shown in FIG. 8B,
the ends of the split ring 526 have converged so that ring 526 is
more constricted about shaft 518. The release of the ends of the
split ring 526, to actuate it from the first position to the second
position between what is shown in FIGS. 8A and 8B, respectively,
may be accomplished by essentially any suitable device or mechanism
which senses or responds to a change in the conditions of the fluid
or by a positive operator action. As such, a "meltable"
spacer/actuator as discussed heretofore would likely produce
favorable results.
[0065] It should be appreciated that, in accordance with the
embodiment illustrated in FIGS. 8A and 8B, the split ring 526
actually enhances actuation of the sliding sleeve 530.
Particularly, as the split ring 526 closes, flow is restricted
through the sleeve annulus, thereby causing a differential pressure
along the sleeve 530 which (as described earlier) causes the
sliding sleeve 530 to move toward the annular face of shaft
appurtenance 534.
[0066] It should be appreciated that a very wide variety of
alternate applications and environments for the salient features of
the embodiments of the present invention are possible. Essentially,
the "split ring" and "sliding sleeve" arrangements discussed
heretofore are incorporable into any workable environment in which
it is desired to make a provision for limiting fluid flow through
an annulus between two circular members, the inner member being a
circular shaft which is normally rotating or reciprocating relative
to the second member, and the second member being a housing which
surrounds the inner circular shaft member. (In actuality, depending
on the application, normal motion need only be relative between the
two members and either one may move in the absolute sense.) While
the inner circular member and the outer housing combine to form a
pressure boundary to a fluid and the interface between the circular
inner member, and the outer housing is normally sealed by an
arrangement which can accommodate the normal relative motion
between the members, the embodiments of the present invention
provide yet additional conceivable arrangements for limiting fluid
flow through the annulus between the inner circular member and the
outer housing member when the normal motion has ceased, and any
subsequent displacements between the members is much more
limited.
[0067] As such, the additional arrangements for limiting fluid flow
could be embodied by a split ring arrangement or sliding sleeve
arrangement, or combination of both, substantially as described
hereinabove but employed in essentially any context involving a
shaft and surrounding housing in which there is relative movement
of at least one with respect to the other as described immediately
hereabove.
[0068] Without further analysis, the foregoing will so fully reveal
the gist of the present invention and its embodiments that others
can, by applying current knowledge, readily adapt it for various
applications without omitting features that, from the standpoint of
prior art, fairly constitute characteristics of the generic or
specific aspects of the present invention and its embodiments.
[0069] If not otherwise stated herein, it may be assumed that all
components and/or processes described heretofore may, if
appropriate, be considered to be interchangeable with similar
components and/or processes disclosed elsewhere in the
specification, unless an express indication is made to the
contrary.
[0070] If not otherwise stated herein, any and all patents, patent
publications, articles and other printed publications discussed or
mentioned herein are hereby incorporated by reference as if set
forth in their entirety herein.
[0071] It should be appreciated that the apparatus and method of
the present invention may be configured and conducted as
appropriate for any context at hand. The embodiments described
above are to be considered in all respects only as illustrative and
not restrictive. All changes which come within the meaning and
range of equivalency of the claims are to be embraced within their
scope.
* * * * *