Note: Descriptions are shown in the official language in which they were submitted.
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NESTED BELLOWS EXPANSION MEMBER
FOR A SUBMERSIBLE PUMP
BACKGROUND OF THE INVENTION
1. Field of the Invention:
This invention relates generally to a seal section for an electrical
submersible
pump. More particularly, the invention relates to a bellows in a seal section
of an
electrical submersible pump.
2. Background:
Electrical submersible pumps (ESPs) have been used to lift fluid from bore
holes, particularly for oil production. In operation, a pump of an electrical
submersible pump is placed below the fluid level in the bore hole. The well
fluid
often contains corrosive compounds such as brine water, COZ, and H2S that can
shorten the run life of an ESP when the ESP is submerged in the well fluid.
Corrosion
resistant units have been developed that have motors that utilize seals and
barriers to
exclude the corrosive agents from the internal mechanisms of the ESP.
A typical submersible pump has a motor, a pump above the motor, and a seal
section between the motor and the pump. The seal section allows for expansion
of the
dielectric oil contained in the rotor gap of the motor. Temperature gradients
resulting
from an ambient and motor temperature rise cause the dielectric oil to expand.
The
expansion of the oil is accommodated by the seal section. Additionally, the
seal
section is provided to equalize the casing annulus pressure with the internal
dielectric
motor fluid. The equalization of pressure across the motor helps keep well
fluid from
leaking past sealed joints in the motor. It is important to keep well fluids
away from
the motor because well fluid that gets into the motor will cause early
dielectric failure.
Measures commonly employed to prevent well fluids from getting into the motor
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include the use of elastomeric bladders as well as labyrinth style chambers to
isolate
the well fluid from the clean dielectric motor fluid. Multiple mechanical
shaft seals
keep the well fluid from leaking down the shaft. The elastomeric bladder
provides a
positive barrier to the well fluid. The labyrinth chambers provide fluid
separation
based on the difference in densities between well fluid and motor oil. Any
well fluid
that gets past the upper shafft seals or the top chamber is contained in the
lower
labyrinth chambers as a secondary protection means.
One problem with the use of an elastomeric bladder is that, in high
temperature applications, elastomeric bladders may experience a short usable
life or
lo may not be suitable for use. Elastomeric materials having a higher
temperature
tolerance tend to be very expensive. An alternative is to replace the
elastomeric
bladder with a bellows made of inetal or another material that may expand as
necessary, but which is suitable for use in high temperature applications,
and/or which
provide improved reliability over an elastomeric bladder. Bellows have been
used
previously in submersible pump applications and other pumping systems. For
example, the use of bellows is taught in United States Patent Nos. 2,423,436,
6,059,539, and 6,242,829. Previous use of bellows in an ESP has required that
the
bellows be placed in an awkward configuration, e.g., as taught in USPN
2,423,436, or
that the bellows be located below the motor in an ESP to avoid interfering
with a shaft
that traverses the length of the ESP to deliver power from the motor to the
pump.
It is desirable to be able to use a bellows to replace an elastomeric
expansion
bag, and that the bellows be configured in a similar manner to the more
commonly
used elastomeric expansion bag.
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SUMMARY OF THE INVENTION
According to the present invention there is provided an improvement in a
positive barrier to well fluid in a submersible pump, wherein the barrier is
suitable for
high temperature applications.
A multi-diameter bellows provides a positive barrier to well fluids. The multi-
diameter bellows is preferably located in a seal section to assist in allowing
expansion
of the dielectric oil, to equalize the casing annulus pressure with the
internal dielectric
motor fluid and to isolate the well fluid from the clean dielectric motor
fluid. The
multi-diameter bellows of the invention may be made fiom materials that are
less
to expensive and are suitable for higher temperatures than an elastomeric bag.
The multi-diameter bellows of the invention is preferably located in a bellows
chamber of a seal section of an electrical submersible pump, wherein the seal
section
is located between a pump and a motor. The bellows chamber has a first end and
a
second end. A shafft communicates the motor with the pump, and runs through
the
bellows chamber in the seal section. The bellows is located in the bellows
chamber
and surrounds the shaft. The bellows is made of a first collapsible section
and a
second collapsible section. The first collapsible section communicates with
the first
end of the bellows chamber. The first collapsible section has a first cross-
sectional
area, e.g., a relatively large diameter. The second collapsible section
communicates
with the second end of the bellows chamber. The second collapsible section has
a
second cross-sectional area, e.g., a relatively small diameter. A first
coupling
member, e.g., a coupling ring, is provided between the first collapsible
section and the
second collapsible section and also surrounds said sha$. A volume within the
bellows
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is varied by movement of the first coupling member towards either of the first
end and
the second end.
In a second embodiment of the bellows of the invention, a large diameter
section is attached to the bellows chamber at a first end. A second end of the
large
diameter section has a coupling member thereon, which transitions the bellows
from
the first large diameter section to a small diameter section. On the other end
of the
small diameter section, a second coupling member is provided to transition the
small
diameter section to a second large diameter section, which is affixed to the
other end
of the bellows chamber. In both embodiments, the ends of the bellows are
fixed. The
volume within the bellows is varied by movement of the coupling member or
coupling
members. For example, to increase the volume of the bellows, the coupling
member
or coupling members are displaced to minimize the volume of the small diameter
section and to maximize the volume of the large diameter sections. Conversely,
to
decrease the volume of the bellows, the coupling members are displaced to
maximize
the volume of the small diameter section and to minimize the volume of the
large
diameter section. One advantage of the second bellows embodiment is that the
bellows is still partially functional even if one of the coupling members
becomes
stuck, thereby increasing reliability of the seal section.
In another embodiment of the invention, a coupling member may be utilized
that is adapted to facilitate a nested bellows. For example, a coupling member
may be
provided with an outside portion for engaging an end surface of a large
diameter
bellows. A transitional portion of the coupling member preferably extends
inside of
the large diameter bellows. An inside portion of the coupling member may be
provided for affixing to an end surface of a small diameter bellows.
Preferably, the
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transitional portion of the coupling member extends within the large diameter
bellows
so that the inside portion of the coupling member is located within the large
diameter
bellows. Therefore, the outside portion of the coupling member lies in a
different
plane than the inside portion of the coupling member, since the outside
portion and
5 inside portion are spaced apart by the transitional portion. As a result, a
portion of the
small diameter bellows extends within a portion of the large diameter bellows,
i.e., is
"nested" therein. A result of nesting the bellows is that for a given length
of a bellows
chamber, volume displaced by a multi-diameter bellows may be increased.
Accordingly, in one aspect of the present invention there is provided a
bellows
for use in an electrical submersible pump comprising:
a first fixed end;
a second fixed end;
a first collapsible section in communication with said first fixed end, said
first
collapsible section having a first cross-sectional area;
a second collapsible section in communication with said second fixed end,
said second collapsible section having a second cross-sectional area; and
a coupling member having an outside portion in a first plane, an inside
portion
in a second plane and a transitional portion therebetween, said coupling
member
between said first collapsible section and said second collapsible section,
wherein said outside portion is affixed to said second collapsible section and
said inside portion is affixed to said first collapsible section,
wherein a motor fluid volume defined by said first collapsible section and
said
second collapsible section is varied by movement of said coupling member
towards
one of said first fixed end and said second fixed end, said coupling member
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movement responsive to accommodate a volume of fluid within said first
collapsible
section and said second collapsible section, said coupling member movement not
subjected to any additional biasing forces, and
wherein said first collapsible section and said second collapsible section
maintain well fluid exteriorly of said first and second collapsible sections.
According to another aspect of the present invention there is provided a
submersible pump comprising:
a motor containing a motor fluid;
a pump above said motor;
a seal section between said motor and said pump, said seal section defining a
bellows chamber having a first end and a second end;
a shafft that communicates said motor with said pump, said shafft running
through said bellows chamber in said seal section;
a communication tube in said bellows chamber surrounding said shaft,
defining an annular passageway in fluid communication with the motor fluid;
a bellows in said bellows chamber and surrounding said communication tube,
said bellows comprised of a first collapsible section and a second collapsible
section,
said communication tube having an aperture for flowing said motor fluid from
the
passageway into an interior of said bellows;
said first collapsible section having a first end secured at said first end of
said
bellows chamber, said first collapsible section having a first cross-sectional
area;
said second collapsible section having a second end secured at said second end
of said bellows chamber, said second collapsible section having a second cross-
sectional area larger than said first cross-sectional area; and
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a coupling member having an outside portion joined to a first end of said
second collapsible section, an inside portion joined to a second end of said
first
collapsible section, and a transitional portion therebetween, said inside
portion and
said transitional portion being located within said second collapsible
section, said
coupling member surrounding said communication tube;
wherein said bellows has a fully expanded position and wherein said second
collapsible section is collapsed fully within said transitional portion of the
coupling
member, and said second collapsible section is fully extended with the outside
portion
of the coupling member bearing against a stop surface on the first end of the
bellows
chamber.
According to yet another aspect of the present invention there is provided a
electrical submersible pump assembly, comprising:
a motor;
a seal section mounted to an end of the motor;
a pump mounted to the seal section;
the motor, seal section, and pump having shafts coupled together;
a bellows chamber in the seal section;
a bellows in the bellows chamber and having first and second collapsible
sections in fluid communication with each other, the first collapsible section
having
an outer diameter that is smaller than the second collapsible section and
having an end
recessed within the second collapsible section, the bellows having a fully
expanded
position with a junction between the first and second collapsible sections in
contact
with a stop surface in the bellows chamber and the first collapsible section
collapsed
and fully recessed within the second collapsible section;
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7a
a motor fluid passageway leading from the motor to an interior of the bellows;
and
a well fluid passageway leading from an exterior of the seal section to the
bellows chamber exterior of the bellows.
A better understanding of the present invention, its several aspects, and its
advantages will become apparent to those skilled in the art from the following
detailed
description, taken in conjunction with the attached drawings, wherein there is
shown
and described the preferred embodiment of the invention, simply by way of
illustration of the best mode contemplated for carrying out the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. lA is a cross-sectional view of a lower section seal section for an
electrical submersible pump having a first embodiment of a multi-diameter
metal
bellows.
FIG. 1B is a cross-sectional view of an upper section of a seal section for an
electrical submersible pump having a second embodiment of multi-diameter metal
bellows.
FIG. 2A is a schematic diagram of the first embodiment of the multi-diameter
bellows of FIG. lA shown in a neutral position.
FIG. 2B is a schematic diagram of the first embodiment of the multi-diameter
bellows shown in FIG. lA shown in a fully collapsed or minimum volume
configuration.
FIG. 2C is a schematic diagram of the first embodiment of the metal bellows
of FIG. lA shown in a completely expanded or maximum volume configuration.
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FIG. 3A is a schematic diagram of the second embodiment of the multi-
diameter bellows shown in FIG. 1 B shown in a neutral position.
FIG. 3B is a schematic diagram of the second embodiment of the multi-
diameter bellows shown in FIG. 1B shown in a fully retracted or minimum volume
configuration.
FIG.3C is a schematic diagram of the second embodiment of the multi-
diameter bellows shown in FIG. 1B shown in a fully expanded or maximum volume
configuration.
FIG. 4A is a schematic diagram of the first embodiment of a nested multi-
lo diameter bellows shown in a neutral position.
FIG. 4B is a schematic diagram of the first embodiment of the nested multi-
diameter bellows shown in a fully collapsed or minimum volume configuration.
FIG. 4C is a schematic diagram of the first embodiment of the nested multi-
diameter bellows shown in an expanded or maximum volume configuration.
FIG. 5A is a schematic diagram of a second embodiment of a nested multi-
diameter bellows shown in a neutral position.
FIG. 5B is a schematic diagram of a second embodiment of a nested multi-
diameter bellows shown in a fully retracted or minimum volume configuration.
FIG. 5C is a schematic diagram of a second embodiment of a nested multi-
diameter bellows shown in a fully expanded or maximum volume configuration.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Before explaining the present invention in detail, it is important to
understand
that the invention is not limited in its application to the details of the
embodiments
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and steps described herein. The invention is capable of other embodiments and
of
being practiced or carried out in a variety of ways. It is to be understood
that the
phraseology and terminology employed herein is for the purpose of description
and
not of limitation.
Referring now to FIGs. lA and 1B, shown is a typical submersible pump
configuration wherein a seal section 10 is located between a pump section 12
and a
motor section 14. Seal section 10 is made up of a lower seal section 16 (FIG.
lA) and
an upper seal section 18 (FIG. 1B). Referring now in particular to FIG. lA,
lower seal
section 16 has a housing 20. A base 22 is located in a lower end of a housing
20.
lo Base 22 defines a sleeve receptacle 24. A lower shaft 26 is located within
housing 20.
A first sleeve 28 surrounds lower shaft 26 and is located in sleeve receptacle
24 of
base 22. Lower sleeve block 30 is at least partially located within housing
20. Lower
sleeve block 30 defines a sleeve receptacle 32 on a lower end and a collar
receptacle
34 on an upper end. A second sleeve 36 is located within the sleeve receptacle
32 of
lower sleeve block 30.
A lower guide tube collar 38 is located within collar receptacle 34 of lower
sleeve block 30. A lower head 40 is at least partially located within housing
20 and is
located above lower sleeve block 30. Lower head 40, housing 20 and lower
sleeve
block 30 define a lower bellows chamber 42. Lower head 40 defines a ring
receptacle
44 on a lower end and a sleeve receptacle 46 above ring receptacle 44. Lower
head 40
also defines a lower shaft seal receptacle 48 on an upper end. Fluid bypass
conduit 50
and fluid passageway 52 are also defined by the lower head 40. Fluid
passageway 52
communicates with an annular space that surrounds lower shaft 26 and also with
lower bellows chamber 42. A check valve 54 is provided in fluid passageway 52
to
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prevent fluid from passing from the lower bellows chamber 42 back into fluid
passageway 52.
A guide tube ring 56 is located within ring receptacle 44. A ring retainer
collar
58 is threadably received on a guide tube ring 56. Ring retainer collar 58 is
preferably
5 provided with a ridge 60 for engaging an inside surface of housing 20. A
lower guide
tube 64 is located inside lower bellows chamber 42. Lower guide tube 64 is
attached
at a first end to the guide tube ring 56 and at a second end to lower guide
tube collar
38 and surrounds lower shafft 26. Lower guide tube 64 is preferably provided
with
orifices 66 proximate an upper end up the lower guide tube 64. A first
embodiment of
10 a multi-diameter bellows 68 surrounds lower guide tube 64. Multi-diameter
bellows
68 has a small diameter portion 70 and a large diameter portion 72. Bellows 68
may
be made of inetal or other high temperature resistant materials or other
suitable
materials as desired.
Referring now to FIGs. 2A-2C, the multi-diameter bellows 68 can be seen in
greater detail. Small diameter portion 70 has an upper end 74 affixed to ring
retainer
collar 58. Large diameter portion 72 has a lower end 76 affixed to lower guide
tube
collar 38. Small diameter portion 70 is separated from large diameter portion
72 by a
coupling ring 78. Coupling ring 78 is attached to an upper end of large
diameter
portion 72 and to lower end of small diameter portion 70. Coupling ring 78 is
preferably provided with a runner 80 for slidably engaging the lower guide
tube 64.
Multi-diameter bellows 68 is also preferably provided with at least one
stabilizer disk
82 that is also provided with a runner 84 on an inner diameter of the
stabilizer disk 82
for slidably engaging lower guide tube 64. Stabilizer disk 82 also
communicates with
an outer diameter of large diameter portion 72. Stabilizer disk 82 preferably
has a first
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side attached to a segment of a large diameter portion 70 and has a second
side
attached to a separate segment of large diameter portion 72. Stabilizer disk
82 is
preferably provided with orifices 83 formed therein for permitting fluid to
pass
therethrough within the multi-diameter bellows 68.
Referring back to FIG. lA, a third sleeve 86 is located in the sleeve
receptacle
46 of lower head 40. A lower shafft sea188 is located partially in the lower
shaft seal
receptacle 48 of lower head 40. Lower shaft sea188 is provided to prevent
fluid
migration along lower shaft 26. A coupling 90 is provided on an upper end of
lower
shaft 26.
lo Referring now to FIG. 1B, upper seal section 18 has an upper base 100
affixed
to an upper end of lower head 40. An upper housing 102 has a lower end has is
affixed to upper base 100. Upper base 100 has a sleeve receptacle 101 formed
in an
upper end. An upper shaft 104 passes through upper housing 102. Upper shaft
104
has a lower end that engages coupling 90. A fourth sleeve 105 is located in
sleeve
receptacle 101. Upper sleeve block 106 is at least partially located within
upper
housing 102. Upper sleeve block 106 defines a sleeve receptacle 108 at a lower
end
thereof and a collar receptacle 110 on an upper end. A fiffth sleeve 112 is
located
within sleeve receptacle 108. A lower guide tube collar 114 is located within
collar
receptacle 110. Upper head 116 is at least partially located within upper
housing 102
and above upper sleeve block 106. The upper head 116, the upper housing 102
and
the upper sleeve block 106 define an upper bellows chamber 118. The upper head
116 defines a ring receptacle 120 on a lower end and a sleeve receptacle 122
above
ring receptacle 120. Additionally, upper head 116 defines an upper shaft seal
receptacle 124 on an upper end. Upper head 116 additionally defines a fluid
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passageway 126 that communicates an annular space around upper shaft 104 with
the
upper bellows chamber 118. A check valve 128 is provided for allowing fluid to
pass
from fluid passageway 126 to the upper bellows chamber 118. The portion of
upper
housing 102 that defines the upper bellows chamber 118 is provided with
perforations
130 to allow well fluids to migrate into the upper bellows chamber 118 to
equalize
pressure between the upper bellows chamber 118 and the wellbore.
An upper guide tube ring 132 is located within ring receptacle 120. An upper
guide tube 138 is attached to the lower guide tube collar 114 on a lower end
and is
attached to the upper guide tube ring 132 at an upper end. A second embodiment
of a
multi-diameter bellows 140 surrounds the upper guide tube 138. Multi-diameter
bellows 140 has a first large diameter portion 142, a second large diameter
portion
144, and a small diameter portion 146. Bellows 140 may be made of inetal or
other
high temperature resistant materials or other suitable materials as desired.
Referring now to FIGs. 3A-3C, multi-diameter bellows 140 is shown in greater
detail. An upper end 148 of the multi-diameter bellows 140 is affixed to the
upper
guide tube ring 132. A lower end 150 of the multi-diameter bellows 140 is
affixed to
the lower guide tube collar 114. Small diameter portion 146 is located between
first
large diameter portion 142 and second large diameter portion 144. A first end
of the
small diameter portion 146 engages the first large diameter portion 142 and is
attached
to a first coupling ring 152. First coupling ring 152 is attached to an upper
end of the
small diameter portion 146 and to a lower end of the first large diameter
portion 142.
The first coupling ring 152 preferably has a runner 154 located thereon for
slidably
engaging upper guide tube 138. A second end of the small diameter portion 146
is
attached to the second large diameter portion 144 by a second coupling ring
156.
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Second coupling ring 156 is attached to a lower end of the small diameter
portion 146
and to an upper end of second large diameter portion 144. Second coupling ring
156
is also preferably provided with a runner 158 for engaging the upper guide
tube 138.
Multi-diameter bellows 140 also is preferably provided with a plurality of
stabilizer disks 160 that have runners 162 provided on an inner diameter of
the
stabilizer disks 160 for slidably engaging upper guide tube 138. The
stabilizer disks
160 communicate with an outer diameter of the first large diameter portion 142
and
with an outer diameter of second large diameter portion 144. The stabilizer
disks 160
preferably have a first side attached to a first segment of the first or
second large
diameter portions 142, 144 and a second side attached to a second segment of
the first
or second large diameter portions 142, 144. Stabilizer disks 160 are
preferably
provided with orifices 161 formed therein for permitting fluid to pass through
the
stabilizer disks 160 within the multi-diameter bellows 140.
Referring back to FIG. 1 B, a sixth sleeve 164 is located in sleeve receptacle
122 of the upper head 116. An upper shaft sea1166 is located partially in the
upper
shaft seal receptacle 124 of the upper head 116. The upper shaft seal 166 is
provided
to prevent fluid migration along the upper shaft 104.
Referring now to FIGs. 4A-4C, a multi-diameter nested bellows 268 is shown.
Small diameter portion 270 has an upper end 274 for affixing to a retainer
such as
collar 58 (FIG. lA). Large diameter bellows portion 272 has a lower end 276
affixed
to a retainer such as lower guide tube collar 38 (FIG. lA). Small diameter
bellows
portion 270 is separated from large diameter bellows portion 272 by a coupling
ring
278. Coupling ring 278 is attached to an upper end of large diameter bellows
portion
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272 and to lower end of small diameter bellows portion 270. Coupling ring 278
has
an outside portion 278a, an inside portion 278b and a transitional portion
278c.
Referring now to FIGs. 5A-5C, a second embodiment of multi-diameter
bellows 340 is shown. An upper end 348 of the multi-diameter bellows 340 may
be
affixed to a retainer such as upper guide tube ring 32 (FIG. 1B). A lower end
350 of
the multi-diameter bellows 340 may be affixed to a lower guide tube collar,
such as
collar 114 (FIG. 1B). Small diameter bellows portion 346 is located between
first
large diameter bellows portion 342 and second large diameter bellows portion
344. A
first end of small diameter bellows portion 346 engages a first coupling ring
352 that
is in communication with first large diameter bellows portion 342. First
coupling ring
352 is attached to an upper end of the small diameter bellows portion 346 and
to a
lower end of the first large diameter bellows portion 342. The first coupling
ring 352
has an outside portion 352a, an inside portion 352b, and a transitional
portion 352c.
A second end of the small diameter bellows portion 346 is attached to second
large
diameter bellows portion 344 by a second coupling ring 356. Second coupling
ring
356 is attached to a lower end of the small diameter bellows portion 346 and
to an
upper end of second large diameter bellows portion 344. Second coupling ring
356
has an outside portion 356a, an inside portion 356b, and a transitional
portion 356c.
In practice, dielectric fluid surrounding motor 14 is heated by operation of
motor 14 and/or by conducting heat from the well environment. As a result, the
dielectric fluid expands and migrates through base 22 past first sleeve 28 and
up lower
shaft 26. The dielectric fluid may continue to migrate past second sleeve 36,
through
lower sleeve block 30 and into the annular space between the lower shaft 26
and the
lower guide tube 64. Once dielectric fluid migrates into lower guide tube 64,
the
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dielectric fluid passes through orifices 66 in lower guide tube 64 and into
the small
diameter portion 70 of the multi-diameter bellows 68. The dielectric fluid may
then
fill the small diameter portion 70 and large diameter portion 72 of the multi-
diameter
bellows 68.
5 Once the volume within the multi-diameter bellows 68 is full of fluid, then
coupling ring 78 will propagate along lower guide tube 64 to increase the
volume
within the large diameter portion 72 until such time as the small diameter
portion 70 is
fully compressed. When the small diameter portion 70 is fully compressed, then
the
multi-diameter bellows 68 is at full capacity. Once the multi-diameter bellows
68 is
lo at full capacity, the dielectric fluid will migrate through fluid
passageway 52 in lower
head 40 and out through check valve 54 into the lower bellows chamber 42. Once
lower bellows chamber 42 becomes full, the fluid may continue to migrate
upwardly
through fluid bypass conduit 50, which allows the fluid to bypass lower shaft
sea188.
If necessary, the dielectric fluid will continue to migrate upwardly in the
seal
15 section 10 past coupling 90 and into the upper seal section 18 where fluid
will migrate
through upper base 100 past fourth sleeve 105 and through the annular space
surrounding the upper shaft 104, and through fifth sleeve 112 in upper sleeve
block
106. Dielectric fluid will then continue to migrate up through the annular
space
between the upper shaft 104 and the upper guide tube 138 where the fluid
migrates out
of upper guide tube 138 and into the multi-diameter bellows 140.
The dielectric fluid fills first large diameter portion 142, small diameter
portion 146, and second large diameter portion 144 of multi-diameter bellows
140.
Once the internal volume of the multi-diameter bellows 140 is completely full
of
fluid, first coupling ring 152 and second coupling ring 156 propagate along
upper
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16
guide tube 138 toward one another, thereby expanding the volume of the first
large
diameter portion 142 and second large diameter portion 144 while compressing
small
diameter portion 146. As more fluid is added to the multi-diameter bellows
140, the
first large diameter portion 142 and second large diameter portion 144 will
continue to
expand until small diameter portion 146 is fully compressed as shown in FIG.
3C,
which illustrates the maximum volume configuration of multi-diameter bellows
140.
Dielectric fluid will then migrate up through fluid passageway 126 and out
through
check valve 128 where the dielectric fluid will co-mingle with well fluids
that are able
to enter through perforations 130 in upper housing 102. Therefore, the
pressure
lo within the multi-diameter bellows 140 will be maintained in equilibrium
with
wellbore pressure.
In the case of nested bellows 268 (FIGs. 4A-4C), once dielectric fluid passes
into the small diameter bellows portion 270 of the multi-diameter bellows 268,
the
dielectric fluid may fill the small diameter bellows portion 270 and large
diameter
bellows portion 272 of the multi-diameter bellows 268.
As the volume within the multi-diameter bellows 268 fills with fluid, coupling
member 278 will propagate along lower guide tube 64 to increase the volume
within
the large diameter bellows portion 272 until such time as the small diameter
bellows
portion 270 is fully compressed or until such time as outer portion 278a of
coupling
ring 278 makes contact with a retainer as shown in FIG. 4C.
In a preferred embodiment, outer portion 278a of coupling ring 278 functions
as a stop against the retainer (FIG. 4C) to prevent over-compression of small
diameter
portion 270 or over-extension of large diameter portion 272, thereby avoiding
the
infliction of potentially damaging stress upon portions 270, 272. During
operation,
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when small diameter portion 270 is fully compressed, the multi-diameter
bellows 268
is at full capacity. Once the multi-diameter bellows 268 is at full capacity,
the
dielectric fluid will migrate out of bellows 268 through a fluid passageway.
Conversely, when nested bellows 268 is in a fully contracted or minimum
volume configuration, as shown in FIG. 4B, large diameter bellows portion 272
is
fully compressed and small diameter bellows portion 270 is fully expanded. In
a
preferred embodiment, inner portion 278b makes contact with a retainer and
functions
as a stop to prevent over expansion of small diameter bellows portion 270 or
over
compression of large diameter bellows portion 272.
With respect to the second embodiment of multi-diameter nested bellows 340
(FIGs. 5A-5C), dielectric fluid fills first large diameter bellows portion
342, small
diameter bellows portion 346, and second large diameter bellows portion 344 of
multi-diameter nested bellows 340. As the internal volume of the multi-
diameter
nested bellows 340 fills with fluid, first coupling member 352 and second
coupling
member 356 propagate along a guide tube, such as upper guide tube 38 (FIG. 1B)
toward one another, thereby expanding the volume of first large diameter
bellows
portion 342 and second large diameter bellows portion 344 while compressing
small
diameter bellows portion 346.
As more fluid is added to the multi-diameter bellows 340, the first large
diameter bellows portion 342 and second large diameter bellows portion 344
will
continue to expand until small diameter bellows portion 346 is fully
compressed or
until outer portion 352a of first coupling member 352 and outer portion 356a
of
second coupling member 356 make contact, as shown in FIG. 5C. FIG 5C
illustrates
the maximum volume configuration of multi-diameter bellows 340. When outer
CA 02508267 2005-05-24
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portions 352a and 356a are allowed make contact, outer portions 352a and 356a
function as a stop to prevent over-expansion of first large diameter portion
342 and
second large diameter portion 344 as well as over-compression of small
diameter
portion 344. Once first large diameter portion 342 and second large diameter
portion
344 are completely expanded, then dielectric fluid will migrate up through a
fluid
passageway.
To minimize volume of bellows 340, small diameter bellows portion 346 is
fully expanded while first large diameter bellows portion 342 and second large
diameter bellows portion 344 are fully compressed, as shown in FIG. 5B.
In a preferred embodiment, inner portions 352b of first coupling member 352
will make contact with a stop, as shown in FIG. 5B, such as sleeve receptacle
32 (FIG.
1B). Similarly, as shown in FIG. 5B, inner portion 356b of second coupling
member
356 will make contact with a stop, such as lower guide tube collar 114 (FIG.
1B).
When inner portions 352b and 356b are allowed to bump against their respective
stops, inner portions 352b and 356b function to prevent over-expansion of
small
diameter bellows portion 346 as well as over-compression first large diameter
bellows
portion 342 and second large diameter bellows portion 344.
Multiple embodiments of multi-diameter bellows are shown, i.e. multi-
diameter bellows 68,140, 268 and 340. The example bellows are shown located in
a
seal section 10 having a lower section 16 and an upper section 18. However, it
should
be understood that any of the multi-diameter bellows may be used in a seal
section 10
having only a single section. Additionally, the multi-diameter bellows may be
used in
a seal section 10 having three or more sections as desired. Although seal
section 10 is
shown for purposes of example having both a first ernbodiment 68 and a second
CA 02508267 2005-05-24
19
embodiment 140, the seal section 10 could be used with two or more of the
first
embodiments 68 or second embodiments 140, or embodiments 268 and 340 in any
desired combination.
One advantage of the multi-diameter bellows is that the upper ends and lower
ends are fixed. Therefore, the multi-diameter bellows occupy the same linear
space of
the seal section regardless of the volume of fluid located therein. The volume
of the
multi-diameter bellows is varied by movement of the coupling rings.
An additional advantage of the end mounted multi-diameter bellows is that the
bellows surround the shafts. As a result, the multi-diameter bellows 68, 140
may be
used above pump motor 14 in the same manner as elastomeric bags have been used
previously.
While the invention has been described with a certain degree of particularity,
it
is understood that the invention is not limited to the embodiment(s) set for
herein for
purposes of exemplification, but is to be limited only by the scope of the
attached
claim or claims, including the full range of equivalency to which each element
thereof
is entitled.
