Note: Descriptions are shown in the official language in which they were submitted.
CA 02835976 2013-11-13
PLUNGER TYPE OIL-SUCKING PUMP AND PLUNGER THEREOF
Field of the Invention
The present invention pertains to a technical field of petroleum exploitation,
and specifically relates to a plunger for a plunger type oil-sucking pump and
the plunger type oil-sucking pump containing the plunger.
Background of the Invention
As one of traditional lifting manners in the global petroleum industry and a
dominant artificial lifting manner to date, a rod plunger pump generally
refers to
a plunger type oil-sucking pump driven by reciprocatingly moving a sucker rod
up and down and is currently used as a main mechanical oil-pumping
equipment in the world.
A typical oil-pumping equipment with a rod available at present is mainly
composed of three parts: a driving device on the ground, i.e., a pumping unit,
a
oil-sucking pump mounted in a lower portion of a tubing string, and a sucker
rod. The sucker rod is connected from above to the pumping unit via a polished
rod and is connected from below to a plunger of the oil-sucking pump thereby
to transmit reciprocating movement and power of the pumping unit on the
ground to the underground oil-sucking pump to reciprocatingly move the
plunger in the oil-sucking pump up and down so that a pressure of liquid in
the
tubing string can be boosted and fluid produced from oil layers can be lifted
to
the ground. The oil-sucking pump is mainly composed of four parts including a
pump barrel, the plunger, a fixed valve assembly and a movable valve
assembly. The pump barrel is a cylinder jacket in which the plunger with the
movable valve assembly is mounted, and a seal is formed between the plunger
and the pump barrel so that liquid in the pump barrel can be discharged. The
fixed valve assembly includes an intake valve of the pump which remains fixed
during pumping. The movable valve assembly includes a discharge valve of
the pump which is moveable along with the plunger.
The pumping equipment equipped with the rod plunger pump has been
developed into a new stage of hydraulic self-sealing plunger pumps. Chinese
patent application No. 200510082603.1 discloses a hydraulic self-sealing
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plunger oil-sucking pump, a plunger of which is enclosed by an elastic sealing
body enclosed by wear resistant diameter variable sealing rings. The sealing
rings include a plurality of rigid metal rings and a plurality of elastic
rings which
enclose the elastic sealing body at intervals. This structure can address pump
leakage issue to a certain extent and improve pump volumetric efficiency.
However, in this structure, since there is no fixed mutual connection among
the
plurality of metal rings of the sealing rings, not only requirements for
machining
are high but also the problem that the wear resistant diameter variable
sealing
rings are not radially centered with the plunger to yield poor coaxiality and
ellipticity is liable to occur. Particularly when the sealing rings are
subjected to
a force during oil exploitation, the problem that the sealing rings are not
radially
centered with the plunger to have poor coaxiality and ellipticity becomes more
prominent, and thus the sealing rings, especially the sealing ring closest to
a
lower pump cavity wears eccentricly and severely so as to have a short life.
Summary of the Invention
In view of the above disadvantages existing in the prior art, the technical
problem to be solved by the present invention is to provide a plunger for a
plunger type oil-sucking pump and the plunger type oil-sucking pump
containing the plunger, wherein the plunger has a simple structure and
excellent sealing performance and can eliminate eccentric wear between the
plunger and a pump barrel.
The technical solution employed to solve the above technical problem
resides in that the plunger for a plunger type oil-sucking pump comprises a
plunger core, wherein a number of liquid passing holes are opened in an outer
wall of the plunger core, a flexible sealing sleeve having elasticity tightly
encloses the outer wall of the plunger core, and the flexible sealing sleeve
is
provided at such a position on the plunger core as to cover said number of the
liquid passing holes of the plunger core.
Preferably, said number of the liquid passing holes comprise multiple
liquid passing holes, and the multiple liquid passing holes have identical
shape
and size and are collectively arranged on the same level of the plunger core
evenly in a circumferential direction of the plunger core.
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Alternatively, said number of the liquid passing holes comprise multiple
liquid passing holes, the multiple liquid passing holes are arranged on
different
levels of the plunger core along an axis of the plunger core, in which a
plurality
of liquid passing holes having identical shape and size are provided on any
level along the axis of the plunger core evenly in the circumferential
direction of
the plunger core.
The number of the liquid passing holes arranged on the same level of the
plunger core is preferably 2-8, and more preferably 4-6.
Preferably, the flexible sealing sleeve includes an elastic body and a
number of wear resistant rings which are embedded in the elastic body at
intervals in an axial direction of the elastic body, wherein the elastic body
is
made of an elastic material and the wear resistant rings are made of a wear
resistant material. Since the wear resistant rings are connected integrally
with
the elastic body, the problem that the sealing rings are not radially centered
with the plunger to have poor coaxiality and ellipticity can be solved
effectively
when the whole flexible sealing sleeve encloses the outer wall of the plunger
core.
Preferably, the elastic body is made of synthetic rubber and the wear
resistant rings are made of nylon or a rigid material such as copper or steel.
Preferably, the wear resistant rings are moulded integrally with the elastic
body by a pouring process, and the flexible sealing sleeve is connected
integrally with the plunger core. Thus, machining precision and mounting
requirements for the flexible sealing sleeve are lowered.
Certainly, the wear resistant rings can be formed integrally with the elastic
body by another processing means.
More preferably, the outer wall of the plunger core is tightly enclosed by
one primary sealing sleeve which is provided on either end of the flexible
sealing sleeve, or the outer wall of the plunger core is tightly enclosed by
two
primary sealing sleeves which are provided on both ends of the flexible
sealing
sleeve respectively, and the primary sealing sleeve(s) is connected integrally
with the flexible sealing sleeve.
More preferably, the outer wall of the plunger core is tightly enclosed by
two primary sealing sleeves including an upper primary sealing sleeve and a
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lower primary sealing sleeve, the upper primary sealing sleeve is provided
above the flexible sealing sleeve to be in threaded connection with the
plunger
core and has a lower end connected to an upper end of the flexible sealing
sleeve, and the lower primary sealing sleeve is provided below the flexible
sealing sleeve to be in threaded connection with the plunger core and has an
upper end connected to a lower end of the flexible sealing sleeve. Through the
upper primary sealing sleeve and the lower primary sealing sleeve which are
connected to the both ends of the flexible sealing sleeve respectively, a
position at which the flexible sealing sleeve is provided on the plunger is
restricted and the plunger is allowed to obtain adequate centerability.
Furthermore, the upper and lower primary sealing sleeves also serve as
primary seals on both ends of the plunger.
Wherein, the upper primary sealing sleeve and the lower primary sealing
sleeve are made of a wear resistant material.
The technical solution of the present invention also resides in that a
plunger type oil-sucking pump comprises a pump barrel and the foregoing
plunger provided in the pump barrel. Wherein, a rigid gap seal which can
perform sealing in a manner the same as that of an existing conventional pump
without action of hydraulic pressure is formed between each of the primary
sealing sleeves provided on the both ends of the flexible sealing sleeve and
the pump barrel so that oil well pressure can be borne effectively and primary
sealing of the oil-sucking pump is realized. Meanwhile, since the two primary
sealing sleeves, the flexible sealing sleeve and the plunger core are formed
integrally, sealing performance of the whole pump is superior and the problem
that oil leaks from a gap between the pump barrel and the plunger of the
existing hydraulic plunger pump is avoided thus to attain stronger
adaptability.
The oil-sucking pump of the present invention can improve coaxiality and
ellipticity between the flexible sealing sleeve and the plunger core,
eliminate
eccentric wear between the flexible sealing sleeve and the pump barrel, and
lower machining precision and mounting requirements for the flexible sealing
sleeve so that sealing performance of the hydraulic plunger pump becomes
better and the pump is operated more stably and reliably.
The plunger in the plunger type oil-sucking pump improves centerability of
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the flexible sealing sleeve by using the structures including the liquid
passing
holes and the flexible sealing sleeve, effectively solves the problem that
poor
coaxiality and ellipticity exist between sealing members on the plunger and
the
pump barrel of the current hydraulic self-sealing pump, that is, eliminates
eccentric wear between the pump barrel and the plunger, and also lowers
machining precision and mounting requirements for the plunger. Moreover, the
oil-sucking pump has better sealing performance with no leakage and
possesses stronger adaptability.
The plunger of the present invention is adapted for all of hydraulic
self-sealing plunger pumps and multi-plunger pumps.
Brief Description of the Drawings
Fig. 1 is a structural schematic diagram showing a plunger according to a
first embodiment of the present invention.
Fig. 2 is a structural schematic diagram showing a plunger type
oil-sucking pump according to the first embodiment of the present invention.
Wherein, 1-upper primary sealing sleeve, 2-plunger core, 3-flexible
sealing sleeve, 4-liquid passing holes, 5-lower primary sealing sleeve, 6-
upper
joint, 7-movable valve assembly, 8-pump barrel, 9-fixed valve assembly,
10-upper pump cavity, 11-lower pump cavity, 31-elastic body, 32-wear resistant
rings.
Detailed Description of the Preferred Embodiments
In order that those skilled in the art can understand technical solutions of
the present invention better, a plunger for a plunger type oil-sucking pump
and
the plunger type oil-sucking pump containing the plunger according to the
present invention will be detailedly described further below in connection
with
accompanying drawings as well as a specific embodiment.
The plunger for the plunger type oil-sucking pump includes a plunger core
2, wherein a number of liquid passing holes 4 are opened in an outer wall of
the plunger core 2, a flexible sealing sleeve 3 having elasticity tightly
encloses
the outer wall of the plunger core 2, and the flexible sealing sleeve 3 is
provided at such a position on the plunger core 2 as to cover said number of
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the liquid passing holes 4 of the plunger core 2.
Wherein, the flexible sealing sleeve 3 includes an elastic body 31 and a
number of wear resistant rings 32 which are embedded in the elastic body 31
at intervals in an axial direction of the elastic body 31. The elastic body 31
and
the wear resistant rings 32 are formed integrally. The elastic body 31 is made
of an elastic material and the wear resistant rings 32 are made of a wear
resistant material.
First Embodiment
As shown in Fig. 2, in this embodiment, the plunger type oil-sucking pump
includes a pump barrel 8 in which components such as the plunger, an upper
joint 6, a movable valve assembly 7 and a fixed valve assembly 9 are
contained, and the plunger has an upper end in threaded connection with the
upper joint 6 and a lower end in threaded connection with the movable valve
assembly 7.
As shown in Fig. 1, in this embodiment, the plunger includes the plunger
core 2, and the outer wall of the plunger core 2 is opened with a number of
liquid passing holes 4 and is tightly enclosed by the flexible sealing sleeve
3,
an upper primary sealing sleeve 1 and a lower primary sealing sleeve 5.
The plunger core 2 is made of a metal material and formed with an internal
hollow structure, and the liquid passing holes 4 have identical shape and
size.
In the present embodiment, the liquid passing holes 4 are in an oval shape.
The liquid passing holes 4 are arranged on the same level in a middle portion
of the outer wall of the plunger core 2 evenly in a circumferential direction
of
the plunger core 2. In comprehensive consideration of penetration of liquid
and
strength of the plunger core 2, the number of the liquid passing holes 4
arranged on the same level of the plunger core 2 is 2-8, and preferably 4-6.
That is, one oval liquid passing hole 4 is opened by a milling process at an
interval of 900 or 600 at the same axial height of the outer wall of the
plunger
core 2. Thus, it can be ensured that liquid in the plunger core 2 is
distributed
well and that the plunger core 2 has enough strength. If a length of the
plunger
core 2 along its axis is relatively long, a round or more rounds of liquid
passing
holes 4 can be added on another different level in the axial direction of the
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plunger core 2.
The flexible sealing sleeve 3 tightly encloses the outer wall of the plunger
core 2 so that all the liquid passing holes 4 of the plunger core 2 can be
covered. The flexible sealing sleeve 3 includes an elastic body 31 and a
number of wear resistant rings 32 which are embedded in the elastic body 31
at intervals in an axial direction of the elastic body 31. The elastic body 31
and
the wear resistant rings 32 are formed integrally. An outer diameter of the
elastic body 31 and the wear resistant rings 32 is smaller than an inner
diameter of the pump barrel 8 and matches with an outer diameter of the
plunger core 2, and a spacing between two adjacent wear resistant rings 32 is
shorter than a length of each of the liquid passing holes 4. The elastic body
31
is made of synthetic rubber, and the wear resistant rings 32 are made of a
wear resistant material, preferably nylon or a rigid material such as copper
or
steel. When liquid is filled up in the plunger core 2, hydraulic pressure
directly
acts on the flexible sealing sleeve 3 through the liquid passing holes 4 to
cause
the flexible sealing sleeve 3 to expand outward, while the liquid passing
holes
4 are provided to disperse high hydraulic pressure in the plunger core 2.
In the embodiment, the elastic body 31 and the wear resistant rings 32 of
the flexible sealing sleeve 3 are moulded integrally by a pouring process.
During fabrication of the flexible sealing sleeve 3, a cylindrical groove
having a
length greater than the length of the liquid passing holes 4 of the plunger
core
2 and having an inner diameter matching with the outer diameter of the plunger
core 2 is firstly formed in a corresponding mold, and a number of wear
resistant rings 32 whose inner diameter matches with the outer diameter of the
plunger core 2 are provided at regular intervals in the cylindrical groove and
positioned fixedly. Then, the mold is overlaid on the plunger core 2 at a
position
corresponding to the liquid passing holes 4 of the plunger core 2 to cover the
liquid passing holes 4, and each of the liquid passing holes 4 of the plunger
core 2 is clogged up by a corresponding tool simultaneously. Next, molten
synthetic rubber is injected into the mold, and a flexible sealing sleeve 3 in
which the wear resistant rings 32 are connected tightly and integrally with
the
elastic body 31 is formed after cooling and moulding so that the flexible
sealing
sleeve 3 is formed integrally with the plunger core 2. As such, the wear
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resistant rings 32 are inserted in the elastic body 31 in an embedded manner
to form the flexible sealing sleeve 3 and the flexible sealing sleeve 3
tightly
encloses the plunger core 2, which solves the problem that sealing members
on the plunger of the conventional hydraulic self-sealing pump include a
plurality of wear resistant rings having no fixed connection therebetween so
that each of the wear resistant rings has poor coaxiality and ellipticity and
is apt
to eccentric wear, and machining precision and mounting requirements for the
flexible sealing sleeve is lowered.
Threads are provided in such places on the plunger core 2 as to be
engaged with both ends of the flexible sealing sleeve 3, and after the
flexible
sealing sleeve 3 is formed integrally with the plunger core 2, the upper
primary
sealing sleeve 1 is provided above the flexible sealing sleeve 3 to be in
threaded connection with the plunger core 2 and has a lower end connected to
an upper end of the flexible sealing sleeve 3. In this embodiment, a lower
section of the plunger core 2 is formed with a step to which a lower end of
the
flexible sealing sleeve 3 is connected, and the lower primary sealing sleeve 5
is in threaded connection with a lower end of the plunger core 2 so that the
flexible sealing sleeve 3 is axially fixed on the outer wall of the plunger
core 2
between the upper primary sealing sleeve 1 and the lower primary sealing
sleeve 5. The upper and lower primary sealing sleeves 1 and 5 play the role of
righting the flexible sealing sleeve 3, namely, righting the whole plunger,
which
can effectively avoid occurrence of a phenomenon that one side of the plunger
core 2 is subjected to a force and the other side of the plunger core 2 keeps
close contact with the pump barrel 8 so as to cause eccentric wear between
the plunger core 2 and the pump barrel 8. Both the upper primary sealing
sleeve 1 and the lower primary sealing sleeve 5 are made of a wear resistant
material, preferably nylon or a rigid material such as copper or steel.
When liquid is filled up in the plunger core 2, liquid spills out through the
liquid passing holes 4 to cause the elastic body 31 of the flexible sealing
sleeve
3 to expand outward, the flexible sealing sleeve 3 is axially fixed by the
upper
and lower primary sealing sleeves 1 and 5 to prevent the flexible sealing
sleeve 3 from travelling up and down on the outer wall of the plunger core 2,
and flexible sealing sleeve 3 is caused to be radially centered with the
plunger
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core 2 so that hydraulic self-sealing of the flexible sealing sleeve 3 with
respect
to the plunger core 2 can be realized. At the same time, the upper and lower
primary sealing sleeves 1 and 5 on both ends of the plunger core 2 also serve
as primary seals on the both ends of the plunger core 2. That is, when liquid
does not reach the flexible sealing sleeve 3, the two primary sealing sleeves
on the both ends of the plunger core 2 serve to address the primary sealing
issue for the oil-sucking pump and bear oil well pressure.
"Centerability" of the above flexible sealing sleeve 3 depends on degree of
tightness between the upper and lower primary sealing sleeves 1 and 5 and
the flexible sealing sleeve 3, in which the flexible sealing sleeve 3 may
protrude outward if it is too tight and the flexible sealing sleeve 3 may not
implement favorable sealing if it is too loose. Adequate centerability can be
obtained by regulating threads between the upper and lower primary sealing
sleeves 1 and 5 and the flexible sealing sleeve 3 integrated with the plunger
core 2. In the present embodiment, since the lower primary sealing sleeve 5 is
not in contact with the flexible sealing sleeve 3, radial centerabilty of the
flexible sealing sleeve 3 with respect to the plunger can be adjusted by only
regulating tightness of the upper primary sealing sleeve 1.
As seen from above, in the embodiment, the upper primary sealing sleeve
1, the plunger core 2 provided with the liquid passing holes 4 and enclosed by
the flexible sealing sleeve 3, and the lower primary sealing sleeve 5 are
formed
integrally to constitute the plunger having a three-segment composite sealing
section which includes rigid plus elastic plus rigid sealing segments and can
serve for primary sealing, centering and righting, which ensures overall
sealing
and hydraulic transmission of the plunger within the pump barrel and solves
the problem that the wear resistant rings are not radially centered with the
plunger to yield poor coaxiality and ellipticity and severe eccentric wear.
As shown in Fig. 2, in the plunger type oil-sucking pump, the ends of the
upper and lower primary sealing sleeves 1 and 5 distant from the flexible
sealing sleeve 3 are also provided with threads by which the upper primary
sealing sleeve 1 is connected to the upper joint 6 and the lower primary
sealing
sleeve 5 is connected to the movable valve assembly 7. The above plunger
having the three-segment composite sealing section is then assembled into
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the pump barrel 8 so as to realize sealing of the plunger type oil-sucking
pump.
The above plunger is adapted for all of hydraulic self-sealing plunger
pumps and multi-plunger pumps. In use, a gap larger than that in a
conventional oil-sucking pump exists between the plunger and the pump barrel.
Since the flexible sealing sleeve is fixed on the outer wall of the plunger
core of
the plunger in the present embodiment, hydraulic self-sealing is formed and
the gap between the plunger and the pump barrel disappears with no leakage
when the pump runs upward, and the gap between the plunger and the pump
barrel is restored and frictional resistance is reduced when the pump runs
to downward.
Operating principles of the plunger type oil-sucking pump in the
embodiment will be described below. In an upward stroke, the plunger is pulled
upward by a sucker rod and the movable valve assembly 7 on the plunger is
initially closed under liquid column pressure within an oil tube. At this
time, a
lower pump cavity 11 downstream the plunger is increased in volume and
reduced in pressure, the fixed valve assembly 9 is opened by a difference
between a submergence pressure (i.e., a pressure when an intake port of the
pump is submerged to a certain depth below a liquid level) and a pressure
within the pump, and fluid is sucked into the lower pump cavity 11. In the
meantime, since a pressure within the upper pump cavity 10 is higher than that
within the lower pump cavity 11, the composite sealing section is allowed to
form a hydraulic seal. In the case that the oil tube is gradually filled up
with
liquid and hydraulic pressure within the plunger rises, liquid acts upon the
elastic body 31 of the flexible sealing sleeve 3 through the liquid passing
holes
4 of the plunger core 2 to cause the elastic body 31 to expand outward, the
wear resistant rings 32 are pushed against the pump barrel 8 to form a seal,
and the movable valve assembly 7 keeps closed under a differential pressure
between pressures above and below itself so that liquid in the upper pump
cavity 10 upstream the plunger is discharged to the ground along the oil tube.
In a downward stroke, the plunger is pushed downward by the sucker rod and
the fixed valve assembly 9 is initially closed so that the plunger compresses
liquid between the fixed valve assembly 9 and the movable valve assembly 7
to raise the pressure within the pump. When the pressure within the pump is
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raised to be higher than hydraulic pressure above the plunger, the movable
valve assembly 7 is opened and liquid in the lower pump cavity 11 enters the
upper pump cavity 10 through the movable valve assembly 7 so that liquid is
discharged from the pump.
Here, it is to be appreciated that a ratio between a length of the flexible
sealing sleeve 3 and that of the whole plunger is not fixed in the present
embodiment as long as the length of the flexible sealing sleeve 3 ensures that
it can cover all the liquid passing holes 4 of the plunger core 2. The length
of
the flexible sealing sleeve 3 can be set agilely according to the type of the
hydraulic plunger pump actually used and the practical operating conditions.
In
addition, in light of requirements of production and operating environment of
the hydraulic plunger pump, fluorine or nitrile can be injected into the
elastic
body 31 of the flexible sealing sleeve 3 to make corrosion or wear resistant
effect of the flexible sealing sleeve 3 better thus to accommodate production
under different temperatures or corrosive conditions.
The plunger type oil-sucking pump in the present embodiment has high oil
pumping efficiency with no oil leakage and operates more stably, and is
adapted to complicated production conditions such as deep well, sanding with
strong adaptability.
It can be understood that the above embodiment is only used as an
exemplary embodiment employed to illustrate principles of the present
invention and the present invention is not limited to it. It is possible for
those
ordinary skilled in the art to make various modifications which fall within
the
scope of the present invention, and such modifications are intended to fall
within the appended claims.
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