Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02915080 2015-12-14
"SPLIT PACKING GLAND INSERTS AND PACKING RETAINERS FOR A
STUFFING BOX"
FIELD OF THE INVENTION
The present invention relates to packing gland inserts and packing
retainers for a stuffing box. More particularly, the invention relates to
packing gland
inserts and packing retainers that are split.
BACKGROUND OF THE INVENTION
The background information discussed below is presented to better
illustrate the novelty and usefulness of the present invention. This
background
information is not admitted prior art.
A stuffing box is an assembly which is used to house a gland seal. It is
used to prevent leakage of fluid, such as water or steam, between sliding or
turning
parts of machine elements. Typically it is used to seal a rotating or
reciprocating
shaft against a fluid using "packing". In oil well applications, the pumping
action of a
beam pump, commonly known as a "pumpjack", moves a rod string in a
reciprocating motion to drive a downhole pump.
For example, an oil well sucker rod pump assembly may include a
pump located in the production tubing of an oil producing well, below the
level of the
liquid in the well. The pump is operated by a string of reciprocating sucker
rods that
extend through the production tubing from the pump to the surface. The rods
are
CA 02915080 2015-12-14
reciprocated by the pumpjack located at the surface. When the fluid being
pumped
reaches the surface, it is directed into a lateral flow line by a stuffing box
mounted
on the wellhead. The stuffing box has an opening through which the top sucker
rod
extends. Seals or packing located in the stuffing box allow the sucker rods to
reciprocate in the opening while preventing the pumped fluid from flowing
through
the top opening. The top sucker rod is usually a special rod, called a
"polished rod",
with an outer surface that is machined to a very smooth finish to reduce the
friction
between the rod and the seals or packing in the stuffing box. Even with a very
smooth "polished rod", the friction generated by the reciprocation of the
polished
rod, however well machined, will produce heat and contributed to the
deterioration
of the seals and packing.
The polished rod extends through an axial bore of a stuffing box. The
stuffing box contains packing which forms a seal against the polished rod. If
the
polished rod is not axially aligned with the axial bore of the stuffing box,
lateral
pressure is exerted upon the stuffing box by the polished rod. This lateral
pressure
leads to wear and premature failure of both the packing and the polished rod.
In order to address problems of wear due to improper alignment,
stuffing boxes have been developed that are self aligning. U.S. Pat. No.
3,887,196
(Renfrow) discloses a self aligning stuffing box in which a first body
provides a
socket and a second body provides a ball. The ball and socket engagement
enables
limited universal movement between the first body and the second body. U.S.
Pat.
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No. 6,412,783 (Finnestad) discloses an alternative configuration of a self
aligning
stuffing box for pumpjacks.
Regardless of the type of stuffing box, most stuffing boxes will utilize
one or more packing glands or packed glands for sealing the polished rod and
maintaining the packing in the stuffing box. Packing glands will typically
have an
inner insert made of a material which is softer than the polished rod, e.g.
bronze;
see FIGURES 1 and 2. This softer inner material reduces scuffing on, and
damage
to, the polished rod as it reciprocates in and out of the stuffing box.
However, being
a softer material, the packing gland insert will experience wear over time and
will
need to be replaced at periodic intervals.
Traditionally, when replacing the packing gland insert, the packing
gland will be unthreaded from the stuffing box and then slid up off the top
end of the
polished rod. However, the top end of the polished rod is typically several
feet
above the ground. Moreover, the polished rod will also typically be connected
to the
head of a pump-jack and will need to be disconnected therefrom, in order to
remove
and replace a typical packing gland and insert. As such, it is often fairly
difficult and
labour intensive to replace such wearable inserts, i.e. having to slide such
inserts
over top of a polished rod.
Similarly, stuffing boxes typically comprise other wearable bearing
members which surround the polished rod, such as top and bottom packing
retainers (see FIG. 1). These packing retainers, like the packing gland
insert, are
typically made of softer material to reduce scuffing on, and damage to, the
polished
rod. Like the packing gland insert, such retainers, or retainer rings, will
also require
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to be slid up off the top end of a polished rod when they are replaced.
Therefore,
what is needed is are packing glands and packing retainers which can easily be
replaced, without need to disconnect a polished rod from the pump-jack.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring to the drawings, several aspects of the present invention are
illustrated by way of example, and not by way of limitation, in detail in the
figures,
wherein;
FIG. 1 is an exploded perspective view of a PRIOR ART stuffing box,
showing a threaded packing gland with insert, top packing retainer and bottom
packing retainer;
FIG. 2 is a bottom perspective view of a PRIOR ART embodiment of a
threaded packing gland with insert;
FIG. 3a is a bottom/side perspective view of one embodiment of a
threaded packing gland with insert of the present invention, showing the
insert in an
operating configuration and positioned within the threaded packing gland;
FIG. 3b is a bottom/side perspective view of the threaded packing
gland with insert of the embodiment of FIG. 3a, showing the insert in an
operating
configuration and positioned outside and adjacent the threaded packing gland;
FIG. 4a is a bottom/side perspective view of the insert for a threaded
packing gland, of the embodiment of FIG. 3a, showing the plurality of insert
segments joined together by means of a plurality of tab members;
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FIG. 4b is a bottom/side perspective view of the insert for a threaded
packing gland, of the embodiment of FIG. 3a, showing the plurality of insert
segments separated from each other in a disassembled configuration;
FIG. 5a is a perspective view of the insert for a threaded packing
gland, of the embodiment of FIG. 3a, showing the plurality of insert segments
separated from each other in a disassembled configuration;
FIG 5b is a perspective, enlarged view of a portion of FIG.5a,
illustrating one of the spacer members;
FIG. 6 is a perspective view of the threaded packing gland with insert
of the embodiment of FIG. 3a, showing the insert in a disassembled
configuration
with one segment positioned inside the threaded packing gland and another
segment positioned outside and adjacent the threaded packing gland;
FIGS. 7a and 7b are perspective views of one embodiment of a
packing retainer assembly, partially captured by a packing gland ring, shown
in an
operating configuration and a partially disassembled configuration,
respectively;
FIGS. 8a and 8b are additional perspective views of the packing
retainer assembly of the embodiment of FIG. 7a shown in a partially
disassembled
configuration and an operating configuration, respectively;
FIGS. 9a and 9b are perspective views of a PRIOR art packing puller;
FIG. 9c is a perspective view of a packing puller threadably attached
to a packing retainer assembly of the embodiment of FIG. 7a; and
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FIGS. 10a ¨ 10c are perspective views of a packing puller threadably
attached to a packing retainer assembly of the embodiment of FIG. 7a and
removing same from a stuffing box.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description is of preferred embodiments by way of
example only and without limitation to the combination of features necessary
for
carrying the invention into effect. Reference is to be had to the Figures in
which
identical reference numbers identify similar components. The drawing figures
are
not necessarily to scale and certain features are shown in schematic or
diagrammatic form in the interest of clarity and conciseness.
A first embodiment of a packing gland 10 with packing gland insert 20
of the present invention is shown in FIGS 3a - 6. The packing gland 10 is
conventional in that it is a generally hollow cylinder having an outer surface
11 with
threaded section 12 suitable for treadable connection to a stuffing box or
component thereof, and an inner bore 14 suitable for accepting packing gland
insert
therein. Packing gland 10 may have an outer end 15 that is flanged and an
inner
20 end 16 suitable for insertion into a knuckle nut or other suitable
component of a
stuffing box. Preferably, packing gland 10 is made from a steel alloy
material, such
as 4140 heat treated stress relieve steel.
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Packing gland insert 20 may be made of any suitable material (e.g.
bronze or nylon) and is preferably of a softer material than the polished rod
and is
corrosion resistant. Packing gland insert 20 comprises a plurality of semi-
cylindrical
segments 22a, 22b which mate or fit together into an operating configuration
OC
(see FIGS. 3a, 3b and 4a). When in the operating configuration OC, segments
22a,
22b form insert 20, preferably having an outer surface which makes a close,
snug
and sliding fit against the wall of inner bore 14. Further, when in the
operating
configuration OC, the plurality of semi-cylindrical segments 22a, 22b form a
substantially hollow cylinder having a longitudinal axis L with an inner bore
24
aligned therealong, a first end 26 and a second, generally opposing, end 27.
Inner
bore 24 is preferably dimensioned to make a close sliding fit against exterior
of any
polished rod. More preferably, inner bore 24 has a cross-sectional profile
that is
substantially circular.
In this embodiment insert 20 comprises two semi-cylindrical segments
22a, 22b. In other embodiments, not shown, insert 20 may comprise three or
more
semi-cylindrical segments. Packing gland insert 20 may further comprise
flanged
end 26f to allow insert 20 to rest on end 16 of the packing gland 10 (using
flanged
end 26f) when inserted or placed substantially inside bore 14 of the packing
gland
10; see FIG. 3a.
A plurality of tab or spacer members 28 join the semi-cylindrical
segments 22a, 22b and maintain said segments in the desired operating
configuration OC. A plurality of spaces 29 between adjacent segments 22a, 22b,
along longitudinal axis L of the insert 20, may result as a function of spacer
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members 28 maintaining the segments 22a, 22b in the desired operating
configuration OC, namely so as to keep a substantially circular cross-section
in bore
24 to allow insert to make a close sliding fit against exterior of any
polished rod.
Typical inside diameters of bore 24 are 1% or 1% inches so as to match the
outside
diameter of a polished rod. Typical space or clearance between segments 22a,
22b
is 1/32 inch to 1/16 inch.
Preferably, packing gland insert 20 is first machined as a cylindrical
member from a single piece or block of material (e.g. bronze) having the
desired
bore 24 dimensions and any flanged end 26, after which a slitting saw or
similar
cutting tool may be utilized to cut spaces 29 between each of the plurality of
segments 22a, 22b. Slitting saw or similar cutting tool is then directed so as
to not
cut completely though said single piece of material, thereby leaving a small
amount
of material remaining between adjacent segments and thereby creating one or
more
spacer member 28. Preferably, spaces 29 between adjacent segments 22a, 22b
tracks or stretches between said adjacent segments 22a, 22b for substantially
all,
but not the entire, length of the longitudinal axis L. If manufactured in this
manner,
packing gland insert 20 may be considered as an integral member comprising a
plurality of segments 22a, 22b maintained as a whole by members 28.
In contrast, if such single piece of material was cut through completely
(and no tab or spacer members 28 were provided), the substantially circular
cross-
section of bore 24 would be offset and changed into a slightly oval cross-
section
(due to removal of the material that used to be in spaces 29) when insert 20
is
placed inside packing gland 10. Having a packing gland insert bore with a
slightly
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oval cross-section is undesirable because: (i) insert 20 may wear unevenly
against
the polished rod and (ii) the tolerances between bore 24 and the outside of a
polished rod are very critical to maintain the packing inside the stuffing box
and
maintain the proper sealing of the stuffing box.
In the embodiment of FIGS. 3a ¨ 4b, spacer members 28 are
positioned near the flanged end 26. In other embodiments, spacer members 28
may be provided at end 27, or at both ends 26, 27. Advantageously, spacer
members 28 maintain segments 22a, 22b together having the desired bore 24
dimensions without the need for additional components such as tape, glue or
retaining rings.
When needing to replace the packing gland insert 20, packing gland
10 may be unthreaded or removed from the knuckle nut of a stuffing box and
insert
removed therefrom. Because spacer members 28 only comprise a small amount
of material, the joint formed by them between adjacent segments (e.g. 22a,
22b) will
15 be weak and easily broken or snapped by an operator. This may be
accomplished
by hand or by insertion of a flat tool (like a flat-end screwdriver) in space
29 and
giving that tool a twist. Advantageously, once adjacent segments are broken
apart
from each other, they can be removed from either side of the polished rod
without
having to fully slide off over the top end of the polished rod. Once adjacent
20 segments are broken apart from each other, the packing gland insert 20
can be
referred to as being in a disassembled configuration DC; e.g. see FIG. 5a.
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Packing Retainer Assembly
A preferred embodiment of a packing retainer assembly 120 of the
present invention is shown in FIGS 7a -8b and 9c ¨ 10c. The packing retainer
120
may be made of any suitable material (e.g. bronze or nylon) and is preferably
of a
softer material than the polished rod R and is corrosion resistant. Packing
retainer
assembly 120 comprises a plurality of semi-cylindrical segments 122a, 122b
which
mate or fit together into an operating configuration OC' (see FIG. 7a). When
in the
operating configuration OC', the plurality of segments 122a, 122b form a
substantially hollow cylinder having a bore axis B with an inner bore 124
aligned
therealong, a first end 126 and a second, generally opposing, end 127. Inner
bore
124 is preferably dimensioned to make a close sliding fit against exterior of
a
polished rod R. More preferably, inner bore 124 has a cross-sectional profile
that is
substantially circular.
In this embodiment packing retainer assembly 120 comprises two semi-
cylindrical segments 122a, 122b. In other embodiments, not shown, packing
retainer assembly 120 may comprise three or more semi-cylindrical segments.
Packing retainer assembly 120 may be supported, and partially captured, by a
packing gland ring 110 when installed in a stuffing box; see, for example,
FIGS.
7a,7b and 8b, where the semi-cylindrical segments 122a, 122b are captured by
packing gland ring 110 at end 127. During operation, packing gland ring 110,
by
virtue of capturing end 127, may maintain the packing retainer assembly 120 in
the
operating configuration OC'.
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Preferably, however, a substantially circular clip member 128 is provided for
fitment around the outside or exterior surface of packing retainer assembly
120
along a substantially continuous exterior groove 129 provided on each segment
122a, 122b. Substantially circular clip member 128 may also contribute to keep
the
packing retainer assembly 120 in the operating configuration OC'. Preferably,
clip
member 128 is fully captured within the depth of groove 129 so as to
facilitate
insertion of the packing retainer assembly 120 within the inner bore of a
stuffing box
S. More preferably, clip member 128 is made from a non-corrosive semi-flexible
metal or other similarly strong material, so as to allow tensional forces
placed on
one of the plurality of segments (e.g. 122a) to be substantially transferred
to any
adjacent segments (e.g. 122b) without breaking or shearing; so that pulling or
lifting
on one segment (e.g. 122a) will result in a similar pulling or lifting action
on the
adjacent segments (e.g. 122b) and the packing retaining assembly 120 as a
whole.
Even more preferably, clip member 128 is not fully circular, but has open ends
(e.g.
FIG. 8a) and has sufficient flexibility or spring-like characteristics to: (i)
maintain
assembly in the operating configuration OC' when installed in groove 129, and
also
(ii) also allow an operator to remove clip member 128 from around assembly 120
and any polished rod R, in a similar fashion to a circlip or c-clip.
Still even more preferably, the packing retainer assembly 120 is provided
with at least one threadable connection point 130 at one end 126 or 127
thereof.
Threadable connection point 130 is capable of threadably engaging an elongate
tool
having a threaded end E which, once threadably engaged to one segment (e.g.
122a) can transmit tensile or pulling forces from a user to said segment (e.g.
122a).
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A suitable elongate tool is a conventional packing puller P having a removable
packing extractor tip T threaded on an end thereon, wherein the packing
extractor
tip T may be untreaded and expose external threads ET on threaded end E (see
FIGS. 9a ¨ 10c).
More preferably, packing puller P has a longitudinal axis PA and threaded
end E has external threads ET wrapped around a thread axis TA, wherein thread
axis TA is substantially parallel to the longitudinal axis PA of the packing
puller.
Likewise, and even more preferably, the threadable connection point 130 has
corresponding internal threads 130i around a thread axis 130a that is
substantially
parallel to the bore axis B. Advantageously, when packing puller P (without
extractor tip T) is inserted into a stuffing box S, then threaded end E can be
easily
threaded into connection point 130, alongside any polished rod R around which
assembly 120 may be placed; see FIGS 9c¨ 10c.
Advantageously, a user or operator can use such elongate tool P to reach
down into a partially disassembled stuffing box, threadbly engage one segment
(e.g. 122a at point 130) and then provide a tensile or pulling force to all
segments
(122a, 122b) and the packing retainer assembly 120 as a whole, by way of clip
member 128; thereby easily removing packing retainer assembly 120 from a
stuffing
box. More advantageously, a plurality of connection points 130 are provided in
a
spaced configuration around one or more ends 126, 127, so as to present easy
threadable access to the packing retainer assembly 120, regardless of which
side of
a polished rod R an operator may happened to be positioned at, when servicing
a
stuffing box S. Even more advantageously, once packing retainer assembly 120
is
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removed from a stuffing box S, clip member 128 can be removed and segments
122a, 122b may be easily removed from either side of the polished rod R
without
having to fully slide off over the top end of said polished rod R.
Preferably, packing retainer assembly 120 is provided with a substantially
circumferential lip or edge 140 at one or more ends 126, 127, along the
circumference of bore 124 and adapted to make a close, snug and sliding fit
against
exterior of any polished rod R; e.g. see FIG. 8b. More preferably,
circumferential lip
140 is provided at an end (126 or 127) that is distal to any packing that may
be in a
stuffing box S when assembly 120 is inserted therein. Advantageously, during
operation of a stuffing box, lip 140 can then function to scrap or remove any
wax or
condensate build-up from the polished rod that may accumulate over time and
which could otherwise damage, or prematurely wear, any packing that may be
inside a stuffing box S. More advantageously, circumferential lip 140 is
positioned
on assembly 120 so as to direct any scrapped wax or condensate back down into
the wellbore or into a collection area inside the stuffing box S, away from
any
packing that may be in the stuffing box S.
Those of ordinary skill in the art will appreciate that various
modifications to the invention as described herein will be possible without
falling
outside the scope of the invention. In the claims, the word "comprising" is
used in
its inclusive sense and does not exclude other elements being present. The
indefinite article "a" before a claim feature does not exclude more than one
of the
features being present.
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