Patent Application
20170167612
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.
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 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. 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
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
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:
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
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
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
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 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 1½ or 1¾ 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 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
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 20 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 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 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
Packing Retainer Assembly
A preferred embodiment of a packing retainer assembly 120 of the present invention is shown in
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,
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.
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 ). 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
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
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 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
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.
