US3076658A - Slush pump piston rod packing - Google Patents

Description

1963 A. L. LEMAN SLUSH PUMP PISTON ROD PACKING 2 Sheet-Sheet 1 Filed Feb. 19, 1959 INVENTOR.

ARTHUR L. LEMAN ATTORNEYS Feb. 5, 1963 A. L. LEMAN 3,076,558

SLUSH PUMP PISTON ROD PACKING Filed Feb. 19, 1959 2 Sheets-Sheet 2 IN VEN TOR.

ARTHUR L. LEMAN 0 8M7: 7M, M411 '0- m ATTORNEYS diameters.

3,076,658 SLUSH PUMP'PISTGN ROD PACKING Arthur L. Leman, R0. 802124068, Houston, Tex. Filed Feb; 19, 1959, Ser. No. 794,429 1 Claim. (Cl. 277-121) This invention relates to reciprocating piston pumps, especially those handling fluids likely to contain abrasive matter, such as slush pumps employed in the oil fields. More particularly it aims to provide for such pumps an improved piston rod packing assembly whereby an eifect-ive seal is maintained despite variations in the piston rod diameter at the packing region such as frequently occurs through wear in the course of the pump operation.

In the drawings illustrating by way of example certain embodiments of the invention:

FIG. 1 is a longitudinal section of a portion of the power end of a pump cylinder having a stuffing box and packing of the invention operatively installed, the piston rod portion thereat being of initial or normal diameter;

FIG. 2 is a similar cross-sectional view showing a worn portion of the rod at the stufling box;

FIG. 3 is a view mainly in longitudinal section of the power end and an intermediate portion of a pump cylinder illustrating a modified application of the invention d thereto; and 4 FIG. 4 shows" separately in perspective a wedge-ring packing element of the invention.

In'reciprocating slush pumps and others handling fluids containing abrasives the piston rods become worn to a reduced diameter. This diameter-reducingv wear generally is greatest at an' intermediate or substantially midlength part of the rod and merges into less worn end portions. If to continue to seal off the fluid effectively the packing must be appreciably tight when it surrounds the rod section of minimum diameter. But in the conventional stuffing box it the packing is made sufiiciently tight for a worn rod section, it is subjected to abnormally high compression at the less worn and hence larger rod There being no place for the packing to escape when entered by a larger-diameter rod' portion, an excessive bearing pressure builds up, causing rapid erosion of the packing as well as further wear of the rod.

In accordance with the invention provision is made for relative relief of the packing at the largerrod portions while at the smaller sections sealing engagement with the worn rod is maintained. The two conditions a's referred to will be apparent from a comparison of FIGS. 1 and 2. In FIG. 2 the packing is-seen sealingly engaged with a worm rod section. At othertimes in the operation, as at the end of a stroke, with a rod portion of normal or less worn and larger diameter at the stuffing box, the

packing elongates axially as represented in FIG. 1. The

dotted line in FIG. 1 shows the corresponding outline of the packing element under the condition such as in FIG. 2. I

Referring to the drawings in more detail, in FIGS. 1 and 2 the reciprocating piston rod is indicated at 5, extending through a portion of apump cylinder wall 6 at the power end of the pump. The adjacent end of a housing for the outwardly extending part of the piston rod 5, that which connects to the cross-head (not shown) is designated at 7. The cylinder wall 6 is apertured for reception of the piston rod stuffing box designated generally at 10. It will be understood'that the piston end of the rod is toward the right in FIGS. 1 and 2, similarly as shown in FIG. 3 where an additional length of the pump cylinder appears, containing a piston 8 on the rod 5 and within a cylinder liner 9.

The stuffing box 10 of FIGS. 1' and 2 comprises a generally cylindrical-body 11- having at the outer end an external circumferential mountingfia'nge 12 and at the op-' posite or inner end an internal flange or annular shoulder 13 surrounding a central aperture dimensioned from free reciprocating passage of the piston rod 5 through it.

In the example of FIGS. 1 and 2 the stufilng box as so far described is conventional. The-bore 14 of the stuffing box body 11 is cylindrical and uniform from the outer end at the mounting flange 12 to the inner wall at the annular shoulder 13. It is of adequate diameter to afford the desired annular space or recess between the box wall and the particular piston rod which it is to be employed. The box 10 is anchored on the cylinder wall as by studs 12 through the mounting flange 12.

Under the invention such uniformly bored stufiingbox is novelly adapted for cooperation with a wedge-ring packing element of the invention to be further described; see FIG. 4. For this purpose inclined wall means 15 is provided that is carried internally by the stufiing box. Such wall means 15 in this instance comprises a separate metal or other rigid sleeve insert having over a major portion of its length an outer diameter for seating lit in thestufling boxbore 14, with the inner end of this boremodifying sleeve 15 abutting the annular shoulder 13 at the inner end of the box 10. p

The inner circumferential wall at the bore of this sleeve 15 is formed along a'shallow incline over a major portion of its length and at a small acute angle relative to the axis of piston rod 5. Such angle of wall inclination'is in the acute range of about 8 to 15, being 'appioximately 11 in the illustrated example. Th'us in'efi'ect there' 'is provided'a gradually inwardly tapering wall" 16- for-die stufling box bore, extending toward the inner end of the box and terminating in a relatively short cylindrical-wall portion 18. At said inner end the minimum" bo'r'e' diameter of the box sleeve 15 is still substantially greater than the maximum diameter of the piston rod 5 so as to provide annular space between the sleeve 15 andthe rod '5, as designated at S, S.

For cooperation with the inclined-wall means 15 of the stuffing box, and with the rod 5, the novel packing proper comprises an annular sleeve-like body or ring 20 of rubb'erous or like elastometric composition of substantial resiliency and capacity toexpand and contract and in ef- 'fec;t to fiow under application of ex'ternalforce and "resiliently to return toward normal free shape and dimens'ion upon release of such force. Noting FIG. 4 as well as the others, this packing ring 2%} in longitudinal section is of predominant wedge form. It has an outer wall 21 molded to taper inwardly over a major axial extent of the packing from a point beyond mid-length toward the outer end 22 and continuing to the inner end 23, in conformity with the degree of incline of the stuifing box inner wall means 15, Le. at an approximate angle of 11" to the piston rod axis in the given example. While in some instances the packing taper at 21- may begin at or substantially at the outer end 22 of the packing ring 20 preferably a relatively short outer end portion 24 is made cylindrical and of a diameter to seat snugly in the bore 14 of the stuffing box 10.

The described structure presents an inwardly tapering packing recess in the stufiing box 10, defined at the radially outer side of the packing by an outer end portion or the stumng box bore 14 and the inner wall 16; 18 of the stufling box sleeve 15, and defined at the radially inner side of the packing by the piston rod 5. The inner end wall of this packing recess is defined by the internal annular shoulder 13 of the box. The length of this packing recess in the direction of taper and including the inner end portions S, S of the cavity is markedly greater than the length of the packing ring 20 therefor in the'normal initial or free form of the latter.

It is understood that'in FIG. 2' as well as in FIG. 1 the parts are installed in operative position in the pump, and

hence that even in FIG. 2, in which the packing ring 20 is relatively unstressed as compared with FIG. 1, it is under a degree of axial elongation and radial compression as compared to the wholly free form of the ring as it comes from the mold. In other words, in said free form the ring 20 of the present example measures somewhat less in length axially and a little greater in thickness radially than in the FIG. 2 condition wherein it is sufficiently stressed to maintain an effective seal at the reduced-diameter rod section there shown, even under the high pressure conditions frequently encountered in slush pump operation.

Conversely stated, the wedge ring or tapered packing 20 of the invention has a free form and dimensioning such that it is of distinctly less length axially than the receiving recess therefor and is of greater thickness radially than the radial dimension of the annular space constituting such recess, having reference to the maximum exceptable radial dimension of said space at the smallest or most worn diameter of the piston rod, such as illus- 'trated at 5 in FIG. 2.

Preferably, in order that the packing 20 may be installed on and removed from the piston rod 5 without having to unscrew or disconnect the rod from the crosshead, it is longitudinally divided along a line of separation 25 seen in FIG. 1 and in more detail in FIG. 4 showing the wedge ring packing element separately, in initial free form. This axial split or division line 25 desirably is sinuous, substantially as illustrated and desirably is somewhat inclined to a true radius of the ring, providing a lateral lap along the abutted longitudinal edges in addition to the sinuous curving interlock in the axial direction. Thus there is no leakage at the split joint 25 of the packing even under a relatively loose status thereof on the rod, such as in FIG. 2, since the constant wedging action keeps the split joint tight.

The packing in each instance being placed about the rod in the pump is set up into wedging engagement with the inclined wall means 15 of the stufiing box and is locked up in such operative position as by a gland 30. The latter is adjustably secured as by nuts 31 threaded on studs 32 extending through a lateral flange 33 on the .gland and tapped into the adjacent outer end of the stuf- 'fing box 10. While the gland may engage the resilient packing 20 direct preferably a fibrous or other substantially rigid intermediary collar 34 is interposed between the gland 30 and the resilient wedge ring 20. Such collar 34 desirably is axially divided, similarly as the wedge ring 20, for lateral installation about the rod 5.

In the embodiment of FIGS. 1 and 2 wherein the stufling box inclined wall such as 16 is provided by an insert wall means or sleeve 15, thus adapting an otherwise generally conventional stufiing box to the purposes of the invention, a secondary or auxiliary packing desirably is provided at the inner end portion of such sleeve. For this purpose the sleeve 15 as illustrated is reduced at the inner end 17 to present a tapering wall 19. It is disposed at a generally similar small acute angle to the rod axis as is the inclined wall 16 already described, being shown as parallel with the latter, at an angle of approximately 11 to the rod axis.

This inclined wall formation 19 gives to the insert sleeve 15 a general shallow Z-form in cross-section and defines with the bore 14 and annular shoulder 13 of the stufling box an auxiliary tapering packing recess or cavity R having the taper reversed to that of the described packing recess for the wedge-ring 20. The auxiliary packing recess R contains a conformably shaped and dimensioned rubberous or other resilient packing ring 28. Here again such packing ring 28, which may be longitudinally divided for mounting purposes, has a normal or initial free axial length less than that of the recess R and a radial thickness in the free form such that when installed as in FIGS. 1 and 2 it is radiatly compressed and axially elongated,

In the modification f0 FIG. 3 all parts not otherwise mentioned may be the same as already described and accordingly have the same reference numerals, including particularly the wedge packing ring 20. In this instance the stufling box is cast, machined or otherwise formed to carry the inclined wall means of the box bore as an integral portion of the box. The low angle of inclination may be the same as in the previous example, i.e. in the range of about 8 to 15 to the rod axis. Likewise the axial and radial dimensioning of the box bore and of the wedge packing ring 20 relative to each other are as already described in connection with FIGS. 1 and 2. Thus the inwardly tapering cavity within the integral inclined-wall bore of the stufiing box 110 has a length in the axial direction greater than that of the packing 20 in the free form of the latter, as seen in FIG. 3 at the recess inner end portions S and S' respectively with tapering and with substantially cylindrical circumferential walls. In other words the integral inclined wall 115 of the stuffing box extends at S somewhat beyond the inner end of the wedge ring 15 and merges into a substantially cylindrical bore terminal at S.

As in the previous example the installed packing 20 is locked up by a gland desirably having an intermediary fibrous or other collar 34 between it and the resilient wedge ring 20. While the anchoring of the stuffing box 110 upon the pump cylinder wall 6 and the ad justable securement of the gland may be provided for in any convenient manner, FIG. 3 shows for the purpose a series of threaded studs 112' tapped into the pump cylinder wall and extending commonly through the stufling box external flange 112 and the lateral flange 133 of the gland and each receiving a pair of lock-up nuts 113, 114 individually engaging the respective flanges.

The invention is not limited to the particular embodiments thereof illustrated and described herein, its scope being set forth in the following claim.

I claim:

A piston rod packing assembly for a reciprocating piston slush pump having a cylinder with an end wall for piston rod entry, said assembly comprising a rod stuffing box on said wall having a generally cylindrical body with inner and outer ends and a central bore of a diameter substantially greater than the piston rod diameter,

an external mounting flange at the outer body end and an internal annular shoulder at the inner body end with a central aperture affording free rod passage,

the packing assembly being characterized by internal circumferential Wall means at the bore of the stuffing box presenting an elongate surface gradually tapering axially toward the annular inner end shoulder of the box at an acute angle to the axis of the rod,

said tapering wall means along with the circumferential wall of the outer portion of the box bore defining around the rod a tapering annular packing recess,

a resilient sleeve-like wedge-form packing having a central axial cylindrical bore for receiving and surrounding the rod,

said packing being of circular cross-section at all transverse planes along it and having a longitudinal crosssectional shape tapering similarly to that of the recess with a free axial length less than that of the recess and a free radial dimension at all points along the packing greater than that of the recess at the corresponding point therealong with reference to the installed position of the packing, said excess radial dimension of the packing being greater than maximum expected variation in diameter of the rod under operative wear,

and gland means for locking up the packing in the recess in such manner that by reason of the relative shape and dimension of the packing and of the recess and the expansion-contraction flow capacity of the packing an automatic self-adjusting action of expansion and contraction axially and radially is accorded to the packing as appropriate to maintain a seal about the rod over varying diameters thereof within the packing,

ing packing recess, and a conformably positioned wedge-section resilient packing ring in said recess and of a free length axially less than the recess length.

References Cited in the file of this patent and the stuffing box bore being formed with a standard UNITED STATES PATENTS uniform diameter throughout the length thereof and the tapering wall means in the stuffing box being 863619 Marten 1907 presented by a separately formed insert sleeve fitted 1 IOOOSQO Belch 1911 into the stufiing box bore, which insert sleeve has a 1320567 Nawn 1919 longitudinally inwardly inclined circumferential wall 52 5 5 'f ggy' g at the inner end portion defining an oppositely taper 2,892,643 Moseley June 30 1959 2,896,980 Dicky July 28, 1959

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