PACKING ASSEMBLY FOR A PUMP

Abstract

A header ring for use in a stuffing box comprising an annular body portion of an elastomeric material, an annular radially inward projecting sealing lip portion formed on said body portion and an annular, axially facing pedestal portion formed on said body portion, said pedestal portion defining an annularly extending radially inwardly facing pedestal surface, the sealing lip portion defining an annularly extending, radially inward facing sealing surface, the sealing surface and the pedestal surface forming a juncture, at least a portion of the pedestal portion adjacent the juncture and forming the pedestal surface and at least a portion of the sealing lip portion adjacent the juncture and forming a portion of the sealing surface being comprised of a layer of reinforced elastomeric material bonded to the body portion.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority of U.S. Provisional Application No. 61/018,538 filed on Jan. 1, 2008, the disclosure of which is incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a packing or seal assembly for a pump and more particularly to a header ring for use in such an assembly.

2. Description of Prior Art

Piston pumps or plunger pumps are positive displacement pumps and are commonly used in environments where the fluids which are being handled pose problems such as high temperatures, viscous and very viscous media or solids-charged liquids.

One important use of plunger pumps is in the oil and gas industry and particularly in the drilling, completion and/or stimulation of oil or gas wells. In these applications, it is common to employ solids laden drilling fluids, e.g., muds, cement slurries, fracturing slurries, acids and the like, which frequently must be pumped under high pressure into the well. This is particularly true in the case of completion and/or stimulation procedures where very high pressures are employed and the fluids being handled are typically slurries which make the fluids highly abrasive because of the large solids content of the slurries.

As is well known in the art, positive displacement reciprocating plunger-type pumps in this environment pose difficult sealing problems at the high pressure end where the abrasive fluid must be prevented from leaking between the reciprocating plunger and the cylinder or housing within which it reciprocates.

Although a variety of sealing or packing systems are known to seal between the reciprocating plunger and the cylinder, a typical seal arrangement comprises one or more V-shaped or Chevron packing rings with various male and female adaptor rings at the forward and rearward ends of the packing assembly. To ensure sealing between the plunger and the cylinder, the sealing assembly can be placed under compression by an adjusting ring, spring loading, etc.

A typical packing assembly of the type under discussion includes a header ring which is typically made of an elastomeric material. The header ring can be constructed of a homogeneous elastomeric material or an elastomeric material containing layers of cloth or other reinforcing type materials. It is also known to cover certain surfaces of the header ring, particularly the so-called rearward surfaces with a reinforcing fabric.

It has been found that, with respect to the header ring, failure of the sealing assembly primarily occurs due to a phenomena known as “nibbling.” This nibbling phenomenon can be best understood by reference to FIGS. 1-4 which depict prior art construction for header rings of the type under consideration. FIG. 1 depicts a typical homogeneous elastomeric header ring shown as 10. As can be seen in FIG. 1, header ring 10 is made of a homogeneous elastomeric material and comprises an annular body portion 12.

Integrally formed with body 12, is an annular, radially inwardly projecting wiping lip 14, an annularly extending, axially facing bead 16, an annular pedestal portion 18. Header ring 10 includes a forwardly facing, annularly extending planar surface 20, an annularly extending, radially outwardly facing cylindrical surface 22, an annularly extending, radially inwardly facing cylindrical surface 24 and a radially inwardly facing convex sealing surface 26, surfaces 24 and 26 being adjoined at an annularly extending juncture 28.

Referring now to FIG. 2, the header ring 10 is shown after use and after a portion of the header ring has been nibbled out. As can be seen, the nibbled out area indicated at 30 comprises a portion of header ring 10 formed by intersecting surfaces 24 and 26. More specifically, it can be seen that the juncture 28 shown in FIG. 1 between surfaces 24 and 26 has been gouged out due to the nibbling effect.

FIGS. 3 and 4 depict another prior art header ring, FIG. 3 depicting the header ring in its original or undamaged state, FIG. 4 depicting the header ring of FIG. 3 following use and damage as a result of nibbling. The header ring 10A shown in FIG. 3 has a body portion 32 comprised of first body section 34 and second body section 36. Section 36 of body portion 32 comprises a fabric or fiber reinforced material while portion 34 is formed of a homogeneous elastomeric material construction. As in the case of header ring 10, there is an annular pedestal 38, an annular bead 40 and an annular sealing lip 32. FIG. 4 shows the header ring 10A of FIG. 3 which has been damaged due to nibbling and once again the nibbling has occurred at the juncture 46 between radially inwardly facing cylindrical wall 43 and radially inwardly facing surface 45.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a header ring for use in a packing or seal assembly between a reciprocating, cylindrical member and a cylindrical wall of a housing in which the cylindrical member reciprocates.

In one aspect, the header ring of the present invention has an annularly extending body portion, at least a portion of which comprises an elastomeric material, an annular pedestal portion formed on said body and having an annular, radially inwardly facing pedestal surface, a radially inwardly facing, annularly extending sealing lip formed on said body and having a radially inwardly facing sealing surface, at least a portion of the pedestal portion forming the pedestal surface and an at least a portion of the sealing lip forming at least a portion of the sealing surface being comprised of a layer fabric reinforced elastomeric material.

In another aspect of the present invention, there is provided a sealing assembly for sealing between a cylindrical movable member and a housing having a cylindrical bore in which the cylindrical member reciprocates, the sealing assembly including a header ring as described above.

The foregoing objects, features and advantages of the present invention, as well as others, will be more fully understood and better appreciated by reference to the following drawings, specification and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a prior art header ring prior to installation.

FIG. 2 is a cross-sectional view of the header ring of FIG. 1 which has been damaged by nibbling.

FIG. 3 is a cross-sectional view of another type of prior art header ring prior to installation.

FIG. 4 is a cross-sectional view of the header ring of FIG. 3 which has been damaged by nibbling.

FIG. 5 is a cross-sectional view of one embodiment of the header ring of the present invention.

FIG. 6 is a cross-sectional view of another embodiment of the header ring of the present invention.

FIG. 7 is a cross-sectional view of another embodiment of the header ring of the present invention.

FIG. 8 is a schematic view, partly in section, of a sealing assembly according to the present invention in the stuffing box of a plunger pump.

FIG. 9 is an enlarged view of the circled portion of the header ring shown in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 5, the header ring 50 comprises an annular body portion 52, an annular axially extending pedestal 53, an annular, axially extending bead 56, distal the pedestal 54, and a radially inwardly facing, annularly extending sealing lip 58. As can be seen, body 52, bead 56, pedestal 53 and sealing lip 58 are integrally formed, for the most part, of a homogeneous, elastomeric material. However, a portion 60 of the pedestal 54 forming the radially inwardly facing cylindrical surface 61 and the portion 62 of the sealing lip 58 forming a portion of sealing surface 64 is comprised of a layer of reinforced, elastomeric material, bonded to the homogeneous elastomeric material of the remainder of header ring 50. As seen, the portions 60 and 62 extend over the juncture 63 of surfaces 61 and 64. When in the relaxed state as shown in FIG. 5, the adjoined fabric reinforced sections 61 and 62 is generally L-shaped when viewed in transverse cross-section.

FIG. 6 shows another embodiment of the present invention wherein the header ring 68 has an annular body portion 70 which is primarily made of a homogeneous elastomeric material. The header ring 68 has an annular, radially outwardly facing cylindrical surface 72. Bonded to the homogeneous elastomeric portion of body 70 is an annular layer 74 of a fabric reinforced elastomer, the layer 74 covering the surfaces of the pedestal 76, the sealing lip 78, the bead 80 and portions of the forward and rearward portions of the body 70 forming surface 72. As is in the case of the embodiment shown in FIG. 5, the portions of the pedestal 76 and sealing lip 78 forming juncture 82 between the pedestal 76 and the sealing lip 78 is formed of a layer of fabric reinforced elastomeric material forming adjoining surfaces 82A and 82B.

Turning to FIG. 7, there is shown another embodiment of the present invention, wherein the header ring, shown generally as 88, has a body 89, the core 90 of which is comprised of an elastomeric material, a portion of annular pedestal 92 and a portion of annular sealing lip 94. Unlike the embodiment shown in FIG. 6, in the embodiment shown in FIG. 7, the reinforced fabric layer 96 completely encapsulates or surrounds the core 90 of body portion 89.

FIG. 8 depicts a typical sealing assembly for use in a stuffing box, shown generally as 100, of a plunger-type pump employing a header ring of the present invention. Stuffing box 100 comprises a housing 102 having a bore 104 extending therethrough, bore 104 defining a cylindrical surface 105. Housing 102 has a shoulder portion 108, movably, e.g., reciprocally, positioned in bore 104 is a plunger, piston or shaft 106. Sealing assembly 101 comprises an annular gland 107, an annular header ring 110, an annular, first seal ring 112, and an annular, second seal ring 114. The sealing assembly 101 also includes a top, annular adaptor ring 116 and an annular bushing 118. As can be seen, header ring 110 forms a wiper ring at the high pressure end of the sealing assembly 101, its primary function being to prevent abrasives/solids from entering the region where the seal rings 112 and 114 are positioned and thereby prevent excessive wear on seal rings 112 and 114. It is also to be noted that, as shown in FIG. 8, header ring 110 no longer has the shape shown in, for example, FIG. 5 since the radially inwardly extending sealing lip 111 has been compressed to effect sealing between the plunger 106 and the housing 102, the cylindrical surface 105 being in sealing engagement with an annular, radially outwardly facing surface 109 which is generally cylindrical.

Referring now to FIG. 9, there is shown an enlargement of the circled portion of FIG. 8. As an example of the present invention, header ring 110 is constructed essentially the same as the header ring shown in FIG. 5 having a generally L-shaped, annularly extending reinforcing section or layer 120 that bridges the juncture 122 between the surface of sealing lip 124 and the surface of pedestal 126.

While packing assembly 101 has been shown as containing two seal rings of the chevron or V-shaped type, it will be appreciated that depending upon the use to which the plunger pump is subjected, fewer or more sealing rings can be employed. It will also be seen that the annular bead 119 of header ring 110 is nested in the annularly extending, axially facing groove in seal ring 112 so as to anchor seal ring 112 to the header ring 110. It will be appreciated that the seal rings 112 and 114 can be constructed of various materials and have various shapes, the only provision being that they have sufficient resiliency to effect sealing between the housing 102 and plunger 106. Generally speaking, components such as throat bushing 108, top adaptor 116, and bushing 110 are made of a metallic material, e.g., brass.

The packing assembly 101 can be energized by header ring 110 and can be made to be adjustable by techniques well known in the art. If, however the packing assembly 101 is preloaded, care must be taken to ensure that the correct amount of preload is employed to prevent movement of the sealing assembly in the housing or stuffing box to prevent excessive wear on the sealing assembly. In this regard, if there is too little preload the packing will move in the housing wearing both the ID and OD of the seal rings as well as the header ring causing premature wear and in extreme cases causing wear in the stuffing box resulting in expensive repair or refurbishment. On the other hand, if the packing assembly is adjusted with too little preload, high friction forces cause accelerated wear of the header ring and the seal rings with premature failure.

The homogeneous elastomeric core of the header ring of the present invention can be made from a number of different natural or synthetic rubbers as, for example, nitrile or butadiene rubber, with a desired degree of hardness again depending upon the use to which the plunger pump is exposed. Likewise, the elastomeric portions of the seal rings 112 and 114 can be of various rubbers with desirable hardness. As indicated, the seal rings, e.g., seal rings 112 and 114, can be reinforced with fabric, can be homogeneous elastomeric materials, can have anti-extrusion portions, etc.

Sections 61 and 62 forming an anti-nibbling section, as seen in FIG. 5 indicated, are generally a fabric reinforced rubber, synthetic or natural. The term fabric as used with respect to the anti-nibbling wear section of the various embodiments of the present invention is used in the broadest sense and includes any cloth or cloth-like structure made by any technique such as knitting, weaving or felting of fibers of natural or synthetic materials as well as mixed fibers and includes, without limitation, fibers of cotton, nylon, polyester, polyester blends, aramid fibers, fiberglass fibers or any combination thereof.

The foregoing description and examples illustrate selected embodiments of the present invention. In light thereof, variations and modifications will be suggested to one skilled in the art, all of which are in the spirit and purview of this invention.

Claims

1. A header ring for use in a stuffing box comprising:

an annular body portion comprising an elastomeric material;

an annular, radially inwardly projecting sealing lip portion integrally formed with said body portion; and

an annular, axially extending pedestal portion integrally formed with said body portion;

said pedestal portion defining an annularly extending, radially inwardly facing pedestal surface, said sealing lip portion defining an annularly extending, radially inwardly facing sealing surface, said sealing surface and said pedestal surface forming a juncture, at least a portion of said pedestal portion adjacent said juncture and forming a portion of said pedestal surface and at least a portion of said sealing lip portion adjacent said juncture and forming a portion of said sealing surface being comprised of a layer of reinforced elastomeric material bonded to said body portion.

2. The header ring of claim 1, comprising an annular, axially extending bead distal said pedestal portion.

3. The header ring of claim 1, wherein said sealing lip portion is generally convex when in a relaxed position.

4. The header ring of claim 1, wherein said body portion comprises a core of elastomeric material and an outer layer of said reinforced elastomeric material bonded to said body portion.

5. The header ring of claim 4, further comprising an annular, axially extending bead distal said pedestal portion and said bead is comprised entirely of said reinforced elastomeric material.

6. The header ring of claim 1, wherein said pedestal portion comprises an axially facing, annularly extending, generally planar surface.

7. The header ring of claim 1, wherein said body portion has an axially extending, radially outwardly facing cylindrical surface.

8. The header ring of claim 1, wherein said layer comprises a fabric reinforced.

9. A stuffing box assembly comprising:

a housing having a generally cylindrical bore extending therethrough and forming a generally radially inwardly facing housing cylindrical surface;

a shaft movably positioned in said bore, an annulus being formed between said housing cylindrical surface and said shaft;

a sealing assembly disposed in said annulus, said sealing assembly comprising: at least one annular sealing ring positioned in said annulus; a header ring positioned in said annulus and in engagement with said at least one sealing ring, said header ring comprising: an annular body portion comprising an elastomeric material; an annular, radially inwardly projecting sealing lip portion integrally formed with said body portion; an annular, axially extending pedestal portion integrally formed with said body portion;

said pedestal portion defining an annularly extending, radially inwardly facing pedestal surface, said sealing lip defining an annularly extending radially inwardly facing sealing surface, said sealing surface and said pedestal surface forming a juncture, at least a portion of said pedestal portion adjacent said juncture and forming said pedestal surface and at least a portion of said sealing lip portion adjacent said juncture and forming a portion of said sealing surface being comprised of a layer reinforced elastomeric material bonded to said body portion; and

a compression assembly forcing said sealing surface into sealing engagement with said shaft and said housing cylindrical surface into sealing engagement with said header ring.

10. The stuffing box of claim 9, comprising an annularly extending, axially facing bead distal said pedestal portion.

11. The stuffing box of claim 9, wherein said sealing lip portion is generally convex when in a relaxed position.

12. The stuffing box of claim 9, wherein said body portion comprises a core of elastomeric material and an outer layer of said reinforced elastomeric material bonded to said body portion.

13. The stuffing box of claim 12, further comprising an annular, axially extending bead distal said pedestal portion and said bead is comprised entirely of said reinforced elastomeric material.

14. The stuffing box of claim 9, wherein said pedestal portion comprises an axially facing, annularly extending, generally planar surface.

15. The stuffing box of claim 9, wherein said body portion has an annularly extending, radially outwardly facing body surface, said body surface being in sealing contact with said housing cylindrical surface.

16. The stuffing box of claim 9, wherein there are a plurality of said sealing rings positioned on said annulus.

17. The stuffing box of claim 9, wherein said sealing rings have a V-shape in cross-section.

18. The stuffing box of claim 9, wherein said compression assembly includes an adjustable gland.

19. The stuffing box of claim 9, wherein said sealing assembly further includes an adaptor ring.

20. The stuffing box of claim 18, wherein said header ring is positioned in said annulus distal said adjustable gland.

21. The stuffing box of claim 9, wherein said sealing assembly comprises said header ring, at least one seal ring, at least one bushing and an adjustable gland.