Compression Seal For Use On Reciprocating Pump

Abstract

The present invention is directed to use of a combined seal involving a compression seal coupled with a metal-to-metal seal for use on the suction and discharge side of the plunger portion of a reciprocating pump. This combined seal results in less vibratory movement and better pumping during use of the pump, and an overall more efficient pump based on the improved seal.

Claims

1. A seal for use with a fluid end assembly for a reciprocating pump that receives fluid through an inlet bore, and ejects fluid from an outlet bore, the fluid end comprising: a body; a plunger bore formed in the body along a first axis; a suction bore formed in the body along a second axis, wherein the suction bore receives fluid from a conduit; a discharge bore formed in the body, aligned perpendicular to the plunger bore and designed to receive a discharge cover; a horizontal bore formed in the body and aligned with the plunger bore, wherein the plunger bore, the suction bore, the discharge bore, and the horizontal bore intersect to form a cavity; a reciprocating plunger that reciprocates in the plunger bore; an inlet valve received by the suction bore for facilitating flow of the fluid from the conduit into the cavity by way of the suction bore; a first valve seat deck at an end portion of the suction bore and in contact with the inlet valve; a pressure relief valve received by the discharge bore for facilitating flow of the fluid from the cavity into the discharge bore; a discharge cover received by the discharge bore and in contact with the pressure relief valve; a second valve seat deck at an end portion of the discharge bore and in contact with the pressure relief valve; and an outlet cavity that is defined at an inner surface of the discharge bore and provides a passage for flow of the fluid from the discharge bore to the pump outlet; the pump outlet is cylindrical and is aligned along a third axis, wherein the inlet valve allows the fluid to flow into the cavity based on a reciprocating motion of the reciprocating plunger by way of the suction bore, wherein the pressure relief valve allows the fluid to flow from the cavity to the discharge bore based on the reciprocating motion of the reciprocating plunger; wherein further the discharge and suction bores are sealed by the seal comprising a compression seal in conjunction with a metal to metal seal that minimizes the sealing extrusion gap.

2. The seal of claim 1, further comprising a suction cover, wherein the suction and discharge covers are secured into the fluid end using retainer nuts having a plurality of lugs such that when the retainer nuts are struck upon their lugs, the retainer nuts tighten against the covers, providing the necessary compression to seal the compression seal.

3. The seal of claim 2, wherein the lugs of each retainer nut are designed to remain outside of the fluid end assembly when the retainer nut is fully tightened.

4. The seal of claim 1, wherein the compression seal comprises an elastomer selected from the group consisting of a thermoplastic elastomer, a natural rubber, a urethane, a pliable composite, and a combination thereof.

5. The seal of claim 1, wherein the compression seal is reinforced with a material selected from the group consisting of a metal, a rigid polymer, a pliable composite, and a combination thereof.

6. The seal of claim 1, further comprising a suction cover, wherein the suction and discharge covers have a mid-height diameter of 3 inches to 12 inches and wherein at least one of the suction cover and the discharge cover has a bevel that meets with a 45 degree bevel in the fluid end body to form the metal to metal seal.

7. A reciprocating pump fluid end bore seal assembly, comprising a retaining nut, a bore cover formed with a metallic discoid of greater diameter extending around the circumference of the bore cover, and a circular elastomeric compression ring, wherein, when the seal assembly is secured within a fluid end bore, the circular elastomeric compression ring is compressed to form a primary seal and the metallic discoid is matable with a metal surface within the fluid end to form a secondary seal.

8. The reciprocating pump fluid end bore seal assembly of claim 7, wherein the metallic discoid has a beveled surface designed to mate with a corresponding beveled surface on the bore wall.

9. The reciprocating pump fluid end bore seal assembly of claim 7, wherein the cover has a groove to receive a retaining ring for securing the retaining nut to an outward facing surface of the bore cover.

10. The reciprocating pump fluid end bore seal assembly of claim 7, wherein the bore cover is a suction cover having a flat, convex, or concave inward facing surface.

11. The reciprocating pump fluid end bore seal assembly of claim 7, wherein the bore cover is a discharge cover having a conical inward facing surface.

12. The reciprocating pump fluid end bore seal assembly of claim 7, wherein the bore cover further comprises a gauge connection extending from the outward facing surface.

13. The reciprocating pump fluid end bore seal assembly of claim 7, wherein the inward facing and outward facing planar surfaces of the circular elastomeric compression ring are textured.

14. The reciprocating pump fluid end bore seal assembly of claim 7, wherein the outer circumference of the circular elastomeric compression ring comprises brass.

15. The reciprocating pump fluid end bore seal assembly of claim 7, wherein, upon use within a reciprocating pump at an operating pressure of up to 15,000 psig with a fluid containing a sand count of between about 210,000 pounds per stage and about 610,000 pounds per stage, the seal assembly resists leaking for more than 100 hours.

16. A reciprocating pump fluid end assembly, comprising: a body having a plunger bore aligned with a horizontal bore and a suction bore aligned with a discharge bore, perpendicular to the alignment of the plunger bore and horizontal bore; a suction cover positioned within the suction bore; a discharge cover positioned within the discharge bore; and at least one circular compression seal; wherein at least one of the suction cover and the discharge cover has a circular extremity with a metal surface that is designed to mate with a metal surface on the interior of the respective suction bore or discharge bore.

17. The reciprocating pump fluid end assembly of claim 16, wherein the circular compression seal is positioned between the suction cover and the suction bore to form a primary seal upon full compression and the suction cover has a circular extremity that provides a metal to metal seal with the metal surface of the suction bore interior wall when full compression of the circular compression seal is sufficient to eliminate a gap between the circular extremity and the metal surface of the bore interior wall.

18. The reciprocating pump fluid end assembly of claim 16, wherein the circular compression seal is positioned between the discharge cover and the discharge bore to form a primary seal upon full compression and the discharge cover has a circular extremity that provides a metal to metal seal with the metal surface of the discharge bore interior wall when full compression of the circular compression seal is sufficient to eliminate a gap between the circular extremity and the metal surface of the bore interior wall.

19. The reciprocating pump fluid end assembly of claim 16, wherein a circular compression seal is positioned in each of the suction bore and the discharge bore and both the discharge cover and the suction cover have a circular extremity that provides a metal to metal seal with the metal surface of the respective bore interior wall upon full compression of the respective circular compression seal.

20. The reciprocating pump fluid end assembly of claim 16, wherein the fluid end assembly is further provided with a plurality of nuts, such that the suction cover is secured in the suction bore with a tightened nut and the discharge cover is secured in the discharge bore with a tightened nut.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The invention is described in detail below with reference to the appended drawings, wherein like numerals designate similar parts. In the Figures:

[0016] FIG. 1 illustrates a front view of a conventional, prior art fluid end assembly having recessed internal hex nuts housed within the assembly.

[0017] FIG. 2 illustrates a front view of an embodiment of the invention housing retaining nuts with lugs on the exterior surface of the fluid end assembly.

[0018] FIG. 3 illustrates a cross sectional view of the conventional fluid end assembly and pump showing the seal arrangement and internal hex, recessed nut arrangement.

[0019] FIG. 4 illustrates a cross sectional view of the new design showing new discharge and suction bores with lug driven nuts, exterior to the fluid end assembly.

[0020] FIG. 5 illustrates a front view of a prior art, conventional suction cover showing the groove that houses a radial seal.

[0021] FIG. 6 illustrates a front view of an embodiment of the new suction cover having a narrower grooved top portion for housing the retainer ring, together with the metal to metal seal. FIGS. 6A, 6B, and 6C are a plan view, a sectional view, and a perspective view, respectively, further illustrating the suction cover of FIG. 6.

[0022] FIG. 7 illustrates a front view of a prior art discharge cap showing the groove for housing the radial seal.

[0023] FIG. 8 illustrates a front view of an alternate conical design for the present invention showing the grooved end for a retainer ring and the metal to metal seal.

[0024] FIG. 9 illustrates an embodiment of the prior art for a gauge connection illustrating the groove for housing a radial seal.

[0025] FIG. 10 illustrates an embodiment of the present invention for a gauge connection showing the conical discharge cap and a retaining ring groove in the middle section.

[0026] FIG. 11 illustrates a plan view of an existing radial seal showing a D-ring.

[0027] FIG. 12 illustrates a sectional view of the radial seal of FIG. 11.

[0028] FIG. 13 illustrates a plan view of an embodiment of the present invention with a textured or ribbed front face and an integrated metal backup ring. FIG. 13A provides a perspective view further illustrating the compression seal of FIG. 13.

[0029] FIG. 14 illustrates a cross section of the textured or ribbed faces of FIG. 13 further showing the brass backup ring. FIG. 14A is an enlarged view of a detail of FIG. 14.

[0030] FIG. 15 illustrates a front view of a prior art retaining nut.

[0031] FIG. 16 illustrates a side view of the prior art retaining nut of FIG. 15.

[0032] FIG. 17 illustrates a front view of the inventive retaining nut showing the lugs along the edges of the nut.

[0033] FIG. 18 illustrates a side view of FIG. 17 and shows the lug protruding.

DETAILED DESCRIPTION OF THE INVENTION

[0034] The invention is described in detail below with reference to several embodiments and numerous examples. Such discussion is for purposes of illustration only. Modifications to particular examples within the spirit and scope of the present invention, set forth in the appended claims, will be readily apparent to one of skill in the art. Terminology used herein is given its ordinary meaning consistent with the exemplary definitions set forth immediately below.

[0035] With respect to the various ranges set forth herein, any upper limit recited may, of course, be combined with any lower limit for selected sub-ranges.

[0036] The transitional phrase consisting essentially of limits the scope of a claim to the specified materials or steps and those that do not materially affect the basic and novel characteristic(s) of the claimed invention. Unless otherwise indicated or readily apparent, an article consists essentially of the recited components when the article includes 90% or more of the recited components. That is, the terminology excludes more than 10% unrecited components.

[0037] As used herein, the term pliable refers to a material supple enough to bend freely or repeatedly without breaking. Ductile refers to a material capable of being bent or pulled into different shapes. The term composite refers to a solid material which is composed of two or more substances having different physical characteristics and in which each substance retains its identity while contributing desirable properties to the whole; an example of a composite is plastic within which a fibrous material is embedded

[0038] Disclosed is a novel combination of metal-to-metal seal and compression seal for use in fluid end assemblies on reciprocating pumps. The combination seal is used on the discharge and suction portion of the pump and provides for a better seal having less extrusion and leakage compared to prior art radial seals. Conventional pumps contain surface bore entries to the fluid end assembly which have radial seals involving D-rings, O-rings, or lip seals as examples of the seals to contain fluid within the assembly and maintain compression during use. D-rings, O-rings, or lip seals are all exterior surface seals. The present invention involves an interior or face seal.

[0039] The invention is directed to the combination of compression seal and metal-to-metal seal for the discharge bore and the suction bore of the fluid end. Therefore, the many interior components of the fluid end will not be discussed herein. But those of skill in the art recognize the interior components remain in existence and have not been modified except as needed to employ the seal combination of the invention. As a summary, and seen in FIG. 3, the fluid end interiors include, as primary components, spring actuated valves, inlet and outlet valves, seat decks, plungers and a crankshaft mechanism to perform the reciprocating motion in the plunger bore.

[0040] The metal to metal seal minimizes the extrusion gap (i.e., clearance between two metal pieces) for the compression seal. The metal to metal seal almost eliminates the extrusion gap to an amount significantly less compared to conventional radial seals for these bores in the fluid end assembly.

[0041] The retaining nut described herein is known in the art for use coupling a hammer union but not heretofore used with a fluid end assembly. Research and development to achieve the inventive combination seal to accommodate the fluid end assembly and accompanying pump and components was not obvious, as the entire assembly had to be refurbished to accommodate the seal. The seal combines a metal-elastomer-metal interface as well as a metal-to-metal interface. Upon initial seal installation, the elastomer is compressed by tightening the respective hammer lug nut to form a primary seal, which upon operation and use becomes further compressed such that the metal of the discharge cover seal element contacts and mates with the beveled metal surface of the matching bore to form a secondary seal. In some cases, the secondary seal is formed upon initial compression. The metal to metal seal formed minimizes or eliminates the leakage of fluid, oil, and/or media pumping through the fluid end assembly. While the initial compression forms a seal sufficient to eliminate or minimize leakage of fluid and media, the metal to metal seal is fully formed when the metal surfaces mate.

[0042] A seal herein is defined as the tight contact between two surfaces, and serves to maintain pressure with the fluid end assembly and to simultaneously contain fluid and media within the fluid end assembly.

[0043] FIG. 1 illustrates a front view of the prior art or conventional complete fluid end assembly 100. The gauge connection 104 found on the top portion of the illustration shows a port for placing a gauge for the fluid end assembly. The conventional assembly has recessed nuts 302 (see FIG. 3) which are standard and therefore not shown in FIG. 1.

[0044] FIG. 2, 200, illustrates a front view of present invention. Shown are hammer lug nuts 201a-201e respectively, along the top portion of the assembly, next to the gauge connection 104 of the fluid end assembly. The inventive fluid end assembly has the lug nuts in all of the service ports 204a-204e so they are easily maintained and opened with just a hammer. Conventional fluid ends with their recessed nuts are shown in FIG. 1. In order to remove the recessed nuts of FIG. 1 for access to the interior and maintenance of the fluid end, the recessed nuts must be removed with the use of a hammer and a hex wrench. Here with the redesigned inventive fluid end having the compression seal, the hammer lugs are on the exterior of the fluid end and can be removed with just a hammer. Being on the exterior allows easier access to the interior of the fluid end and therefore easier, simpler maintenance of the fluid end. The use of one tool to help maintain the fluid end makes this design more efficient for the operator and simplifies the maintenance of the fluid end assembly.

[0045] FIG. 3 illustrates a cross sectional view of a conventional fluid end having a discharge bore 298, a suction bore 300, and a horizontal bore 304, wherein the top section is the gauge connection 104 having a small radial seal around the connection 104. The sealing arrangement of FIG. 3 shows the interior, recessed nuts 302 discussed above. This embodiment of a conventional fluid end shows two (2) different sizes of radial seals; a smaller one on the discharge covers 102, and a larger radial seal on the horizontal bore 304.

[0046] FIG. 4 illustrates a cross sectional view of an embodiment of the present invention, 400. Shown in FIG. 4 is a single seal and single nut 402. Illustrated is the gauge connection 104 now modified to accept a compression seal. There is a retaining ring 406 which keeps two pieces together (here the discharge cover and the nut). This novel approach and modification to the fluid end assembly results in improved operation of the pump, less leaking, and extended maintenance cycles during operation. The lug nut 402 compresses the discharge cover 102. There is also a same size nut 404 shown to seal the service port 408. Shown in FIG. 4 are now discharge and suction seals of the pump having the same nut and the same seal, even in the gauge connection position. Keeping the nuts the same, including the same seal, simplifies inventory for the user including what is needed for future maintenance.

[0047] FIG. 5 illustrates the prior art suction cover. 502 illustrates the conventional groove found in the suction cover where a radial seal sits inside for compression and retention of fluids.

[0048] FIG. 6 illustrates the newly designed suction cover 600, having a large radius extremity 602 (i.e., a metallic sealing element extending radially from the circumference of the cover, also described as a metallic discoid) which is seen as rounded or beveled and forms the metal to metal seal. 602 has a radius of about 3 inches to 5 inches. The top portion of this embodiment 600 has a groove 604 to contain a retaining ring. The nut (not shown but equivalent to lug nuts 402 and 404) against suction cover 600 maintains compression on the suction bore seal. The retaining ring contained in groove 604 keeps the suction cover 600 together with nut during removal of the suction cover for maintenance. FIGS. 6A-6C further illustrate the inventive suction cover. While the suction cover illustrated in FIG. 6 has a concave inward facing surface, the surface may in some cases be flat or convex.

[0049] FIG. 7 illustrates an alternate embodiment of the prior art discharge cover. Shown as 702 is the standard groove formed to house the typical radial seal for this type of cover.

[0050] FIG. 8 illustrates a discharge cover 601 variation of the suction cover of FIG. 6. Note the new tapered shape illustrated which works in combination with recessed seat decks in the fluid end bore as discussed in more detail in copending application Ser. No. 15/978,745 herein incorporated by reference for related and relevant information. FIGS. 5 and 7 illustrate prior art embodiments, while FIGS. 6 and 8 illustrate the new designed suction and discharge caps having the large-radiused extremity 602, providing a metal to metal seal, and retaining ring groove 604.

[0051] FIG. 9 illustrates a prior art cover with gauge connection 104 and groove 902 for housing a radial seal.

[0052] FIG. 10 illustrates a newly designed discharge cover 601 with gauge connector 104, a metal to metal seal provided by large-radiused extremity 602, and a retaining ring groove 604. FIGS. 9 and 10 gauge connections house a port for a gauge for the fluid end assembly.

[0053] FIG. 11 illustrates a plan view embodiment of an existing or conventional radial seal showing a D-ring, the most commonly used for reciprocating pump sealing bore applications. FIG. 12 illustrates a cross sectional view of the radial seal of FIG. 11 and shows the D-shape. Note the tips of FIG. 12 illustrate the curved or beveled edging commonly seen on D-rings. For these types of radial seals, FIGS. 11 and 12 show the sealing surface being on the outer radius. While a D-ring is illustrated, those of skill in the art recognize that an O-ring or lip seal are equivalents.

[0054] FIG. 13 illustrates a plan view embodiment of the modified compression seal of the present invention. Here, the inside and outside faces are textured or herein shown as ribbed so as to prevent material contamination on either face of the seal. 1302 shows the texturing or ribbings of the seal. Alternatives to the ribbing include stepping or waving. Although FIG. 13 illustrates a textured surface, in some cases, the seal is not textured. FIG. 14 illustrates a planar cross section of FIG. 13. An embodiment includes a brass backup as shown on the tip 1402, and 1404 to prevent extrusion of the seal through the extrusion gap. The seal can be made of a variety of elastomeric materials including but not limited to thermoplastic elastomers, natural rubber, pliable composites, nitriles, Teflon, Kevlar, or urethane, or combinations thereof. These materials are generally pliable or ductile, although the composite or metal is not limited with respect to pliability or ductility. During servicing, the compression seal is placed within the fluid end assembly prior to inserting the discharge or suction cover and lug nut. As the nut is tightened, the elastomeric seal is compressed. Once the elastomeric seal is fully compressed, the metal surface of the cover seal is brought into direct contact with the mating surface of the corresponding bore. FIGS. 13A and 14A further illustrate the inventive compression seal.

[0055] While brass is disclosed herein as a preferred metal and used for descriptive purposes, other metals may be employed. For example, metals which can be used are those with pliable characteristics but will withstand the stress and corrosive environment of a fluid end assembly during use. The metal must be capable of compression without destruction. Besides brass, other exemplary metals include stainless steel, Inconel, carbon steel.

[0056] FIG. 15 illustrates the front view of the existing or prior art retainer nut. The interior hexagon shape requires a hexagonal wrench to remove the nut when any type of maintenance is needed for the fluid end assembly. FIG. 16 illustrates a side view of the FIG. 15 nut and illustrates its complete threaded state and absence of lugs.

[0057] FIG. 17 illustrates a front view of an embodiment of the inventive retaining nut. The lugs 202a-c can be seen with this new retaining nut. The retaining nuts depicted in FIG. 17 can be machined from solid bar stock or machined from a net shape forging.

[0058] FIG. 18 illustrates a side view of the lugs 202a and 202c of FIG. 17. It is apparent that the lugs are on the exterior of the fluid end assembly. The lugs are used in conjunction with a hammer to tighten the lug. The retaining nut presses against the suction cover 600 or the discharge cover 601 and retaining ring at groove 604 and presses the large-radiused sealing portion 602 into a bevel on the fluid end to form the metal to metal seal. The bevel on the fluid end matches a bevel on the large-radiused extremity of the suction cover or discharge cover. The angle of the bevel may be, for example, 45. To remove these inventive lug nuts requires a hammer. Using a hammer is easier and more efficient for the operator of the fluid end assembly than having to carry and use three different tools to open the fluid end assembly. The prior art/conventional assembly required use of a hammer, wrench, and cap puller. This efficiency in time for the operator also yields efficiency for the pump itself, as this combination metal to metal seal and compression seal results in less weakening or degradation of the seals and subsequent fluid leaks within the fluid end assembly.

EXAMPLES

[0059] The use of the current inventive compression seal in a fluid end offers solutions to the aforementioned issues. This type of seal does not rely on radial compression and does not have to be forced into a small radial gap around the sealing plug. This makes installation and removal easier and quicker by eliminating the need for a specialized puller. The plug can be installed and removed by hand.

[0060] It has been shown through field trials that the inventive compression seal does not leak within common maintenance cycles. Fluid ends are commonly maintained when valve and seat components are replaced. This often occurs after 50-60 hours of operation.

Comparative Example 1

[0061] D-Ring-Radial Seal:

[0062] Location: Odessa, Tex.

[0063] Operating pressure: 9,000-11,000 psig

[0064] Sand Count: Approx. 210,000 lbs. per stage

[0065] Stage Length: Approx. 2 hours

[0066] D-Ring stage count (seal life) was erratic. Seals lasted from 1-10 stages. Seal life varied widely depending on the age of the fluid end and extent of sealing area washout or wear. Fluid ends that had extensive leaking before had significantly diminished seal life. D-rings were changed more frequently than valves and seats.

Example 1

[0067] Compression seal

[0068] Location: Gonzalez, Tex.

[0069] Operating pressure: 9,000-10,000 psig

[0070] Sand Count: Approx. 610,000 lbs. per stage

[0071] Stage Length: Approx. 4 hours

[0072] Total Number of Stages Tested: 72 (Approx. 280 hours)

[0073] The seals that were installed at the start of the test exceeded the length of two valve and seat maintenance intervals and continued to operate without any leaks.

Example 2

[0074] Compression seal

[0075] Location: Odessa, Tex.

[0076] Operating pressure: 8,500-9,000 psig

[0077] Sand Count: Approx. 210,000 lbs. per stage

[0078] Stage Length: Approx. 2 hours

[0079] Total Number of Stages Tested: 112 (Approx. 224 hours)

[0080] The seals that were installed at the start of the test went two valve and seat maintenance intervals without any leaks. Use of this sealing arrangement reduced the length of valve and seat maintenance of typical fluid ends from 45-60 minutes to 20-30 minutes, a reduction of approx. 50%.

[0081] While the invention has been described in detail, modifications within the spirit and scope of the invention will be readily apparent to those of skill in the art. In view of the foregoing discussion, relevant knowledge in the art and references discussed above in connection with the Background and Detailed Description, the disclosures of which are all incorporated herein by reference, further description is deemed unnecessary. In addition, it should be understood that aspects of the invention and portions of various embodiments may be combined or interchanged either in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention.