WO1999050578A9

WO1999050578A9 - Packing seal assembly for a pump

Info

Publication number: WO1999050578A9
Application number: PCT/IB1999/000658
Authority: WO
Inventors: Heinz Hammacher
Original assignee: Halliburton Energy Serv Inc; Heinz Hammacher
Priority date: 1998-03-30
Filing date: 1999-03-30
Publication date: 1999-11-25
Also published as: GB9806828D0; WO1999050578A1

Abstract

A packing seal (10) assembly for sealing an annular space (12) between a pump plunger (16) and a pump body (20) of a reciprocating plunger pump. The assembly comprises a sealing ring (40) adapted to be disposed in said annular space (12), wherein the sealing ring (40) includes a seal body (36), first sealing formation (42) on the seal body (36) adapted to sealingly engage a surface of the pump body (20), and a second sealing formation (44) on the seal body (36) adapted to sealingly engage a surface of the pump plunger (16), said sealing formations (42, 44) are resiliently deformable, and said formations (42, 44) are adapted to engage a respective one of the pump body and the plunger in order to provide a seal within the annular space.

Description

PACKING SEAL ASSEMBLY FOR A PUMP

This invention relates to a packing seal assembly for a pump. More particularly, the present invention relates to a packing seal assembly for use in an annular packing space between a first cylindrical member which reciprocates within a cylindrical bore of a second member.

During the completion and/or stimulation of an oil or gas well, fluids such as cement slurries, fracturing slurries, acids and the like are pumped under pressure into the well. Very high pressures of the order of tens of MPa, or more, are typically involved in these pumping operations. Additionally, the fluids are often very abrasive because they carry large quantities of solid particles therein. This pumping operation is typically achieved by large positive displacement reciprocating plunger type pumps.

A very difficult sealing problem is encountered at the high pressure end of these pumps, where the abrasive fluid must be prevented from leaking between the reciprocating plunger and the cylinder within which it reciprocates.

Typically the seal between the reciprocating plunger and the cylinder comprises a seal arrangement including a plurality of V-shaped packing rings constructed of cloth and binder, with various male and female adaptors at the forward and rearward ends thereof. A longitudinal compression is applied to the packing rings by an adjusting ring. Problems encountered in the use of such seals include the deterioration of the

V-shaped cloth and binder packing rings due to the hydraulic load from the high pressure fluid end of the pump. Another problem typically encountered is extrusion of the V-shaped cloth and binder packing rings between the small annular clearances present-between-the female adaptor supporting the rearward end of the packing rings and the pump plunger and pump cylinder. This is caused by the excessive longitudinal compression applied upon the seal assembly.

The difficulties involved in these pumping conditions has resulted in increasingly complex solutions to the sealing problems. One of these solutions is disclosed in US patent no. 4440404 which describes a packing assembly for sealing the annular space between a pump plunger and the pump body of a reciprocating plunger pump. This assembly includes a radially compressed elastome c header ring disposed in a high pressure end of the annular space for preventing migration of fluid through the annular space. The assembly also includes a V-shaped packing ring disposed in the annular space behind the header ring with a concave side thereof facing the header ring. A female adaptor ring is disposed in the annular space behind the V-shaped packing ring, and an anti-extrusion ring is disposed in the annular space between the V-shaped packing ring and the female adaptor. The packing assembly disclosed in US patent no. 4440404 must be pre-compressed, and this causes wear on the plunger, and reduces the lifetime of the seal assembly. In addition, the precompression makes it more difficult to fit the packing assembly on the plunger. Modifications to the arrangement described in US patent no. 4440404 are described in US patent nos. 4474382 and 4478423.

In UK patent nos. 2231104, 2102898 and 2085983 and US patent no. 4627332, a variety of seals are disclosed. There is no suggestion that the seals disclosed in these patents could be used in a reciprocating plunger pump. In US patent no. 4592558, there is described a spring-energized seal.

We have now found a way to provide a seal assembly for a reciprocating plunger pump, in which it is not necessary to provide any precompression of the packing seal assembly. According to one aspect of the present invention there is provided a packing seal assembly for sealing an annular space between a pump plunger and a pump body of a reciprocating plunger pump, comprising a sealing ring adapted to be disposed in said annular space, wherein the sealing ring includes a seal body, and first and second sealing formations on the seal body, wherein said sealing formations are adapted to engage a respective one of the pump body and the plunger in order to provide a seal within the annular space, the .

In a preferred embodiment, a header ring is provided in said annular space, the header ring being positioned closer to a high pressure end of said annular space than the sealing ring. The header ring acts as a retaining means for the sealing ring. The header ring can act as a means for longitudinally supporting the sealing ring against forward extension when the pump plunger reciprocates forward relative to the pump body.

Advantageously, the sealing formations are arranged so that, upon insertion into the annular space, they are deformed towards one another by contact with the pump body and plunger. This can be achieved by making the sealing ring of a size such that the distance between the sealing surfaces on the sealing formations, before insertion into the annular space, is greater than the thickness of the annular space. Preferably the first and second sealing formations each include a radially outwardly extending lip which is adapted to engage the pump body and plunger respectively. Advantageously also the sealing formations are arranged such that the hydraulic pressure within the pump urges the sealing formations into contact with the pump body and plunger. For this reason, it is preferred that the header ring does not form a seal between the pump body and the pump plunger.

It is preferred that there are no other components between the header ring, the sealing ring and the anti-extrusion ring. This arrangement has been found to result in the least wear of the packing assembly.

In a preferred embodiment, an anti-extrusion ring is provided on the opposite side of the sealing ring to the header ring. It is preferred that the spacer ring also acts as an spacer ring, to enable the packing assembly according to the invention to be used as a direct replacement for the header ring adaptor means, the header ring means, the V- shaped packing rings, the female adaptor ring and the V-shaped anti-extrusion ring means used in the pump described in US patent no. 4440404. This enables the packing seal assembly according to the invention to be used as a direct replacement for prior art packing seal assemblies, without the need to make any modifications to the pump. It is preferred that the radial thickness of the part of the seal body adjacent the anti- extrusion ring is smaller than the radial thickness of the part of the anti-extrusion ring adjacent the seal body.

It is preferred that the sealing formations and the body form a generally U-shaped configuration, more specifically a generally Y-shaped configuration. It is particularly preferred that the sealing ring is made of polyurethane. We prefer to provide only one sealing ring, as this is usually suitable for most purposes. Furthermore, we have found that the use of more than one sealing ring tends to reduce the lifetime of the packing assembly. However, it will be appreciated that more than one sealing ring may be provided, if desired. When more than one sealing ring is used, we prefer to provide a separate anti-extrusion ring for each sealing ring. The sealing ring may be provided with one or more further sealing formations for engaging the pump body or plunger.

According to another aspect of the invention there is provided a reciprocating plunger pump comprising a pump body having a pump plunger reciprocatable therein and an annular space between the pump plunger and the pump body, wherein the packina seal assembly as described above disposed within the annular space.

Preferably the sealing ring is arranged in the annular space in such a way that the sealing formations are disposed closer to the high pressure end of the annular space than the seal body. The pump according to the invention is capable of pump highly abrasive fluids at high pressures which typically exceed about 30-70 MPa. The pump can operate at pressures up to about 138 MPa or higher.

Although the invention has been described in relation to reciprocating plunger pumps, it will be appreciated that the packing seal assembly according to the invention may be used in other pumps which operate at high pressures of greater than about 1 -10 Mpa, typically greater than 34-69 MPa.

In another aspect the invention comprises the use of a reciprocating plunger pump as described above to pump highly abrasive fluids, such as cement slurries, fracturing slurries and acids. The packing seal assembly according to the present invention does not require precompression of any of its parts. It leads to reduced wear on the plunger and can be used for up to three times as long as prior art assemblies without having to be replaced. Furthermore, the packing seal assembly according to the invention is easier to install than packing seal assemblies in the prior art, has fewer parts than the packing seal assemblies in the prior art, and it uses less oil.

Reference is now made to the accompanying drawings, in which:

FIG. 1 is a schematic sectioned elevation view of a reciprocating plunger pump having an embodiment of a packing seal assembly according to the present invention disposed therein,

FIG. 2 is a schematic sectioned elevation view of part of the reciprocating plunger pump shown in FIG 1 , on an enlarged scale;

FIG. 3 is an exploded side view of an embodiment of a packing seal assembly according to the present invention; FIG. 4 is an exploded side view of another embodiment of a packing seal assembly according to the present invention; and

FIG. 5 is a cross-sectional view of the sealing ring of the packing seal assembly shown in FIG. 4.

In FIG. 1 , a reciprocating pump 24 contains a packing seal assembly according to the present invention, which is generally designated 10. The sealing assembly 10 is shown in place within an annular space 12 defined between a radially outer surface 14 of a pump plunger 16 and a cylindrical bore 18 of a pump body 20.

The plunger 16 reciprocates within the pump body 20 to pump a fluid located in a high-pressure end 22 of the pump 24 through a series of inlet and outlet valves (not-shown) in a manner which is generally known to those skilled in the art. The pump 24 can be any reciprocating plunger pump and particularly may be reciprocating plunger pump-for pumping cement slurries, fracturing slurries, acids and the like for completion and stimulation of an oil or gas well.

The sealing assembly 10 includes a header ring 26. The header ring 26 is disposed in a high pressure end of the annular space 12, which is the end adjacent the high pressure end 22 of the pump 24. The header ring 26 may be made of brass or bronze, for example. The header ring 26 provides a means for longitudinally supporting the sealing ring 40 against forward extension thereof when the pump plunger 16 reciprocates forward relative to the pump body 20. The header ring 26 has not been precompressed, and does not provide a seal for preventing migration of fluid from the high pressure end 22 of pump 24 through the annular space 12.

The header ring 26 includes a forward facing flat annular surface 28, and a radially outer cylindrical surface 30. The header ring 26 also includes a rearward facing flat annular surface 32, and a radially inner cylindrical surface 38.

The sealing assembly 10 further includes a sealing ring 40 disposed in the annular space 10 behind the header ring 26. The sealing ring 40 includes a seal body 36 and two resiliently deformable sealing formations 42 and 44 extending outwardly from the body 36.

The sealing ring 40 is slidable relative to the header ring 26 during reciprocation of the pump plunger 16.

A bullet shaped spacer 52 is disposed in the annular space 12 between the sealing ring 40 and a carrier 80, which is also disposed in the annular space 12, directly behind the spacer 52. The spacer 52 acts as an anti-extrusion means for preventing extrusion of the sealing ring 40 between the carrier 80 and each of the pump plunger 16 and the cylindrical bore 18 of the pump body 20.

The spacer 52 includes a substantially flat side 54 facing, adjacent and engaging a substantially flat side 46 of the sealing ring 40. The spacer 52 also includes a convex rear side 56 facing, adjacent and engaging a forward concave side 58 of the carrier 80. The spacer 52 also includes radially inner and outer surfaces 60 and 62 respectively, which may or may not engage pump plunger 16 and cylindrical bore 18 of pump body 20 respectively. As can be seen in the drawings, the radial thickness of the body 36 is less than the radial thickness of the spacer 52.

The carrier 80 has an oil passage 84 disposed therethrough for conducting lubricating oil from a lubricating oil supplv line 86 to the pump plunger 16 for lubricating the pump plunger 16 along the area of sealing engagement with the packing seal assembly 10. The carrier 80 includes inner and outer seals 94 and 96 for sealing against plunger 16 and cylindrical bore 18 of the pump body 20 respectively. The inner seal 94 is a lube ring, and the outer seal 96 is an O-ring.

A packing adjustment ring 88 is located behind and directly engages a rear end 90 of the carrier 80. The packing adjustment ring 88 may be adjusted by rotation thereof at threaded connection 92, for advancing the packing adjustment ring 88 relative to the pump body 20, thereby adjusting the longitudinal position of the packing seal assembly 10.

In the sealing assembly 10, a high sealability against leakage of fluid from high pressure end 22 is provided by the sealing ring 40. This is the primary seal against fluid leakage. It is not necessary for any of the components of the sealing assembly 10 to be provided with any radial pre-compression, and it is desirable that such pre-compression is not provided in order to improve the life of the assembly 10.

The structure of the sealing ring 40 is shown most clearly in figures 2 and 3. Before being disposed in the annular space 12, the sealing ring 40 has the annular flat rear surface 46, an inner substantially cylindrical surface 70, and an outer substantially cylindrical surface 72. The formations 42 and 44 are separated by a U-shaped surface 74. The part of each formation furthest from the seal body 36 is provided with radially outwardly extending lips 76 and 78 respectively. The formations 42 and 44 are dimensioned so that the distance between an outermost part 42a of the formation 42 and an innermost part 44a of the formation 44 is greater than the thickness of the annular space 12. This causes the formations 42 and 44 to be pressed together upon insertion into the annular space 12. The formations 42 and 44 are biased outwardly into engagement with the surfaces 18 and 14 by the resilience of the material of the sealing ring 40. The formations are also configured so that they tend to be forced apart, and into the surfaces 18 and 14, when subjected to the pressure from the high pressure end 22 of the pump 24. This further improves the seal between the sealing ring 40 and the surfaces 18 and 14. The radial surfaces 70 and/or 72 may have sealing formations (not shown) thereon, which engage the surfaces 18 and 14. It will be noted that the sealing ring 40 is only in contact with the pump body 20 and plunger 16 by the formations 42 and 44: seal body 36 does not contact the pump body 20 or the plunger 16. The formations 42 and 44 are arranged on the body in such a manner that the application of pressure on the seal ring 40 by the header ring 24 and the spacer 52 can cause the formations 42 and 44 to deform outwardly into contact with the pump body 20 and plunger 16. The resilience of the formations 42 and is an important feature of the invention as it allows the formations 42 and 44 to apply a pressure radially outwardly onto the pump body 20 and plunger 16 in order to maintain the seal. The arrangement of the formations 42 and 44 closer to the high pressure 22 than the seal body 36 helps the pressure from the high pressure end 22 to push the formations 42 and 44 further apart radially; this arrangement also makes it easier to insert the sealing ring 40 into the annular space 12.

In FIGS. 4 and 5 an alternative embodiment of packing seal assembly is generally designated 100. Many of the parts of the assembly 100 are identical to the parts of the assembly 10, and like parts have been designated with like reference numerals. The only difference relates to the sealing ring, which has been designated 40' in Fig. 4. In Fig. 4, the formation 44' is shorter than the formation 42', and there is an additional formation 48' on the radial surface 70'.

It will be appreciated that modifications may be made to the invention described above.

Claims

1. A packing seal assembly for sealing an annular space between a pump plunger and a pump body of a reciprocating plunger pump, comprising, in sequence, a header ring, a sealing ring and an anti-extrusion ring each adapted to be disposed in said annular space wherein the header ring is adapted to retain the sealing ring within the annular space during reciprocation of the pump plunger, the sealing ring includes a seal body, first and second deformable sealing formations on the seal body each adapted to engage a respective one of the pump body and the plunger in order to provide a seal within the annular space, the radial spacing between the sealing formations, when uncompressed, being greater than the radial dimension of the annular space, so that, upon insertion into the annular space, they are deformed towards one another by contact with the pump body and plunger.

2. A packing seal assembly according to claim 1 , wherein the sealing formations are arranged such that they can be urged into contact with the pump body and plunger by hydraulic pressure with the pump.

3. A packing seal assembly according to claim 1 or 2, wherein the radial thickness of the part of the seal body adjacent the anti-extrusion ring is smaller than the radial thickness of the part of the anti-extrusion ring adjacent the seal body.

4. A packing seal assembly according to claim 3, wherein the anti-extrusion ring also acts as a spacer means, the size of which is selected so that the packing assembly can replace an existing packing assembly in an existing pump.

5. A packing seal assembly according to any preceding claim, wherein the sealing ring is made of polyurethane.

6. A packing seal assembly according to any preceding claim, wherein the sealing ring includes at least one further sealing formation on the seal body for engaging the pump body or plunger.

7. A packing seal assembly according to any preceding claim, wherein the sealing formations and the body form a generally Y-shaped configuration, the arms of the Y corresponding to the sealing formations, and the base of the Y corresponding to the seal body.

8. A packing seal assembly according to any preceding claims, wherein the first and second formations each include a radially outwardly extending lip which is adapted to engage the pump body and plunger respectively.

9. A packing assembly according to any preceding claim, wherein the header ring is configured such that, when installed in the pump, it does not seal the annular space.

10. A packing assembly according to any preceding claim, further comprising a seal carrier ring disposed on the opposite side of the anti-extrusion ring to the sealing ring.

11. A packing assembly according to claim 10, wherein the seal carrier ring has a convex surface which is adapted to be engaged by a concave surface on the anti-extrusion ring.

12. A packing assembly according to claim 10 or 11 , wherein the seal carrier ring is provided with an oil passage adapted to allow lubricating oil to flow from an oil reservoir to the plunger pump.

13. A packing assembly according to any preceding claim, wherein there are no other components between the header ring, the sealing ring and the anti-extrusion ring.

RECTIFIED SHEET (RULE 91) ISA/EP

14. A packing assembly according to any preceding claim, further comprising a packing adjustment ring adapted to adjust the longitudinal position of the packing seal assembly relative to the pump body and the pump plunger.

15. A packing assembly according to any preceding claim, wherein the sealing ring is slidable relative to the header ring during reciprocation of the pump plunger.

16. A reciprocating plunger pump comprising a pump body having a pump plunger reciprocatable therein, an annular space between the pump plunger and the pump body, and a packing seal assembly according to any of claims 1 to 14 disposed within the annular space, and wherein the packing assembly is not subjected to any radial precompression.

17. A pump according to claim 16, wherein the sealing ring is arranged in the annular space in such a way that the sealing formations are disposed closer to the high pressure end of the annular space than the seal body.

18. A reciprocating plunger pump according to claim 16 or 17, which is adapted to operate at pressures over 30 MPa.

19. The use of a reciprocating plunger pump according to claim 16, 17 or 18 to pump highly abrasive fluids, such as cement slurries, fracturing slurries and acids.

20. A method of pumping fluids comprising providing a pump according to claim 16, 17 or 18 and pumping a highly abrasive fluid therethrough.

RECTIFIED SHEET (RULE 91) 1SA/EP