Seal for a reciprocating pump

Abstract

A seal (1) for a reciprocating pump (2), which can be applied to a rod (3) of a piston (4), comprises a housing (5) having a first opening (6), a second opening (8), and a main cavity (9) between the first opening (6) and the second opening (8). The housing (5) further comprises a plurality of annular shells (10) distributed along the main extension axis (X-X), which are located outside and concentric with the main chamber (9). The seal (1) comprises a plurality of sealing modules (11), each comprising: a sealing ring (12) configured to be in contact with the rod (3) of the piston (4); and a resilient element (14) configured to hold the respective sealing ring (12) attached to the rod (3) of the piston (4). The sealing ring (12) and the spring element (14) are inserted into the respective annular housing (10).

Description

Technical Field

[0001] The invention relates to a seal for a reciprocating pump, ie a seal for a pump in which a piston slides in a reciprocating manner along a main axis.

[0002] In particular, reciprocating pumps find application in all sectors of industry where it is necessary to move pressurized fluids, including, for example, the chemical, petrochemical and extraction sectors. Background Art

[0003] Reciprocating pumps are known in the prior art. A known type of reciprocating pump comprises a plurality of cartridges. Each cartridge comprises a chamber for a working fluid which is isolated from the external environment by a seal, an inlet valve and an outlet valve inside the chamber, and a piston which flows in a reciprocating motion inside the chamber. During the suction phase, the inlet valve is opened to introduce the working fluid into the chamber, while the outlet valve remains closed. In contrast, during the compression phase, the inlet valve is closed. The piston pushes the working fluid toward the outlet valve, which, by opening, allows the working fluid to leave the chamber.

[0004] In order to avoid leakage during the operation of the piston, it is known to apply a seal around the piston rod. The seal comprises a gland seal having a cavity in which the piston rod slides. Inside the cavity a packing is placed around the piston rod. The packing comprises a mesh made of cables, for example made of Kevlar, Teflon or graphite, placed in contact with the surface of the piston rod. Before starting the pump, the packing is inserted into the cavity of the gland seal and pressed against the piston rod by tightening the closing element of the gland seal.

[0005] Document US2013292909A1 discloses a sealing assembly comprising an element with which a mud delivery pipe of a drilling rig is connected to a rotary drive device of the drilling rig, which enables high-pressure mud to be supplied to a drilling pipe.

[0006] Document US2009114086A1 describes compressing useful gas by means of a compressor and using a pressurized barrier gas to reduce leakage of the useful gas.

[0007] Document US2005253340A1 discloses a sealing system having a seal which can be engaged with a movable element (eg a rotating shaft and / or a reciprocating shaft) in turn by relative movement between a barrier element and a lip seal element. Summary of the invention

[0008] Disadvantageously, in order to maintain an adequate level of sealing and limit leakage, periodic interventions are required to restore the tightening of the closing element.

[0009] Furthermore, the pressurized contact between the filler fibers and the piston rod can damage the piston rod, causing it to wear more quickly.

[0010] In this context, the technical task of the present invention is to propose a seal for a reciprocating pump, which overcomes the above-mentioned defects of the prior art.

[0011] In particular, it is an object of the present invention to provide a seal for a reciprocating pump which requires a reduced number of maintenance operations.

[0012] Another object of the invention is to provide a pump that ensures a long service life of the piston.

[0013] The technical task mentioned and the aims specified are substantially achieved by a seal for a reciprocating pump comprising the technical specification set out in one or more of the appended claims.

[0014] Advantageously, the seal for the reciprocating pump comprises a sealing ring inside the housing, which is held attached to the piston rod by an elastic element. In particular, the sealing ring is designed to recover from wear, and after an initial period of starting the reciprocating pump, they reach their optimum operating region and are held in place by the elastic element.

[0015] Advantageously, the sealing ring exerts a much lower friction effect on the piston rod than the packing, thereby ensuring a sufficient degree of sealing and at the same time significantly limiting the wear on the piston rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other features and advantages of the present invention will become more apparent from the description of an exemplary but non-exclusive and therefore non-limiting preferred embodiment of a seal for a reciprocating pump as shown in the accompanying drawings, in which:

[0017] - Figure 1 A perspective view showing a section of a first embodiment of a seal according to the invention;

[0018] - Figure 2 Shown from Figure 1 An exploded side view of some sealing components;

[0019] - Figure 3 A second embodiment of a seal according to the invention is shown;

[0020] - Figure 3a Shown from Figure 3 an enlarged view of a portion of a housing;

[0021] - Figure 3b Shown from Figure 3a A magnified view of the details;

[0022] - Figure 4 A third embodiment of a seal according to the invention is shown;

[0023] - Figure 5 Shows Figure 1 A cutaway perspective view of a detail of a seal in FIG. 1 ; and

[0024] - Figure 6 shows a schematic side view of a reciprocating pump. DETAILED DESCRIPTION

[0025] The invention relates to a seal 1 for a reciprocating pump 2 , which can be applied to a rod 3 of a piston 4 .

[0026] In detail, the reciprocating pump 2 schematically shown in FIG. 6 includes at least one barrel 51 configured to accommodate a working liquid. The barrel 51 includes an input valve 52 configured to input the working liquid into the barrel 51 and an output valve 53 configured to output the working liquid from the barrel 51. The inlet valve 52 and the outlet valve 53 are opened alternately. The reciprocating pump 2 includes at least one piston 4 sliding along the main extension axis XX inside the barrel 51. The reciprocating pump 2 also includes a seal 1 applied to the rod 3 of the piston 4. In particular, the reciprocating pump 2 includes an opening 54. The seal 1 is applied to the opening 54.

[0027] like Figure 1 As shown, the seal 1 comprises a housing 5 extending along a main extension axis XX. Preferably, the housing 5 has the function of a gland seal. The housing 5 comprises a first opening 6 facing the head 7 of the piston 4 and a second opening 8 opposite the first opening 6. The first opening 6 and the second opening 8 are arranged along the main extension axis XX. In addition, the housing 5 defines a main cavity 9 extending between the first opening 6 and the second opening 8. The rod 3 of the piston 4 can slide in the main cavity 9 and pass through the first opening 6 and the second opening 8. In one embodiment, as Figure 2 As shown, the housing 5 comprises a bottom 46 at the first opening 6 .

[0028] The casing 5 comprises an outer surface 36 and a plurality of annular seats 37 distributed along the main axis of extension XX and situated on the outer surface 36 .

[0029] It should be noted that the housing 5 has a plurality of annular shells 10 distributed along the main extension axis XX. Furthermore, the annular shells 10 are located outside the main cavity 9 and are concentric with the main cavity 9. Each annular shell 10 comprises a first wall 68 and a second wall 69 spaced apart along the main extension axis XX, and an annular wall 60 positioned between the first wall 68 and the second wall 69. Figure 1 In the illustrated embodiment, the number of the annular housings 10 is at least six.

[0030] In an alternative embodiment of the invention, the annular casing 10 is defined by an outer ring 71 described later in this description.

[0031] In more detail, the casing 5 comprises a plurality of sections 19. Each section 19 comprises a respective annular housing 10. It should be noted that preferably in each section 19, the annular housing 10 is positioned directly facing one of the adjacent sections 19.

[0032] The seal 1 further comprises a plurality of sealing modules 11. Each sealing module 11 comprises a sealing ring 12 and an elastic member 14. Figure 3a shown.

[0033] The sealing ring 12 is inserted into the corresponding annular housing 10 and has an inner surface 13 which is configured to be in contact with the rod 3 of the piston 4. In more detail, the sealing ring 12 is a ring made of a polymer material. It should be noted that each sealing ring 12 is configured to allow the pressure of the working fluid to be locally reduced relative to the next sealing ring 12 along the main extension axis XX from the first opening 6 towards the second opening 8. The flow of the working fluid is laminar along the main extension axis XX from the first opening 6 towards the second opening 8. Preferably, the sealing ring 12 has an L-shaped cross section.

[0034] Preferably, each sealing module 11 comprises a further sealing ring 12 a configured to come into contact with the rod 3 of the piston 4 .

[0035] The elastic member 14 is inserted into the corresponding annular housing 10, arranged outside the corresponding sealing ring 12 and in contact with the corresponding sealing ring 12. The elastic member 14 is configured to keep the inner surface 13 of the corresponding sealing ring 12 attached to the rod 3 of the piston 4. The elastic member 14 has an outer surface 50 facing the annular wall 60 of the annular housing 10. The elastic member 14 is made of steel. Preferably, the elastic member 14 has a cross-section formed into an L-shape complementary to the cross-section of the sealing ring 12, such as Figure 3b shown.

[0036] Each sealing module 11 includes a channel 70 arranged outside the elastic member 14 in the annular housing 10. The channel 70 is placed in fluid communication with the main chamber 9. The channel 70 is configured to receive the working fluid from the main chamber 9.

[0037] Preferably, each sealing module 11 comprises the aforementioned outer ring 71. Preferably, the outer ring 71 has an inner surface 71a facing the elastic element 14.

[0038] Preferably, the outer ring 71 has an L-shaped cross section. Preferably, the outer ring 71 has a first portion 72 parallel to the main extension axis XX and a second portion 73 orthogonal to the main extension axis XX. Preferably, each outer ring 71 has at least one channel 70 at the second portion 73 .

[0039] Preferably, the channel 70 has a groove 70a extending orthogonally from the main cavity 9 relative to the main axis XX at the outer ring 71. In a preferred embodiment, the groove 70a extends from the main cavity 9 at the second portion 73 of the outer ring 71. The groove 70a is placed between the second portion 73 of the outer ring 71 and the elastic member 14. Advantageously, during use, the working liquid exerts a pressure on the corresponding sealing module 11 parallel to the main extension axis XX.

[0040] Preferably, the channel 70 has a gap 70b in fluid communication with the groove 70a. Preferably, the gap 70b is placed between the outer ring 71 and the elastic member 14. Preferably, the gap 70b is placed between the first portion 72 of the outer ring 71 and the elastic member 14. In other words, the gap 70b is located in the portion of the annular housing 10 that is freely maintained outside the elastic member 14. Advantageously, during use, the working liquid flows from the central cavity 9 into the groove 70a and into the gap 70b to exert radial pressure on the corresponding sealing module 11 and in particular on the elastic member 14, thereby ensuring adhesion on the piston 4.

[0041] In a preferred embodiment, the seal 1 comprises a plurality of support rings 40. It should be noted that each support ring 40 is inserted into a respective annular housing 10. In particular, each support ring 40 is positioned in contact with a respective sealing module 11 along the main extension axis XX. In the embodiment shown, each support ring 40 is positioned closer to the second opening 8 than the respective sealing module 11. In a preferred embodiment, the support rings 40 are made of a polymeric material. It should be noted that the sealing module 11 and the respective support ring 40 are made in contact with a first wall 68 and a second wall 69 of the annular housing 10, respectively.

[0042] Preferably, each other sealing ring 12 a is arranged between the sealing ring 12 and the corresponding support ring 40 .

[0043] Special References Figure 1 and Figure 3 , the housing 5 includes at least one exhaust channel 15 placed in fluid communication with the main chamber 9. The exhaust channel 15 is configured to discharge the working fluid from the main chamber 9. In particular, the exhaust channel 15 includes an inlet 16 positioned between the two sealing modules 11.

[0044] The discharge channel 15 is configured to receive residual working liquid in the main chamber 9. It should be noted that the discharge channel 15 has a straight section 44 extending outside the main chamber 9 and parallel to the main extension axis XX. The inlet 16 connects the straight section 44 to the main chamber 9. In a preferred embodiment, the straight section 44 of the discharge channel 15 has a discharge opening 33, which protrudes to the outside of the housing 5, close to the second opening 8. The discharge opening 33 is configured to discharge the residual working liquid. Preferably, the residual working liquid is collected and reintroduced into the reciprocating pump 2.

[0045] The inlet 16 defines a first set 32 ​​of sealing modules and a second set 21 of sealing modules. In particular, the first set 32 ​​of sealing modules is positioned between the inlet 16 and the first opening 6. The second set 21 of sealing modules is positioned between the inlet 16 and the second opening 8. Figure 1 In the embodiment shown, the number of sealing modules 11 in the first set 32 ​​of sealing modules is five. Figure 1 In the embodiment shown, the sealing modules 11 of the first set 32 ​​of sealing modules are equally spaced along the main axis of extension XX. Figure 1 In the embodiment shown, the second set 21 of sealing modules comprises at least one sealing module 11 .

[0046] The seal 1 comprises a second discharge channel 17 having a second inlet 18. The second inlet 18 protrudes into the main cavity 9 and is positioned between the inlet 16 and the first opening 6. In a preferred embodiment, as Figure 2 As shown, the second inlet 18 is positioned between two consecutive sealing modules of the second set 21 of sealing modules. Advantageously, when a leakage of the operating fluid from the second drain channel 17 is detected, maintenance of the seal 1 can be scheduled.

[0047] The seal 1 comprises at least one bushing 20 configured to keep the rod 3 of the piston 4 aligned inside the main chamber 9. The bushing 20 is positioned between the first opening 6 and the first set 32 ​​of sealing modules or between the second opening 8 and the second set 21 of sealing modules. Preferably, the bottom 46 comprises a bushing seat 45 and the bushing 20 is mounted to the bushing seat 45 by interference.

[0048] In a preferred embodiment, Figure 3 As shown in FIG. 1 , the seal 1 comprises two bushings 20. Each bushing 20 is positioned between the first opening 6 and the first set 32 ​​of sealing modules and between the second opening 8 and the second set 21 of sealing modules. In a preferred embodiment, the bushings 20 are made of a polymeric material.

[0049] In a preferred embodiment, each bushing 20 has at least one axial groove 34, which faces the rod 3 of the piston 4 and is oriented parallel to the main extension axis XX. The axial groove 34 is configured to reduce the pressure inside the main chamber 9, thereby allowing the working fluid to pass. In other words, the bushing 20 provided with the axial groove 34 does not act as a sealing element. Preferably, the number of axial grooves 34 is comprised between four and eight, even more preferably equal to six.

[0050] The seal 1 comprises an isolating ring 22 positioned between the second opening 8 and the second set 21 of sealing modules. In an embodiment in which the seal 1 comprises a bushing 20 positioned between the second opening 8 and the second set 21 of sealing modules, the isolating ring 22 is preferably positioned between the bushing 20 and the second set 21 of sealing modules. The isolating ring 22 has an inner isolating surface 23 configured to contact the rod 3 of the piston 4. Preferably, the isolating ring 22 is defined by a double lip ring. In a preferred embodiment, each isolating ring 22 is made of a polymer material. In a preferred embodiment, the isolating ring 22 is inserted into a housing 65, which is configured to impart the necessary degree of hardness. Preferably, the housing 65 is made of steel.

[0051] The seal 1 further comprises a plurality of elastomeric rings 38 , and each elastomeric ring 38 is inserted into a corresponding annular seat 37 .

[0052] The seal 1 comprises a locking element 24 placed at the second opening 8. The housing 5 comprises a fastening channel 26 passing through each portion 19 and configured to receive a tie rod 28 which can be fastened by a fastening device 29 and configured to hold the portions 19 of the housing 5 together. Note that the bottom 46 of the housing 5 comprises an additional clamping channel, not shown in the figures. In particular, the other clamping channels are configured to align with the clamping channels 26. Preferably, the clamping channels comprise a thread (also not shown in the figures) configured to fix the tie rod 28 to the bottom 46. In a preferred embodiment, the clamping device 29 comprises a washer and at least one nut.

[0053] It should be noted that Figure 4 In the first embodiment shown, the locking element 24 is defined by a ring nut 80, which can be coupled to the housing 5 by means of a thread. The ring nut is made of steel. In particular, the housing 5 comprises a support 71 comprising a clamping ring nut configured to be coupled to the thread of the housing 5. Furthermore, in a preferred embodiment, the seal 1 comprises at least one anti-rotation pin 72, inserted into the support 71 and resting against the ring nut. The anti-rotation pin 72 is configured to hold the ring nut in place.

[0054] In e.g. Figure 1In the second embodiment shown in , the locking element 24 is defined by a flange 81 which can be coupled to the housing 5 by means of bolts 31. The number of bolts 31 is comprised between twelve and eighteen and is preferably equal to fifteen and is arranged along the circumference. The flange is made of steel.

Claims

1. A seal (1) for a reciprocating pump (2), the seal being of a type suitable for application to a rod (3) of a piston (4), the seal (1) being characterized in that it comprises: - a casing (5) extending along a main extension axis (XX) and comprising a first opening (6) designed to face the head (7) of the piston (4) and a second opening (8) opposite to the first opening (6), the first opening and the second opening both being arranged along the main extension axis (XX), the casing (5) defining a main chamber (9) extending between the first opening (6) and the second opening (8), the rod (3) of the piston (4) being able to slide in the main chamber (9) and pass through the first opening (6) and the second opening (8), the casing (5) further comprising a plurality of annular shells (10) distributed along the main extension axis (XX), the annular shells (10) being arranged outside the main chamber (9) and concentric with the main chamber (9), - A plurality of sealing modules (11), each comprising a sealing ring (12) which is inserted into a corresponding annular housing (10) and has an inner surface (13) which is configured to come into contact with the rod (3) of the piston (4), - an elastic member (14) inserted into the corresponding annular housing (10) and arranged outside the corresponding sealing ring (12) and in contact with the corresponding sealing ring (12), the elastic member (14) being configured to force the inner surface (13) of the corresponding sealing ring (12) to adhere to the rod (3) of the piston (4), The invention is characterized in that the housing (5) comprises at least one discharge channel (15) in fluid communication with the main chamber (9), and the discharge channel (15) is configured to discharge the working fluid from the main chamber (9).

2. A seal (1) according to claim 1, wherein each sealing module (11) comprises at least one channel (70), which is placed between the elastic member (14) and the corresponding annular shell (10) in a manner that is fluidly connected to the main chamber (9), and the channel (70) is formed to receive the working fluid from the main chamber (9).

3. A seal (1) according to claim 2, wherein each sealing module (11) comprises an outer ring (71), and the channel (70) comprises a groove (70a), which extends from the main cavity (9) at the outer ring (71) in a manner orthogonal to the main extension axis (XX).

4. The seal (1) according to claim 3, wherein the channel (70) comprises a gap (70b) placed between the outer ring (71) and the elastic member (14) in fluid communication with the groove (70a).

5. The seal (1) according to claims 1 to 4, wherein the sealing ring (12) has an L-shaped cross section and the elastic member (14) has an L-shaped cross section shaped complementary to the cross section of the sealing ring (12).

6. A seal (1) according to claims 1 to 5, wherein the discharge channel (15) comprises an inlet (16) located between two consecutive sealing modules (11), the inlet (16) defining a first set (32) of sealing modules located between the inlet (16) and the first opening (6) and a second set (21) of sealing modules located between the inlet (16) and the second opening (8).

7. The seal (1) according to claim 6, wherein the housing (5) comprises a second discharge channel (17) having a second inlet (18) which protrudes into the main cavity (9) and is located between the inlet (16) and the first opening (6).

8. The seal (1) according to any one of claims 1 to 7, wherein the casing (5) comprises a plurality of parts (19), each part (19) comprising a respective annular housing (10).

9. A seal (1) according to any one of claims 6 to 8, comprising at least one bushing (20), which is positioned between the first opening (6) and the first set of sealing modules (11) and / or between the second opening (8) and the second set (21) of sealing modules, and the bushing (20) is configured to keep the rod (3) of the piston (4) aligned in the main chamber (9).

10. A seal (1) according to any one of claims 6 to 9, wherein the seal (1) comprises an isolating ring (22), the isolating ring (22) being positioned between the second opening (8) and the second set (21) of sealing modules, the isolating ring (22) having an isolating inner surface (23) configured to contact the rod (3) of the piston (4), the isolating ring (22) being preferably defined by a double lip ring.

11. A seal (1) according to any one of claims 8 to 10, comprising a locking element (24) located at the second opening (8), the cover (5) comprising a locking channel (26) extending through each part (19), the locking channel (26) being configured to receive a pull rod (28), the pull rod being designed to be locked by means of a locking device (29) and being configured to hold the parts (19) of the cover (5) together.

12. The seal (1) according to claim 11, wherein the locking element (24) is defined by a ring nut designed to be coupled to the housing (5) by means of a thread.

13. The seal (1) according to claim 11, wherein the locking element (24) is defined by a flange designed to be coupled to the housing (5) by means of bolts (31).

14. A seal (1) according to any one of claims 1 to 13, wherein the housing (5) comprises an outer surface (36) and at least one annular seat (37) distributed along the main extension axis (XX) and located at the outer surface (36), and the seal (1) comprises at least one elastomeric ring (38), each elastomeric ring (38) being inserted into a corresponding annular seat (37).

15. A reciprocating pump (2), comprising: - at least one cartridge (51) configured to contain a working fluid; - at least one piston (4) which slides inside said cylinder (51) along a main axis of extension (XX) and comprises a rod (3); A seal (1) according to any one of claims 1 to 14 applied to the rod (3) of the piston (4).

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