WO2011160069A1

WO2011160069A1 - Pump cavitation device

Info

Publication number: WO2011160069A1
Application number: PCT/US2011/040960
Authority: WO
Inventors: Joseph H. Byrne
Original assignee: S.P.M. Flow Control, Inc.
Priority date: 2010-06-17
Filing date: 2011-06-17
Publication date: 2011-12-22
Also published as: CN103069167A; US20110308967A1; CA2802712A1

Abstract

A sacrificial body mitigates cavitation damage to components within a pump. The sacrificial body is mounted in the pump so that flowing fluid passes over the sacrificial body, which causes the sacrificial body to shed electrons into the flowing fluid in the vicinity of the cavitation. The excess electrons tend to suppress hydrogen ions from releasing, which can mitigate cavitation. The sacrificial body is formed of a material having less resistance to corrosion due to the flowing fluid than the components of the pump. Needles are attached to the sacrificial body for immersion in the flowing fluid to facilitate the release of the electrons for the sacrificial body.

Description

PUMP CAVITATION DEVICE

Cross-Reference to Related Application

This application claims priority to provisional patent application S.N. 61/355,878, filed June 17, 2010.

Technical Field

This disclosure relates in general to pumps and in particular to a sacrificial body that mitigates pitting and corrosion due to cavitation.

Background of the Disclosure

Cavitation in pumping devices causes early failure of components due to

erosion/corrosion and the resulting pitting. The pitting causes several problems: leaks in sealing areas, loss of pressure integrity, or loss of pressure integrity due to sudden catastrophic failure from a crack in the pressure chamber that begins at a cavitation corrosion pit and rapidly propagates through the pressure containing wall of the pumping chamber. Cavitation usually initiates in predictable places such as, but not limited to, near the edge of a sealing surface, areas where there is a sudden drop in pressure that produces turbulent fluid flow, or at microscopic discontinuities in the surface of the metal grain and composition properties.

Cavitation occurs when there is a rapid drop in pressure in areas of turbulence, particularly at the beginning of the suction stroke on a reciprocating pump or on the trailing edge of an impeller style centrifugal pump. Small air bubbles are formed and the collapsing of the bubbles can reach boundary velocities high enough to erode the metal away, causing pitting. During the formation and collapse of these bubbles chemical changes also occur, due to the rapid phase change from a liquid to gas, and back from a gas to liquid which propagates the release of hydrogen ions. These hydrogen ions have a corrosive effect on the molecular structure of the metal, causing small particles of the metal to separate and enter into the fluid stream, contributing to further acceleration of the pitting process. These hydrogen ions cause the formation of hydrogen embrittlement cracks, which propagate during each pumping stroke of a reciprocating pump. Eventually this cracking begins to penetrate into the pressure containing wall and rapidly results in a structural failure of the pressure vessel.

In applications where a lot of fluid is pumped at high velocities, the maintenance costs due to cavitation erosion/corrosion can be a significant part of the operating costs. Eliminating cavitation is unrealistic due to the high pressures and rapid flow rates needed in many industries. An industry that experiences high costs of "expendables" is the well service frac industry. Due to governmental limitations on the weight and the width of vehicles that are allowed highway access, frac trucks used in the well service frac industry are made as light and as small as possible while still being able to achieve the pumping pressures and flow required. Designed to be as light as possible, the fluid end and its internal components of the pumps associated with such well service equipment can wear and fail quickly, due to erosion and corrosion. When pitting occurs in the pumping chamber of the fluid end, the stresses concentrate in the pit with the result that corrosion cracking is initiated and results in the failure of the fluid end to hold pressure. Replacing of fluid ends is one of the highest maintenance costs of the well service frac business. Obtaining a longer lasting fluid end and longer lasting valves, seats and packing is an important objective of this industry. Efforts are commonly made to either reduce the cavitation or to select materials that are more resistant to cavitation erosion and corrosion. Valves, seats and packing are also destroyed quickly due to erosion and corrosion, which are accelerated when cavitation occurs. Slowing the pump speed down can mitigate this problem, but due to the competitive nature of the business, and the demand for higher pressure operations, the pumps are run at high speeds, and cavitation is unavoidable at these speeds.

Raising the supercharge pressure to the inlet of the pump may reduce cavitation. Using a properly sized suction pulsation device can reduce cavitation. But with these solutions implemented in the industry, and with cavitation erosion/corrosion still causing expensive maintenance issues, the demand continues for equipment that will last longer so that operating costs can be further reduced. Summary

In a first aspect, embodiments are disclosed of a method that reduces cavitation damage to a component within a pump including mounting a sacrificial body within the pump and operating the pump to pump fluid at a rate that causes at least some cavitation to occur on the component, wherein the pumped fluid flows over the sacrificial body to shed electrons into the flowing fluid in the vicinity of the cavitation. Since the cavitation damage of a component having a sacrificial member is reduced as compared to component not having a sacrificial body, the sacrificial member advantageously extends the working life of the component beyond a component not having a sacrificial body mounted therein.

In certain embodiments, the sacrificial body includes a material that is more easily corroded than the component within a pump.

In yet other embodiments, during use, the operating step causes hydrogen ions to release from the component within the pump, the release of which is mitigated by the shedding of electrons from the sacrificial body.

In certain embodiments, the method includes attaching at least one needle to the sacrificial body to facilitate the shedding of electrons from the sacrificial body.

In other embodiments, in use the needle is pointing downstream.

In certain embodiments, the needle is formed of a metal that is less subject to corrosion than the sacrificial body.

In certain embodiments, the method further comprises the step of mounting an upstream portion of the sacrificial body into the pump, the sacrificial body having a profile to enhance turbulence of the fluid flowing over the sacrificial body.

In certain embodiments, the pump is positioned such that no portion of the pump is immersed in the fluid to be pumped by the pump. In certain embodiments, the sacrificial body is formed from one or more materials from the group comprising zinc, aluminum, magnesium or alloys thereof.

In certain embodiments, the turbulence created from mounting the sacrificial body in the component produces cavitation on a surface of the sacrificial body rather than allowing the cavitation bubbles to form on the component. The amount of purposely created cavitation bubbles and the resulting deterioration of the sacrificial body is related to the energy needed to overcome the energy consumed as a gas phase changes to a liquid and a liquid phase changes back to a gas during cavitation. The energy of the phase change demands the release of hydrogen ions, which is a corrosion phenomenon. The sacrificial body is made from materials that more readily release ions than does the steel of the fluid chamber; which directs the damaging cavitation corrosion pitting to the sacrificial body.

In yet another embodiment, the component includes a fluid end block having a chamber, a plunger bore leading to the chamber, a suction valve port leading to the chamber, and a discharge valve port passing from the chamber.

In certain embodiments, the method includes mounting the sacrificial body within the chamber.

In certain embodiments, the method includes mounting the sacrificial body stationarily within the plunger bore surrounding the plunger.

In certain embodiments, the method includes mounting the sacrificial body to the suction valve for movement therewith.

In certain embodiments, the method includes mounting the sacrificial body within the suction valve port upstream from a suction valve.

In another embodiment, the component includes a plunger in the plunger bore.

In yet another embodiment, the mounting step includes mounting a sacrificial body to the plunger. In certain of the embodiments, the component includes a housing having a rotatable impeller therein.

In certain of the embodiments, the method includes mounting the sacrificial body within the housing adjacent a periphery of the impeller.

In certain of the embodiments, the method includes mounting the sacrificial body to the impeller for rotation therewith.

In a second aspect, an embodiment is disclosed of a pump having a fluid end block containing a chamber, a plunger bore leading to the chamber, a suction valve port leading to the chamber, and a discharge valve port passing from the chamber. The suction and discharge valves are mounted for reciprocation within the suction valve port and discharge valve port, respectively. A sacrificial body is mounted within the fluid end block for immersion during use in the fluid flow as the plunger strokes. The sacrificial body is formed of a material less resistant to corrosion as compared to the fluid end block. The embodiment advantageously provides a pump having a targeted area of cavitation to mitigate cavitation on the fluid end block, which extends the working life of the fluid end block. Moreover, the sacrificial member targeted for cavitation can be replaced over the life of the fluid end block.

In certain embodiments, at least one needle is mounted to the sacrificial body, the needle in use being immersed in the flowing fluid and pointing in a downstream direction.

In certain embodiments, the needle is formed of a metal more resistant to corrosion due to the fluid flowing over the needle than the sacrificial body.

In certain of the embodiments, a profile configured to enhance turbulence is located on an upstream portion of the sacrificial body.

In certain embodiments, the sacrificial body is formed from one or more materials from the group comprising zinc, aluminum, magnesium or alloys thereof. In certain of the embodiments, the sacrificial body includes a sleeve mounted stationarily within the plunger bore surrounding the plunger.

In certain of the embodiments, the sacrificial body is mounted to a forward end of the plunger for movement therewith.

In certain of the embodiments, the sacrificial body is mounted to the suction valve for movement therewith.

In certain of the embodiments, the sacrificial body is mounted within the suction valve port upstream from the suction valve.

In a third aspect, an embodiment is disclosed of a pump including a housing, a rotatable impeller mounted within the housing, and a sacrificial body mounted within the housing for immersion within fluid flow as the impeller rotates during use. The sacrificial body formed of a material less resistant to corrosion due to the fluid flow than the impeller and the housing.

In certain of the embodiments, the sacrificial body is mounted to an interior portion of the housing adjacent a periphery of the impeller.

In certain of the embodiments, the sacrificial body is mounted to the impeller for rotation therewith.

In a fourth aspect, an embodiment is disclosed of an apparatus for retarding damage to a pump due to cavitation including a sacrificial body adapted to be mounted within the pump, the sacrificial body being formed of a material selected to shed electrons when immersed within a flowing fluid of the pump. At least one needle is mounted to the sacrificial body and formed of a material more resistant to corrosion due to the flowing fluid than the sacrificial body. In certain embodiments, the sacrificial body includes a sleeve having a profile formed on an exterior surface to enhance turbulence of fluid flowing over the sleeve, the profile adapted to be upstream of the at least one needle.

In certain embodiments, the sacrificial body includes a disk having a circular periphery and adapted to be mounted to an inner end of a plunger of the pump. The needle is mounted to a face of the disk in alignment with an axis of the disk.

In certain embodiments, the needle is recessed within a cavity formed in the face of the disk. A flow port extends through a portion of the disk to a base of the cavity for directing fluid to the needle.

In certain embodiments, the sacrificial body includes a ring adapted to be mounted to a downstream face of a suction valve of the pump. The needle is mounted to the face of the ring in alignment with an axis of the ring.

In certain embodiments, a flow port leads from one side of the ring to the face of the ring adjacent the needle, the flow port being outboard of an inner diameter of the ring.

In certain embodiments, the sacrificial body is mounted on a support rod. The support rod adapted to be mounted to an interior portion of the pump.

In certain of the embodiments, the sacrificial body is formed from of a material from the group consisting of zinc, aluminum, magnesium or alloys thereof.

Other aspects, features, and advantages will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, the principles disclosed. Description of the Fi2ures

The accompanying drawings facilitate an understanding of the various embodiments.

Figure 1 is sectional view of a fluid end of a reciprocating frac pump having a cavitation device in accordance with this disclosure.

Figure 2 is an enlarged sectional view of a portion of the cavitation device of Figure 1.

Figure 3 is a sectional view of a fluid end of a reciprocating pump having a second embodiment of a cavitation device.

Figure 4 is an enlarged sectional view of a portion of the cavitation device of Figure 3.

Figure 5 is a sectional view of a fluid end of a reciprocating pump having another embodiment of a cavitation device.

Figure 6 is an enlarged sectional view of a portion of the cavitation device of Figure 5.

Figure 7 is a sectional view of a fluid end of a reciprocating pump having another embodiment of a cavitation device.

Figure 8 is an enlarged sectional view of a portion of the cavitation device of Figure 7.

Figure 9 is a schematic view illustrating a centrifugal pump having a cavitation device in accordance with this disclosure.

Figure 10 is a schematic view of a centrifugal pump having another embodiment of a cavitation device in accordance with this disclosure. Detailed Description

Referring to Figure 1, a fluid end 11 illustrates one portion of a reciprocating pump of a type that is typically used in the well frac industry. The fluid end 11 is part of a surface mounted pump, typically mounted on a truck. The fluid end 11 is not submersed in the fluid to be pumped; rather a flowline leads to the fluid 11 to convey it to be pumped. The fluid end 11 includes a fluid end block 13 having a chamber 15. A plunger bore 17 intersects the chamber 15 on one side. A discharge valve port or passage 19 leads from the chamber 15; a suction on inlet port or passage 21 leads from the chamber 15 in a generally opposite direction. In this embodiment, the discharge and suction passages 19 and 21 are coaxial and perpendicular to the plunger bore 17, but they could be at different angles relative to each other and to the plunger bore 17.

A discharge valve 20 is shown located in the discharge passage 19. The discharge valve 20 is spring-biased to a closed position, and will open when the pressure in the chamber 15 is sufficiently high. A suction valve 22 is located in the suction passage 21. The suction valve 22 is biased to a closed position and will open when the pressure differential of the intake pressure over the pressure in the chamber 15 is sufficient to overcome the bias of the spring and allow fluid to be admitted to the chamber 15.

A flange connector 23 secures to the fluid end block 13 on one side around the plunger bore 17. A plunger 25 reciprocates within the flange connector 23 and the plunger bore 17 and strokes between an outer intake position and an inner discharge position by a conventional power source (not shown). A seal or packing assembly 27 is located in the flange connector 23 and sealingly engages the outer diameter of the plunger 25. A packing nut 29 secures to internal threads at the outer end of the flange connector 23. The packing nut 29, when rotated, preloads the packing 27 to provide a seal for the plunger 25. Normally, the fluid end block 13 will have three or five of the chambers 15, plungers 25, and sets of valves 20 and 22.

A device is shown for retarding the effects of cavitation includes a sacrificial body in the form of a sleeve 31 , which surrounds the plunger 25 and fits stationarily within the bore of the flange connector 23 and the plunger bore 17. As shown in Figure 2, the sleeve 31 has an inner diameter with a turbulence enhancing profile including one or more grooves 35 or other shapes that can disrupt laminar flow of fluid. In this example, the groove 35 is helical. The inner diameter of the sleeve 31 optionally may be in sliding contact with the outer diameter of the plunger 25. In this example, the sleeve 31 has an external flange 33 on its outer end that mates with a shoulder within the flange connector 23. The inner end or rim 40 of the sleeve 31 may be substantially flush with the inside wall of the chamber 15. Consequently, when the plunger 25 is in the full power stroke position, which will be to the right of the position shown in Figure 1, the inner end of the plunger 25 will be protruding farther into the chamber 15 than the rim 40 of the sleeve 31.

Referring still to Figure 2, bypass ports 37 extend through the sidewall of the sleeve 31. The inner end of each of the bypass ports 37 intersects one turn of the helical groove 35. The bypass ports 37 are spaced circumferentially around the sleeve 31 and along a portion of the length of the sleeve 31. In this embodiment, the outer diameter of the sleeve 31 is smaller than the inner diameter of the plunger bore 17, creating an annulus surrounding the sleeve 31. This arrangement causes some of the fluid being pushed by the plunger 25 during the inward or power stroke to flow through the bypass ports 37 and into the annulus between the outer diameter of the sleeve 31 and the plunger bore 17. A turbulence creating profile 38 on the outer diameter of the sleeve 31 may also include a helical groove or other shapes. The helical groove 35 and the ports 37 enhance turbulence and cause cavitation to occur in the annulus during the power stroke. The sacrificial body includes a number of needles 39 (only one shown) mounted around rim 40 of the sleeve 31. The turbulent fluid flowing out the annulus during the power stroke flows around them. Each of the needles 39 has a sharp tip and protrudes inward or downstream from the rim 40 into the chamber 15 (Fig. 1). Each of the needles 39 may be parallel to the axis of the plunger bore 17.

The sleeve 31 is a sacrificial body formed of a material or materials that has characteristics for easily releasing electrons. The material may be, for example, zinc, aluminum, magnesium or alloys of these metals. This material is of a less noble metal than the fluid end block 13, which is formed of a steel alloy. The material of the sleeve 31 has a lower electrochemical potential than the steel alloy of the fluid end block 13, thus the sleeve 31 will corrode more easily due to fluid flowing over it.

The needles 39 can be made of a metal more resistant than the metal of the sleeve 31 to mitigate corrosion and pitting of the needles. Thus the needles 39 will be of a material with a higher electrochemical potential than the sleeve 31. For example, the needles 39 may be formed of stainless steel. The metal of the base of each of the needles 39 will be in contact with the metal of the sleeve 31 such that the needles 39 and the sleeve 31 serve to shed or emit electrons from the sleeve 31 into the fluid flowing past the needles 39.

As mentioned, the sleeve 31 may have profiles to enhance cavitation, causing the formation and collapse of bubbles which, if unchecked, can result in chemical changes of the steel components, particularly the release of hydrogen ions. Hydrogen ions have a corrosive effect on the molecular structure of the metal of the fluid end block 13, causing small particles of the metal to separate and enter the fluid stream. This release of metal particles contributes to pitting. The release of negatively-charged electrons from the needles 39 mitigates the formation of hydrogen ions, which are also negatively charged. Because of the cavitation, erosion and corrosion will occur on the sleeve 31; however, it is intended to be expendable. The sleeve 31 is not connected to any voltage potential, rather releases electrons as a result of the turbulent fluid flowing over it.

Referring to Figures 3 and 4, in this second embodiment, the fluid end 41 has conventional discharge and suction valves 43, 45 as in the first embodiment. The fluid end 41 has a chamber 47, and a plunger 49 extends inward through a flange connector 51. In this embodiment, a disk 53 mounts to the inner end 57 of the plunger 49 to serve as a sacrificial body. Referring to Figure 4, a coaxial cylindrical recess 55 is formed in a plunger inner end 57. The disk 53 is secured within the recess 55, such as by a retainer ring 59. Small, cylindrical cavities 61 are formed within the face of the disk 53. Each of the cavities 61 has an open inner end exposed to chamber 47 (Figure 4), and a closed base. A needle 63 is secured in metal-to-metal contact in the base of each of the cavities 61. In this example, the needles 63 do not protrude past the face of the disk 53, rather are fully recessed. A bypass port 65 extends from an outer diameter of the plunger 49 into one of the cavities 61. The intersection of the bypass port 65 with the cavity 61 is near the base of the cavity 61. Although only a single one of the bypass ports 65 is shown, preferably other of the bypass ports 65 will connect the other cavities 61 to the outer diameter of the plunger 49.

As the plunger 49 strokes inward, the fluid will flow into each of the cavities 61, around one of the needles 63, then out one of the bypass ports 65 to the outer diameter of the plunger 49. The swirling fluid causes cavitation to occur as it flows around the needles 63. The components of the needles 63 and the disk 53 may be the same materials as in the first embodiment to facilitate the shedding of electrons for the same purpose as discussed above.

Referring to Figure 5, a fluid end 67 is constructed generally as in the first two embodiments. The fluid end 67 has a chamber 69 and discharge and suction valves 71, 73. A plunger 75 extends into the chamber 69 from one side. Discussing the suction valve 73 in more detail, the body of the suction valve 73 has a seal 77 that may be of conventional design. The suction valve 73 is biased by a spring 79 to force the seal 77 into sealing engagement with a seat 81. The seat 81 is a cylindrical member having a sealing surface on its inner edge or rim. Referring to Figure 6, the body of the valve 73 has an outer diameter 83 and an inner or upper end 85. An annular recess 87 is formed at a junction of the inner end 85 and the outer diameter 83. A sacrificial body comprising a ring 89 is mounted in the recess 87. The outer diameter of the ring 89 is flush with the outer diameter 83, and the inner end of the ring 89 is flush with the valve body inner end 85.

The ring 89 has a plurality of needles 91 (only one shown) mounted to its face. The needles 91 extend inward, parallel with an axis of the seat ring 81. The needles 91 protrude inward past the inner end 85 of the suction valve 73. The ring 89 and the needles 91 may be formed of the same materials as the first embodiment for emitting electrons. To facilitate the cavitation occurring in the vicinity of the needles 91, a number of bypass ports 93 (only one shown) extend obliquely from the inner side of the ring 89. Each of the bypass ports 93 also extends to the valve body outer diameter 83 so that the bypass port 93 is located outboard of the inner side of the ring 89 and functions to place the valve outer diameter 83 and the upper end 85 in fluid communication. As the valve 73 strokes toward and away from the seat 81, fluid will be forced through the bypass ports 93 and around the needles 91. Preferably one of the bypass ports 93 will be located adjacent each of the needles 91.

Another embodiment is illustrated in Figures 7 and 8. A fluid end 95 has the same general construction as in the other embodiments. The fluid end 95 has a chamber 97, discharge and suction valves 99, 101 and a plunger 103. In this example, a sacrificial body 105 is located near the base or lower end of the suction valve 101. The sacrificial body 105 is a block of electron emitting material mounted to a curved support rod 107, which may be bent into a desired position. The support rod 107 has an axially extending portion that positions the sacrificial body 105 within the seat ring 109. In this example, the support rod 107 is bent into a right angle and has a mounting plug 111 on its outer end. The plug 111 secures to a flange port 113 that extends through a intake fluid end 114. The plug 111 seals the flange port 113 to prevent fluid from passing through the port 113. The sacrificial body 105 is spaced from contact with any portion of the suction valve 101.

As shown in Figure 8, the sacrificial body 105 has one or more needles 115 that face upward. The needles 115 are subjected to fluid flow by bypass ports 117 extending through the sacrificial body 105. In this embodiment, at least two of the needles 115 are mounted to the sacrificial body 105. A portion of the fluid flowing upward toward the suction valve 101 will be diverted through the bypass passages 117 to flow around the needles 115. The sacrificial body 105 is formed of a metal that is good at shedding electrons, as previously discussed. Electrons will inhibit hydrogen ions being formed that could otherwise result in pitting of the body of the seat 109 and the valve 101.

At least some of the embodiments for the reciprocating pumps illustrated in Figures 1- 8 may be combined with others. For example, the embodiments dealing with pitting of the valves, shown in Figures 5 - 8, could be employed in connection with one of the devices shown in Figures 1-4. Similarly, an arrangement to avoid pitting of the valves may be employed with the discharge valve in the same manner as employed with the suction valve.

Referring to Figure 9, a different type of pump 119 is illustrated. Pump 119 is a centrifugal pump having a housing 121 with an outlet 123. The inlet is not shown. One or more impellers 125 is mounted in the housing 121 and rotates relative to the housing 121. Each of the impellers 125 has a hub 127 about which the impeller 125 is rotated via a shaft (not shown). Each of the impellers 125 has a plurality of vanes 129 that spiral outward from the hub 127. The spaces between the vanes 129 include passages for fluid that enters near the hub 127. The fluid flows outward and discharges through the outlet 123. In this embodiment, a number of sacrificial bodies 131 are mounted stationarily around the inner wall of the housing 121. The sacrificial bodies 131 include needles 135 that point generally in a downstream direction so that fluid flowing past will collect electrons to suppress hydrogen ions that might otherwise occur in the vicinity of the inner wall of the housing 121. In this example, the sacrificial body 131 has a mounting portion shown on the exterior of the housing 121. The mounting portion could be located within the interior. Also, the inner wall of the housing 121 could include a portion of a diffuser for each of the impellers 125. As in the other embodiments, the sacrificial bodies 131 are formed of a sacrificial metal for shedding electrons into the fluid flow.

In the embodiment of Figure 10, a centrifugal pump 137 is also schematically shown to include a housing 139 and an impeller 140. In this embodiment, sacrificial bodies 141 are mounted to several vanes 145 for rotation therewith. Each of the sacrificial bodies 141 includes a needle 143 that points in a direction opposite to the direction of rotation of the impeller 140, as shown by the arrow. The sacrificial bodies 141 are formed of a material for shedding electrons as previously discussed in connection with the other embodiments.

The various embodiments in Figures 1-10 disclose sacrificial bodies that corrode as a result of fluid flowing over them. The corrosion of the sacrificial bodies releases electrons into the fluid flow that inhibit corrosion of more expensive components of the pumps, such as fluid end blocks and housings. The sacrificial bodies are readily replaced and inexpensive.

In the foregoing description of certain embodiments, specific terminology has been resorted to for the sake of clarity. However, the disclosure is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes other technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as "left" and right", "front" and "rear", "above" and "below" and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms.

In this specification, the word "comprising" is to be understood in its "open" sense, that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense of "consisting only of. A corresponding meaning is to be attributed to the corresponding words "comprise", "comprised" and "comprises" where they appear.

In addition, the foregoing describes only some embodiments of the disclosure, and alterations, modifications, additions and/or changes can be made thereto without departing from the scope and spirit of the disclosed embodiments, the embodiments being illustrative and not restrictive.

Furthermore, the disclosure has been described in connection with what are presently considered to be the most practical and preferred embodiments. It is to be understood that the disclosure is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the disclosure. Also, the various embodiments described above may be implemented in conjunction with other embodiments, e.g., aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments. Further, each independent feature or component of any given assembly may constitute an additional embodiment.

Claims

Claims:

1. A method of reducing cavitation damage to a component within a pump, comprising:

(a) mounting a sacrificial body within the pump; and

(b) operating the pump to pump fluid at a rate that causes at least some cavitation to occur on the component,

wherein the pumped fluid flows over the sacrificial body to shed electrons into the flowing fluid in the vicinity of said cavitation.

2. The method according to claim 1, wherein the sacrificial body comprises a material that is more easily corroded than the component.

3. The method according to claim 1, wherein in use the operating step causes hydrogen ions to release from the component, the release of which is mitigated by said shedding of electrons from the sacrificial body.

4. The method according to claim 1, further comprising attaching at least one needle to the sacrificial body to facilitate the shedding of the electrons from the sacrificial body.

5. The method according to claim 4, wherein in use the needle is pointing downstream.

6. The method according to claim 4, wherein the needle is formed of a metal that is less subject to corrosion than the sacrificial body.

7. The method according to claim 1, further comprising the step of mounting an upstream portion of the sacrificial body into the pump, the sacrificial body having a profile to enhance turbulence of the fluid flowing over the sacrificial body.

8. The method according to claim 1, wherein the pump is positioned such that no portion of the pump is immersed in the fluid to be pumped by the pump.

9. The method according to claim 1, wherein the sacrificial body is formed from one or more materials from the group comprising zinc, aluminum, magnesium or alloys thereof.

10. The method according to claim 1, wherein the component comprises a fluid end block having a chamber, a plunger bore leading to the chamber, a suction valve port leading to the chamber, and a discharge valve port passing from the chamber.

11. The method according to claim 10, wherein step (a) comprises mounting the sacrificial body within the chamber.

12. The method according to claim 10, wherein step (a) comprises mounting the sacrificial body stationarily within the plunger bore surrounding the plunger.

13. The method according to claim 10, wherein step (a) comprises mounting the sacrificial body to the suction valve for movement therewith.

14. The method according to claim 10, wherein step (a) comprises mounting the sacrificial body within the suction valve port upstream from a suction valve.

15. The method according to claim 10, wherein the component comprises a plunger in the plunger bore.

16. The method according to claim 15, wherein step (a) comprises mounting a sacrificial body to the plunger.

17. The method according to claim 1, wherein the component comprises a housing having a rotatable impeller therein.

18. The method according to claim 17, wherein step (a) comprises mounting the sacrificial body within the housing adjacent a periphery of the impeller.

19. The method according to claim 17, wherein step (a) comprises mounting the sacrificial body to the impeller for rotation therewith.

20. A pump, comprising:

a fluid end block having a chamber, a plunger bore leading to the chamber, a suction valve port leading to the chamber, and a discharge valve port passing from the chamber; suction and discharge valves mounted for reciprocation within the suction valve port and discharge valve port, respectively;

a sacrificial body mounted within the fluid end block for immersion during use in fluid flow; and

the sacrificial body being formed of a material less resistant to corrosion as compared to the fluid end block.

21. The pump according to claim 20, further comprising at least one needle mounted to the sacrificial body, the needle being immersed in use in the fluid flow.

22. The pump according to claim 21, wherein the needle is formed of a metal more resistant to corrosion than the sacrificial body.

23. The pump according to claim 20, further comprising a profile configured to enhance turbulence.

24. The pump according to claim 23, wherein the profile being located on an upstream portion of the sacrificial body.

25. The pump according to claim 20, wherein the sacrificial body is formed from one or more materials from the group comprising zinc, aluminum, magnesium or alloys thereof.

26. The pump according to claim 20, wherein the sacrificial body comprises a sleeve mounted stationarily within the plunger bore surrounding the plunger.

27. The pump according to claim 20, wherein the sacrificial body is mounted to a forward end of the plunger for movement therewith.

28. The pump according to claim 20, wherein the sacrificial body is mounted to the suction valve for movement therewith.

29. The pump according to claim 20, wherein the sacrificial body is mounted within the suction valve port upstream from the suction valve.

30. A pump, comprising:

a housing;

a rotatable impeller mounted within the housing;

a sacrificial body mounted within the housing for immersion within fluid flow as the impeller rotates during use; and

the sacrificial body formed of a material less resistant to corrosion than the impeller and the housing.

31. The pump according to claim 30, wherein the sacrificial body is mounted to an interior portion of the housing adjacent a periphery of the impeller.

32. The pump according to claim 30, wherein the sacrificial body is mounted to the impeller for rotation therewith.

33. An apparatus for retarding damage to a pump due to cavitation, comprising:

a sacrificial body adapted to be mounted within the pump, the sacrificial body being formed of a material selected to shed electrons when immersed within a flowing fluid of the pump; and

at least one needle mounted to the sacrificial body and formed of a material more resistant to corrosion due to the flowing fluid than the sacrificial body.

34. The apparatus according to claim 33, wherein the sacrificial body comprises a sleeve having a profile formed on an exterior surface to enhance turbulence of fluid flowing over the sleeve in use, the profile adapted to be upstream of the at least one needle.

35. The apparatus according to claim 33, wherein the sacrificial body comprises a disk having a circular periphery and adapted to be mounted to an inner end of a plunger of the pump, wherein the at least one needle is mounted to a face of the disk in alignment with an axis of the disk.

36. The apparatus according to claim 35, wherein the at least one needle is recessed within a cavity formed in the face of the disk and a flow port extends through a portion of the disk to a base of the cavity for directing fluid to the needle.

37. The apparatus according to claim 33, wherein the sacrificial body comprises a ring adapted to be mounted to a downstream face of a suction valve of the pump, wherein the at least one needle is mounted to the face of the ring in alignment with an axis of the ring.

38. The apparatus according to claim 37, further comprising a flow port leading from one side of the ring to the face of the ring adjacent the at least one needle, and the flow port being outboard of an inner diameter of the ring.

39. The apparatus according to claim 33, further comprising a support rod upon which the sacrificial body is mounted and the support rod is adapted to be mounted to an interior portion of the pump.

40. The apparatus according to claim 33, wherein the sacrificial body is formed from of a material from the group consisting of zinc, aluminum, magnesium or alloys thereof.