Pump Cavitation Device

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

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims priority to provisional patent application Ser. No. 61 / 355,878, filed Jun. 17, 2010.TECHNICAL FIELD[0002]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[0003]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 ...

AI Technical Summary

Benefits of technology

[0007]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.

[0013]In certain embodiments, the method step of mounting an upstream portion of the sacrificial body into the pump, provides a sacrificial body having a profile to enhance turbulence of the fluid flowing over the sacrificial body.

[0028]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.

[0041]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.

Problems solved by technology

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.

Small air bubbles are formed and the collapsing of the bubbles can reach boundary velocities high enough to erode the metal away, causing pitting.

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 propogate 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.

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.

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.

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.

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