Jet pump slip joint with axial grooves

Abstract

A uniform leakage flow device for the slip point of piping systems, and particularly in reactor pressure vessels, selectively imposes a steady, uniform flow of fluid through the slip joint between two adjacent pipe surfaces to thereby eliminate the detrimental flow-induced vibration associated with the unsteady and non-uniform leakage of fluid through the slip joint field. The uniform leakage flow device comprises a plurality of axial grooves that are formed in the wall surface of the slip joint.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001]This application is a non-provisional application claiming priority to provisional patent application Ser. No. 60 / 834,929 filed Aug. 2, 2006.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]This invention relates generally to tubular jet pumps used in various industries to transport and / or circulate cooling liquid in heat-generating systems, such as nuclear reactors and hydroelectric generation systems. More particularly, this invention relates to means for uniformly controlling the leakage flow rate through a slip joint to thereby eliminate detrimental vibration in the slip joints of such jet pumps.[0004]2. Description of Related Art[0005]Pipes, tubes and cylinders are used to transport a variety of fluids, such as water, oil, and liquid chemicals in various industries including the nuclear industry, the electric power industry, such as for internal components of heat exchangers, the hydroelectric power generation industry...

AI Technical Summary

Benefits of technology

[0020]Further, in known slip joint structures, both the total leakage flow and the leakage flow around the annulus and within the slip joint varied depending on the relative position of the mating parts. Non-uniform slip joint leakage flow, in both the total flow and peripheral flow, incurred time-varying lateral forces on the mating parts of the slip joint. These time-varying lateral forces incurred relative motion of the mating parts. This relative motion lead to increased non-uniform flow and higher fluid forces that, in turn lead to higher levels of vibration and wear of the mating jet pump components. This spiraling condition lead to higher and higher vibration levels of the mating parts. The axial grooves of the present invention impose uniform leakage flow at the slip joint location. The imposed uniform leakage flow does not change in its total amount, nor periphery within the slip joint annulus due to relative motion of the slip joint mating parts. The uniform leakage flow cannot incur net, time-varying lateral fluid forces that cause detrimental vibration and relative lateral motion of the slip joint mating parts.

[0021]The placement of axial grooves in the slip joint reduces or eliminates non-uniform or unsteady leakage flow through the slip joint and thereby reduces or eliminates vibration levels associated with non-uniform or unsteady slip joint leakage flow. The present invention provides the further advantage of allowing axial movement between the jet pump components and supporting structure to accommodate thermal expansion in the jet pump assembly, and does not impose undue stress in the inlet mixer. The present invention also eliminates the use of structures, such as clamps and the like, which present a potential detriment of having loose parts moving in the jet pump assembly, recirculation system or reactor core. These and other advantages of the present invention will become more clear in light of the following detailed description.

Problems solved by technology

Recent engineering experience has shown that if a sufficient pressure gradient exists across these slip joint interfaces, the connecting tubular components may incur detrimental flow-induced vibration, and failure results from either excessive wear or fatigue of the piping material or support / restraining apparatus.

Excessive leakage flow, however, can cause oscillation motion in the slip joint, which is a source of detrimental vibration excitation in the jet pump assembly.

Additional detrimental conditions that may lead to damaging vibration between the inlet mixer and diffuser of the jet pump assembly are well-known, such as loss of the set screw support in a jet pump assembly as described in U.S. Pat. No. 6,394,765 to Erbes, et al.

The resultant increased vibration levels and corresponding vibration loads on the piping and supports can cause jet pump component degradation from wear and fatigue.

High levels of flow-induced vibration (FIV) are possible in some jet pump designs at some abnormal operational conditions having increased leakage flow rates.

Each of the previously disclosed inventions has demonstrated some characteristic which has rendered the device or method insufficient in producing effective reduction of slip joint-induced vibration, and none has been directed to providing a means for selectively controlling leakage flow rate through the slip joint to ameliorate the damaging effects of excessive leakage flow rate through the slip joint.

In addition, those devices and methods that impose a lateral force on the slip joint also prevent axial movement in the slip joint, which does not properly allow for thermal expansion in the slip joint.

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