Branch fitting for reducing stress caused by acoustic induced vibration

Abstract

A contoured branch fitting for reducing stress in a header pipe caused by acoustic induced vibration that includes a maximum width, a maximum length, a thickness that is greater along the maximum length and a constant radius between the branch connection and the header connection.

Claims

1. A branch fitting, which comprises: a maximum width (MW); a maximum length (ML), wherein the ML is at least 1.10 times longer than the MW; a maximum height (MH); a constant inside radius (BR.sub.i) between a branch connection for the branch fitting and a header connection for the branch fitting; a constant outside radius (BR.sub.o) between the branch connection and the header connection; wherein the branch fitting at the branch connection includes an outside diameter (d.sub.o) and a header pipe at the header connection includes an inside radius (HR.sub.i) and a thickness (T); and wherein the MW=(d.sub.o0.04(d.sub.o.sup.2)) (2+0.14(HR.sub.i+T)0.0024(HR.sub.i+T).sup.2).

2. The branch fitting of claim 1, wherein the ML is no greater than three times the MH.

3. The branch fitting of claim 1, wherein the BR.sub.i=X(d.sub.o) and X is at least 0.5.

4. The branch fitting of claim 3, wherein X is no greater than 1.5.

5. The branch fitting of claim 1, wherein the BR.sub.o=Y(BR.sub.i) and Y is at least 0.5.

6. The branch fitting of claim 5, wherein Y is no greater than 3.0.

7. The branch fitting of claim 1, wherein the MH is no greater than the BR.sub.o.

8. The branch fitting of claim 1, wherein the MH=A(BRi) and A is at least 1.1.

9. The branch fitting of claim 8, wherein A is no greater than 1.5.

10. The branch fitting of claim 1, wherein the ML=Z(BR.sub.o) and Z is at least 2.5.

11. The branch fitting of claim 10, wherein Z is no greater than 4.0.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The detailed description is described with reference to the accompanying drawings, in which like elements are referenced with like reference numbers, and in which:

(2) FIG. 1 is a plan view for one embodiment of a contoured branch fitting according to the present disclosure illustrating a maximum width and a maximum length of the branch fitting.

(3) FIG. 2 is a cross-sectional side-view of the branch fitting along 2-2 in FIG. 1 illustrating the branch fitting attached to a header pipe.

(4) FIG. 3 is a cross-sectional front-view of the branch fitting along 3-3 in FIG. 1 illustrating the branch fitting attached to the header pipe.

(5) FIG. 4 is a graphical display comparing simulated sound power levels in the same header pipe for a contoured branch fitting according to FIG. 1 and a conventional contoured branch fitting as a function of a ratio between the inside diameter of the header pipe and the thickness of the header pipe.

(6) FIG. 5 is a graphical display comparing real stress measurements over time for a six (6) inch contoured branch fitting according to FIG. 1 and a conventional six (6) inch contoured branch fitting attached to the same header pipe.

(7) FIG. 6 is a graphical display comparing real stress measurements over time for a four (4) inch contoured branch fitting according to FIG. 1 and a conventional four (4) inch contoured branch fitting attached to the same header pipe

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

(8) The subject matter disclosed herein is described with specificity, however, the description itself is not intended to limit the scope of the disclosure. The subject matter thus, might also be embodied in other ways, to include different structures, steps and/or combinations similar to and/or fewer than those described herein, in conjunction with other present or future technologies. Although the term step may be used herein to describe different elements of methods employed, the term should not be interpreted as implying any particular order among or between various steps herein disclosed unless otherwise expressly limited by the description to a particular order. Other features and advantages of the disclosed embodiments will thus, be or become apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such features and advantages be included within the scope of the disclosed embodiments. Further, the illustrated figures are only exemplary and are not intended to assert or imply any limitation with regard to the environment, architecture, design, or process in which different embodiments may be implemented. Thus, the embodiments disclosed herein may be implemented in many different piping systems to achieve the results described herein. To the extent that temperatures and pressures are referenced in the following description, those conditions are merely illustrative and are not meant to limit the disclosure.

(9) The contoured branch fitting embodiments disclosed herein overcome one or more of the prior art disadvantages by reducing stress in a header pipe caused by acoustic induced vibration through a branch fitting that includes a maximum width, a maximum length, and a constant radius between the branch connection and the header connection.

(10) In one embodiment, a contoured branch fitting is disclosed, comprising: i) a maximum width (MW); ii) a maximum length (ML), wherein the ML is at least 1.10 times longer than the MW; iii) a maximum height (MH); iv) a constant inside radius (BRi) between a branch connection for the branch fitting and a header connection for the branch fitting; v) a constant outside radius (BRo) between the branch connection and the header connection; vi) wherein the branch fitting at the branch connection includes an outside diameter (d.sub.o) and a header pipe at the header connection includes an inside radius (HR.sub.i) and a thickness (T); and vii) wherein the MW=(d.sub.o0.04(d.sub.o.sup.2)) (2+0.14(HR.sub.i+T)0.0024(HR.sub.i+T).sup.2).

(11) Referring now to FIG. 1, a plan view illustrates a maximum width MW and a maximum length ML for one embodiment of a contoured branch fitting 100 according to the present disclosure. The maximum length ML is at least 1.10 times longer than the maximum width MW. The branch fitting 100 may be used on any size header pipe, however, preferably having a diameter between 3 inches and 48 inches. The branch fitting 100 may be forged from any sustainable metal however, preferably includes A105N carbon steel, A350 LF2 carbon steel or A182 F304/304L stainless steel to match the header pipe material. The branch fitting 100 is welded in place using a butt weld.

(12) Referring now to FIG. 2, a cross-sectional side-view of the branch fitting 100 along 2-2 in FIG. 1 illustrates the branch fitting 100 attached to a header pipe 202. The branch fitting 100 includes a maximum height MH, an inside radius BR.sub.i and an outside radius BR.sub.o. The inside radius BR.sub.i and the outside radius BR.sub.o are constant between a branch connection 204 for the branch fitting 100 and a header connection 206 for the branch fitting 100. The outside radius BR.sub.o is preferably at least half the size of the inside radius BR.sub.i but no greater than 3 times the size of the inside radius BR.sub.i. The maximum length ML of the branch fitting 100 is preferably no greater than three times the maximum height MH. And, the maximum height MH of the branch fitting 100 is preferably no greater than the outside radius BR.sub.o. The maximum height MH of the branch fitting 100 is also preferably 1.1 times the size of the inside radius BR.sub.i but no greater than 1.5 times the size of the inside radius BR.sub.i. The maximum length ML of the branch fitting 100 is at least 2.5 times the size of the outside radius BR.sub.o but no greater than 4 times the size of the outside radius BR.sub.o.

(13) Referring now to FIG. 3, a cross-sectional side-view of the branch fitting 100 along 3-3 in FIG. 1 illustrates the branch fitting 100 attached to the header pipe 202. The branch fitting 100 at the branch connection 204 includes a predetermined outside diameter d.sub.o and a predetermined inside diameter d.sub.i. The header pipe 202 at the header connection 206 includes a predetermined inside radius HR.sub.i and a predetermined thickness T. The inside radius BR.sub.i is preferably at least half the size of the outside diameter d.sub.o but no greater than 1.5 times the size of the outside diameter d.sub.o. The maximum width MW may be calculated using equation
MW=(d.sub.o0.04(d.sub.o.sup.2))(2+0.14(HR.sub.i+T)0.0024(HRi+T).sup.2).(1)

(14) The branch fitting 100 reduces stress in the header pipe 202 at the header connection 206 caused by AIV when fluid is transmitted through the header pipe 202 connected to the branch fitting 100 because the inside radius BR.sub.i and the outside radius BR.sub.o are constant between the branch connection 204 and the header connection 206. In this manner, a sound power level of at least 168 dB may be maintained in the header pipe 202 when a ratio between the inside diameter HRi of the header pipe 202 and the thickness T of the header pipe 202 is at least 30. The stress caused by shell mode vibration, such as AIV, is proportional to this ratio. In FIG. 4, a graphical display illustrates a comparison of simulated sound power levels (PWL) in the same header pipe attached to a contoured branch fitting according to FIG. 1 and a conventional contoured branch fitting as a function of a ratio between the inside diameter of the header pipe and the thickness of the header pipe (D/T). For the contoured branch fitting according to FIG. 1, the sound power level may be maintained at slightly above 180 dB when the ratio is 32. And, the sound power level may be maintained at 168 dB when the ratio is 128. By comparison, the sound power levels for the contoured branch fitting according to FIG. 1 are significantly higher than the sound power levels for the conventional contoured branch fitting over a broad range of ratios.

(15) Branch connections with rounded edges are successful in addressing flow-induced-acoustic-resonance (AR) issues by stabilizing the shear layer thereby, reducing vortex excitation. The inside radius BR.sub.i of the curvature is thus, designed first in order to minimize flow-induced AR. Then, the outside radius BR.sub.o of the curvature is designed in order to reduce AIV and internal static pressure. Once the inside radius BR.sub.i and the outside radius BR.sub.o are designed, the maximum width MW is determined using equation (1) because the curvature of the contoured branch fitting needs to be tangent to the curvature of the header pipe. Once the inside radius BR.sub.i, the outside radius BR.sub.o, and the maximum width MW are determined, the maximum height MH and the maximum length ML are determined based on the outside diameter d.sub.o of the branch fitting 100 at the branch connection 204. A slant angle 208 is selected to reduce the maximum height MH and the maximum length ML. Based on these design criteria, the maximum height is 1.68 times the outside diameter d.sub.o of the branch fitting 100 at the branch connection 204. If the outside diameter d.sub.o of the branch fitting 100 at the branch connection 204 is 20 inches, then the maximum height MH could be about 34 inches. Using a slant angle between 10 and 20 degrees can therefore, significantly reduce the maximum height MH and the maximum length ML without compromising the reduction of stress in the header pipe 202 caused by AIV. As demonstrated herein, the unique design of the branch fitting 100 reduces stress in the header pipe 202 caused by AIV when fluid is transmitted through the header pipe 202.

EXAMPLES

(16) In FIG. 5, a graphical display is illustrated comparing real stress measurements over time for a four (4) inch contoured branch fitting according to FIG. 1 and a conventional four (4) inch contoured branch fitting attached to the same header pipe. In FIG. 6, a graphical display is illustrated comparing real stress measurements over time for a four (4) inch contoured branch fitting according to FIG. 1 and a conventional four (4) inch contoured branch fitting attached to the same header pipe. In each example, an average pressure of approximately 1580 psig was recorded upstream of the relief valve during pseudo steady-state conditions. To maintain this upstream pressure, an average flowrate of approximately 84 mmscfd was maintained-resulting in a sound power level of approximately 163 dB. As demonstrated by these examples, the contoured branch fitting according to FIG. 1 results in less stress than the conventional contoured branch fitting during the same AIV. In FIG. 5, an average stress reduction of 25% to 50% was recoded between the contoured branch fitting according to FIG. 1 and the conventional contoured branch fitting. In FIG. 6, an average stress reduction of 30% to 50% was recoded between the contoured branch fitting according to FIG. 1 and the conventional contoured branch fitting.

(17) The contoured branch fittings disclosed herein accommodate higher sound power levels along with all design loading, without compromising project cost and schedule. Besides reducing stress in the header pipe caused by AIV, the contoured branch fittings also avoid vortices, another fluid structure interaction issue commonly found in piping systems. The contoured branch fittings thus, reduce stress concentration and vortex shedding frequencies, while adhering to industry codes and standard requirements. The contoured branch fittings provide an integrated solution to piping vibration that will help engineering and construction projects with cost and schedule completions, and avoid expensive re-work on existing projects.

(18) While the present disclosure has been described in connection with presently preferred embodiments, it will be understood by those skilled in the art that it is not intended to limit the disclosure to those embodiments. It is therefore, contemplated that various alternative embodiments and modifications may be made to the disclosed embodiments without departing from the spirit and scope of the disclosure defined by the appended claims and equivalents thereof.