US2639127A - Return bend for fired coils - Google Patents

Description

May 19, 1953 H. M, BECNEL 2,639,127

RETURN BEND FOR FIRED cons I Filed NOV. 30, 1950 D ECTION Flow Herman. m. becfael ins/ember abhor-nag Patented May 19, 1953 RETURN BEND FOR FIRED COILS Herman M. Becnel, Baton Rouge, La., assignor to Standard Oil Development Company, a corporation of Delaware Application November 30, 1950, Serial No. 198,288

7 3 Claims.

This invention relates to headers or return bends especially intended for distillation or cracking furnace coils and relates more particularly to closure devices for such return bends.

In pipe stills for cracking and/or distilling petroleum oils return bends are often provided which serve as headers for a plurality of tubes. Often two or more tubes discharge into the header and two or more discharge therefrom. It is quite usual for more tubes to be used on the outlet side than on the inlet side. For example, a five tube header may be used in which two tubes carry the oil into the header and three tubes carry the oil away. In such installations it has been the practice to provide deflector plugs opposite the outside inlet tube and the outside outlet tube to facilitate the flow of oil. The remainder of the header surface has usually been fiat or nearly so. It is also usual to provide plugs with fiat internal surfaces opposite each of the internal inlet and outlet tubes. However, it has een found that with this type of construction stream line fiow is established in the header with the result that centrifugal separation of vapor and liquid occurs in the header and the liquid to vapor ratio in the exit tubes is unequal. This further results in severe coking of one or more tubes because of the presence of lesser amount of liquid.

It is therefore the main object of this invention to provide an improved construction for return bend fittings of the character described, including a removable curved deflector plug at the end of each pipe section whereby turbulence is promoted and liquid/vapor ratio is maintained the same for each exit tube.

It is a further object of this invention to provide means whereby the coking of certain exit tubes due to unequal supply of liquid is avoided.

The foregoing enumerated objects and the ad'- vantages inherent in the invention will all be more readily comprehended from the following detailed description of the accompanying draw- Referring to this drawing, I is a return bend or header having a body portion with a return bend bore I l, which is provided with a plurality of orifices [2, I3, l4, l5 and I6 adapted to receive the ends of tubes (not shown). The opposite wall of the header II], at points substantially in alignment with orifices l2, l3, I4, [5 and N5 is provided with bores or openings I1, I 8, l9, 2|] and 2| which communicate with channel H and thus provide access to the tubes for the periodical cleaning especially necessary in oil cracking as crude distillation fired coils.

The bores 11, it, 19, 20 and 2| are intended to receive disclosure members or plugs 22, 23, 24, 25 and 26. These plugs are of a deflector type wherein the inner ends are provided with a curved surface. Outside plugs 22 and 2 B are formed with the surface curved in the direction of oil flow, while inside plugs 23, 24 and 25 have their inner curved surfaces oriented in the same direction as outside plug 2-6. In the drawing orifices l2 and it receive the oil being introduced to the header, while orifices l4, l5 and I6 are exit ports for the discharge of oil. It follows that plug 23 opposite orifice l3 has its curved surface oriented in a direction opposite to the oil flow. It has been the practice to provide headers with outside plugs of the type of 22 and 26 for the purpose of creating stream line flow and consequent reduced corrosion at these points, but heretofore it has not been considered necessary or desirable to provide inner plugs such as 23, 24 and 25 with curved surfaces. According to the present invention, however, it has been found that turbulence, accompanied by vapor/liquid mixing, is readily promoted by the provision of curved surfaces on the inside of the center plugs. Further in connection with the invention it has been found particularly desirable in more instances to progressively decrease the radius of curvature of the inside surface of plugs 23, 24 and 25 in the direction of oil flow.

In order that the closure elements or plugs 22, 23, fi l, 25 and 26 may be properly positioned in the bores 11, I8, I51, 20 and 2|, each closure member or plug is preferably provided with a radially disposed extension or lug 21.

The nature of the present invention having been thus fully set forth and specific examples of the same given, what is claimed as new and useful and desired to be secured by Letters Patent is:

1. Improved return bend header comprising a header provided with a passage having a plurality of inlet and outlet orifices located in one wall communicating with said passage having a plurality of openings communicating with said passage on the opposite wall, closure plugs in said openings extending into said passage, said closure plugs being characterized by the two outside plugs having a surface curved to conform with the direction of fiow with respect to said orifices, said intermediate closure plugs having an inner surface curvature oriented in the same direction as the curvature of said outside plug opposite the exit orifice.

2. Apparatus as defined by claim 1 wherein the extent said closure plugs extend into said passage 3 decreases in the direction away from said closure References Cited in the tile 0! this patent plug opposite said exit orifice. TED NTS 3. Apparatus as defined by claim 2 wherein the UNI STATES FATE curvature of the ends of sad closure plugs within Number Name Date said passage decreases in the direction away from 5 337-582 Ordway 1906 said plug opposite the exit orifice. 1,655,053 Fleming 1923 2,174,893 Praeger et a1. Oct. 3, 1939 HERMAN M. BECNEL.

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