US2217000A - Fluid conduit - Google Patents

Description

@a & EQ FFQQ M. W. BARNES FLUID CONDUIT.

Filed NOV. 26, 19.37

INVENTOR MARION W. BARNES 04% ATTORNEY FIG.

Patented Oct. 8, 1940 UFFH FLUID CONDUIT Marion W. Barnes, Chicago, Ill, assignor to Universal Oil Products Company, Chicago, Ill a corporation of Delaware Application November 26, 1937, Serial No. 176,547

2 Claims. (Cl. 285-56) This invention particularly refers to improvements in fluid conduitssuch as tube banks for furnaces, heatexchangers and the like, of the type wherein the tubular elements are expanded 5 at their ends into headers or return bends by rolling.

The utility and primary objects of the invention can be best explained by a brief review of the art which has preceded the invention.

It has long been the practice to provide tube headers or return bends with sharp shouldered grooves in the port into which the tube is rolled and to provide a flare or pronounced taper at the inner end of the port over which the end of the w tube is flared or belled. With the advent of tubes for high temperature service, containing alloying elements which materially increase the hardness of the metal or which have a hard coating or surface, the rolling required to sumciently de- 2d form the metal of the tube walls and obtain a good fit between the same and the grooved walls of the tube port resulted in considerable cracking in the rolled walls of the tube, particularly at its flared end. If rolling of this type of tube is stopped before cracks develop, the expanded tube will not fit closely into the grooves and, even with tubes of this type which have been heattreated at their ends to soften the same, facilitate rolling and prevent pronounced cracking, it

80 has been found that rapid corrosion occurs at the rolled ends of [the tubes when they are subjected to corrosive conditions ordinarily present, for example, in cracking service.

This difficulty is only partially overcome by eliminating the pronounced flare or belling at the ends of the tubes and subsfituting a slight taper throughout the length of tube port. furthermore, this practice presents another difiiculty since, with the tapered tube port the metal of the so tube walls will creep upon rolling and unless some means is provided for preventing this, the resulting elongation of the tube decreases its expansion to such an extent that the metal of, the

tube walls will not expand sharply into the,

grooves of the tube port Without excessive rolling. To avoid both of the above mentioned difficulties, a shoulder or stop'was provided in the header or return bend at the end of the tube. By butting the tube end against the shoulder or stop before rolling, elongation of the tube was prevented and a good fit was obtained between the tube walls and the grooved and tapered tube ports without excessive rolling and cracking of the metal. However, this practice involved another serious disadvantage since the inside diameter of the tube portat the shoulder or stop was less than the outside diameter of the tube and, therefore, tubes could not be replaced through this restriction in the port. In replacing a damaged or badly corroded tube, it was nec- 5 essary to sacrifice a companion tube (i. e., the tube next adjacent the one to be replaced).

In an attempt to overcome the last mentioned dimculty, the heighth of the shoulder or stop was decreased so that the inside diameter of the port 10 at this point was approximately inch greater than the outside diameter of the tube,'the theory being that the tube wallswould expand sufiicient-- 1y upon initial rolling and before substantial elongation of the tube occurred so that the end of the tube would rest against the shoulder or stop. Although it is possible to obtain good results with this method, it is often unsatisfactory in practice'because. extreme care and skill must be exercised in rolling the tubes into the headers 0 to insure that the tube end will be expanded sufiiciently to engage the shoulder or stop before it has become substantially elongated. The rolling operation is, therefore, too critical to insure uniformly satisfactory results. I 25 In the present invention, in order to overcome all of the above mentioned difficulties, instead of providing an integral shoulder or stop in the tube header or return bend, it is provided with a recess adjacent the end of the tube and a metal 0 ring is provided which can be inserted into said recess and against which. the end of the tube will bear to prevent the same from creeping. For relatively large diameter tubes this ring may be split so that it may be compressed slightly and sprung 35 into place in the groove. It is preferably made of chrome-alloy steel or other metal resistant to corrosion, and in form may closely resemble a piston ring. With relatively small diameter tubes, a split ring may not be feasible and in such so cases the invention contemplates a ring comprising two or more separate "arc-shaped pieces which may be individually placed in the groove provided in the tube header or return bend.

The use of a separate ring, as above described, 45 inserted in a groove proyided in the tube header or return bend adjacent the end of the tube, permits readily replacement of any individual tube in the nest orbank without sacrificing an adjacent tube. This is accomplished by removingor 0 destroying the ring so that the replacement tube can be inserted through the, port in the header or return bend. It is obvious that, with the present invention, the inside diameter of the ring or stop is not limited and may be only sufliciently less ness at .the end of the port into which the tube is rolled is sufficient to permit providing the same with the necessary grooves.

The accompanying diagrammatic drawing comprises nine figures. Figures 1, 2, 3, 4, and 5 each illustrate that portion of a tube header,

- return bend or tube sheet disposed adjacent a or belled is also provided in Figure 1.

port therein into which the end of a tube, also illustrated, is rolled. The five different types of ports above described are illustrated, in the order above mentioned, by the respective Figures 1, 2, 3, 4 and 5. Figure 6 is an end view of one form of split ring provided by the invention and illustrated in section in Figure 5. Figure 7 is a side view of the same ring shown in Figure 6. Figure 8 is an end view of a modified form of ring of the nature provided by the invention and intended for use with tubes of relatively small diameter. Figure 9 is a side view of the same ring shown in Figure 8.

In each of the Figures 1 to 5 inclusive that portion of the header or tube sheet adjacent the port into which the tube is rolled is indicated at l and a portion of the tube, including the end which is rolled into the header or return bend is indicated at 2.

It will be noted that in Figure l the bore of the tube port 3 is substantially straight and slightly larger in diameter than the outside diameter of the tube. Tube port 3 of Figure 1 is provided with a groove 4, the side walls 5 of which have relatively sharp corners and are cut at substantially right-angles t0 the bottom of the groove and the side walls of the tube port. A flared portion 6, adjacent the inner end of the tube port, over which the end of the tube is flared The tube 2 is of relatively hard metallic alloy or has a hard surface and it will be noted with reference to Figure 1, which shows the end of the tube rolled into port 3 and into the serrations provided therein, that the rolling required to bell or flare the end of the tube results in cracks such as indicated at l, and that the expanded tube does not fit closely into the groove 4. t is, therefore, obvious that the manner of joining the tube to the header or tube sheet, as illustrated in Figure 1, is not satisfactory. a

In each of the Figures 2 to 5 inclusive, the wall of the tube ports are cut on a slight taperto obviate pronounced flaring or belling of the extreme end of the tube as in Figure 1. In practice a taper of approximately inch to the foot has been found satisfactory, but for better illustration the taper has been somewhat exaggerated. in the drawing.

With reference to Figure 2, it will be noted that groove 8 is tapered slightly in a direction opposite to the taper of the tube port, and better contact is obtained between this groove or serration and the expanded walls of the tube. With a relatively soft tube of ordinary carbon steel, for example, the end of the tube, which is located at approximately the dotted line 9 when the rolling operation is star-ted, would be depressed into the serration or groove l0 and shoulder II would act as a stop. However, with a relatively hard tube of the nature above mentioned, the rolling will result in an elongation of the tube, as indicated checking of the tube walls. due to excessive rolling.

The tube port in Figure 3 is similar to that of Figure 2 except that a shoulder or stop 14, integral with the tube sheet or return bend, which is more pronounced than shoulder H of Figure 2, is provided. It will be oted with reference to Figure 3 that there is good contact between the expanded Walls of the tube and the grooves 8 and I0 and that shoulder I4 acts as an effective stop. However, it will also be noted with reference to Figure 3 that the opening provided between the walls of shoulder I4 is somewhat smaller in diameter than the outside diameter of the tube. This prevents inserting a replacement tube into the tube port through this restricted portion and necessitates removal of a companion tube along with the tube which requires replacement.

Figure 4 indicates the result of decreasing the height of shoulder or stop l6, as compared with shoulder M of Figure 3, so that the diameter of the tube port at this point is slightly greater than to obtain better contact tended to cause cracking or checking of the tube walls.

Also, due to creepingof the With the form of tube stop illustrated in Figure 4, difficulty is also encountered in properly installing the tubes. Since the diameter of the tube port at the stop is somewhat larger than the outside diameter of the tube, the tube end cannot be butted against the stop and is apt to either lap or fall too far short of the tube stop. Unless the end of the tube is spaced at just the proper location with reference to the stop, rolling ,spective Figures 3 and 4 are replaced in Figure 5 by a deeper groove I8 into which a metal ring I9 is inserted. Ring I9 is split as indicated at 20 to provide for its compression so that it may be slipped intov the tube port and allowed to spring into groove l8, this being accomplished, for example, by the use of a tapered sleeve or the like inserted in the extreme end of the port over shoulder 2|, into and through which sleeve the ring l9is forced by a suitable plug or dolly whereby it is compressed sufiiciently to enter the tube port and, upon leaving the sleeve, will expand into groove IS. The approximate location of the end of the tube before the rolling operation'is since the inside diameter of ring l9, when expanded into groove I 8, is "appreciably less than the outside diameter of the tube the ring acts as an effective tube stop during the entire rolling operation. This prevents any substantial elongation of the tube due to creeping of the metal upon rolling and the tube walls can, therefore, be.

expanded into grooves 8 and l 0 to give a satisfactory fit without excessive rolling.

To replace a damaged tube when employing the improvements provided by the invention and illustrated in Figure 5, the end of the tube is cut or chipped from the header or tube sheet in the usual manner and ring [9 is removed. Suitable means may be provided within the scope of the invention to compress ring l9 and remove the same from groove l8 without destroying it, although such means are not illustrated in the drawing. However, since no great expense is involved, ring I9 is ordinarily broken by a sharp blow with a hammer or chisel or by prying up one end of the ring adjacent slot 20 and may then be readily removed from groove I 8.

Except for the restriction provided by ring l8, the minimum diameter of the tube port of Figure 5 is somewhat greater than the outside diameter of the tube and, upon removal of a damaged tube and removal of ring I9, a replacement tube may be readily inserted through the tube port from the inner face H) of the tube sheet.

End and side views of the ring is provided in Figure 5 are illustrated in Figures 6 and 7, respectively which are self-explanatory.

Figures 8 and 9 are end and side views, respectively, of a modified type of ring contemplated by the present invention. The type of ring shown in Figures 8 and 9 will ordinarily be found more satisfactory for tubes of relatively small diameter than the type of ring indicated in Figures 5, 6 and 7.

The ring 21 of Figures 8 and 9 is divided into three are shaped portions 28, 28 and 29. It is,

of course, also within the scope of the invention to divide this type of ring into any desired number of pieces. The separate pieces of ring 21 are separately inserted into a groove of the header or tube sheet similar to that of groove I8 in Figure 5 and when all sections of the ring are in place they will prevent each other from falling out of the groove.

I claim as' my invention:

1. In an apparatus of the class of tube sheets, headers and return bends having a port for the reception of an end of a tubular member, said port being provided with a groove into which a portion of the metal of the tube walls is expanded by rolling to secure the tube in said port, a second groove provided in said port adjacent the end of the tube, and a metal ring insertable into said second groove and adapted to serve as a stop for preventing substantial elongation of the tube upon rolling.

2. In an apparatus of the class of tube sheets, headers and return bends having a port for the reception of an end of a tubular member, said port being provided with a groove into which a portion of the metal of the tube Walls is expanded by rolling to secure the tube in said port, a second groove provided in said port adjacent the end of the tube, and a metal ring insertable into said second groove and adapted to serve as a stop for preventing substantial elongation of the tube upon rolling, said port being further characterized in that it is tapered slightly from adjacent the end of the tube to adjacent the opposite end of the port, the minimum diameterof said port being adjacent said opposite end thereof and being slightly greater than the normal outside diameter of the tube before rolling and said ring being further characterized in that its inside diameter, when the ring is in place in said second groove, is appreciably less than the said normal outside diameter of the tube.

MARION W. BARNES.

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