US2868513A

US2868513A - Heat exchanger

Info

Publication number: US2868513A
Application number: US638516A
Authority: US
Inventors: Stanley C Orr; Donald E Kropp
Original assignee: Pfaudler Permutit Inc
Current assignee: Pfaudler Permutit Inc
Priority date: 1957-02-06
Filing date: 1957-02-06
Publication date: 1959-01-13
Anticipated expiration: 1976-01-13

Description

Jan. 13, 1959 s. c. ORR EI'AL HEAT EXCHANGER Filed Feb. 6, 1957 m X WWW W m E e N 0W m I V Z mi A M 7 Z R 1 MW 5 5 M United w States Patent 2,868,513 HEAT EXCHANGlIR Stanley C. Orr and Donald E. Kropp, Elyria, Ohio, as-

signors to Pfaudler Permutit Inc.

Application February 6, 1957, Serial No. 638,516 Claims. (Cl. 257-236) This invention relates to the heat exchanger art and is particularly concerned with a ferrous metal heat'exchanger lined with non-ferrous metal which is substantially unaffected by extremely corrosive fluids and is practically unweldable to ferrous metal.

Heretofore heat exchangers have been constructed of mild steel for use With fluidswhich are not more than mildly corrosive and stainless steel and other metals and alloys have been used in constructing heat exchangers for use with the more highly corrosive commonfluids. However, there are certain fluids which are so corrosive that they will attack even stainless steel. Proposals have been made to construct heat exchangers entirely of metals which can resist such highly corrosive fluids but such exchangers would be prohibitively expensive. So far as we are aware, no heat exchanger of economical construction was known or was available prior to the present invention which would be satisfactory for use with these extremely corrosive fluids.

The present invention attains its object of providing an economical heat exchanger which would be suitable for use with these extremely corrosive fluids by using mild steel or stainless steel as base metal and employing highly resistant metals such as titanium, tantalum and zirconium to make or cover the steel parts of the heat exchanger. with which such corrosive fluid would otherwise come into contact.

This invention will be better understood by those skilled in the art from the following specification and the accompanying drawings in which: i

Fig. l is a fragmentary side elevational view, partly in section, of a heat exchanger embodying the present invention;

Fig. 2 is an enlarged fragmentary sectional view of Fig. 1; and

Fig. 3 is a view similar to Fig. 2 but showing a modified form of the invention.

The heat exchanger shown in Figs. 1 and 2 consists of the conventional, tubular, ferrous metal shell 1 which has inlet and outlet connections 2 and 3 through which fluid may flow into and out of the interior of the shell. At its ends, the shell is provided with spaced, ferrous metal tube sheets 4 which are of greater outside diameter than shell 1 and which are secured to the shell in any suitable manner but, preferably, by welding as indicated by weld metal 5. The usual supporting brackets 6 may be welded to the outside of the shell. The shell 1 and tube sheets 4 define a chamber 7 for fluid which may flow there through between the inlet 2 and outlet 3. Bonnets or domes 8 attached to the tube sheets form chambers 9 at each end of the heat exchanger. The shell and tube sheets may be made of mild or stainless steel depending to some extent on the fluid which is to pass through the chamber.

Metal covers 10 bear against the remote or outer surfaces of tube sheets 4, as is better shown in Fig. 2. Tubes are expanded, as by rolling, into the tube receiving holes in the tube sheets and extend through covare 10 and tube sheets 4 and through the chamber 7 in shell 1 and serve to conduct the highly corrosive fluid from one chamber 9 to the other chamber 9 through chamber 7 wherein it may be subjected to heating or cooling temperatures. The outer ends of these tubes 15 are secured to the outer surfaces of the metal sheets 19 in any suitable manner but, preferably, by being electrically welded thereto, as by the tungsten arc inert gas shielded method, the weld metal being indicated at 11. Each tube sheet is preferably provided. with two tube grooves 13 in each tube receiving hole for mechanical strength in the assembly.

Each bonnet or dome 8 is provided with a flanged outlet tube 17 and a bolt flange 18 and has a marginal outwardly extending flange 20 to engage a gasket 21 which bears on the outer surface of cover 10. A bolt ring 22 bears against the outer sidej of flange 20. Bolts 24 extend through ring 22 and tube sheets 4 and nuts 25 are on said bolts. By drawing up the nuts on the bolts, a fluidtight joint may be made between the flange 2t), gasket 21 and cover 10. v j

.The modification shown in Fig. 3 is quite like that shown in Fig. 2, the differences being in the details of the dome. The bonnet or dome consists of a ferrous metal outer part8a and a liner 8b of non-ferrous metal like that of parts 10 and 15. The part So has a bolt ring 22a welded to it and provided with holes for bolts 24. The liner 8b covers the inner surface of dome part do and has a flange 20a to project into the space between and engage ring 22a and gasket 21. This flange is shown 1 as being attached by weld metal to the remainder of liner 8b. In Fig. 3 the cover 1011 is thicker than cover 10 of Fig. 2 and the end surfaces of tubes 15 lie within the covers'and are welded to the covers by weld metal 11 also lying between the side surfaces of the covers.

According to the present invention, all parts of the illustrated heat exchanger which are to come into contact with the extremely corrosive fluids are composed of non-ferrous metals and alloys which are satisfactorily resistant to those fluids, and which are substantially nonweldable to ferrous metals. Examples of such metals are titanium, tantalum and zirconium and alloys of each.

' Since thesejmetals and alloys cannot be satisfactorily welded to ferrous metals the parts made of those metals are, according to the present invention, welded to each other and are so arranged and so cooperate with the ferrous metal parts that they protect the ferrous metal parts from contact with the corrosive fluids.

The welding of the non-ferrous parts is described above and the arrangement of those parts with the ferrous metal parts is shown in the drawings. There the covers 10' and Mia which protect the tube sheets are clamped against those sheets by bolts 24 and ring 22 or 22a. Shell 1 prevents movement of the tube sheets toward and away from each otherxand also from covers lo and Ida. Furthermore, the tubes are rolled into the tube sheets and hence firmly fastened thereto. Thus the welds which join the tubes to the covers are not required to absorb large forces due to differential expansion and contraction of dissimilar metals.

While the foregoing specification names certain nonmetals and their alloys, it is to be understood that those metals are merely illustrative of the class of metals which are characterized by being resistant to extremely corrosive fluids and by being substantially non-weldable to ferrous metal and that the present invention contemplates the use of any of the metals of that class.

Having thus described this invention in such full, clear, concise and exact terms as to enable any person skilled in the art, to which it pertains, to make and use the same, and having set forth the best mode contemplated of carrying out this invention, we state that the subject-matter which we regard as being our invention is particularly pointed out and distinctly claimed in what is claimed, it being understood that equivalents or modifications of, or substitutions for, parts of the above specifically described embodiment of the invention may be made without departing from the scope of the invention as set forth in what is claimed.

What is claimed is:

1. A heat exchanger comprising spaced, ferrous metal tube sheets, covers on the remote outer surfaces of said tube sheets, tubes extending through and expanded into engagement with said tube sheets, weld metal joining the ends of said tubes to said covers, said covers and tubes being composed of non-ferrous metal resistant to extremely corrosive fluids and substantially non-Weldable to ferrous metal, and means for securing the covers to the tube'sheets and serving to maintain the covers in contact with the adjacent tube sheets during changes in temperature.

2. The combination of elements set forth in claim 1 in which the said non-ferrous metal parts are composed of metal selected from the group of metals consisting of titanium, tantalum, zirconium and their alloys.

3. A heat exchanger comprising a tubular, ferrous metal shell, ferrousmetal tube sheets of greater diameter than the shell and connected to the shell at its ends to define therewith a chamber for fluid, covers on the remote outer surfaces of said tube sheets, tubes extending through said chamber and tube sheets and expanded into engagement With said tube sheets, Weld metal joining the ends of said tubes to said covers, bonnets for the ends of '4 said exchanger defining with said covers chambers for extremely corrosive fluid flowing into and through said tubes, said covers, tubes and bonnets being composed of non-ferrous metal resistant to said fluids and substantially unweldable to ferrous metal, and means for securing the bonnets to the tube sheets.

4. A heat exchanger comprising a tubular, ferrous metal shell, ferrous metal'tube sheets of greater diameter than the shell and connected to the shell at its ends to define therewith a chamber for fluid, covers on the remote outer surfaces of said tube sheets, tubesextending through said chamber and tube sheets and rolled into said tube sheets, weld metal joining the ends of said tubes to said covers, bonnets for the ends of said exchanger defining with said covers chambers for extremely corrosive fluid flowing into and through said tubes, each of said bonnets including an outer part and an inner liner,

said covers, tubes and liners being composed of non ferrous metal resistant to said fluids and substantially non-Weldable to ferrous metal, and means for securing the bonnets to the tube sheets.

5. The combination of elements set forth in claim 3 in which the said non-ferrous parts are composed of metal selected from the group consisting of titanium, tantalum, and zirconium and their alloys.

References Cited in the file of this patent UNITED STATES PATENTS 2,108,087 Thayer Feb. 15,1938 2,336,879 Mekler Dec. 14, 1943 2,618,846 Morris et a1. Nov. 25, 1952. 2,785,459 Carpenter Mar. 19, 1957