US 2633414 A
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Mflmh 1953 J. H. BOIVINET PROTECTIVE LINER FOR AUTOCLAVES Filed June 7, 1948 Fiel- INVEN 1 OR ATTORNEY Patented Mar. 31, 1953 UNITED STATES PATENT OFFICE PROTECTIVE LINER FOR AUTOCLAVES ration of France Application June 7, 1948, Serial No. 31,559 In France June 16, 1947 Claims.
Autoclave containers of the type used in the chemical industry are required to possess both mechanical resistance to stresses to which they may be subjected, in use and chemical resistance to the corrosive action of the materials they are to contain.
It is not always practicable to fulfil both the above conditions through the use of a metal or of only one metal. In general, a metal will be sufiiciently resistant mechanically but will not resist corrosion, or, if it does withstand corrosion, it will not show sufficient resistance to mechanical stresses.
Certain substances (such as soft metals, plastics and the like), resist a large number of chemical reactions, but their tensile resistance is very low.
This leads to the idea of using such substances as internal liners for containers the shell of which consists of a metal having a sufficient resistance to mechanical stresses.
In structures of such type, there are certain precautions to be taken and in particular it is necessary that any gases or liquids, entrapped between the liner or coating material and the wall of the stressed shell, be capable of escaping towards the outer atmosphere. In the absence of such a precaution, there would occur, between the liner and the shell, a succession of alternate compressions and expansions which would quickly result in a breakdown of the liner and, as a consequence, the resulting breakdown of the shell of the apparatus, since the chemical agents will then be capable of coming into contact with the latter.
The present invention is concerned with a method of protecting an autoclave by means of an internal liner, which overcomes the above drawbacks.
Said method is characterized in that the protective liner, which is preliminarily prepared separately, is applied to the wall of the container by a pressure which is Very gradually exerted from the interior of the container, with the interposal of a device for venting or draining any gases or liquids from between the wall of the container and the liner.
There will be described hereinafter by way of example, the procedure for internally lining a cylindrical container with a lead liner. It will be obvious that the liner might also be formed of any other suitable material such as tin, silver, various metals and alloys, plastic materials such as vinyl chloride, and so on.
The accompanying drawing illustrates by way of example one embodiment of the invention:
Fig. 1 is a fragmentary view in longitudinal cross section of an autoclave including an internal protective liner embodying the invention.
Fig. 2 is a transverse cross section online .2...,- 2 of Fig. 1.
Fig. 2a is a similar view of a modification, and
Fig. 3 is a view on an enlarged scale oia-por: tion of Fig. 2.
As shown in Fig. 1, the autoclave comprises-a cylindrical shell I made of a metal possessing sufficient resistance to mechanical stresses; said shell is provided at each end thereof with an annular flange 2; the end covers 3 are adapted to be secured to said flanges by means of bolts.
Metal bars 4 are arranged to. extend along the generatrices of the internal surface of the shelll. Said bars preferably have a rounded crosssection, being for instance of the commercially available half roundsection type; the rounded portion of the barsections is directed inwardly,
while the flat portion thereof is slightly grooved throughout its entire length with a shallow and narrow channel 5. Saidchannel is placed in communication with the atmosphere either through small apertures ll, perforated through the shell 5, or through apertures formedbetw'een the flanges 2 of the shell and the covers 3. Between each successive pair of saidbars there is arranged a wire mesh 6 of relatively large mesh size (see Fig. 3).
The barsB and the mesh 6 may be maintained in place by the provision of a few spotwelds, as for instance at S. The mesh 6 or the M1754 might be used alone, depending on the sizes and shapes of the apparatus. v
There is then inserted into the container the cylindrical lead liner it, which is to form the internal coating of the container and which has been formed and welded separately. Said liner should have an external diameter very slightly smaller than the diameter of the circumference which is internally tangent to the longitudinal bars t. There may be preferably formed in the lead liner, which in this case will be formed with a diameter equal to the internal diameter of the apparatus, a fold having very carefully rounded curvatures adapted to facilitate the insertion of the liner into the apparatus (as shown at l2 in Fig. 2a).
The edges 1 of the liner are folded back (see Fig. 1) into the recess provided for that purpose in each of the flanges 2. Said folded edges do not entirely fill said recess, and the sealing of the liner is completed with a wiped plumbing joint. If the liner includes a preliminarily formed fold l2; it should be carefully hammered down at both ends of the cylinder, so as to properly apply the lead liner at both ends thereof against the internal surface of the apparatus and facilitate the folding back of its edges.
Moreover, the end covers will have preliminarily been plumbed with a wiped joint and the surface of the lead which is to engage the flanges 1 is rectified. If tube connections 9 are to be provided, the latter are filled with molten lead and the perforation is made with a drill. The end covers 3 are put into place with the interposal of a lead lining 8 and are carefully bolted in position.
The autoclave is then filled with water, steam or a gas at a suitable temperature allowing for a certain amount of extension in the material constituting the liner and, by means of a test pump, the pressure is very gradually built up to a value in excess of the normal operating pressure. It is essential that said pressure increase should be effected very slowly, thereby enabling the liner I to be applied very uniformly in the first place upon the bars 4, then, by a very gradual and uniform extrusion effect exerted between two edges of adjacent bars 4, against the wire mesh 6. Since, as stated above, the wire mesh is of relatively large mesh size, the plastic lead metal of the liner is eventually extruded through the mesh openings as the internal pressure is built up inside the autoclave, and the extruded metal is applied against the interior surface of the shell. The air entrapped between the lead liner l0 and the inner wall I of the autoclave is thus very gradually forced out through all of the apertures provided to that end.
The above described device furthermore makes it possible to immediately detect the presence of any leakage in the lead liner. The gases or liquids, contained in the autoclave, should by any accident the lead liner be perforated, will follow the path followed by the air in the coating operation. They will then appear at the outlet of any one of the vents and this will be a warning to halt the operation of the apparatus in ample time to prevent the corrosion of the metal forming the shell reaching an excessive value.
The method and protective device described above involving a lead liner are particularly suitable for the construction of apparatus or parts of apparatus to be used in the synthetic manufacture of urea from carbonic acid gas and ammonia.
What I claim is:
1. The method of lining an autoclave shell, subjected in normal operation to mechanical stresses and corrosive action, with a smooth corrosion resisting lining, comprising the steps of: disposing spacing means at intervals on the interior of the shell; introducing into the shell a cylindrical, unitary, deformable, open-ended lining having a diameter smaller than the internal diameter of said shell; securing the cylindrical edges of said lining to both ends of said shell; closing oil both ends of the shell; gradually applying fluid pressure in excess of the normal operating pressure to the interior surface of said lining, whereby the entire unsecured part of said lining is progressively deformed and applied against the spacing means and against a multiplicity of uniformly distributed areas on the interior surface of the shell, and simultaneously expelling to the atmosphere any fluid entrapped between the lining and the shell.
2. An autoclave comprising an outer shell resistant to mechanical stresses, a unitary, smooth, corrosion-resisting deformable inner lining substantially continuous with and coextensive in area with the inner surface of said shell, separate spacing means between said shell and lining uniformly distributed over the entire circumference of said shell, said lining contacting the inner surface of the shell at a multiplicity of areas uniformly distributed over the entire inner surface, and venting means connecting the space between the liner and the shell to the outer atmosphere whereby, in normal operation, the space between the shell and lining is substantially free of fluid.
3. An autoclave according to claim 2, in which the spacing means comprise a wire mesh.
4. An autoclave according to claim 2, in which the spacing means comprise a plurality of bars disposed along the inner circumference of the autoclave and extending parallel to the longitudinal axis of the autoclave.
5. An autoclave according to claim 2 in which the bars comprise shallow grooves communicating with the venting means.
JEAN HENRI BOIVINET.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 341,435 Russell May 4, 1886 353,731 Bremaker Dec. 7, 1886 390,727 Wagg Oct. 9, 1888 1,651,521 Girardville Dec. 6, 1927 1,892,433 Huif Dec. 27, 1932 1,894,116 Pier Jan. 10, 1933 1,911,608 Davis et a1 May 30, 1933 1,940,277 Stresau Dec. 19, 1933 2,100,895 Austin Nov. 30, 1937 2,329,970 Zimmerman Sept. 21, 1943 2,428,542 Bernhardt Oct. 7, 1947 2,460,820 Hagopian Feb. 8, 1949