GRINDSTAFF, Landon (Crane ChemPharma Resistoflex, 1 Quality WayMarion, NC, 28752, US)
KALNINS, John (Crane ChemPharma Resistoflex, 1 Quality WayMarion, NC, 28752, US)
KELLERMAN, Thomas (Crane ChemPharma Resistoflex, 1 Quality WayMarion, NC, 28752, US)
YANIK, David (Crane ChemPharma Resistoflex, 1 Quality WayMarion, NC, 28752, US)
GRINDSTAFF, Landon (Crane ChemPharma Resistoflex, 1 Quality WayMarion, NC, 28752, US)
KALNINS, John (Crane ChemPharma Resistoflex, 1 Quality WayMarion, NC, 28752, US)
KELLERMAN, Thomas (Crane ChemPharma Resistoflex, 1 Quality WayMarion, NC, 28752, US)
| WHAT IS CLAIMED IS: 1. A highly corrosion-resistant metal product for the handling or transport of corrosive materials, said product comprising: a body made of a metallic material and having an interior surface; a plastic liner lining the interior surface of the body; and a protective material separating the liner from the interior surface of the body, and contacting the liner. 2. A metal product according to Claim 1, wherein the protective material comprises a corrosion-resistant paint. 3. A metal product according to Claim 2, wherein the paint comprises an organic material and is resistant to high temperatures and/or to corrosive materials. 4. A metal product according to Claim 1 , wherein the protective material comprises a diamond-like carbon material. 5. A metal product according to Claim 1, wherein the protective material comprises a second metallic material. 6. A metal product according to Claim 5, wherein the second metallic material is selected from the group consisting of silver, nickel, chromium and gold. 7. A metal product according to Claim 1, wherein the protective material comprises a plastic material lying between and separating the interior surface of the body and the plastic liner. 8. A metal product according to Claim 7, wherein the plastic material of the protective material comprises a material selected from the group consisting of PFA, PVDF and PTFE. 9. A metal product according to Claim 1, wherein the metallic material of the body is selected from the group consisting of ferrous metals and non-ferrous metals. 10. A metal product according to Claim 1, wherein the plastic liner comprises a material selected from the group consisting of PFA, PVDF and PTFE. 11. A metal product according to Claim 1, wherein the product is selected from the group consisting of pipes, valves, fittings, reactors, pressure vessels and containers. 12. A metal product according to Claim 1, wherein the body is provided with at least one vent hole, and wherein the additional protective material lines or coats the interior wall of the vent hole to place a portion of the outer surface of the liner in communication with the atmosphere. 13. A method of manufacturing a highly corrosion-resistant metal product for the handling or transport of corrosive materials, comprising the steps of: providing a body made of a metallic material and having an interior surface; applying a protective material to the interior surface of the body; and drawing a plastic liner into the body to contact and cover the protective material and line the interior surface of the body. 14. A method according to Claim 13, wherein the protective material comprises a corrosion-resistant paint, and wherein said applying step is performed using a rotary spray -paint head. 15. A method according to Claim 14, wherein the paint comprises an organic material and is resistant to high temperatures and/or to corrosive materials. 16. A method according to Claim 13, wherein the protective material comprises a diamond-like carbon material. 17. A method according to Claim 13, wherein the protective material comprises a second metallic material. 18. A method according to Claim 17, wherein said applying step is performed by means of electroplating. 19. A method according to Claim 18, wherein the second metallic material is selected from the group consisting of silver, nickel, chromium and gold. 20. A method according to Claim 13, wherein the protective material comprises a plastic material lying between and separating the interior surface of the body and the plastic liner, and wherein said applying step is performed by applying the plastic material in a suspension or as a powder, and sintering the plastic material of the protective material. 21. A method according to Claim 20, wherein the plastic material of the protective material comprises a material selected from the group consisting of PFA, PVDF and PTFE. 22. A method according to Claim 13, wherein the metallic material of the body is selected from the group consisting of ferrous metals and non-ferrous metals. 23. A method according to Claim 13, wherein the plastic liner comprises a material selected from the group consisting of PFA, PVDF and PTFE. 24. A method according to Claim 13, wherein said step of providing the body includes providing at least one vent hole in the body, and wherein said applying step includes causing the additional protective material to line or coat the interior wall of the vent hole to place a portion of the outer surface of the liner in communication with the atmosphere. |
RELATED APPLICATIONS
[0001] This application is based on U.S. provisional application A.N.
61/106,009, filed October 16, 2008, and claims benefit of that application under the Paris Convention. The entire disclosure of that prior application is hereby incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] This application relates generally to pipes, fittings, valves, and reactor or pressure vessels for use in chemical processes, and more particularly relates to pipes, fittings, valves reactor or pressure vessels for use in handling highly- corrosive fluids, such as strong acids.
[0003] It is known to make such a pipe, fitting, valve, reactor or pressure vessel by installing a plastic liner such as a polyvinylidene fluoride ("PVDF"), perfluoroalkoxy ("PFA"), or polytetrafluoroethylene ("PTFE") liner into a ferrous metal housing. (For brevity's sake, reference will generally be made simply to "pipes", but fittings, valves and reactor or pressure vessels are also included, except where there is an explicit statement to the contrary.) A plastic-lined piping system made in this way is highly resistant to corrosion. It has been found, however, that the life of a pipe made in this fashion is limited by the eventual permeation of the liner by the liquid with which the pipe is used. When this occurs, the liquid begins to corrode the ferrous metal housing in spite of the presence of the liner, and eventually it may become necessary to replace the pipe. It would be very desirable to be able to provide
a piping system that avoids this problem, without being unreasonably expensive to manufacture.
[0004] For this purpose it might be considered simply to make the standard liner thicker. While this might postpone the time at which the material pumped through the pipe would reach the steel of the pipe body, the extra lifetime obtained in this way could be modest, and would be obtained at the price of either a reduction in the open bore size of the piping, or an increase in the inner diameter ("ID") of the pipe itself so as to obtain a finished product with no reduction in bore.
SUMMARY OF THE INVENTION
[0005] Applicants have found that they are able to make a pipe, fitting or valve having the characteristics desired, including a great reduction (at least 50%) in permeation-related corrosion, and that need not be unduly expensive to make.
[0006] Applicants achieve this by providing a piping system having a plastic liner of the sort used conventionally, for example, of PTFE, but also provided with a second protective material, between that liner and the ID of the metal housing, to delay or prevent the corrosive fluid contacting the steel. Applicants have developed several ways to do this.
[0007] In the first approach, the inner diameter of the metal housing may be provided with an organic coating ("organic" here signifies that the chemical make-up of that protective second material includes one or more chemically organic materials). This is done using a paint having characteristics that will protect the ferrous metal housing material from damage.
[0008] A second approach involves providing the ID of the metal housing with a coating of diamond- like carbon ("DLC"), of the type described in U.S. Patent 4,981,717. Such coatings can be applied by existing vendors, such as Sub- One Technology, Inc. This application is also preceded by cleaning steps. The PTFE or other plastic liner is again installed in the housing in the conventional fashion.
[0009] In a third approach, the ID of the metal housing is electro-plated with a metal, and the PTFE or other plastic liner is drawn through. It has been found that different metals are needed depending on the type of fluid transported by the system. While gold is technically suitable as such a metal for most corrosive fluids, the cost of that metal is too high to be economically feasible, although the use of gold is, technologically, within the scope of the present invention. Silver, nickel, chromium or other metals can be used for specific fluid applications. It should be noted that while the inventors are aware that corrosion or temperature resistant paints, as well as DLC, electroplated layers and other materials have been used for many purposes, the inventors are not aware of these types of materials having been used to improve the properties of plastic-lined pipes or similar products, and in particular the specific problem described above, which occurs in the use of such pipes with very corrosive and/or hot materials.
[00010] In a fourth approach, the secondary barrier can be provided in the form of a second layer of fluoropolymer. This is done, however, not by using a second PTFE or other plastic liner but by applying PTFE or another fluoropolymer in a suspension or powder form to the ID of the housing, typically by spraying. The coated work piece is then sintered. Multiple coats can be applied to improve corrosion resistance, after which the plastic liner can be installed in the conventional way.
[00011] These and other objects, features and advantages of the present invention will be more fully appreciated from a consideration of the following detailed description and of the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[00012] Fig. 1 is a sectional view illustrating the construction of a conventional pipe. Fig. 2 is a similar view illustrating schematically the permeation of the conventional liner by a material used with the pipe, after a period of use.
[00013] Fig. 3 is a sectional view illustrating the construction of a pipe according to several of the preferred embodiments of the present invention.
[00014] Fig. 4 is a schematic illustration of one example of a method according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[00015] As shown in Fig. 1, a conventional plastic-lined steel pipe 10 for use in handling corrosive materials has a metallic body 12, which may for example be stainless steel, and, lining the interior surface of the pipe body 12, a plastic liner 14, typically of PTFE, PFA or PVDF. Such a pipe 10 is manufactured using well-known techniques, and it is common for a pre-formed plastic liner 14 to be drawn through the pipe body 12. Such pipes display strong resistance even to highly corrosive materials, and serve to protect the material of the pipe body 12 from the corrosive properties of the materials being pumped through the pipe.
[00016] As described above, however, such a pipe 10 can, after enough use, begin to suffer from permeation of the material with which it is used, into the material of the liner (see Fig. 2, where the presence of the corrosive material in liner 14 is indicated schematically by the stippling in region 14). Eventually, this process can result in the corrosive material coming into contact with the metal pipe body 12, in spite of the presence of the plastic liner 14, resulting in the very kind of damage that the liner 14 is intended to prevent.
[00017] The present inventors have determined that it is possible to obtain a very significant improvement in performance of such pipes and other products, by providing a pipe 100 having an additional protective material 130 between the lining 120 and the interior surface of the pipe body 110, as shown generally in Fig. 3. In this figure, the thicknesses of the additional protective material 130 and of the liner 120 are much exaggerated for clarity's sake (this is also true of the liner thickness in Figs. 1 and T). In fact, in this embodiment, the additional protective material 130 is a paint containing tiny particles or flakes of a glass material (not shown), and forms a very thin layer on the pipe body 110. That is, the presence of the paint does not decrease the size of the useful bore of the finished pipe 100 to any significant extent. Using such a paint, however, an improvement of over 50% in resistance to damage from corrosive materials handled by the pipe 100 has been obtained.
[00018] One example of such a paint is sold under the name Thermaline 450, by the Carboline Company ("Thermaline" and "Carboline" are trademarks of the Carboline Company; attached as Appendix A is a specification sheet of this paint). The paint may be applied in various ways, one of which is by means of a conventional rotary spray-paint head. [00019] Thus, the process of manufacturing such a pipe or similar product using this embodiment involves preparing the metal pipe 110, which is most typically stainless steel. The preparation includes cleaning the interior surface of the pipe 110 by heating or sandblasting, to remove any contaminants that may be present. The interior surface is then spray-painted with the paint, which must be applied carefully to ensure that there are no pinholes in the paint coating. This process is illustrated in Fig. 4, where the paint is supplied through a supply hose 140 to a rotary spray-paint head 150, which applies the paint to the interior of the pipe body 110. In practice it may be necessary to apply two coats to be sure that protective material 130 forms a complete protective barrier without holes. The plastic liner 120 is then drawn through the metal pipe 110 in the conventional way, completing the main steps of the manufacturing process.
[00020] Another important feature of the preferred embodiments is the provision of one or more vent holes (not shown) in the pipe body. These holes may be on the order of for example 1 A inch or less in diameter, and their sidewall is coated with the paint of other protective material. Thus, the outer surface of the primary liner is exposed through these holes. In a pipe of up to about 20 feet in length, it is sufficient to provide two such holes, one about 18 inches (preferably) from each end, and if the pipe is very short (e.g., less than 18 inches in length) then one hole will suffice.
[00021] The importance of these vent holes is that the textured outer surface of the primary liner makes it possible for molecules of permeants to be present between that liner and the secondary liner (the additional protective material); by providing these vent holes, it becomes possible for any such small amounts of permeants to reach the atmosphere, thus further reducing the likelihood of corrosive damage to the pipe body.
[00022] In another preferred embodiment of the invention, the protective layer 130 is formed not of paint, but of a diamond- like carbon material. Such materials have been developed relatively recently, and are commonly formed by means of detonations in a carbon-bearing plasma formed by application of laser pulses. Purely by way of example of one such technique there is mentioned U.S. Patent 4,981,717. Since the techniques of forming such layers are in themselves now well known, it is not believed to be necessary to describe them in detail. As a practical matter, in any event, it may be most feasible to have this process performed by a contractor specializing in the technology relating to the production of such materials.
[00023] If this latter embodiment is adopted, the metal pipe is cleaned, just as in the first embodiment, and its interior surface is then coated with the DLC coating. When this is completed, the conventional plastic liner is drawn through the coated pipe, again using conventional techniques.
[00024] In another preferred embodiment, the interior surface of the pipe 110, again after cleaning, is covered with a metal coating preferably by means of well-known electroplating techniques. The electro-plated surface is then provided with the plastic liner 120, which is drawn through in the conventional manner.
[00025] In a fourth preferred embodiment, the additional protective material is plastic, and may be either the same material as the liner 120, or a different material. This embodiment avoids the drawbacks noted above that would occur if one were simply to make the liner thicker, or if one provided two liners, because the additional material is applied in the form of a powder or a suspension. The deposited material is then sintered, producing a continuous protective covering for the metal surface of the pipe body. As a result of this technique the additional material forms only a thin deposit on the interior surface of the metal pipe body 110. The standard liner 120 can then be drawn through in the conventional fashion, just as with the other preferred embodiments.
[00026] According to the preferred embodiments the additional protective material is applied to a thickness that will vary considerably depending on the material used, but in general will be quite thin compared to the primary liner (typically about 1 A inch in thickness), with a thickness of not more than .015 inch, and most typically .008 to .010 inch for paint, and less than .001 inch for an electroplated layer. Thus, the present invention permits a significant extension of the useful life of the pipe, without significantly reducing the inner diameter of the conduit.
[00027] It has been found that the present invention provides a pipe, valve, fitting or container that performs in the same way as, and to no lesser standards than, conventional lined products, but which exhibits a 50% or greater reduction in susceptibility to corrosion damage by the materials handled using the product. In particular it is believed that this invention is capable of achieving these results for pipe diameters of anywhere from 1 inch up through 20 inches. 28] Many variations and modifications of the foregoing preferred embodiments will now be apparent to those skilled in the art, and are also deemed to be within the scope of the invention. Accordingly, the scope of the invention is not to be limited by the details of the foregoing preferred embodiments, but only by the terms of the appended claims.