Patent Application
20180299211
The present disclosure is directed to joints between dissimilar pipes and more particularly to brazed joints.
In air conditioning and heating systems there are various alloys and metals used for the different pipes, heat exchangers and other parts. The decision of what material to use in which section can depend on factors such as temperature, the type of fluid carried within the part, swelling from temperature changes, exposure to the elements and more. A common problem is how to join pipes or parts made from different materials. Because different materials swell differently, react to water or other substances differently and other factors, joints between two different materials can become sources of corrosion or wear. One common joint in heating and cooling systems is between aluminum and copper pipes.
Brazing is a typical method of joining two dissimilar pipes together. In brazing, a material of a lower melting point is heated and melted in an overlapping portion of the two dissimilar pipes, the larger diameter pipe placed around the smaller diameter pipe. The overlapping portion between the pipes is the site of the brazing. One common brazing alloy is aluminum 4047. The pipes, being of a higher melting point will not melt, but the brazing material will melt and then solidify, forming a strong bond between the two pipes.
At joints connecting two different pieces there is an increased risk of corrosion and galvanic corrosion. Joints provide seams and crevices into which water or other substances can enable erosion of the surrounding materials. One solution to the problem of galvanic corrosion is to provide a coating on the dissimilar pipes. Such coatings can be types of paints or elastomeric materials such as shrink wrap. However, these solutions can interfere with protective coatings on the surrounding pipes.
Aluminum, for example, because of its susceptibility to corrosion, is often given a diffused anodal alloy treatment for protection. Testing has shown that when an aluminum tube is being protected by this anodal treatment, paint is lifted from the surface as the alloy preferentially corrodes. When the paint lifts, it no longer provides galvanic corrosion protection at the copper-aluminum junction. This leaves the braze joint susceptible to shortened corrosion life resulting in non-reparable leaks.
In addition, treatments like shrink wrap may interact with the anodal protective coating. Testing has shown that the protective alloy corrodes under elastomeric seals, starting at the edge and tunneling under. After the corrosion process has tunneled sufficiently, a different corrosion mechanism, crevice corrosion, is enabled. This mechanism acts relatively quickly and creates a pit under the elastomeric material, leading to a non-reparable leak.
Especially problematic are brazed joints with a “short fuse.” This occurs when the brazing does not cover the entire overlapping surface area between the pipes, also called a partial fill. Corrosion works its way up the partial fill quicker than it would on a larger brazing surface.
An improved brazed joint is described for connecting pipes within a heating or cooling system. One advantage of the disclosure is a joint that is protective against galvanic and other types of corrosion. Another advantage is compatibility with anodal treatments or other coatings that are common on the surface of metal piping. Another advantage is that the joint prevents water and other materials from entering the brazed joint between dissimilar pipes where they can cause harmful corrosion. One embodiment is a downward opening flare in an aluminum tube at a copper-aluminum braze joint that acts as an umbrella to prevent ambient wetness from flowing across the braze joint galvanic couple, and also provides a faying volume allowing placement of an adhesive sealant to both the copper tube outside surface and the aluminum tube inside surface (where no anodal treatment has been applied), thus acting as a moisture barrier at the braze joint.
One embodiment comprises a brazed joint connecting an aluminum pipe of larger diameter to a copper pipe of smaller diameter wherein the aluminum pipe is vertically above the copper pipe, an improvement comprising: the aluminum pipe comprising a flare extending radially outward and toward the copper pipe, the flare operable to direct fluid away from the brazed joint.
Another embodiment comprises a brazed joint comprising: a first pipe; a second pipe, the second pipe comprising a flare, the flare extending outward radially and toward the first pipe and operable to direct fluid away from the brazed joint; and a brazing alloy, the brazing alloy connecting an inner surface area of the second pipe to an outer surface area of the first pipe.
Another embodiment comprises a method of connecting a larger diameter pipe to a smaller diameter pipe, comprising: brazing the pipes together with a brazing alloy, the brazing connecting an outer surface of the smaller pipe to an inner surface of the larger pipe; providing a flare, the flare extending from the larger pipe toward the smaller pipe and extending radially outward; and making the flare operable to direct fluid away from the brazed joint.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.
For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
The preferred embodiment is for a joint between copper and aluminum pipes. Copper and aluminum are common materials used in heating and air condition systems. Areas of condensation within these systems cause water to bead up on the exterior of some pipes. Condensed water may contain ions. The water then drips along the exterior of the pipes and can pick up additional ions from aluminum, copper or other metals while it falls and travels down the pipes. These ions in moisture can be particularly harmful to joints or other connection sites, increasing the risk of galvanic corrosion. For example, copper ions can be detrimental to aluminum. The preferred embodiment therefore helps prevent corrosion enabling ions from coming into contact with and potentially harming the braze joints between aluminum and copper piping. However, the ideas described can be used for joints between pipes of various materials with various types of coatings. Various brazing alloys can be used. One or both of the pipes may have anodal coatings such as zinc or other treatments. In some situations the teachings may be used for joints between pipes of the same material to provide extra corrosion protection.
The flare described does not have to be of a particular shape.
For increased protection from corrosion, a sealant 470 may be used as shown in
The preferred embodiment, shown in
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
This application is a continuation of U.S. patent application Ser. No. 14/674,719, filed on Mar. 31, 2015. U.S. patent application Ser. No. 14/674,719 is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14674719 | Mar 2015 | US |
| Child | 16018132 | US |
