Patent Application
20230220937
Spud connection points are typically provided at external surfaces of liquid tanks. Such spud connections allow for access to the internal volume of the tank, such as to connect plumbing lines, control devices, measurement devices, and the like in a leak-free fashion. Often, such spuds are connected to the tank wall via welding.
Spud weld connections for cylindrical tanks such as water heaters are known to be locations at which tank failure (e.g. leakage) is prone to occur. Failures at these connections typically result from cyclic fatigue, caused by pressure and/or temperature cycling. Such cycling causes high stresses to occur at the weld connection locations, as the presence of the welded spud creates a stress riser at that location. The extent to which the shell is locally deformed by the welding of the spud can strongly influence the magnitude of the stress riser, and therefore can impact the fatigue life of the tank.
A spud weld connection according to embodiments of the present invention alleviates the known fatigue issues by reducing the stress riser that is created during traditional spud weld attachment.
In embodiments of the present invention, a spud connection to a cylindrical tank wall includes a spud body welded to a cylindrical tank wall. In at least some embodiments, the spud body has an arcuate and concave first end surface, and a planar second end surface. The planar second end surface is spaced apart from the first end surface, and an outer surface is arranged between the first and second end surfaces. A central bore extends through the spud body. In some embodiments, the central bore includes a female thread profile.
In at least some embodiments, the spud weld connection includes a weld joint between the first end surface of the spud body and an outer surface of the cylindrical tank wall. The weld joint surrounds an aperture that extends through the cylindrical tank wall, so that a leak-free fluid connection to an interior volume of the tank can be achieved.
In some embodiments the first end surface is concentric with the cylindrical tank wall. In such embodiments, the arcuate and concave shape of the first end surface defines an axis of revolution that is aligned with a central axis of the cylindrical tank wall. In other embodiments, the arcuate and concave shape of the first end surface defines an axis of revolution that is parallel to, but offset from, the central axis of the cylindrical tank wall. In some such embodiments the concave and arcuate shape defines a diameter that is greater than an outer diameter of the cylindrical tank wall, while in other such embodiments the concave and arcuate shape defines a diameter that is less than the outer diameter of the cylindrical tank wall. In some embodiments the outer diameter of the cylindrical tank wall is between 70% and 150% of a diameter defined by the concave and arcuate shape of the first end surface of the spud body.
According to another embodiment of the invention, a method of creating a spud weld connection to a cylindrical tank wall includes providing a cylindrical tank wall with an aperture extending therethrough, and also providing a spud body that has an arcuate and concave first end surface, a planar second end surface spaced apart from the first end surface, an outer surface arranged between the first and second end surfaces, and a central bore extending through the spud body. The first end surface of the spud body is disposed against an outer surface of the cylindrical wall such that the first end surface surrounds the aperture, and a weld joint is created around the aperture between the spud body and the cylindrical tank wall at the first end surface.
In at least some embodiments, creating the weld connection includes placing a planar surface of a first welding electrode against the planar second end surface of the spud body, and placing an arcuate and convex surface of a second welding electrode against an inner surface of the cylindrical tank wall. A compressive force is applied to the spud body and the cylindrical tank wall through the first and second electrodes, and an electrical current is conducted through the spud body and the tank wall between the first and second electrode in order to create the weld joint.
In at least some embodiments, the second welding electrode has a protrusion that extends from the arcuate and convex surface, and the method includes inserting the protrusion into the aperture of the tank in order to align the second welding electrode with the first welding electrode.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.
A water heater tank 300 with two spud weld connections 100 according to an embodiment of the present invention is depicted in
The water heater tank 300 is equipped with a water inlet port 303 and a water outlet port 304 that are welded to the upper tank head 302. The water inlet port 303 (which can optionally include a dip tube extending into the tank volume to a location near the lower end of the tank) allows for cold water to flow into the tank, and the outlet port 304 allows for heated water to be drawn from the tank 300 and delivered to users upon a demand for heated water.
A pair of additional ports 305 are provided at the cylindrical tank wall 301 itself, by way of the spud weld connections 100. The ports 305 can be used to, for example, circulate a flow of water from one portion of the tank 300 by way of one of the ports 305 to an external heat sink or heat source, and to return that flow of water back to the tank 300 by way of another of the ports 305. It should be understood that while a pair of ports 305 are depicted in
The spud weld connection 100 includes a spud body 200 (
The spud body 200 further includes a central bore 204 that extends through the spud body 200, penetrating both the first end surface 201 and the second end surface 202 to allow for fluid flow and/or physical access through the spud body. The exemplary spud body has a female thread profile 205 provided within the central bore, to allow for the easy connection of a standard threaded pipe nipple to the spud body 200 for connection to other portions of a plumbing system. In other embodiments, the thread profile 205 can be omitted, and such a connection can be made by other means such as, for example, welding.
As best seen in the cross-sectional view of
As can be seen in
During the welding process, a clamping force is applied through the first and second electrodes 400 and 500 in direction that are generally perpendicular to the surface 202 of the spud body 200, as generally depicted by the arrows in
In at least some embodiments, the arcuate shape of the concave end surface 201 of the spud body 200 can define a cylindrical shape with a diameter that is equal to, or approximately equal to, the diameter of the outer surface 306. In such embodiments, the cylindrical shape of the concave end surface 201 defines an axis of revolution that is in alignment with a central axis of the cylindrical tank wall 300, so that the surfaces are concentric. In other embodiments, a diameter defined by the surface 201 can intentionally vary from the diameter of the outer surface 306. In such embodiments, the axis of revolution define by the concave end surface 201 is parallel with the central axis of the cylindrical tank wall 300, but is offset therefrom. Such an intentional variation, when maintained within a defined range, can allow for the same size spud body 200 to be used with a variety of differing tank sizes without compromising the weld joint 101. By way of example, a spud body with an arcuate concave surface defining a cylindrical diameter of 17″ may be used on cylindrical tank walls with outer diameters of 12″, 14″, 18″, 24″, 26″ etc. In other words, the outer diameter of the cylindrical tank wall varies between about 70% and 150% of the diameter of the spud body surface that is to be welded to the tank wall. Since the size of the central bore that needs to be encircled by the weld joint is relatively small (e.g., on the order of 1-2″) in comparison to the tank wall diameter, the amount of tank wall distortion that would be necessary to place the welding surfaces in intimate contact at the extremes of those mismatches in diameter is still minor in comparison to a planar spud surface.
Various alternatives to the certain features and elements of the present invention are described with reference to specific embodiments of the present invention. With the exception of features, elements, and manners of operation that are mutually exclusive of or are inconsistent with each embodiment described above, it should be noted that the alternative features, elements, and manners of operation described with reference to one particular embodiment are applicable to the other embodiments.
The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention.
