FIELD OF INVENTION

[001] The present invention leads to Welding of Nozzle with Connecting Sphere in High Pressure High Temperature Steam Generators. More specifically this invention relates to elimination of Backing Ring during Welding. More particularly this invention further relates to introduction of TIG welding and subsequent SMAW welding.
BACKGROUND OF THE INVENTION
[002] The connecting Sphere in High Pressure High Temperature Steam Generators is manufactured by welding 3 nozzles of F12 specification to the sphere. The Nozzles are of OD ranging from 368.3 to 571.8 mm, thickness ranging from 56.35 to 86.4 mm, Length ranging from 565 to 765 mm and weighing from 500 to 700 kg. The original design has called for backing ring for welding of nozzles with sphere to ensure full penetration of welding. After the welding, heat treatment and NDE testing of the Connecting Sphere, the backing ring 3 nos has to be removed by grinding or machining. Removal of backing ring by Machining is difficult due to higher length of the nozzle. Removal of backing ring by Grinding is difficult due to smaller inner diameter of the nozzle. Hence there is a need for improved method of welding nozzle with connecting sphere.
[003] Accordingly, Fig 1 shows the connecting sphere model with Sphere (2), Two Nozzles placed 45 deg apart (1) and third nozzle (3) vertically downwards. Fig 2 shows the prior art method in welding of Nozzle (1) with Sphere (2) using Backing Ring (4) having weldment (5). Fig 3 shows the Backing Ring (4) model with R8 groove to ensure full penetration. Fig 4 shows prior art method in welding of Nozzle (1) with Sphere (2) using Backing Ring (4) with the detailed weldment (5) including angles.
OBJECTS OF THE INVENTION
[004] It is an object of the present invention is to propose a new method of nozzle welding.
[005] Other object of the present invention is to propose a new method of nozzle welding which eliminates backing ring in connecting spheres of high-pressure high temperature generators.
[006] Yet another objective of the invention is to propose a new type of Edge Preparation on the both the components of Sphere & Nozzle.
[007] A still further objective of the invention is to provide a new method of welding for the Sphere and the Nozzle which is able to avoid the provision of Backing Ring.
[008] These and other objects and advantages of the present subject matter will be apparent to a person skilled in the art after consideration of the following detailed description taken into consideration with accompanying drawings in which preferred embodiments of the present subject matter are illustrated.
SUMMARY OF THE INVENTION
[009] The edge preparation of the Sphere is modified to enable full penetration of the weld. Edge preparation style is chosen by calculating the weld volume to ensure same weld reinforcement. In the process the sequence of operation of connecting sphere manufacturing is cirseam welding of the connecting sphere followed by fit-up and welding of the nozzles. Once the nozzle welding is completed the component is subjected to Heat Treatment, Non Destructive Examination (NDE) and Hydro Test. NDE is conducted to inspect full penetration weld and complete weld metal deposition. After NDE, the component is Hydro tested. The reports certified the Proposed Edge preparation Style met the intended Statutory and design requirements. In the process the requirement and further removal of the backing ring is completely eliminated. Thus the proposed method of changing the EP style reduced the cycle time of manufacturing the connecting sphere.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0010] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods or structure in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
[0011] Fig 1 shows the schematic view of Connecting Sphere with Nozzles;
[0012] Fig 2 shows the typical arrangement of welding of Connecting Sphere and nozzles with Backing Ring in position;
[0013] Fig 3 shows the enlarged view of Backing Ring showing the circumferential Groove;
[0014] Fig 4 shows the Existing Welding details of Connecting Sphere and Nozzle using Backing Ring;
[0015] Fig 5 shows the developed Welding process of Welding Connecting sphere and Nozzle without Backing Ring.
[0016] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

[0017] While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

[0018] The terms “comprises”, “comprising”, or any other variations thereof used in the disclosure, are intended to cover a non-exclusive inclusion, such that a device, system, assembly that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such system, or assembly, or device. In other words, one or more elements in a system or device proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or device.
[0019] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that 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 subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject matter. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, 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.
[0020] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope. The present invention will now be described more specifically with reference to the following specification.
[0021] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that 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 subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, 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.
[0022] According to the present invention and referring to Fig 5 the method of welding (6) the Nozzle (1) with Connecting sphere (2) along with detailed weldment and Edge Preparation style of Nozzle and Connecting sphere. The welding process for proposed style are done by Root Welding using Tungsten Inert Gas Welding (TIG), followed by Shielded Metal Arc Welding (SMAW). The proposed welding sequence with TIG, and SMAW ensured full penetration welding. The proposed style eliminated the backing ring. NDE and Hydro test were conducted, and reports certified the Proposed Edge preparation Style met the intended Statutory and design requirements. By the modified Edge Preparation, the use of backing ring is completely eliminated and cycle time of manufacturing the Connecting sphere is reduced.

[0023] At step 1, the Nozzle (1) and Connecting sphere (2) are edge prepared as per Fig 5 (modified for welding without backing ring). During edge preparation material along the edges of metal surface to be used for welding is removed. Edge preparation is done by machining operation. Edge preparation is done for welding when parts or assemblies requires some strength. To achieve full penetration, the edges of the metal is cut. The weld replaces the removed material and makes a complete bridge between the joining parts.
[0024] At step 2, the nozzle (1) and the connecting sphere (2) are placed in the position as per the joint design. According to one embodiment of the present invention, two nozzles (1) are placed 45o apart on the upper side of the connecting sphere (2) and third nozzle (3) is placed vertically downwards and equally apart from the nozzles (1) on the lower side of the connecting sphere (2).
[0025] At step 3, welding of Root layer is done by Tungsten Inert Gas (TIG) Welding. Root layer is the lower most layer of the joint between the nozzle (1, 3) and the connecting sphere (2).
[0026] At step 4, welding of the balance portion is done by Shielded Metal Arc Welding (SMAW). Balance portion is the remaining layers of welding except root layer.
[0027] At step 5, after completion of welding heat treatment of the welded arrangement is done. Post welding heat treatment is done to ensure the material strength of the welded arrangement. Heat treatment is used to reduce residual stresses or to enhance material strength. If heat treatment is neglected this residual stress can combine with load stress to exceed the material’s design limitation. This can lead to weld failures, higher cracking potential, and increased susceptibility to brittle fracture.
[0028] At step 6, radiography test is performed on all Weld Joints of the welded arrangement. Radiography test is a method of non-destructive testing used to detect discontinuities within the internal structure of the welds. The advantage of this method of testing is its ability to determine weld internal integrity without destroying the welding component. In this method X-rays or Gamma rays are used. Penetrating radiation is passed through the welded arrangement, onto a photographic film, resulting in an image of the welded arrangement's internal structure being deposited on the film. The amount of energy absorbed by the welded arrangement depends on its thickness and density. Energy not absorbed by the welded arrangement will cause exposure of the radiographic film. These areas will be dark when the film is developed. Areas of the film exposed to less energy remain lighter. Therefore, areas of the welded arrangement where the thickness has been changed by discontinuities, such as porosity or cracks, will appear as dark outlines on the film. Inclusions of low density, such as slag, will appear as dark areas on the film while inclusions of high density, such as tungsten, will appear as light areas. All discontinuities are detected by viewing shape and variation in density of the processed film.
[0029] At step 7: Hydro Test to be performed to check leakage which indicated Weld defect. Hydro test is a kind of pressure test in which the welded arrangement being tested is filled completely with water or another liquid. Pressure, if required, is then applied to the liquid for the required time and the outside of the component is examined visually for leaks.
[0030] At step 8: If no leakage occurs weld quality is good.
[0031] The welding done by the method disclosed in present invention eliminate use of backing ring on the connecting sphere, which is hard to remove after welding. The present method can achieve full penetration without using backing ring.
[0032] Although embodiments for the present subject matter have been described in language specific to package features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/device of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.

[0033] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”
[0034] It will be further appreciated that functions or structures of a plurality of components or steps may be combined into a single component or step, or the functions or structures of one-step or component may be split among plural steps or components. The present invention contemplates all of these combinations. Unless stated otherwise, dimensions and geometries of the various structures depicted herein are not intended to be restrictive of the invention, and other dimensions or geometries are possible. In addition, while a feature of the present invention may have been described in the context of only one of the illustrated embodiments, such feature may be combined with one or more other features of other embodiments, for any given application. It will also be appreciated from the above that the fabrication of the unique structures herein and the operation thereof also constitute methods in accordance with the present invention. The present invention also encompasses intermediate and end products resulting from the practice of the methods herein. The use of “comprising” or “including” also contemplates embodiments that “consist essentially of” or “consist of” the recited feature.
[0035] Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/component of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.

We claim:

1. A method of nozzle welding for elimination of backing ring in connecting spheres, the method comprises:
Preparing edges of a nozzles (1,3) and a connecting sphere (2) before welding;
Placing the nozzles (1, 3) as per the joint design on the connecting sphere (2) for welding;
Welding root layer between the nozzles (1, 3) and the connecting sphere (2) by tungsten inert gas welding (TIG):
Welding the balance portion between the nozzle (1) and the connecting sphere (2) by Shielded Metal Arc Welding (SMAW);
Performing heat treatment on the welded arrangement;
Performing radiography test on all welded Joints; and
Performing hydro test to check leakage which indicate weld defect.
2. The method of nozzle welding as claimed in claim 1, wherein the edge of nozzle is prepared by machining operation.
3. The method of nozzle welding as claimed in claim 1, wherein two nozzles (1) are placed 45o apart from each other on the upper side of the connecting sphere (2).
4. The method of nozzle welding as claimed in claim 1, wherein nozzle (3) is placed between nozzles (1) on the lower side of the connecting sphere (2).
5. The method of nozzle welding as claimed in claim 1, wherein root layer is the lowermost layer of the joint between the nozzle (1, 3) and the connecting sphere (2).
6. The method of nozzle welding as claimed in claim 1, wherein balance portion is the remaining layers of welding except root layer.