Description:METHOD FOR WELDING VARYING TUBE DIAMETERS BY ORBITAL TIG WELDING

FIELD OF THE INVENTION:
[001] The present invention relates to Orbital TIG welding of tubes of different outer diameters of D1 and D2 with same inner diameter for RRP assemblies.

BACKGROUND OF THE INVENTION:
[002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[003] Rear Roof Panels (RRP) of high pressure boilers consist of T12 material tubes of length 11-meter x diameter D1 of 57 mm welded with safe ends of T22 tubular material of length 150 mm x diameter D2 of 51 mm with same ID bore size. The RRP tubes are subjected to VOP & Rotary bending and heat treated by Solution annealing process and the safe end are of different outer diameters of D1 (57 mm) and D2 (51 mm) respectively. In conventional method only tubes of same diameter are welded after edge preparation (J groove style) in O-TIG welding station. Only manual TIG welding process was earlier possible to weld such different diameter tubes. But the manual process has cons such as long cycle time, low productivity and also prone for weld defects contributed by tube to tube butt alignment issue. Hence there is a necessity for a mechanized welding of such two different tube diameters to enhance productivity and production of defect free welded joints in O-TIG welding machine. Accordingly, the welding passes are executed by altering the weld angles of the welding torch to execute the welding of tubes with different diameter of D1 (57 mm) and D2 (51 mm) in O-TIG welding station.

OBJECTS OF THE INVENTION:
[004] An object of the invention is to provide method for welding varying tube diameters by orbital TIG welding, which obviates short comings of the prior art(s).

[005] The principal object of the present method is to provide a new operating procedure to carry out O-TIG welding for different diameters of tube of D1 and D2 aiming at increased productivity, better utilization of the O-TIG welding station and ensuring defect free welded joints.

[006] Another object of the invention is to provide method for welding varying tube diameters by orbital TIG welding, which is simple.

[007] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY OF THE INVENTION:
[008] One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus/composition and a method as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be part of the claimed disclosure.

[009] A standard fit-up procedure is developed and adapted for the welding of the tubes of different diameters of D1 (57 mm) and D2 (51 mm) in the O-TIG welding station. The RRP tubes of length 11-meter of tube diameter D1 of 57 mm is set in the Orbital TIG welding station by fit up clamp along with the safe end of diameter D2 of 51 mm. Then the welding root pass, filler passes 1 to 4 are carried out by maintaining the welding torch in 90 deg. perpendicular to the tube center axis. Then for filling the tapered angle gap between the tube diameter of D1 (57 mm) and tube diameter D2 (51 mm) is completed by welding, which is carried out by maintaining the welding torch in 116.5 degrees for filling passes 5,6 and 7 by minor modification in the torch mounting bracket assembly to vary the angle of the O-TIG welding torch.

[0010] The welding was executed for 10 tubes, checked for Radiographic test (RT) and found OK. Then the new operating procedure is established for the welding of different diameter tubes of D1 (57 mm) and D2 (51 mm) respectively and used for regular production cycles of RRP tube welding.

[0011] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

[0012] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.

[0013] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
[0014] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:-

[0015] It is to be noted, however, that the appended drawings illustrate the steps in welding of different diameters of tube of D1 (57 mm) and D2 (51 mm) in the O-TIG welding station at filling passes.

[0016] Figure 1 illustrates the filling passes 1 to 4 with welding torch angle of 90 degree, which indicates as follows:
RRP tube of diameter 57mm - 1
Safe end tube of diameter 51mm - 2
O-TIG welding torch at 90deg. for root pass & filling passes 1,2,3,4 - 3A

[0017] Figure 2 illustrates the filling passes 5 to 7 with welding torch angle of 116.5 degree, which indicates as follows:
RRP tube of diameter 57mm - 1
Safe end tube of diameter 51mm - 2
O-TIG welding torch at 116.5 deg. for filler passes 5,6 and 7 - 3B

[0018] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily 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.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:
[0019] 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.

[0020] This invention makes a disclosure regarding a technology pertaining to invention directing to method for welding varying tube diameters by orbital TIG (O-TIG) welding.

[0021] Welding passes are nothing but the flow of the welding process or the sequence in which welding should be carried out.

[0022] The welding sequences are known as welding passes. A typical welding process comprises four passes. They are Root Pass, Hot Pass, Fill up Pass and Capping.

Types of Welding Passes:--

Root Pass:
[0023] Root pass refers to the first pass in any welding process, which combines two pieces or members into one structure. Subsequent passes increase the weld depth to the desired thickness, yielding the necessary strength. The first pass usually provides the base for subsequent filler passes.

[0024] Let’s consider a root pass on a set of pipes. The root pass is welded with a technique called drag method. The tip of the electrode is held in contact with both pipes and dragged around the circumference of the pipe, advancing vertically downward.

Fill Up Pass:
[0025] To fill the bevel portion, the pass that is made is known as a “fill up pass”.

[0026] It is also referred to as a fill pass as it is the amount of weld bead necessary to fill the weld joint. This pass comes after the root pass or hot pass and before the cap pass or capping.

[0027] The basic procedure to determine the number of welding passes required is by the following the Welding Procedure Specification. But, in case there is no mention of the necessary number of passes, one is free to use the number of passes depending upon one’s skills and the following factors:
They are:
[0028] Travel Speed – Travel speed is directly proportional to the number of welding passes. Higher the travel speed, lower the weld volume and more the number of passes.

[0029] Width of the weave (oscillation) – It works in a way like the travel speed.

[0030] Joint configuration – A bevel groove needs more passes than a V-groove, keeping other conditions constant.

[0031] Electrode diameter – Larger electrode diameter increases the volume per pass and decreases the number of passes.
[0032] For the welding of different diameters of tube of D1 of 57 mm and D2 of 51 mm in the O-TIG welding station, the RRP tube of diameter 57 mm (1) and Safe end tube of diameter D2 [51 mm] (2) are fitted up using clamp and then welded in the O-TIG welding station using the TIG welding torch (3) at an angle of 90 degrees for the filler passes 1,2,3 and 4. Then for the tapered gap between the different tube diameters of D1 (57 mm) and D2 (51 mm) constitute for about 3 mm is planned for filling using the welding torch (3) in altering the angular position of the welding torch (3) by slight adjustment in the torch mounting bracket. Then the filling passes 5,6 and 7 required to fill the 3 mm nominal gap between tubes of diameter D1 [57 mm] (1) and tube diameter of D2 [51 mm] (2) is carried out by welding torch (3) at 116.5 deg. position.
[0033] The welding pass 1 is a route pass, passes 2,3,4 are filler passes carried out at 90 degree torch angle and passes 5,6,7 are filler passes carried out at 116.5 degree torch angle.

ADVANTAGES OF INVENTION:
- Increases productivity,
- Better utilization of the O-TIG welding station,
- User Friendly.

TEST RESULT:
[0034] Weld defect rate is reduced to 4% by the new process compared to that of earlier process of manual welding at 22 %.

[0035] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.

[0036] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.

[0037] 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 particulars 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 analogues 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”.

[0038] The above description does not provide specific details of manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.

[0039] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.

[0040] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.

[0041] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
, Claims:WE CLAIM:

1. A method of O-TIG welding of tubes of different diameter D1 and D2 comprising steps of:
- fitting up of the different tube diameters using clamps;
- positioning of RRP tube diameter D1 of 57 mm (1) and Safe end diameter D2 of 51 mm (2) in the clamp unit ensuring alignment;
- welding of root pass between RRP tube (1) and safe end tube (2);
- welding of filling passes 1,2,3 and 4 between RRP tube (1) and safe end tube (2) by maintaining welding torch in 90 deg. position;
- welding of filling passes 5,6, and 7 in taper angular gap between RRP tube (1) and safe end tube (2) by maintaining welding torch in 116.5 deg. position.

2. The method as claimed in claim 1, wherein the welding pass 1 is a route pass and the passes 2,3,4 are filler passes carried out at 90 degree torch angle.

3. The method as claimed in claim 1, wherein the passes 5,6,7 are filler passes carried out at 116.5 degree torch angle.

4. The method as claimed in claims 1-3, wherein the tapered gap between the different tube diameters of D1 and D2 constitute for about 3 mm is provided for filling using the welding torch (3) in altering the angular position of the welding torch (3) by adjustment in the torch mounting bracket, which is followed by filling passes 5,6 and 7 to fill the about 3 mm gap between tubes of diameter D1 (1) and tube diameter of D2 (2) by welding torch (3) at 116.5 deg. position.