Claims:

We claim:
1. A method for forming welded triple elbows for super critical boilers to meet American Society of Mechanical Engineers (ASME) code requirement in place of forged triple elbows, the method comprising:
preparing edge on fins (04) of single elbows (02);
tack welding stub tubes (03) with the single elbows (02);
full welding butt joints between the single elbows (02) and the stub tubes (03) by a welding process;
subjecting the weld to Radiography Test (RT);
If RT is acceptable, tack welding the single elbows (02) as an assembly (01) to match the dimensions of the single elbows (02) with a root gap of 2 mm;
welding the assembly (01) to a job by a fusion welding process;
after welding from one side, back gouging the weld by grinding;
performing dye penetrant test to ensure that no defect is present in the root area;
weld from another side;
performing magnetic particle inspection (MPI) of the joints formed at both sides of the assembly to ensure full penetration and to ensure integrity of a triple elbow; and
assembling the triple elbow with a transition panel.

2. The method as claimed in claim 1, wherein the preparing of the edge on fins (04) of single elbows (02) is performed either as square butt, single V, or single J groove.

3. The method as claimed in claim 1, wherein the full welding is performed by either automated welding process, mechanized welding process, robotic welding process, or manual welding processes.

4. The method as claimed in claim 1, wherein the fusion welding process includes Shielded Metal Arc Welding (SWAM), Manual Metal Arc Welding (MMAW), and Gas Metal Arc Welding (GMAW).

5. The method claimed as in claim 1, wherein the single elbows (02) are provided with a root gap of 2 mm to 3 mm for welding.
, Description:FORMING METHOD FOR TRIPLE ELBOWS FOR PANELS IN SUPER CRITICAL BOILERS

TECHNICAL FIELD
[0001] This present disclosure relates to forming of triple elbows by welding instead of forging for super critical boilers heat exchangers, etc. The present disclosure, in general, relates to the development of procedure for achieving full penetration welds with square butt edge preparation by fusion welding processes (Shielded / Manual Metal Arc Welding (SMAW / MMAW), Gas Metal Arc Welding (GMAW or MIG / MAG) to form triple elbows as per ASME or equivalent code, etc.
[0002] The present disclosure serves the purpose of ensuring flaw less joints in fusion welding of the elbow fins with square butt edge preparation for increased productivity.
[0003] This present disclosure related to the process development for joining triple elbows with a different innovative method of welding instead of forging method.
BACKGROUND
[0004] 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.
[0005] Presently, the triple elbows 01 (FIG. 1) are fabricated as a forged piece and are used in panels of super critical boilers. The joining of the elbows with abutting panel tubes was found to be difficult. To ease site fabrication, it was decided that an extension (spool piece) tubes will be welded to the elbow during supply, so that there is increased flexibility and access for site welds. As the triple elbows are available as a single forged piece, automation of elbow welding with extension tubes could not be made successfully. The main hindrance is the pitch between the elbows which is very close (14 mm) in the triple elbows. Hence, the elbows are joined with the extension tubes by manual Gas Tungsten Arc Welding (GTAW) process at shop floors and subjected to 100% Radiography Test (RT). This assembly is then welded to the panels. Then the tubes are joined with the three elbows by manual TIG process. The entire process takes a long cycle time and also there are quality related issues necessitating rework, considering the access limitations.
[0006] Various approaches have been proposed in the state of the art to overcome the productivity and quality related issues in welding of triple elbows assembly with extension stub tubes.
[0007] For instance, IN288KOL2014A dated 2015-09-25 having title “A METHOD AND DEVICE FOR FABRICATION OF STEAM GENERATOR PACKAGE OF SUPER CRITICAL HIGH-PRESSURE BOILERS” relates to a method of holding Elbows and reducers for conventional welding process. More particularly, the invention relates to a joining of multi plane bend pipes called steam generator package links in supercritical steam generators. The invention further relates to a device for fabrication of steam generator package links of super critical high-pressure boilers.
[0008] JP5552226B2 dated 2014-07-16 having title “DEVICE AND METHOD FOR REPAIRING A CORE SPRAY LINE ELBOW WELD JOINT” relates to an elbow clamp assembly structurally supports or replaces a connection between a main pipe and an elbow pipe. The elbow clamp assembly includes an upper clamp body and a lower clamp body securable on opposite sides of the main pipe in facing relation. The upper and lower clamp bodies are connected by a clamp bolt extendable through the main pipe. An elbow boss is securable to the elbow pipe, and a cross bolt is extendable through the elbow pipe and connected between the elbow boss and the clamp bolt.
[0009] JP2012067864A dated 2012-04-05 having title “WELDING JOINT, WELDING DEVICE AND WELDING METHOD” relates to a synthetic resin welding joint has a joint body which is held to a clamp of a welding device A so as to surround it and to be held thereto, and a pipe end which can be engaged with the end of the synthetic resin tube. The pipe end is externally surrounded by a heat generation part of the welding device in order to heat and weld a joint s formed by the engagement of the tube end and the pipe end, and the joint body can be attached to the welding device, while being externally surrounded by the clamp. Outer peripheral irregularities engaged with inner peripheral irregularities formed at the internal periphery of the clamp are formed at the joint body, and in a clamped state, an angular position with respect to the clamp of the joint body around the axial core of the pipe end is fixed by the engagement of the inner peripheral irregularities and the outer peripheral irregularities.
OBJECTS OF THE DISCLOSURE
[0010] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed herein below.
[0011] It is a general object of the present disclosure is to provide an innovative welding method to form the triple elbows for super critical boilers to meet ASME code requirement.
[0012] It is another object the present disclosure is to develop welding method for achieving full penetration welds between the fins of the elbows by fusion welding processes (Shielded / Manual Metal Arc Welding (SMAW / MMAW), Gas Metal Arc Welding (GMAW or MIG / MAG) to form the triple elbows.
[0013] It is another object of the present disclosure is directed to improve upon the productivity using the new forming process.
SUMMARY
[0014] This summary is provided to introduce concepts related to a method of forming welded triple elbows in lace of forged triple elbows for super critical boilers. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0015] In an embodiment, the present disclosure relates to a method for forming welded triple elbows for super critical boilers to meet American Society of Mechanical Engineers (ASME) code requirement in place of forged triple elbows. The method includes preparing edge on fins (04) of single elbows (02); tack welding stub tubes (03) with the single elbows (02); full welding butt joints between the single elbows (02) and the stub tubes (03) by a welding process; subjecting the weld to Radiography Test (RT); if RT is acceptable, tack welding the single elbows (02) as an assembly (01) to match the dimensions of the single elbows (02) with a root gap of 2 mm; welding the assembly (01) to a job by a fusion welding process; after welding from one side, back gouging the weld by grinding; performing dye penetrant test to ensure that no defect is present in the root area; weld from another side; performing magnetic particle inspection (MPI) of the joints formed at both sides of the assembly to ensure full penetration and to ensure integrity of a triple elbow; and assembling the triple elbow with a transition panel.
[0016] In an aspect, the preparing of the edge on fins (04) of single elbows (02) is performed either as square butt, single V, or single J groove.
[0017] In an aspect, the full welding is performed by either automated welding process, mechanized welding process, robotic welding process, or manual welding processes.
[0018] In an aspect, the fusion welding process includes Shielded Metal Arc Welding (SWAM), Manual Metal Arc Welding (MMAW), and Gas Metal Arc Welding (GMAW).
[0019] In an aspect, the single elbows (02) are provided with a root gap of 2 mm to 3 mm for welding.
[0020] Therefore, to overcome the productivity and quality related issues in welding of triple elbows assembly with extension stub tubes in shop, it is proposed to form them as single elbows to the required size and then weld the extension tubes were welded with the elbows by automated GTAW / GMAW process which are very productive and of consistent high quality. After welding, the single elbows can be joined as a triple elbow, by welding the webs of the fin together to the exact dimensions without any concerns.
[0021] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] 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 apparatuses, systems, and methods that are consistent with the subject matter as claimed herein, wherein:
[0023] FIG. 1 illustrates a forged piece of a triple elbow, in accordance with an embodiment of the present disclosure;
[0024] FIG. 2 illustrates a triple elbow as an assembly, in accordance with an embodiment of the present disclosure; and
[0025] FIG. 3 illustrates macrographs of welds and illustrates full fusion joint without any defect/discontinuity to validate the procedure/process developed, in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION
[0026] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0027] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0028] Embodiments herein describe an apparatus consisting of one C channel, stopper plate, two adjustable pivots, two movable screw rods with holder, two box nuts, one locknut, stopper plate locking device, apparatus locking device and lifting handle (FIG. 1).
[0029] In the current practice, the triple elbows are fabricated as a forged piece and are used in panels of super critical boilers. The joining of the elbows with abutting panel tubes was found to be difficult. To ease site fabrication, it was decided that an extension (spool piece) tube will be welded to the elbow during supply, so that there is increased flexibility and access for site welds. As the triple elbows are available as a single forged piece, automation of elbow welding with extension tubes could not be made successfully. The main hindrance is the pitch between the elbows which is very close (e.g., 14 mm) in the triple elbows. Hence, the elbows are joined with the extension tubes by manual Gas Tungsten Arc Welding (GTAW) process at shop floors and subjected to 100% Radiography Test (RT). This assembly is then welded to the panels. Then the tubes are joined with the three elbow by manual TIG process. The entire process takes a long cycle time and also there are quality related issues necessitating rework, considering the access limitations.
[0030] In the new innovative forming method developed, full penetration welds were achieved between the fins of the elbows to form the triple elbow by the following procedure:
• Do edge preparation on the fins of the elbows (square butt, single V or single J groove).
• Tack weld the stubs with the single elbows.
• Full welding of butt joint between elbow and stub by automated / mechanised / robotic / manual welding processes.
• Subject the weld to RT.
• If RT is OK, tack weld the single elbows as an assembly to match the dimensions of the elbow) with a root gap of 2 mm (min).
• Ensure cleanliness of weld joint area. Joint area should be free from oil / grease / water, etc.
• Preheat the job (if necessary) and weld the assembly by fusion welding process. Typical welding parameters for SMAW process are given in Table 01.
• After welding from one side, back gouge the weld by grinding.
• Carry out dye penetrant test to ensure that no defect is present in the root area.
• Weld from the other side also.
• Clean the Weld.
• Carry out visual inspection.
• Carry out MPI of the joints to ensure full penetration and to ensure integrity of the triple elbow.
• Assemble the elbow with transition panel and process further as one triple elbow.
[0031] FIG. 2 shows the triple elbow as an assembly (01). The parted single elbows (02) are tack welded with the stub tube (03) by welding. After welding of stub tubes and elbows as single elbows, the single elbows are reassembled to convert them as a triple elbow (01). The joints are welded between fins (04) for making the assembly.
[0032] In an aspect, the method prospoed herein can be used to make welded triple elbows using any filler wire / welding consumable suitable to the material for welding.
[0033] In an aspect, the method prospoed herein can be used to make welded triple elbows with or without preheating and or post heating.
[0034] In an aspect, the method prospoed herein can be used to make welded triple elbows by selecting suitable welding voltage, current and travel speed.
[0035] In an aspect, the method prospoed herein can be used to make welded triple elbows with short / medium / long arc depending upon the welding parameters.
[0036] In an aspect, the method prospoed herein can be used to make welded triple elbows with suitable size of filler wire / electrode for welding.
[0037] In an aspect, the method prospoed herein can be used for welding of similar dissimilar weld joints in making welded triple elbows.
[0038] In an aspect, the method prospoed herein can be used for any type of elbows.
[0039] In an aspect, the method prospoed herein can be used to make welded triple elbows to meet the requirements of ASME code or equivalent code.
[0040] In an aspect, the method prospoed herein can be used for such applications of any sizes / dimensions.
[0041] Typical welding parameters for SMAW process are shown in Table 01:
DESCRIPTION VALUE
Process SMAW
Type of current DCEP
Electrode specification E 8018 B2
Size Dia 3.15
Voltage 16 – 18 V
Current 120 – 125 A
Preheat temp 120° C
Arc length Short arc
Root Gap 2 to 3 mm
Table 1

[0042] In the experimental work, the welded samples were subjected to Tensile and bend test and macrograph of the welds. Since all the test met the requirements of ASME, it is concluded that the developed welding method could be implemented for fin to fin welding for forming triple elbows.
Table 02

[0043] Further, it will be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its scope.
[0044] Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention 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. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.
[0045] Further, it will be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its scope.
[0046] Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention 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. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.
[0047] The above description does not provide specific details of the 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.
[0048] 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.
[0049] 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.
[0050] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.