Claims:We claim:
1. A novel equipment (10) for welding of tubes (hanger tubes) with plates (spacer bars) for fabrication of coils for boilers, heat exchangers and pressure vessels, the equipment (10) comprising:
a spacer bar/ plate (01) tack welded with a hanger tube / tube (02), the space bar/ plate (01) is loaded on an adjustable base (03) and kept in a position so that welding is performed simultaneously on both sides;
a torches/ welding guns (04) kept in position on both sides of the plate, the torches/ guns (04) kept on a moving trolley/ a wheel mounted a trolley (05) and each torch is connected to the GMAW power source fitted with a wire feeder (06);
a shielding gas/ gas mixture supplied from one or more cylinder (07);
a gas flow rate regulated through a flow meter and a gauges;
an arrangement of the equipment (10) kept on a base (08); and
a start and a stop switches (09) are provided to operate the system.

2. The equipment (10) as claimed in claim 1, wherein the equipment (10) is used in any variant of GMAW process or any gas shielded welding process with welding parameters to produce acceptable quality weld as per ASME or any other equivalent code.

3. The equipment (10) as claimed in claim 1, wherein the equipment (10) is unique for welding of the spacer bars (plates) (01) with hanger tubes (tubes) (02) which are part of coils for boilers / heat exchangers / pressure vessels, etc. in mechanized mode.

4. This equipment (10) as claimed in claim 1, wherein the equipment (10) uses two torches/ welding guns (04) kept on both sides of the plate and welded with the tube.

5. This equipment (10) as claimed in claim 1, wherein the equipment (10) is used to keep the job stationary and the torches/ welding guns (04) moves along with the length of the tube, the plate assembly, and welding is performed in 2G position.

6. The equipment (10) as claimed in claim 1, wherein the equipment (10) is used to make the weld by an any filler wire/ welding consumable which is suitable for the materials to be welded.

7. The equipment (10) as claimed in claim 1, wherein the equipment (10) is used to make the weld with or without preheating, and or post heating.

8. The equipment (10) as claimed in claim 1, wherein the equipment (10) is used to make the weld with or without purging gas.

9. The equipment (10) as claimed in claims 1, wherein the equipment (10) is used to make the weld in horizontal position of the welding (2G / 2F).

10. The equipment (10) as claimed in claims 1, wherein the equipment (10) is used to make the weld by selecting suitable parameters like viz. a torch angle, a lap distance, a weld position, a stand of distance, a distance between lead and a follower torches, a welding current, a welding voltage, a polarity, a shielding gas, a gas flow rate, a torch travel speed and a wire feed to produce flawless welds.
, Description:A NOVEL EQUIPMENT AND PROCEDURE FOR JOINING OF PLATES WITH TUBES FOR BOILERS, HEAT EXCHANGERS, AND PRESSURE VESSELS
TECHNICAL FIELD
[0001] The present invention relates to a novel equipment and procedure for joining of plates with tubes for boilers, heat exchangers and pressure vessels. More particularly the invention relates to the development of an equipment comprising a base, wheel mounted trolley to carry the welding torches, start / stop switches, guide ways for movement of trolley, GMAW power sources, wire feeder and welding torches and an adjustable base to keep the hanger tube assembly and development of a procedure for joining a plate with a tube for fabrication of such coil assemblies for boilers / heat exchangers / pressure vessels, etc. The invention serves the purpose of ensuring increased productivity in fabrication of such coils assemblies for boilers / heat exchangers / pressure vessels, etc. The invention also reduces the production cycle time from the present method of fabrication and also enhances the quality. The invention also results in reducing the level of distortion in the welded components.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention.
[0003] In fabrication of components for boilers, pressure vessels, heat exchangers welding of plates with tubes by a method called as fillet joint is required. For example, in fabrication of Reheater Coils (RH), welding of hanger tubes with plates known as spacer bars is a critical stage of the procedure. The no. of hanger tubes per coil varies from 4 to 6 depending upon the design of the coil.
[0004] In the present art, the welding is being done by Shielded Metal Arc Welding (SMAW) process involving the skilled welders. It requires one man day to weld one such component i.e. for welding the hanger tubes with spacer bars.
[0005] Due to the inherent issues in SMAW process, the productivity and quality of the component is not up to the expected level. Further, it depends upon the skill of the welders. Since, there is a restriction in the travel speed not much improvement could not be made with SMAW process, as for as productivity is concerned. Further, it often results in distortion and bow correction after welding. The drawbacks in the prior are can be summarized as
• More deposition time due to low welding speed.
• Distortion due to improper weld sequence and more heat input.
• Deployment of skilled welders
• More weld reworks
• More cycle time

[0006] Therefore, it will be beneficial, if we could develop and deploy a mechanized equipment for welding of tubes (hanger tubes) with plates (spacer bars) by Gas Metal Arc Welding (GMAW) process at the shop floor for enhanced quality and productivity.
[0007] From the literature available in the public domain and the feasibility trials done by BHEL we could infer the following.
• Hanger tubes and spacer involve welding of dissimilar and similar welding combinations involving ferrous materials esp. the carbon steel and alloy steel materials.
• GMAW process could be deployed successfully for welding of tubes (hanger tubes) with plates (spacer bars).
• No readymade mechanized equipment is available for welding of hanger tubes with spacer bars and such an equipment has to be invented as a novel equipment.

[0008] A tailor made mechanised spacer bar to hanger tube GMA welding equipment capable of welding for varying lengths ranging from 2 m to 5 m, has been developed for the first time in the world and implemented at shop floors of BHEL.
PRIOR ART SEARCH
[0009] The patent research carried out through BHEL enabled web site for patent research relates to
• Fabrication of boilers yielded 4 results which are not relevant to our invention.
• Boiler manufacturing yielded 257 results and none of them related to our invention.
• Boiler pressure parts yielded 86 results and none of the patents are related to our invention.
• Heat Exchanger fabrication yielded 3000 results and no patent is related to our invention.
• Coil fabrication yielded 336 documents and no document is related to ours.

[0010] From the patent search no patent has provided any reference to the proposed process for fabrication of coil assemblies.

[0011] United States Patent Publication US20100307429A1 discloses welding structure of tube stubs and tube header.
[0012] In order to provide a welding structure of a tube header and tube stubs which successfully improves the durability thereof against creep and fatigue damage of the tube stubs without interposing a component of a different material between the tube header and the tube stubs, i.e. requiring additional components, a welding structure of the present invention comprises: a tube header (2) being made of ferritic heat resisting steel; a plurality of tube stubs (4) which are welded onto an outer surface of the tube header, each of the tube stubs having a bended section, in which the plurality of tube stubs (4) are made of austenite stainless steel, and welded to the tube header (2) by using nickel base alloy as a welding material. Moreover, annular chases (10) are respectively formed on the outer surface of the tube header (2) to surround welding portions of the tube header (2); joining portions (14) are formed on an inner side of the annular chases (10); butt grooves are formed by joining surfaces of the tube stubs (4) and the joining portions (14) in a continuous manner and welded by using the nickel base alloy as a welding material, the tube stubs having a diameter substantially same as those of the joining portions.
[0013] United States Patent Publication US3262497A discloses header-tube assembly and fitting therefor.
[0014] The present invention relates broadly to a fitting for connecting a tube to a header and to the assembly of a plurality of said fittings and tubes with said header. More specifically, the present invention relates to a fitting for connecting a plurality of tubular elements to a pipe header and to the assembly of a plurality of said fittings and tubes with said header.
[0015] Therefore, there is a need for a novel equipment and procedure for joining of plates with tubes for boilers, heat exchangers, and pressure vessels.
OBJECTS OF THE DISCLOSURE
[0016] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed herein below.
[0017] The principal object of the present subject matter is to develop an equipment for welding of tubes (hanger tubes) with plates (Spacer bars) for fabrication of coils for boilers / heat exchangers / pressure vessels, etc. in mechanized mode.
[0018] Another object of the present invention is to develop the equipment with GMAW process.
[0019] Another object of the present invention is to develop the equipment with two torches / welding guns so that welding can be carried out simultaneously on both sides of the plate.
[0020] Another object of the present invention is to develop the equipment so that the torches / welding guns can move along the length of the job and the job will be kept stationary for carrying out the welding simultaneously on both sides of the plate.
[0021] Another object of the present invention is to develop a welding procedure and establish GMAW process parameters by moving the torches / welding guns along the length of the job and the job will be kept stationary for carrying out the welding simultaneously on both sides of the plate.
[0022] Another object of the present invention is to improve upon the productivity using the new equipment and process.
[0023] Another object of the present invention is to reduce the level of distortion and to improve weld quality.
[0024] Another object of the present invention is to deploy lesser skilled persons and to redeploy the skilled welders for other productive jobs.
[0025] Another object of the present invention is to use any type of filler wire viz. solid, flux cored, metal cored, etc.
[0026] These and other objects and advantages will become more apparent when reference is made to the following description and accompanying drawings.

SUMMARY
[0027] This summary is provided to introduce concepts related to a novel equipment and procedure for joining of plates with tubes for boilers, heat exchangers, pressure vessels, etc. made of plates of thickness ranging from 4 – 10 mm and varying tube diameter from 33 – 69 mm size. The novel invention relates to the development of an equipment comprising a Base, Wheel mounted trolley to carry the welding torches, Start / stop switches, Guide ways for movement of trolley, GMAW power sources, wire feeder & welding torches and an adjustable base to keep the hanger tube assembly and development of a procedure for joining a plate with a tube for fabrication of such coil assemblies for boilers/ heat exchangers / pressure vessels, etc. The invention uses GMAW process and keep the job stationary with two torches for carrying out simultaneous welding. The invention reduces the production cycle time from the present method of fabrication.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The illustrated embodiments of the subject matter will be 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 methods that are consistent with the subject matter as claimed herein, wherein:
[0029] Fig. 1 shows the arrangement of the equipment and its parts, in accordance with an embodiment of the present subject matter.
[0030] 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.
DETAILED DESCRIPTION
[0031] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein 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 scope of the present disclosure as defined by the appended claims.
[0032] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0033] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a",” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0034] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0035] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0036] Fig. 1 shows the arrangement of the equipment and its parts. according to some example embodiment of the invention. In an embodiment, the spacer bar / plate (01) is tack welded with the hanger tube / tube (02) and loaded on the adjustable base (03) and kept in a position so that welding can be done simultaneously on both sides. The torches / welding guns (04) is kept in position on both sides of the plate so that the fusion will take place both in plate and tube. The torches / guns are (04) kept on a moving trolley / wheel mounted trolley (05) and each torch is connected to the GMAW power source fitted with wire feeder (06). The shielding gas / gas mixture is supplied from a cylinder / cylinders (07). The gas flow rate is regulated through a flow meter and gauges. The total arrangement is kept on a base (08). Start and stop switches (09) are provided to operate the system.
[0037] Suitable filler wire and size are decided depending upon the properties of materials to be welded. The welding parameters for GMAW process viz. Torch angle, Lap distance, Weld Position, Stand of Distance, distance between lead and follower torches, welding current, welding voltage, Polarity, Shielding Gas, Gas Flow Rate, Torch Travel Speed, Wire feed and preheat (if necessary), which are established by conducting trials will be used to perform the weld.
[0038] Further, the present invention involves development of a novel equipment and procedure for joining of plates with tubes for boilers, heat exchangers, pressure vessels, etc. made of plates of thickness ranging from 4 – 10 mm and varying tube diameter from 33 – 69 mm size. The present invention involves development of an equipment (10) comprising a base, wheel mounted trolley (05) to carry the welding torches, Start / stop switches (09), guide ways for movement of trolley (05), GMAW power sources, wire feeder (06) and welding torches and an adjustable base to keep the hanger tube assembly and development of a procedure / parameters for joining a plate with a tube for fabrication of such coil assemblies for boilers / heat exchangers / pressure vessels, etc. The purpose is to develop the equipment (10) with GMAW process, with two torches / welding guns (04) so that welding can be carried out simultaneously on both sides of the plate. The present invention also aims to develop the equipment (10) and parameters to produce flawless welding in such a way that the torches / welding guns (04) can move along the length of the job and the job will be kept stationary for carrying out the welding simultaneously on both sides of the plate. The present invention serves the purpose of ensuring increased productivity in fabrication of such coils assemblies for boilers / heat exchangers / pressure vessels, etc. The present invention also reduces the production cycle time from the present method of fabrication and also enhances the quality and makes significant improvements over the prior art. This invention also results in reducing the level of distortion in the welded components.
[0039] The advantages of the novel equipment and procedure for joining of plates with tubes for boilers, heat exchangers, and pressure vessels is that the equipment (10) is used for any range of boilers / pressure vessels / heat exchangers. The equipment (10) is used for in any diameter/ size of tubes, plates for any high temperature and high pressure applications. Further, the equipment (10) is used to make welds with or without root gap and to make welds with or without full or partial grooves. The equipment (10) is also used to weld any size of the tube and plate. Furthermore, the equipment (10) is used to make the welds with short / medium / long arc depending upon the welding parameters. Moreover, the equipment (10) is used to make the welds with suitable size of filler wire.
[0040] The significant differences between the prior art and the innovation is detailed below.
Description Prior Art Developed Method
Technology SMAW process GMAW (FCAW / Solid Wire GMAW / Metal Cored GMAW) can be used
From the literature available in the public domain, we understood that no such system is available. Collaborator also has also recommended SMAW process only. A mechanized system with twin torch is developed for the first time in the world by bhel. Total development was made in-house.
Lesser travel speed due to restrictions in the speed of hand travel Higher travel speed could be obtained on the mechanized system
Skill requirement Skilled and qualified SMA welder is required to make the welds. Can be done by mechanized GMAW process. Dependency of welders’ skill component is eliminated.
Occurrence of defects & Distortion More Negligible
Cost Man hours required per annum is between 7000 -7500 man days. Man hours required will be 360 only.
Hot / cold correction is required to maintain the straightness Eliminated
Required more energy Less energy consumption.

[0041] 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.”
[0042] 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.