Claims:We claim:
1. A method of welding a ‘T’ forging (04) with horizontal hanger tube (03) and vertical hanger tube (02), the method comprising:
reducing (702) height of the ‘T’ Forging (04);
welding (704) the vertical hanger tube (02) with the ‘T’ forging (04);
increasing (706) straight portion (S2) at one end of the horizontal hanger tube (03); and
welding (708) the horizontal hanger tube (03) with the ‘T’ forging (04) welded with the vertical hanger tube (02).

2. The method as claimed in claim 1, wherein the reducing (702) height (H1) of the ‘T’ forging (04) upto height (H2) which is equivalent and smaller than diameter (D) of chuck (05A) of straight tube butt welding machine.

3. The method as claimed in claim 1, wherein the welding (704) the vertical hanger tube (02) with the ‘T’ forging (04) is done by straight tube butt welding machine.

4. The method as claimed in claim 1, wherein the welding (708) of the horizontal hanger tube (03) with the ‘T’ forging (04) welded with the vertical hanger tube (02) is done by orbital TIG welding machine.

5. The method as claimed in claim 1, wherein the straight portion at one end of the horizontal hanger tube (03) is increased to length (S2) from length (S1).

6. The method as claimed in claim 1, wherein dimensions (P, V) of the horizontal hanger tube (03) remains same after increasing the straight portion at one end.

7. The method as claimed in claim 1, wherein height of the ‘T’ forging (04) is reduced by machining.

8. The method as claimed in claim 1, wherein straight tube butt welding machine has two chucks (05A, 05B) to hold the vertical hanger tube (02) and the ‘T’ forging (04).
, Description:PROCESS OF INTERCONNECTION OF VERTICAL HANGER TUBE TO HORIZONTAL HANGER TUBE THROUGH AUTOMATED WELDING METHODS IN ECONOMISER UPPER COIL ASSEMBLY
FIELD OF INVENTION:
[001] The present subject matter described herein, relates to process of inter connection of vertical hanger tube to horizontal hanger tube through an automated welding methods in an economiser upper assembly. More particularly the present invention relates to a method for welding the vertical hanger tubes with the horizontal hanger tubes of the economiser upper assembly using straight tube butt welding machine and orbital TIG welding machine.
BACKGROUND AND PRIOR ART:
[002] The function of an economiser in a steam generating unit is to absorb heat from the flue gases and add this as sensible heat to the feed water before the water enters the evaporative circuit of the boiler. Earlier the economisers were introduced mainly to recover the heat available in flue gas that leaves the boiler and provision of this additional heating surface increased the efficiency of steam generation, saving in fuel consumption, thus the name “Economiser” christened. Economiser coils are designed for horizontal placement which facilitate draining of the coil and favors the arrangement in second pass of boiler. In a typical tower type once through super critical boiler there are two banks of economiser. The upper bank economiser coil is designed with tube D42.4 x 5/SA210GrC. These economiser coils are supported by vertical hanger tubes (D47.63 x 10/T91). Also in this design there are horizontal hanger tubes (D47.63 x 6.6/T22). These vertical hanger tubes are connected at the bottom to horizontal hanger tube with inter connecting ‘T’ forging of F91 material. The arrangement is illustrated in Figure 1. As indicated in figure 1, there is no need to do post weld heat treatment for D42.4 x 5/SA210GrC after bending and welding. But there is a need to do post weld heat treatment at 745 ± 15 °C for the welding of vertical hanger tube (D47.63 x 10/T91) and horizontal hanger tube (D47.63 x 6.6/T22) with F91 forging. In an assembly there are six vertical and six horizontal hanger tubes and each of vertical and horizontal hanger tubes are connected to each other by a ‘T’ forging. There are around 82 assemblies of economiser in the upper bank. So there are about 492 numbers of butt welding have to be made between vertical hanger tube and ‘T’ forging and 492 numbers of butt welding have to be made between horizontal hanger tube and ‘T’ forging. Totally 984 numbers of manual butt joints have to be made to manufacture upper bank economiser of a typical tower type boiler. The cycle time for manual welding of this 984 manual butt joint accounts to 123 production shifts which is equal to 41 days of 3 shift productions.
[003] Accordingly, the technical problem of the existing solution is high number of manual butt joints which increases the production time which is equal to 42 days of 3 shifts production in a day.
[004] Hence there is a need to innovate automation in welding of vertical and horizontal hanger tubes with ‘T’ forging by the way of experiments.
OBJECTS OF THE INVENTION:
[005] The principal objective of the present invention is to provide method of automated welding of ‘T’ forging with vertical and horizontal hanger tubes.
[006] Another object of the present subject matter is to provide an automated welding process in two stages.
[007] Another object of the present subject matter is to eliminate manual butt welding of ‘T’ forging with vertical and horizontal hanger tubes and thereby to minimize the cycle time.
SUMMARY OF THE INVENTION:
[008] The subject matter disclosed herein relates to a method of welding a T forging with the horizontal hanger tube and vertical hanger tubes in straight tube butt welding machine and orbital TIG welding machine. The present method reduces the overall turnaround time of the welding process by using two stage welding process. In order to minimize the cycle time, the present method performs machine welding of ‘T’ forging with vertical and horizontal hanger tubes. Accordingly in first stage the welding of vertical hanger tube with ‘T’ forging was planned and performed in straight tube butt welding machine. The problem faced while this welding is the height of ‘T’ forging was 117mm (H1) as per drawing. But the internal bore diameter of chuck of Straight tube butt welding machine was only 95mm (D). With this constrain, the ‘T’ forging along with vertical hanger tube couldn’t be taken out of chuck after straight tube butt welding. This constrain was overcame by reducing the forging height from initial 117mm (H1) to 90mm (H2) by machining. This reduction in height was compensated by adding additional material in horizontal hanger tube.
[009] After completion of welding the vertical hanger tube with ‘T’ forging, in second stage it was planned to weld this ‘T’ forging –vertical hanger tube assembly to horizontal hanger tube on Orbital-TIG welding machine. The constrain faced here was that the Orbital-TIG welding machine needs minimum 350mm straight portion in any one side of the mating tubes for mounting the machine and free rotation of the machine components over the tube. In this welding one mating component is ‘T’ forging and other mating component is horizontal hanger tube. This horizontal hanger tube have a multi plane offset bend at a distance of 204.7mm (S1) from end of the tube which will be getting welded with the ‘T’ forging. With this constrain it is not possible to mount and rotate the Orbital-TIG welding machine over the tube. On experimental basis, this 204.7mm (S1) was increased gradually and optimised to 403.3mm (S2) and this increase in length was adjusted in the remaining length of horizontal hanger tube after bends.
[0010] With these two modification, it is possible to automate the welding of vertical and horizontal hanger tube with ‘T’ forging in straight tube and orbital TIG welding machines, respectively. The cycle time before improvement. The output per shift for manual butt joint is 5. The cycle time of 984 manual butt joints (492 between ‘T’ forging and vertical hanger tube + 492 between ‘T’ forging and horizontal hanger tube) is 197 shifts. The cycle time after improvement: The output per shift for STB butt joint is 36 and O-TIG butt joint is 8. The cycle time of 492 STB butt joints between ‘T’ forging and vertical hanger tube is 14 shifts and the cycle time of 492 O-TIG butt joints between ‘T’ forging and horizontal hanger tube is 61 shifts. The total cycle time for STB and O-TIG is 74 shifts.
[0011] In order to further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit scope of the present subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] 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, the left-most digit(s) of 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 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:
[0013] Fig. 1 illustrates schematic view of the typical economiser coil assembly with vertical and horizontal hanger tube as known in the art;
[0014] Fig. 2 illustrates the schematic view of vertical and horizontal hanger tube with ‘T’ forging as known in the art;
[0015] Fig. 3 illustrates the welding of ‘T’ forging with vertical hanger tube before modification in ‘T’ forging height, in accordance with the present subject matter;
[0016] Fig. 4 illustrates welding of ‘T’ forging with vertical hanger tube after modification in ‘T’ forging height for the first stage of welding, in accordance with the present subject matter;
[0017] Fig. 5 illustrates the horizontal hanger tube before modification of arm length, in accordance with the present subject matter;
[0018] Fig. 6 illustrates the horizontal hanger tube after modification of arm length for the first stage of welding, in accordance with the present subject matter; and
[0019] Fig. 7 illustrates the method of welding of horizontal hanger tube with the vertical hanger tube using T forging, in accordance with the present subject matter.
[0020] 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.
DESCRIPTION OF THE PREFERRED EMBODIMENTS:
[0021] The subject matter disclosed herein relates to a method of welding a T forging with the horizontal hanger tube and vertical hanger tubes in straight tube butt welding machine and orbital TIG welding machine. The present method reduces the overall turnaround time of the welding process by using two stage welding process. In order to minimize the cycle time, the present method performs machine welding of ‘T’ forging with vertical and horizontal hanger tubes. Accordingly in first stage the welding of vertical hanger tube with ‘T’ forging was planned and performed in straight tube butt welding machine. The problem faced while this welding is the height of ‘T’ forging was 117mm (H1) as per drawing. But the internal bore diameter of chuck of Straight tube butt welding machine was only 95mm (D). With this constrain, the ‘T’ forging along with vertical hanger tube couldn’t be taken out of chuck after straight tube butt welding. This constrain was overcame by reducing the forging height from initial 117mm (H1) to 90mm (H2) by machining. This reduction in height was compensated by adding additional material in horizontal hanger tube.
[0022] After completion of welding the vertical hanger tube with ‘T’ forging, in second stage it was planned to weld this ‘T’ forging –vertical hanger tube assembly to horizontal hanger tube on Orbital-TIG welding machine. The constrain faced here was that the Orbital-TIG welding machine needs minimum 350mm straight portion in any one side of the mating tubes for mounting the machine and free rotation of the machine components over the tube. In this welding one mating component is ‘T’ forging and other mating component is horizontal hanger tube. This horizontal hanger tube have a multi plane offset bend at a distance of 204.7mm (S1) from end of the tube which will be getting welded with the ‘T’ forging. With this constrain it is not possible to mount and rotate the Orbital-TIG welding machine over the tube. On experimental basis, this 204.7mm (S1) was increased gradually and optimised to 403.3mm (S2) and this increase in length was adjusted in the remaining length of horizontal hanger tube after bends.
[0023] With these two modification, it is possible to automate the welding of vertical and horizontal hanger tube with ‘T’ forging in straight tube and orbital TIG welding machines, respectively. The cycle time before improvement. The output per shift for manual butt joint is 5. The cycle time of 984 manual butt joints (492 between ‘T’ forging and vertical hanger tube + 492 between ‘T’ forging and horizontal hanger tube) is 197 shifts. The cycle time after improvement: The output per shift for STB butt joint is 36 and O-TIG butt joint is 8. The cycle time of 492 STB butt joints between ‘T’ forging and vertical hanger tube is 14 shifts and the cycle time of 492 O-TIG butt joints between ‘T’ forging and horizontal hanger tube is 61 shifts. The total cycle time for STB and O-TIG is 74 shifts. Saving in cycle time: So the net saving in cycle time is 123 shifts.
[0024] 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.
[0025] 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.
[0026] Referring to fig.1, the schematic view of tower type economiser coil is shown. The economiser coil tube (D42.4 x 5/SA210 Gr.C) is indicated as item no 01. The vertical hanger tube (D47.63 x 10/SA213 T91) is indicated as item no 02. The horizontal hanger tube (D47.63 x 6.6/SA213 T22) is indicated as item no 03A, 03B, 03C, i.e., three variants. The F91 ‘T’ forging is indicated as item no 04.
[0027] Figure 2 shows the separate schematic view of vertical hanger tube (02) and horizontal hanger tube (03A) with ‘T’ forging (04).
[0028] Figure 3 indicates the welding of ‘T’ forging (04) with vertical hanger tube (02) in straight tube butt welding machine. The chuck (05B) of the straight tube butt welding machine holds vertical hanger tube (02) and other chuck (05A) holds ‘T’ forging (04) before and during welding. The internal diameter of chuck is D and height of ‘T’ forging is indicated by ‘H1’. The value of ‘H1’ is more than ‘D’. With this constrain, the ‘T’ forging couldn’t be taken out of chuck after welding.
[0029] In order to minimize the cycle time, it is planned to perform machine welding of ‘T’ forging with vertical and horizontal hanger tubes. Accordingly in first stage the welding of vertical hanger tube with ‘T’ forging was planned in straight tube butt welding machine referring to figure 3. The problem faced while this welding is the height of ‘T’ forging was 117mm (H1) as per drawing. But the internal bore diameter of chuck of Straight tube butt welding machine was only 95mm (D). With this constrain, the ‘T’ forging along with vertical hanger tube couldn’t be taken out of chuck after straight tube butt welding. This constrain was overcame by reducing the forging height from initial 117mm (H1) to 90mm (H2) by machining referring to figure 4. This reduction in height was compensated by adding additional material in horizontal hanger tube.
[0030] After completion of welding the vertical hanger tube with ‘T’ forging, in second stage it was planned to weld this ‘T’ forging –vertical hanger tube assembly to horizontal hanger tube on Orbital-TIG welding machine. The constrain faced here was that the Orbital-TIG welding machine needs minimum 350mm straight portion in any one side of the mating tubes for mounting the machine and free rotation of the machine components over the tube. In this welding one mating component is ‘T’ forging and other mating component is horizontal hanger tube. This horizontal hanger tube have a multi plane offset bend at a distance of 204.7mm (S1) from end of the tube which will be getting welded with the ‘T’ forging referring to figure 5. With this constrain we were not able to mount and rotate the Orbital-TIG welding machine over the tube. On experimental basis, this 204.7mm (S1) was increased gradually and optimised to 403.3mm (S2) and this increase in length was adjusted in the remaining length of horizontal hanger tube after bends referring to figure 6.
[0031] The present method of automating the manual butt welding in two different stages. In first stage, the welding of vertical hanger (02) tube with ‘T’ forging (04) was done in straight tube butt welding and in second stage the welding of horizontal hanger tubes (03A, 03B, 03C) with ‘T’ forging (04) was done in orbital TIG welding machine. The height ‘H1’ of the ‘T’ forging (04) is reduced to ‘H2’ to facilitate welding in straight tube butt welding machine. Also the dimension ‘S1’ of horizontal hanger tube is increased to ‘S2’. However the overall dimension of horizontal hanger tube is kept same. Because of this modification 984 manual butt joints were converted to automated machine welding thereby the cycle time saving accounts to 123 production shifts which is equal to 41 days of 3 shift productions.
[0032] With these two modification, it is possible to automate the welding of vertical and horizontal hanger tube with ‘T’ forging in straight tube and orbital TIG welding machines, respectively. The cycle time before improvement. The output per shift for manual butt joint is 5. The cycle time of 984 manual butt joints (492 between ‘T’ forging and vertical hanger tube + 492 between ‘T’ forging and horizontal hanger tube) is 197 shifts. The cycle time after improvement: The output per shift for STB butt joint is 36 and O-TIG butt joint is 8. The cycle time of 492 STB butt joints between ‘T’ forging and vertical hanger tube is 14 shifts and the cycle time of 492 O-TIG butt joints between ‘T’ forging and horizontal hanger tube is 61 shifts. The total cycle time for STB and O-TIG is 74 shifts. Saving in cycle time: So the net saving in cycle time is 123 shifts.
[0033] Fig. 7 illustrates the method of welding of horizontal hanger tube with the vertical hanger tube using T forging, in accordance with the present subject matter. The method starts with step 700 when all tubes and forging are ready for welding. At step 702, height of the T forging is reduced as per straight tube butt welding machine. Referring to figure 4 for detailed explanation of step 702, the height of ‘T’ forging (04) was reduced to H2 from H1 of figure 3. The height H2 is made less than D by machining. With this modification, the ‘T’ forging (04) is able to come out of chuck (05A or 05B) after butt welding.
[0034] At step 704, the T forging 04 with reduced height is welded with the vertical hanger tube 02 in the straight tube butt welding machine.
[0035] At step 706, straight portion length at one end of the horizontal hanger tube is increased to S2. Referring to figure 5 and 6 for detailed explanation of step 704, the straight portion length at one end of horizontal hanger tube (03) is indicated by S1. The length S1 is not sufficient to hold and weld the tubes by orbital TIG welding machine. Therefore, the straight portion at one end of horizontal hanger tube 03 is increased to S2 from S1 referring to figure 5. This leads to corresponding change in dimensions like Q2, R2, T2 and U2 in figure 6 from Q1, R1, T1 and U1 in figure 5 respectively. Note that the overall dimensions P and V remain same in figure 5 and figure 6. The dimensions S1, S2, Q2, R2, T2 and U2 are the various straight portion dimensions of the horizontal hanger tubes. The dimension P and V are the overall dimensions of the horizontal hanger tube. Inorder to facilitate holding of horizontal hanger tube in O-TIG machine the straight portion was increased by maintaining the overall dimension P and V same. This is done by reengineering of the design of horizontal hanger tube.
[0036] At step 708, the vertical hanger tube 02 with the T forging 04 is welded with the horizontal hanger tube 03 using the orbital TIG welding machine. In this way, drawbacks said in the background are eliminated.
[0037] Advantages of the Invention
[0038] The present alternate design by modifying the height of ‘T’ forging and the arm length of horizontal hanger tubes eliminates the need of manual welding of ‘T’ forging with vertical and horizontal hanger tubes.
[0039] This modification converts 984 manual butt joints to automated machine welding thereby the cycle time saving accounts to 123 production shifts which is equal to 41 days of 3 shift production.
[0040] 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.