FIELD OF THE INVENTION
The invention relates to manufacturing of high pressure boiler super heater links formed of pipes. More particularly, the invention relates to a device for joining two pipes without stiffener plates. The invention further relates to a method of welding two tubular members of dis-similar materials without stiffener plates to produce super heater links for high pressure boiler.
BACKGROUND OF THE INVENTION
High pressure boiler super heater links are made up of carbon steel and low alloy steel pipes. The outside diameter of the pipes varies from 219.1mm to 457.2mm, wherein the length of the link is 12 meters. The standard pipe length commercially available is only 6 meters. So to get full length of 12 meter link, the standard pipes are to be joined by conventional butt welding. The root welding is carried out by conventional TIG welding process. For the requirement of TIG welding, the concentricity of the two pipes to be jointed, is to be maintained. Accordingly, stiffener plates of thickness 25mm having width 80mm X 250mm are to be tack welded by equally placing on a first outside end of the pipes. After checking the concentricity, the root welding is started. After completion of the welding, the stiffener plates are removed by either gouging or gas cutting. Because of the gouging or gas cutting, the parent material gets damaged which is ground by a portable grinding machine. Sometimes uneven surfaces are still found after the surface grinding, which is finally subjected to non-destructive testing.

The above prior art method requires more welding touchup and grinding work resulting in higher circle time. Moreover, the setting time of the stiffener plates is also substantial. Additionally, a mobile crane is also required to move the fit-up joints for full welding from one work center to another work center . So in order to reduce the cycle time there is a method and device is required for making butt joint.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a method of welding two tubular members of dis-similar materials without stiffener plates to produce super heater links for high pressure boiler.
Another object of the invention is to propose a device for holding two pipes inline alignment position butt to make a weld joint.
A further object of the invention is to propose a method of welding two tubular members of dis-similar materials without stiffener plates to produce super heater links for high pressure boiler, which reduces the total manufacturing cycle time.
SUMMARY FO THE INVENTION
According to a first aspect of the invention there is provided a method of welding two tubular members of dis-similar materials without stiffener plates to produce super heater links for high pressure boiler. As per the invention, the two work pieces are placed on a roller stand. Length of each work-piece is 6meter, with

outside diameter ranging from 219.1mm to 457.2mm. 4nos of angle plates made up of low alloy steel are fabricated so as to cover the entire length of each work-piece.
Two of the four angle plates are inter-connected by at least one first support plate. Similarly, the balance two angle plates are interconnected by a second support plate. 4 numbers of hexagonal nuts are welded at each end of the angle plate assembly on the same side. The bottom nut acts as a lock nut and the top nut acts as a guiding piece. Two numbers of eye bolts are screwed simultaneously through guiding nut and up to the lock nut. 4 numbers of screw rod made of M16 external thread and, 8 numbers of M16 hexagonal nuts are screwed at each end of said 4 numbers M16 screws. A first end of the M16 screw with nut assembly is welded with the support plate and a second end with an internal threaded sleeve. The internal thread sleeve is already assembled with a hinge screw rod which is having a M30 left-hand thread on a first side and a M30 right-hand thread on a second side. This hinge screw rod is having a hexagonal nut welded at the middle of the rod. The above total assembly is having a weight of one kg and can be easily handled. Now the total assembly is opened on one end by screwing the eye bolt anticlock-wise so as to release from the lock nut and move up to the guiding nut allowing the device to accommodate any diameter of the pipe ranges given above. After opening the assembly, the device is then inserted into the pipes which are to be welded by conventional welding process. Now the total length of the device is adjusted linearly so that equal

distance is maintained from the end of the pipes to be welded. The top and bottom angle plate assembly is tightened by rotating the hinge screw rod. Now the device with the pipes is confirmed in respect of welding by simply rotating the pipe on the rollers which ensures tight fittings. Thus the drawbacks of conventional method of welding using the stiffener plates are completely avoided.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows the hinge screw rod with a hexagonal nut of the holding device.
Figure 2 shows a welding of the angle plates with the support plates.
Figure 3 shows a hinge nut.
Figure 4 shows the stud with a left hand thread at first end and a right hand thread at second end.
Figure 5 shows the elevation view of the device along with two work pieces which are to be welded.
Figure 6 shows the plan view of figure 5.
Figure 7 shows a view of figure 5 taken at p-plane.

DETAIL DESCRIPTION OF THE INVENTION
According to the present invention , a pipe butt joint fit up and welding is carried out by positioning the work pieces in the device having angle plates and adjustable screws at two places. One is in the vertical direction used for locking purpose only and two angle plate clamps are in the horizontal direction. The whole assembly is attached to the stud with a threaded sleeve (shown in figure 5). As the roller stand pipe butt joint is carried out with easy handling of the device with the work piece without much effort.
Figure 1 shows the different parts of the device with a first work piece (01) and a second work piece(02). A first pair of angle plate (04) is of having inclined opening for easy positioning of the work and the angle taper is made 55 degree to the horizontal. The first pair of angle plate (04) is welded with a first horizontal support plate (07) to perfect seating of the work pieces (01 and 02) during clamping with a second pair of semi-circular angle plates (04) and tightened with adjustable hinge screws (06). The second pair of the angle plates is locked (10) on eye bolts (05) at these two clamps, and is also tightened with adjustable hinge screws (06) respectively.
The maximum outside diameter of the work piece is 457mm and thickness of the pipe is 45mm and these pipes are used as steam generator package links.
The horizontal pipes (01, 02) are welded for fixing the pairs of angular plates (04, 06) so as to use the adjustable hinge screws effectively.

WE CLAIM :
A method of welding two tubular members of dis-similar materials without stiffener plates to produce super heater links for high pressure boiler comprising the steps of:
placing the horizontal pipes (01.02) at a 55 degree slant opening on a device to position the job with two pairs of angle plates (04) welded on the top and bottom, the job position can be adjusted by a plurality of adjustment screws (03) on both sides;
positioning the horizontal directions by said adjustable screws (03, 06) in respect of the first and the second pair of semi angular plate (04) respectively,
fixing the work pieces on the horizontal pipe (01, 02) and two pairs of plates (04) with at least two support plate (07) fitted on each side of the work pieces, wherein the size of the angle plates (04, 07, 05, 10) can be varied according to the outside diameter of the pipe (01, 02) and tightening the hinge screw rod (03) to hold cylindrical objects.