FIELD OF THE INVENTION
The present invention generally relates to circular pipes welding for riser pipes used in boilers for steam generation. More particularly, this invention relates to a method of root welding of riser pipe to elbow without bridge piece in boiler manufacturing process.
BACKGROUND OF THE INVENTION
In the manufacturing of boilers, the riserpipes of outside diameters varying from 88.9 mm to 168.3 mm are used for the usage from the top headers to the water walls to the drum for evacuating the steam and water mixture. The riser pipes come with a 90 degree bend required at site at some positions where a 90 degree elbow is used for manufacturing the shape required in site. Hence joining is necessary of the riser pipes in the shop. The grade of the materials varies from carbon steel to alloy steel of P22 and P91 grades.
Normally, the pipe to elbow joints are first made with welding bridge pieces on the circumference of the pipe and then root welding is carried out. In this process after the root welding, the bridge pieces are removed by hammering and subsequent grinding of the pipe. Since the pipe is under high pressure category, a non-destructive test is to be

carried out such as Liquid Penetrant Inspection (LPI) to find out the surface defects on the ground portion. Moreover, the bridge pieces once used cannot be used again. New bridge pieces are to be fabricated for further joining process. In this process, it takes substantial cycle time to complete one pipe to elbow joint.
Considering the time take and the man power used in this process, new method and device is developed for root welding of pipe to pipe joining for riser pipes.
OBJECTS OF THE INVENTION
It is therefore the object of the invention is to propose a method of root welding of riser pipe to elbow without bridge piece in boiler manufacturing process. A further object of the invention is to propose a device for root welding of riser pipe to elbow without bridge piece in boiler manufacturing process.
A still further object of the invention is to propose a method of root welding of riser pipe to elbow without bridge piece in boiler manufacturing process, which reduces the manufacturing cycle time.
SUMMARY OF THE INVENTION
Accordingly, there is provided a method of root welding of riser pipe to elbow without bridge piece in boiler manufacturing process.

A riser pipe which is to be joined to an elbow is placed on the surface plate. A bottom plate is welded with an elbow locating angle on either side and at the central axis of the base plate. The pipe locating angle of (size higher than the elbow locating angle), is attached to the either side of the bottom plate with a stiffener. The bottom plate is drilled with holes for connecting the top plate by means of bolts. Similarly, top plates are designedsame as that of bottom plate. The root gap 2 mm is maintained by a 2 mm circular rod in between the pipes and the elbow, and the bolts are tightened with nuts and washer. Fixture adjustment is carried out by turning the bolt fixed on the vertical pipe. Now the device is ready for root welding.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows an isometric view of the device with riser pipes and elbow for root welding.
Figure 2 shows a top view of a bottom plate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
The riser pipe (9) which is to be joined to the elbow (10) is placed on the surface plate pipe. The bottom plate (1) is welded with the elbow locating angle (2) on either side and at

the central axis of the base plate. The pipe locating angle (3) is attached to the either side of the bottom plate (1) with stiffener (4) of size 225x110x10 mm. The bottom plate (1) is drilled with holes for connecting the top plate by means of bolts (5). Similarly, top plates (6) are designed same as bottom plate. The root gap of 2 mm is maintained by 2 mm circular rod in between the pipes and the elbow, and the bolts (5) are tightened with nuts and washer. Fixture adjustment is carried out by turning the bolt (7) fixed on the vertical pipe (8). Now the set up is ready for root welding. Instead of 2 shifts per pipe with elbow joint for root welding, this is carried out in 1 hour.

WE CLAIM :
A method of root welding of riser pipe to elbow without bridge piece in boiler manufacturing process comprising the steps of:
- placing the riser pipe (9) to be joined to the elbow (10) on a surface plate; welding a bottom plate (1) with an elbow locating angle (2) on either side and at the central axis of the base plate; attaching a pipe locating angle (3) to either side of the bottom plate (1) with at least one stiffener (4); drilling the bottom plate (1) to form holes for connecting the top plate by means of bolts (5);
- designing a plurality of top plates (6) identical to the bottom plate; maintaining a root gap of 2 mm using a 2 mm circular rod in between the pipes and the elbow; tightening the bolts (5) with nuts and washer; adjusting the formed device by turning the bolt (7) fixed on the vertical pipe (8); and root welding of pipe to pipe joining of the riser pipes.