FIELD OF THE INVENTION
The field of invention is generally related to circular pipes welding for riser pipes
used in boilers for steam generation. More particularly the present invention
relates to device and method of fixing the pipes for root welding.
BACKGROUND OF THE INVENTION
In the manufacturing of boilers, riser pipes of outside diameters varying from
88.9mm to 168.3mm are used to the top headers, the water walls and to the drum
for evacuating the steam and water mixture. The length of the riser pipes are
varying from 8000mm to 11960mm to be sent as single piece to site for assembly,
whereas the supplied length of the pipe is only 6000mm. Hence joining is
necessarily done in shop. The grade of the materials vary from carbon steel to
alloy steel of P22 and P91 grades.
Normally, the pipe to pipe joints are made with welding bridge pieces on the
circumference of the pipe and then root welding is carried out. In this process,
after root welding, the bridge pieces are removed by hammering and subsequent
grinding the pipe. Since the pipe is under high pressure category, non-destructive
test is mandatory and 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 reused again. Again fresh bridge pieces are to be fabricated
for further joining process. In the older process, it takes two shifts to complete
one pipe to pipe joint.
Considering the time taken and the man power used in the previous process, like
welding with bridge pieces and further removing new method and device have
been developed for root welding of pipe to pipe joining for riser pipes.

OBJECTS OF THE INVENTION
o An object of the present invention is to develop an arrangement and method
of fixing pipes for root welding.
o Another object of the invention is to develop a method of root welding that
do not require bridge pieces.
SUMMARY OF THE INVENTION
The riser pipes which are to be joined are placed in the middle with surface plates
(1L, 1R) and (4L, 4R) on either side. The two surface plates (1L, 1R) and (4L, 4R)
which are placed side by side are already ensured to be in the same plane. Each
surface plate (1L, 1R, 4L, 4R) is welded with the locking angle of size 75 x 75 x
6mm at the middle of the base plate. A pair of support angle of size 50 x 50 x
6mm is welded on each side of the locating angle to provide necessary supports.
The bottom plate (1L, 1R) is drilled with holes for connecting with the top plates
(4L,4R) by means of bolts with nut and washer. The left and right side of the
bottom plate are connected by handling stiffener. Similarly top plates are
connected by another handling stiffener. The root gap of 2mm is maintained by a
2mm circular rod in between the pipes and the bolts are tightened with nuts and
washer. Fine adjustment is carried out with less effort by turning the bolt fixed
on the vertical pipe. Now the set up is ready for root welding. Instead of 2 shifts
per pipe joint for root welding, this is carried out in 1 hour.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure.1: shows the isometric view of the set up with pipes for root welding.

DETAILED DESCRIPTION OF THE INVENTION
The riser pipes (11,12) which are to be joined together are placed face to face
between two surface plate assembly, one (13) at the top and the other (14) at the
bottom (14) for holding the riser pipes (11,12) firmly.
The top surface plate assembly (13) comprises of a pair of surface plates (4L and
4R) joined together by a handling stiffener (8) such that the surface of (4L) and
(4R) are co-planar. Similarly the bottom surface plate assembly (14) comprises of
a pair of surface plate (1L) and (1R) connected together by a another handling
stiffener (8) such that the surfaces of (1L) and (1R) are also co-planar.
Now each surface plate (4L, 4R, 1L, 1R) is welded with one locating angle (2) at
the centre flanked by a pair of support angle (3) on either side on the surface
facing the riser pipes. A bolt (9) disposed in the rod (10) which is fitted on the
surface of one of the surface plates is used for adjusting the alignment of pipes 11
and 12).
The surface plate assemblies (13) and (14) are held together by an arrangement
of bolts (5), nuts (6) and washer (7). When the bolts (5) are tightened the
surface assemblies (13,14) grips the riser pipes (11,12) through the V-shaped
surface of locating angle (2), wherein the alignment of the pipes are done by the
bolts (9) fitted in the pipe (10).

WE CLAIM
1. A set up for fixing riser pipes (11,12) in boilers for root welding without
bridge pieces comprising:
a pair of top and bottom surface plate assemblies (13,14), the said each
surface plate assembly (13,14) comprises a pair of surface plates (4L, 4R)
connected by handling stiffener (8) on the top side and a similar pair of
surface plates (1L, 1R) connected by another handling stiffener (8) on the
bottom side wherein each surface plate (4L,4R,1L,1R) comprises a locating
angle (2) flanked by a pair of support angle (3) on either side, welded on to
its surface for reinforcement when the surface plate assemblies (13,14) are
attached to each other gripping the riser pipe (11,12) by means of bolts
(5), nuts (6) and washer characterized in that the riser pipes (11,12) are
held together by means of V-shaped locating angle (2) that ensure proper
gripping wherein a bolt (9) is disposed in the pipe (10) for alignment of
riser pipes (11,12).
2. A method of fixing the riser pipes for root welding by a set up as claimed in
claim 1 comprising:
Placing the riser pipes (11,12) facing each other in the same axis between
two surface plate assemblies (13) and (14) guided by four locating angles
(2) for gripping the riser pipes (11,12) from either side of joints;
maintaining a root gap of 2mm by a 2mm circular rod (not shown)
between the pipes (11,12);
inserting four bolts (5) through the holes on the surface plates (1L, 1R, 4L,
4R) for tightening by nuts (6) and washer (7);
adjusting the fixture for alignment of riser pipes (11,12) by turning bolt (9)
fixed on vertical pipe (10) such that the set up is ready for root welding.