FIELD OF THE INVENTION
The invention generally relates to Double Side Arc Welding process (DSAW) for
plates to plate and pipe to pipe joints of various sizes.
The invention in particular relates to a process for double side arc welding
(DSAW) of components to ensure full penetration of the weld joint by welding
simultaneously from both sides. More particularly, the invention relates to an
apparatus and process for double side arc welding for steel material.
BACKGROUND OF THE INVENTION
Manufacturing of pipes for different applications with the thickness range from
12 mm to 65 mm and larger pipe diameter upto 3000 mm are made by using arc
welding processes. Similarly where the fabrication involves plates of various
dimensions with the range of 20 mm to 200 mm thick are also welded by using
arc welding processes.
For welding of pipes and plates of above said ranges, at present, the root pass is
made with or without a hot pass. Then the bottom of the root pass is back
gouged / ground to have a smooth surface. The surface is checked by a Liquid /
Dye penetrant NDT method to ensure that the surface is free from flaws. Then
welding from both the side are completed as per the welding plan. In this
process, the welding is done from one side only, at a given time.

According to the prior art, K-grooved joint preparation is used and it is filled by
using single sided arc welding process which involves welding of root pass
followed by hot pass from one side and then back gouging from other side. After
the back gouging, liquid penetrant inspection is done to ensure the root
soundness. The welding from the other side is carried out thereafter in the
similar process.
Considering the lower productivity, high distortion rate and more time
consumption, there exists a need for development of a technology to allow
simultaneous welding from both sides wherein the weld deposition rate can be
significantly improved, and wherein the need of back grinding or gouging
requires liquid penetrant inspection for root run inspection, can be eliminated.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose an apparatus and
process for double side arc welding for steel material.
Another object of the invention is to propose an apparatus and process for
double side arc welding process of steel plates of various dimensions.
A still another object of the invention is to propose an apparatus and process for
double side arc welding of steel pipes of various dimension.

Yet another object of the present invention is to propose an apparatus and
process for double side arc welding for steel material which improves the
productivity by allowing simultaneous welding from either side of the groove.
Another object of the invention is to propose an apparatus and process for
double side arc welding for steel material, which reduces the problem of
distortion, by deploying uniform heat input and simultaneously welding from
either side of the groove.
A further object of the present invention is to propose an apparatus and process
for double side arc welding for steel material, which eliminates the operation of
back grinding / back gouging after root pass.
A still further object of the present invention is to propose an apparatus and
process for double side arc welding for steel material, which eliminates liquid /
dye penetrant testing to ensure the soundness of root run.
These and other objects and advantages of the invention will be apparent from
the ensuing description. At the outset of the description, which follows, it is to be
understood that the ensuing description only illustrates a particular form of this
invention. However, such a particular form is only an exemplary embodiment and
the teachings of the invention are not intended to be taken restrictively.

SUMMARY OF THE INVENTION
Accordingly, there is provided an apparatus and process for welding of carbon
steel plates and pipes, where the welding can be done from either side of the
groove simultaneously.
The advantages of the invention can be seen, inter alia, in the fact that the steel
plates and pipes can be simultaneously welded from either side using two
welders or two orbital welding heads.
The advantages of the invention can be seen, inter alia in the fact that the steel
plates and pipes can be either welded without back gouging or back grinding
operation.
The technology developed is suitable for pipes in open yard application where
the welding can be done from the either side using two orbital welding heads in
any position.
The technological parameters for achieving full penetration welds by
simultaneous welds from either side of the groove, are established.

The head rotation speed, delay time, pulse current and wire feed speed has
significant influence on the weld penetration and the optimum process
parameters, which give best results in terms of penetration, bead shape and
mechanical properties, have been established successfully.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 illustrates formation of T-joint with double K-joint edge preparation of
three plates using two torches on either side of the groove operating
simultaneously.
Figure 2 illustrates an alternative embodiment where two large diameter pipes
placed on a strand arc welded by two orbital head mounted on either side of the
weld.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The Double Sided Arc Welding Process (DSAW) of the invention has the
advantage to control heat input from either side by welding simultaneously in
either side.

The weld is free from any root defect due to the protection of simultaneous weld
from either side. The simultaneously welding also eliminates the need of back
gouging and back grinding which further avoid the need of liquid penetrant
testing of root pass.
By eliminating the back gouging and back grinding and simultaneously welding
from either side, the welding cycle time is improved significantly.
In Double sided arc welding process of the invention, the welder / welding
system carry out the welding from either side of the groove simultaneously and
the welding is continued from either side till the final run is completed.

WE CLAIM:
1. An improved Double sided arc welding process for Steel grade material for
power application comprising the steps of:
- providing a plurality of thick section plate or a plurality of large diameter
pipes for simultaneous welding from either side of the joint to avoid root
gouging to ensure soundness of root pass;
- implementing a double sided arc welding for plate to plate symmetrical
joint, and/or for large diameter pipes buff joint with symmetrical weld
design, wherein the welding head is disposed in either side, characterized
in that the welding is carried out with a wide range of welding speed
corresponding to the wall thickness, with symmetrical type of edge
preparation, in that the welding parameters are selected in such a way
that full penetration weld joints meeting radiographic quality are produced
for applications in pressure parts of boilers, as per ASME sec IX and IBR
regulations, and in that the welding is carried out with fine range of
welding delay time based on the diameter and wall thickness.

2. The process as claimed in claim 1, wherein the Steel Group of material is
welded.
3. The process as claimed in claim 1, wherein both manual/semiautomatic
and automatic mode of operation is adopted.
4. The process as claimed in claim 1, wherein the job is kept on the system
in any position.
5. The process as claimed in claim 1, wherein a fixture as per the job
requirement is used to fix the components for welding.

ABSTRACT

An improved Double sided arc welding process for Steel grade material for power application comprising the steps of providing a plurality of thick section plate or a plurality of large diameter pipes for simultaneous welding
from either side of the joint to avoid root gouging to ensure soundness of root pass; implementing a double sided arc welding for plate to plate symmetrical joint, and/or for large diameter pipes butt joint with symmetrical
weld design, wherein the welding head is disposed in either side. The welding is carried out with a wide range of welding speeds corresponding to the wall thickness, with symmetrical type of edge preparation, in that the welding parameters are selected in such a way that full penetration weld joints
meeting radiographic quality are produced for applications in pressure parts
of boilers, as per ASME sec IX and IBR regulations, and in that the welding is
carried out with fine range of welding delay time based on the diameter and
wall thickness.