FIELD OF THE INVENTION
The present invention relates a method for Dual connection of Manual Metal Arc
Welding (MMAW) machine during high pressure welding of boiler related
components.
BACKGROUND OF THE INVENTION
Welding is used in every fabrication industry. It is a principal means of
fabricating or repairing metal products. The process is efficient, economical and
dependable as a means of joining metals.
For MMAW application welding machine used are rated maximum for 400A
(100% duty cycle). Some of the welding process such as Boiler drum down
comer, nozzle welding, etc. require welding current of more than 400A. To get
this required current Dual connection of welding machine is used.
In the prior art method of Dual connection of welding machines (Fig.1), the dual
connection of welding machines is achieved with the help of cables & special
connectors. Each power source is having positive & negative terminals at the
backside with female connectors.

For making a Dual connection, in a first power sources, at a backside positive
female connector terminal, at least one end of a plurality of ‘T’ type male
connectors is inserted. In the ‘T’ connector, a welding cable with a female
connector is inserted to a male terminal opposite to the connected terminal. Dual
connection of a positive output terminal is completed by connecting the other
end of the welding cable at said backside positive female connector terminal in a
second power source. Output is taken from the left out male terminal in the ‘T’
connector by connecting a cable with the female connector.
Dual connection of a negative output terminal is done by using the similar
connectors & carrying the same procedures used for the positive output
terminal.
According to the known method of Dual connection, the welding positive &
negative cables are directly connected to the job through the ‘T’ connector. As
the welding is carried out at different locations of the job and the jobs are of
varying in dimensions, these MMAW machines are enabled to be shifted from
one location to other location based on requirement. For safety reasons, the
positive & negative output cables are disconnected from the ‘T’ connector
whenever the power source is shifted.

Due to frequent connection and disconnection of the cables at the ‘T’
connectors, a looseness in the cable terminals is developed, which leads to
generation of heat and subsequently burning of connectors. As these ‘T’
connectors are placed close to the machine terminal, the burning of the ‘T’
connectors interlia damages other constituting components of the power source
(welding machine).
Hence, a different method of obtaining Dual connection is necessary to overcome
the above problems.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose Dual connection of Manual
Metal Arc Welding (MMAW) machine during high pressure welding of boiler
related components.
A further object of the machine is to propose Dual connection of Manual Metal
Arc Welding (MMAW) machine during high pressure welding of boiler related
components, which eliminates burning of T-connectors including damage of the
constituent components of the welding machines.

SUMMARY OF THE INVENTION
Accordingly, there is provided Dual connection of Manual Metal Arc Welding
(MMAW) machine during high pressure welding of boiler related components.
The invention proposes method of Dual connection of MMAW welding machines
as shown in Fig.2.
In this method, two welding cables with male connectors at one end are
connected to the positive terminals of the two power sources. The other end of
these two welding cables are terminated by using az Ring type lugs made up of
tinned copper.
Similarly, two welding cables with male connectors at one end are connected to
the negative terminals of the two power sources. The other end of these two
cables are terminated by using Ring type lugs made up of tinned copper.
A base plate made up of MS is welded to the machine trolley base. Two ‘L’ type
metal pieces are fixed to this MS base plate. A Hylemn sheet is fixed to these ‘L’
type metal pieces by using screws.

Two pieces of Copper bus bars are fixed to the Hylemn sheet. The copper bus
bars mounted such that it is at equal distance from the either side of the Hylemn
sheet and one end of the copper bus bar is facing the power source backside. In
each of the copper bus bars, at both the ends, a hole is drilled for cable
connection.
The two welding cables coming from the positive terminal of the two power
sources terminated with at least Ring type copper lugs are connected to one of
the copper bus bars called ‘Positive output terminal’. Similarly the two welding
cables coming from the negative terminal of the two power sources are
terminated with at least two other Ring type copper lugs are connected to the
other copper bus bar called ‘Negative output terminal’.
The welding torch is connected through a welding cable having a Ring type lug
termination at the other end of the ‘Positive output terminal’. The welding return
cable from the job is connected through a welding cable having another Ring
type lug termination at the other end of the ‘Negative output terminal’.
In this method of Dual connection of MMAW welding machines, use of ‘T’
connectors at the positive & negative output terminal of the power source for
Making of the prior art Dual connection is eliminated. This avoids direct
connection of the welding cables by the welder to the power source terminal.

This also eliminates the chances of loose connection at the power source
terminal and hence burning of connectors is avoided.
Also in this method of Dual connection, the connection terminals are kept
sufficiently away from the power source; hence, chances of damage to
components inside the power source is eliminated.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 – shows a schematic illustration of prior art method of Dual connection
of SMAW machines.
Figure 2 – shows a schematic illustration of the inventive method of Dual
connection of welding machines for MMAW application.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fig.2 showing the machines for dual connections, have the following elements:

Each power source is having separate switches (4, 6) for power on and power
OFF. Also each power source is having separate displays for displaying welding
program and welding parameters (1,5). The power source is mounted on a
trolley (37) and can be moved from one place to another place with the help of
wheels of diameter 500mm made up of rubber (2,7,11,18). For mechanical
rigidity, both the power sources are connected through one each MS plate (38)
at two locations.
Each power source is having one positive output terminal with female connectors
(9,22). Similarly each power sources is having one negative output terminal with
female connectors (15,16).
A MS base plate (31) is welded on the trolley (37) at the back side of the power
source terminal. On the MS base plate (38), two ‘L’ type MS plates are fixed (not
shown in the figure).
A Hylemn sheet is fixed to these ‘L’ type metal pieces by using screws.The
Hylemn sheets (35) are used for supporting including insulating purposes. Two
pieces of Copper bus bars (30, 34) are fixed to the Hylemn sheet (35). The
output current from the welding power sources are routed through these copper
bus bars to the welding cable. In each copper bus bars, a hole is drilled at both
the ends for connecting the welding cables.

A welding cable with male connector is connected at the positive terminal in the
first power source (29). Similarly a welding cable with male connector is
connected at the positive terminal of the second power source (28). The other
end of these two cables are connected to the copper bus bar (30).
In the same way, a welding cable with the male connector is connected at the
negative terminal of the first power source (26) and a welding cable with the
male connector is connected at the negative terminal of the second power
source (36). The other end of these two cables are connected to the copper bus
bar (34). In this way Dual connection of the two MMAW welding machine is
completed and the output current can be taken from the copper bus bars
(30,34).
Welding is carried out on the job (14) by connecting the welding cable (32)
having the welding torch (21) at one end and connecting the other end of this
welding cable (32) to the copper bus bar (30). To close the circuit for the
welding current, a welding cable (33) is connected between the job (14) and the
copper bus bar (34).

Experiments are conducted at different weld current settings to ascertain the
correct functioning of the device by measuring the current at the output of each
power source (28,29) and after the copper bus bar (32). The results showed that
the current after copper bus bar is the summation of the current output from
each power source.
i.e., Total output current = Current output measured in power source 1 +
Current output measured in power source 2
This result shows that, the Dual connection of MMAW power sources are
successfully carried out in this method.
In this method, the dual connection is made without using ‘T’ connectors and the
male and female connectors are fixed permanently. This eliminates the chances
of loose connection, generation of heat & hence burning of connectors.
The terminals where the dual connection is made is kept sufficiently away from
the power source and this prevents damage to internal components in the power
source.

WE CLAIM :
1. A method for Dual connection of Manual Metal Arc Welding (MMAW)
machine during high pressure welding of boiler related components, each
of the Manual Metal Arc Welding (MMAW) machine comprising switches
(4, 6) for power on/off, displays (1, 5) respectively displays welding
sequence and welding parameters, a positive output terminal with female
connectors (9, 22), a negative output terminal with female connectors
(15, 16), the (MMAW) being mounted on a trolley (37) with a plurality of
rubber wheels (2, 7, 11, 18), the method comprising the steps of:
- welding a metal base plate (31) on the trolley (37);
- fixing at least two ‘L’ type metal pieces on the base plate (31);
- screw-fixing of a hylemn sheet (35) the L-type metal pieces;
- attaching two pieces of copper lens buses (30, 34) to the hylemn
sheet (35), the output current from the MMAW being routed through
the copper buses (30, 34);
- connecting at least two ring type copper lugs with the first copper base
(30) acting as the position output terminal;

connecting at least two other ring type copper lugs with the second
copper buses (34) acting as the negative output terminal,
characterized in that a first pair of welding cables exiting from the
positive terminals of the two MMAW (28, 29) are terminated with the
ring type copper lugs of the positive output terminal, in that a second
pair of welding cables exiting from the negative terminal of the MMWS
(28, 29) are terminated with the ring type copper lugs of the negative
output terminal, and in that the welding cable for the welding torch
and the return welding cable from the specimen are respectively
connected to the other sides of the positive output terminal and the
negative output terminal through separate ring-type lug termination.