FIELD OF INVENTION
The invention relates to an improved pulsed GMAW technique for hand-hole pipe
welding. More particularly the invention relates improved pulse GMAW
techniques for hand-hole to dish end cover pipe butt welding in headers
adaptable to the welding of the boiler components.
BACKGROUND OF THE INVENTION
There is no such technique existing till now especially for Hand-hole to dish end
cover pipe butt welding in headers using semi automatic pulsed current GMAW
procedure. However, some of the articles related to hand hole pipe in reference
to design aspects and quality improvement techniques are available has been
given below. In addition, some of the literature related to electrical and
telephone cable protections are also available but such an article is not at all
relevant to the present invention.
HAND-HOLE PIPE-COUPLING ATTACHMENT FOR BOILER-HEADS
Patent number: 881045, Filing date: Feb 12, 1907, Issue date Mar 3, 1908.
In this investigation the author (ARTHUR C BADGER) claims that a hand hole
bushing having an external member adapted for attachment to a receptacle head
a conduit section having one end enlarged the said bushing and enlarged end
having reciprocal bearing faces forming a tight joint and means for detachably
securing the section to the bushing. An appliance of the character stated
comprising an externally threaded hand hole bushing having an external member
adapted for attachment to a receptacle head and a conduit section enlarged at
one end and having a reduced pipe engaging socket at its opposite end the
bushing end of the conduit section being provided with reciprocal bearing faces
adapted to maintain a tight joint and a coupling nut adapted to engage the

external thread of the bushing and having an inwardly projecting flange to
engage the enlarged portion of the conduit section. An appliance of the character
stated comprising an externally threaded hand hole bushing adapted for
attachment to a receptacle head and a conduit section enlarged at one end and
having a reduced pipe engaged socket at its opposite end the bushing and the
enlarged end of the conduit section being provided with reciprocal bearing faces
adapted to maintain a tight joint and a coupling nut adapted to engage the
external thread of the bushing and having inwardly pro flange to engage the
enlarge portion of the conduit section said nut having a reduced wrench-
engaging end surrounding socket.
2. METHOD FOR REMOVING SPATTERS FROM A PIPELINE
Patent number: 4559085
Inventors: Eddy Y. L. Liu et al
Filing date: Jun 18, 1984
Issue date: Dec 17, 1985
The main claim is, when a pipe is joined to another pipe by welding, spatters
formed at or near the welded joint can be removed by hand through the hand
hole.
3. CONNECTING TUBULAR BODY FOR HANDHOLE OR MANHOLE, BLOCK BODY
FOR THE TABULAR BODY, AND HANDHOLE OR HANDHOLE STRUCTURE
Patent number: United States Patent 5950369
Inventors: Amatsutsu , Hiroyuki, Kikumori, Yasuhiro (Osaka, JP)
Application Number: 09/075256
Publication Date: 09/14/1999
Filing Date: 05/11/1998

The main claim of the invention is a connecting tubular body for a hand-hole
which is fitted into a pipe connecting hole of the hand-hole when used. The cut
edge face at one open end side of the tubular body having square walls in cross
section and circular walls in cross section which are alternately disposed in its
axial direction in the boundary portion between a side wall portion forming the
square wall in cross section and a peripheral wall portion forming the square wall
in cross section, and is cut in the boundary portion on the side apart from the
open end side or in the proximity thereof.
The length of the tubular body is set greater than the wall thickness of the hand-
hole. In addition to the tubular body, a block body for the tubular body is formed
with square and circular recessed portions conforming to the outer peripheral
face of the open end side portion of the tubular body. Further, a hand-hole is
such that the cut edge face of the tubular body and the inner wall surface of the
hand-hole are arranged substantially on the same plane, and the other end side
portion of the tubular body being projected outside the hand-hole, and besides
the tubular body or the block body is water tightly fixed by a curing filler such as
cement mortar or gelation resin filled in the pipe connecting hole.
In addition to that, some of the information related to hand hole pipe is also
given below.
Publication Number JP3390750
Application Number JP/2001139644.

OBJECTS OF THE INVENTION
1. It is therefore the object of the invention to provide a simplified and improved
pulsed GMAW technique for hand hole pipe to dished end cover butt welding
under semi automatic condition
2. Another object of the invention is to provide improved pulsed GMAW
technique for hand hole pipe welding which improves the productivity of boiler
components such as p-22, p-91/92 and carbon steel.

3. A still another object of the invention is to provide an Improved pulsed GMAW
technique for hand hole pipe welding which eliminate the requirement of skilled
welder as well as two welding process such as GTAW (Gas Tungsten Arc
Welding) and SMAW (Shielded Metal Arc Welding).
4. A further object of the invention is to provide an improved pulsed GMAW
technique for hand hole-pipe welding which improves the quality of the weld
joint in reference to soundness, mechanical and metallurgical properties as well
as reduction in defects.
SUMMARY OF THE INVENTION
The present invention is an advanced semi-automatic pulsed current GMAW (Gas
Metal Arc Welding) welding process involving Surface Tension Transfer (STT)
root pass and pulsed current GMAW filler pass for joining the pipe and
hemispherical dished end which replaces the existing manual process for Gas
Tungsten Arc Welding (GTAW) for root pass and shielded metal Arc Welding
(SMAW) process for further passes.

Brief description of accompanying drawings
Fig 1 - Description of weld in the prior art with different numerals indicating the
weld deposit in the root pass and filler pass
Fig 2 - Groove design for weld deposit in the improved process
Fig 3 - Longitudinal sectional view of the flat end cover of the header
Fig 4 - Longitudinal sectional view of dish end cover
Fig 5 - Photographic view of header
Fig 6 - Photographic view showing details of hand-hole pipe, Dish end cover and
Groove
Fig 7(a) - Schematic diagram showing the experimental set up of GMA (Gas
Metal Arc) torch nozzle location with suitable fixture for holding the pipes in the
invention
Fig 7(b) - Photographic view of the experimental set up
Fig 8 - Macro photograph of welding sequence using newly developed sequence'
Detailed Description of the preferred embodiment of the invention -
Hand-hole pipe having a hemispherical dished end (11) and pipe dia 127 X 20
mm of SA 106 Gr C is welded to the flat end cover (12) of pipe in fig 7(a). The
pipe (14) and the dished end (13) are joined by a butt joint.
The welding was carried cut by multi pass GMA welding process. During welding
the pipes were held horizontally with the help of 3 jaws clamping system in a
rotating table and the welding is carried out in 1GR position as shown in Figure
7(a). The photographic view of the experimental set up is shown in figure 7(b).
The root pass was carried out by using wave form controlled GMAW (Gas Metal
Arc Welding) process commonly referred as surface tension transfer (STT)
process followed by improved pulse current gas metal arc welding (P- GMAW)

process for filler passes, The welding was carried out in semi automatic condition
using welding positioner.
By using the positioner, full GMAW technology for hand-hole pipe to dish end
cover butt welding were established. Up till now Gas Tungsten Arc Welding
(GTAW) for root pass weld and shielded Metal Arc Welding (SMAW) for further
passes were followed. Then the joints were subjected to Radiographic test as per
ASME section V to meet the code requirement of ASME section IX and
subsequently they were subjected to stress relieving and hydraulic test. However
the inherent problems of the current process like lesser deposit rates, multi
number of passes, frequent changes of electrodes/ filler wires, skill requirement
of the task performer etc remained, which were overcome by the instant
invention.
The advantage of the present invention is to eliminate two different welding
process as well as changing from manual to semi automatic welding.
After establishing the welding procedure by the instant invention necessary
destructive and non destructive tests were carried out and found to meet the
code requirements.
Details of welding condition and parameters are given in Table 1
Root Gap : 2.5 mm
Electrode Polarity : DCEP (Direct Current Electrode positive)
Welding Position : 1GR
Shielding Gas & Flow Rate : 80%Ar+20%CO2&20 litre/min
Preheating Temperature :150°C
Inter pass Temperature :100-220°C
Total Amount of Weld Metal Deposited: 650±20 grms

WE CLAIM
1. A process for improved pulsed GMAW (Gas Metal Arc Welding) technique for hand-
hole pipe welding comprising
- Preparing groove in the pipe end and dish end cover on the interfacing side by
machining operation for accommodation of welding material
- Positioning the pipe and dish end in a separate set up for
- Joining pipe and Dish end by tag welding at few points
- Holding the hand-hole pipe horizontally with the help of 3 jaws clamping system in
rotating table.
- Bringing the welding nozzle near the interfacing groove where weld is to be deposited.
- Carrying out welding for the root pass by controlled GMAW commonly referred as
surface Tension Transfer process
- Following up the welding for fillers passes by pulsed current Gas Metal Arc welding (P-
GMAW)
- Checking by visual observation in between each weld pass for uniform weld deposit.

2. The process as claimed in claim 1 where the butt welding of hand-hole pipe to dish
end cover is carried out from single side with full penetration joint.
3. The process as claimed in claim 1 where the welding is carried out at 1 GR
position.
4. The process as claimed in claim 1 where the shielding Gas is having composition of
Argon 80% and Co2 20% and gas flow rate maintained at 20 litre/minute.

ABSTRACT

The invention relates to improved pulsed GMAW technique for hand hole pipe welding
and in particular for hand-hole pipe to dish end cover butt welding in headers for boiler
components where the conventional adopted process was by Gas Tungsten Arc Welding
(GTAW) for root passes and shielded Metal Arc Welding (SMAW) for further passes.
The improved process discloses root pass welding by using wave form controlled Gas
Metal Arc Welding (GMAW) commonly referred as Surface Tension Transfer (STT)
process followed by pulsed current GMAW (P-GMAW) process for filler passes by setting
parameters and setting arrangement which has ensured higher productivity, minimized
rejection rate as well as eliminating dependency over skilled welding personnel.