FIELD OF THE INVENTION:
The present invention relates to gas cutting of high thickness pipes. More
particularly, the invention relates to pipe gas cutting and machining for conventional
welding process and to joining of lines and links called steam generator package
links in high pressure steam generators.
BACKGROUND AND PRIOR ARTS OF THE INVENTION:
The closed stationary installation for transporting/distribution fluids like steam and
water in high pressure boilers called as “stream generators package links”. These
steam generator package links are made up of high thickness pipes ranging from
(25mm to 102mm) and having outside diameter ranging from 219mm to 813mm.
The pipe materials are carbon steel and alloy steels of P22 grade. Different lengths
of these pipes are to be joined by SAW (submerged arc welding) to form one link.
For preparing for SAW, these pipes are required to be cut and edge-prepared to
required length. The conventional way of cutting these pipes is by gas-cutting using
oxy-acetylene torch. For this, pipes are marked with cutting tolerance and held in
position with help of crane. Cutting is carried out by cutting torch held manually and
moving along the cutting line. As the cutting progresses pipe has to be rotated for
every segment of cutting surface with the help of crane. During this time, the crane
is fully engaged with one job. Since cutting is manual and the surface finish is
uneven and also the final cut edge is very rough.Due to this method of cutting,
tolerance required is more which in turn leads to longer cycle time and vibrations
while edge-preparation.
Hence there is a necessity to find out an alternate method to avoid continuous usage

of crane and also the cutting allowance to be reduced to reduce the machining time
further and also to savethe high costof material.
In the above cutting process, due to uneven surfaces obtained at the end, the
machining allowance is required 40mm and the time taken in the edge preparation
machine is also moresince the depth of cut is limited to 4mm at a time.
The flow diagram (fig-5) shows the cutting sequence of the exiting process.
Prior art JP2013128954A provides a gas cutting device capable of easily switching
/adjusting intensity of preheating flame according to a situation with no possibility of
accidental fire which does not look into any solution to the existing problem as such.
OBJECTS OF THE INVENTION:
The object of the invention is to develop a method of cutting pipes of high thickness
by gas cutter to achieve smooth pipe ends and good quality.
Another object of the invention is to reduce cycle time improving productivity of the
link fabrication especially pipe-edge preparation.
Further object of the invention is to avoid crane usage for cutting.
SUMMARY OF THE INVENTION:
Considering the requirement of good quality gas-cutting, a technique was adapted
wherein the job is placed in between the motorized roller and guide roller and the
speed of the motorized roller can be controlled by means of speed regulator. Once
the roller is switched on, the job will rotate on the rollers. The auto gas cutting-torch
is placed on the developed device. The device has arrangement for changing height
and also can be moved right and left. It can be rotated along hinge. The torch is
connected to oxygen and acetylene cylinders by means of special rubber hose. Once
fuel supply is turned on, the flame mixture at cutting torch nozzle can be maintained
by knob controls provided in the torch. The high temperature at flame tip starts

melting the metal at end and slowly by moving the swivel head of torch, flame is
progressed in to the metal. This avoids need for drilling a pilot hole for heavy
thickness pipes. Along with this the motorized rotor is turned on for which, speed
can be maintained based on pipe thickness and cutting speed. As the flame
progresses, the rotation of rotor brings new pipe surface under flame and thus no
need for engaging cranes for cutting. The cut portion of pipe automatically gets
separated from pipe due to the rotation of job. Once cutting is completed, this scrap
portion comes out in the form of ring and falls down on the scrap tray by gravity.
Since the torch is fixed and flame strength is uniform, the end surface received is
very smooth and cutting tolerance is reduced to 10 mm. For final edge preparation
due to smooth surface and lesser excess stock, time taken is reduced, thus leading
to increased productivity in cutting, edge-preparation and material saving.
BRIEF DECRPTION OFTHE ACCOMPANYING DRAWINGS:
Figure 1 shows cutting torch assembly.
Figure 2 shows swivel arrangement with components in the assembled condition.
Figure 3 shows moving carriage and vertical post connected details.
Figure 4 shows the developed device with cutting set in the assembled condition.
Figure 5 shows the flow diagram for the prior art.
Figure 6 shows the flow diagram for the cutting process with developed apparatus.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION:
Figure 1 shows the different parts of the cutting torch assembly with torch vertical
adjustment screw rod (08), (09) with connected backup plate (07) is welded with
back arm (05).The two outer tubes (23) are welded in the top and bottom of the
back arm (05).

Figure 2 shows the swivel arrangement with components in the assembled condition
as detailed below:
The collar pipe (25) is welded with balancing plate assembly (03) on one side and
the swivel head assembly is welded directly opposite to the balancing plate assembly
(03). One no of connecting tube (21) is welded on one side with swivel head
assembly and on the other side welded with centre tube (22). The locking screw-I
(14) is welded on the centre of the collar pipe (25).
Figure 3 shows the 2 no’s of horizontal sliding pipe (20) welded with a rectangular
outer tube holding plate (24). The holding pipe (26) is welded withouter tube
holding plate (24). The vertical post (18) is vertically inserted in the holding pipe
(26) and tightened with 2 no’s of locking screw II (15). The 4 no’s of height
adjustment holes (19) with 200 mm pitch are drilled on vertical post (18). The
seating clamp (11) is inserted to the vertical post (18) and locked with seating clamp
stopper (17).
Figure-4 shows the complete assembly of the gas cutting machine. In this a base
plate assembly a pair of carriage pillar (01) is attached on both ends, which hold a
pair of carriage polish rods (02). The moving carriage assembly (10) is pre- inserted
on the carriage polish rod (02) with two ball bearings (16) an either side for smooth
sliding. A vertical post (18) is inserted in the holding post (26) and fastened with the
locking screw-II (15). The seating clamp (11) put over the vertical post (18) and
fixed with seating clamp stopper (17) at required height which can be adjusted for
height adjustment.
The fig-2 assembly is assembled with the vertical post (18) so that it rests on the
seating clamp (11) with desired height which swivels over 360 degree horizontal.
Then the fig-1 assembly is assembled with the fig-2 assembly where the item No 22
and 23 are fixed with a vertical locking bolt (06) for 180 degree horizontal swivel
movement. Finally the cutting torch assembly (09) connected to an oxy-acetylene
hoses (12) are assembled on the vertical adjustment screw rod (08). The oxy-
acetylene cylinder set which supplies fuel is (not shown) connected to the cutting
torch assembly (09).

Accordingly, the work piece is marked with required length and a pilot hole is drilled
from one end with cutting allowance. The marked pipe is placed between the two
roller supports. One roller support is automatic rotary roller for the rotation of the
work piece. Another roller is supported on the other end which guides for cutting.
The above setup is nearer to the developed device.
Now moving carriage (10) is slides horizontally over the polish rod (02)
approximately nearer to the cutting torch (09) and work piece to be end cut and
locked. The finer adjustment of the cutting torch is carried out by rotating the torch
assembly horizontally and vertically through rake and pinion arrangement provided
in front of the backup plate (07). The cutting torch assembly (Refer fig-1) can be
moved downward and upward by sliding the collar pipe (25) and locked at any
position by means of inserting the seating clamp stopper (17) and tightened with
locking screw-I (14). The above assembly can be put vertically at any position by
resting on the seating clamp (11) which can be locked by seating clamp stopper
(17). The cutting torch assembly can be rotated at any desired angle by means of
connecting with centre tube (22) and outer tubes (23) which are already linked by
vertical locking bolt (06).
By the above arrangement the device can be used for gas cutting operation of the
operation work piece at one end and the moved other end can be simply cut by
unlocking with locking screw-II (15) and sliding the moving carriage (10) on the
carriage polish rod (02). The setting operation is repeated for this gas cutting
operation, by means of the above adjustment for pipe outside diameter 219 mm to
813 mm can be easily gas cutting operation carried out for the thickness range of 25
mm to 120 mm with grade of carbon steel and alloy steel. There by the drawback
said the background of invention is eliminated. The flow diagram fig-6 represents
the new process of cutting operation with developed device.

WE CLAIM:
1) A device and a method for automatic gas cutting of high thickness pipes of
varied diameters comprising : -
• A fabricated frame having 2 nos. of carriage pillar (01) connected with two
nos. of base plate assembly (13); the two nos. of carriage polish rod (02)
welded vertically on the carriage pillar (01) with a gap of 450mm;
• A moving carriage (10) consisting of holding pipe (26), movable
horizontally in the left and right direction by means of horizontal sliding
pipe inserted on the carriage polish rod (02) and the vertical post (18)
inserted in the holding pipe (26) and locked by means of locking screw-II
(15);
• A rotating collar pipe (25), inserted in the vertical post (18) having
balancing plate assembly on one side of the collar pipe and swivel head
assembly on diametrically opposite side are disposed, rotating 360 degree
and locked in any position by means of locking screw- I (14);
• A back arm (05), rotating 90 degree on either side by means of center
tube (22) and outer tubes (23), fastened by means of vertical locking bolt
(06) and the center tube (22), and connected to the swivel head assembly
(04) by means of connecting tube 21;
• A torch vertical adjustment screw rod (08) connected to back up plate
(07), and connected in turn to the back arm (05) for up and down finer
vertical movement;
• An arrangement of motorized roller and guide roller for holding and
guiding the rotating pipe during gas cutting operation.
2) A method for gas cutting of high thickness pipes of varied diameters, wherein
the job is placed in between the motorized roller and guide roller allowing to
rotate the job during gas cutting.

3) The method as claimed in claim 2, wherein the height of the flame and
movement through left and right adjusted and fixed for accuracy of cutting.
4) The method as claimed in claim 2, wherein the speed of the motorized roller
is regulated based on pipe thickness and cutting speed.