FIELD OF THE INVENTION
The present invention relates to a method of metal cutting in high thickness plates for
the fabrication of boiler plates. More particularly, the invention relates to a method of
chamfering high thickness metal plates simultaneously on both top and bottom sides of
the plate in a fabrication process of boiler plates.
BACKGROUND OF THE INVENTION
During edge preparation of high thickness plates for fabrication of boiler plates,
chamfering operation is to be carried out on the both sides of the plates. Accordingly,
the cutting machine is placed on a first side to finish the chamfering on the first side
and then the plate is reversed in such way that the bottom side is positioned as the top
side now to finish the chamfering on the second side. The thickness of the plate may be
more than 20 mm and less than 63 mm. These chamfered portions are used for
welding these carrier / lug plates to the headers of high pressure boiler applications.
Since the edge preparation is to be carried out on both sides, the time taken to
complete the process is more which needs to be reduced so as to bring the operational
time to half than that of time taken in prior art process, without compromising the
quality of work.
US Patent No. US 8395075 entitled 'Plasma torch cutting device and process' teaches a
method of operating a plasma arc torch system comprising the steps of placing a work
piece to be cut on a table of the plasma arc torch system,

wherein at least a portion of the work piece has a planer surface facing away from the
table. A plasma arc torch is positioned adjacent to the planar surface of the work piece
using a positioning apparatus, wherein the positioning apparatus has at least five
degrees of freedom about which it can move the plasma arc torch relative to the work
piece for cutting the work piece on the table. The method further includes angling the
torch relative to the planar surface of the work piece such that the torch is held at an
angle of between about 1 and about 4 degrees from perpendicular with the planar
surface to back burn a produced kerf such that a kerf edge is perpendicular relative the
planar surface of the work piece. Additionally, the planar surface of the work piece is
calculated by contacting the work piece with the torch at least three times.
The prior art describes a cutting process with torch positioning but there is no
simultaneous operation.
Japanese Patent No. JP 158673 entitled Gas Cutting Device, provides a gas cutting-off
apparatus which can cut off a preset position by turning a work piece. The gas cutting-
off apparatus includes a table, a supporting base for supporting the table so as to
elongate its rotational axis in the vertical direction, a rotationally driving means for
turning the table supported by the supporting base, and a gas cutting-off tool which
directs a cutting-off nozzle toward the work piece at the position on the side of the
supporting base. The supporting base has a plurality of supporting pillars arranged side
by side at a constant angular interval about the rotational axis, a plurality of cross
beams which are arranged on the upper end portions of the supporting pillars arranged

at the opposed position on both sides of the rotational so as to elongate in the radial
direction, rotationally supporting means which are arranged at the middle positions of
the cross beams in the longitudinal direction, and support the table, a plurality of
connecting beams to be arranged between the upper ends of neighboring supporting
pillars, and auxiliary rollers which are arranged at the middle positions of the connecting
beams in the longitudinal direction, and are brought into contact with the lower surface
of the table.
The above Patent describes a cutting process with offset position of the work piece, and
that a rotational method is used for cutting.
OBJECTS OF THE INVENTION
It is therefore an object of the present to propose a method of chamfering high
thickness metal plates simultaneously on both top and bottom sides of the plate in a
fabrication process of boiler plates.
Another object of the invention is to propose a method of chamfering high thickness
metal plates simultaneously on both top and bottom sides of the plate in a fabrication
process of boiler plates, in which chamfering on both sides is done along the length
precisely at the same speed and at the same time.
A further object of the present invention is to propose a method of chamfering high
thickness boiler metal plates simultaneously on both top and bottom sides of the plate
in a fabrication process of boiler plates which eliminates job setting twice for the
operation.

SUMMARY OF THE INVENTION
Accordingly, there is provided a second torch on known cutting machine having one
torch so as to produce a double torch plug cutting apparatus. The method consists of
the following steps, placing the connecting rod by two screws on the body of said
double torch plug cutting apparatus which carries the moving plate including the
connecting tube with the second torch in position; forming an included angle of 135
degree to determine the chamfering angle between the positions of the first torch and
the second torch; and adjusting positions of the second torch by manipulating the
moving plate corresponding to varying plate thickness of 20 mm to 63 mm in the work
piece.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows a pre chamfered work piece in position on the base plate' and the
double torch plug cutting machine.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
According to the present invention, the chamfering operation is carried out in a single
stroke. The required chamfering angle is arrived by positioning the two cutting torches,
viz, first torch (02), and the second torch (03) depending on the thickness of the work
piece, the included angle is 135 degree between the two torches was arrived based on

the trial and error experiment and it has been found that all the thickness of the plates
varying from 20 mm to 50 mm, the included angle 135 degree is constant.
Figure 1 shows a plug cutting machine (01) is placed over a machine rail (07) for
longitudinal movement for job cutting. The first torch (02) is used for the upper portion
chamfering of the work piece (05). To make the bottom portion chamfering, another
cutting nozzle with a second torch (03) is fixed on the connecting rod (04) with a
provision of left-right movement by a moving plate assembly (09). A connecting tube
(10) provides the supply of gases for cutting into the second torch (03). The connecting
rod (04) is fixed on the machine frame (01) by means of two screws. The longitudinal -
simultaneous movement is facilitated to the second torch (03) by a roller (08) attached
to the connecting rod (04) and the bottom of the roller rests on the work piece (05) to
be chamfered which is used for stability of the second torch (03).
Because of the provision of a second torch (03), chamfering taking place on both sides
that is top and bottom in the same angle required at a single stroke, there by the
chamfering is reduced to half of the time than that of the prior art method of gas
cutting used for plates of boiler components.

WE CLAIM :
1. A method of simultaneous chamfering of top and bottom plates used for
fabrication of carrier plates and lug plates weldable with headers of high
pressure super critical boiler and sub critical boilers, comprising the steps of:
- providing a plug cutting machine (1) having at least one first torch (02), a
connecting rod (04) axially movable by a moving plate (09);
- disposing a second torch (03) connected by means of the connecting rod (04)
with a roller (08) for longitudinal movement, the second torch (03) receiving
cutting gas supply from a connecting tube (10);
- placing the connecting rod by two screws on the body of said double torch plug
connecting apparatus which carries the moving plate including the connecting
tube with the second torch in position;
- forming an included angle of 135 degree to determine the chamfering angle
between the positions of the first torch and the second torch; and
- adjusting positions of the second torch by manipulating the moving plate (09)
corresponding to varying plate thickness of 20 mm to 63 mm in the work piece.

2. The method as claimed in claim 1, wherein the angle of chamfer cutting is 45
degree and the induced angle is 135 degree between the first torch (01) and the
second torch (03).

ABSTRACT

The invention relates to a method simultaneous chamfering of top and bottom plates
used for fabrication of carrier plates and plug plates weldable with headers of high
pressure super critical boiler and sub critical boilers, comprising the steps of providing a
plug cutting machine (1) having at least one first torch (02), a connecting rod (04)
axially movable by a moving plate (09), disposing a second torch (03) connected by
means of the connecting rod (04) with a roller (08) for longitudinal movement, the
second torch (03) receiving cutting gas supply from a connecting tube (10); placing the
connecting rod by two screws on the body of a double torch plug cutting apparatus
which carries the moving plate including the connecting tube with the second torch in
position; forming an included angle of 135 degree to determine the chamfering angle
between the positions of the first torch and the second torch; and adjusting positions of
the second torch by manipulating the moving plate corresponding to varying plate
thickness of 20 mm to 63 mm in the work piece.