FIELD OF THE INVENTION
The present invention relates to a method of profile machining in high thickness
metal tube for fabricated perpendicular branch line. More particularly, the
invention relates to a method of profile machining of high thickness pipe
materials to fabricate Tee-joints in high pressure steam generators.
BACKGROUND OF THE INVENTION
During manufacturing of branch nozzles for high pressure steam generators, the
nozzles are to be ground manually for profile making. For low alloy steels,
plasma cutting with cutting allowa.nce is the only way of me.tal removal process.
After plasma cutting, hand grinding to be carried out for closer tolerance which
leads to more cycle time, improper profile and environmental pollution.
United States Patent· No.4167836 describes a profile grinding machine for
grinding the contour surface of an article to be ground such as a wrist watch
case or the like is disclosed. Both the work shaft and the profile can shaft are
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rotatably supported by a head sWing supporting shaft provided on a profile slide
and driven in synchronism each other. The profile side is biased in a direction
towards the profiling can flower so as to usage the profiling can against the
profiling can follower.
US Patent No. 4296571 discloses a profile grinding apparatus comprising a
stationary frame, a template support table and a work piece support table. The
apparatus further comprises pantograph means movable in a horizontal plane in
response to the positioning of a gUiding means and first and second moveable
support means mounted on the stationary frame.
US Patent No.5127195 describes a profile grinding machine and method with at
least two tool holders which are fixed in a frame and on each of which is fixed a
grinding tool for machining work pieces transported past the grinding machine in
a working plane. The tool holders are arranged in various angular positions and
their tools component each other to give the desired profile shape.
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However, the prior art machining processes for high thickness tubes, in particular
for edge preparation to fabricate Tee-joints are complex, cost-intensive, and do
not provide accurate profiles.
OBJECT OF THE INVENTION
It is therefore, an object of the present invention to propose a method of profile
machining in high thickness pipe materials to fabricate Tee-joints which
eliminates the draw backs in the prior art methods, and increases productivity.
Another object of the invention is to propose a method of profile machining in
high thickness pipe materials to fabricate Tee-joints, which allows easy-holding
of the pipe on a vertical boring machine so that the required profile can be
accurately generated.
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A further object of the present invention is to propose a method of profile
machining in high thickness pipe materials to fabricate Tee-joints, which
eliminatesmanual grinding particularly in low alloy steels.
SUMMARY OF THE INVENTION
Accordingly, there is provided a method of profile machining of high thickness
pipe material to fabricate Tee-joints in high pressure steam generators, the
methodcomprisingthe steps of:
placing horizontally at least two nozzles on the bed of a horizontal
boring machine spaced apart with the tube portions of the nozzles
facing each other, the intermediate distance between the nozzles
depending on the diameter of the header to be jointed with the
nozzles, and the nozzlesclamped between at least two v-blocks and
the tool holder of the machine;
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forming a profile at a first stage simultaneously, on the tube portions
of the two nozzles to reduce the thickness in a clampable portion of
the profile;
positioning at least one of the profiled nozzles vertically in a chuck of
the machine with jaws, and edge preparation of the tube portion being
carried out at a second stage through eccentric turning operation on
the profiled side of the tube without affecting the configured profile of
the nozzle,
characterized in that the nozzle with the tube portion in the second stage is
,disposed with an offset setting, and in that the offse~ distance is determined
by summation of the tube thickness plus 20 mm.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows a pre-machined and post-machined branch nozzle produced
in the conventional way of machining outside diameter, inside diameter and
chamfering.
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Figure 2 shows the position of nozzle in the bed of a vertical boring machine for
profile cutting according to the invention.
Figure 3 shows the finished nozzle after the profile machining according to the
invention.
Figure 4 shows position of the nozzle in the chuck with jaws of the machine for
edge preparation as per the invention.
Figure 5 shows the position of the nozzle produced as per the inventive process
and ready for welding to a header pipe.
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DETAILED DESCRIPTION OF A PREFERRED EMBODlMENT OF THE
INVENTION
According to the present invention, the machining operation is carried out in two
stages. In the first stage, the required radius is made with two number of tubes
of the nozzles placed in a horizontal direction (opposite to opposite), and the
required distance is maintained in a vertical boring machine. The offset is made
in the second stage when eccentric turning is carried. out for the edge
preparation on the same sides of the profiles where the metal removal taken
place during profile machine.
Figure 1 shows a pre-machined branch nozzle, and the machined nozzle formed
by conventional machine process with machining of inner diameter, outer
diameter and chamfering of the end nozzle. This requires manual grinding for
profile making.
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Figure 2 shows the inventive method of making profile by placing the nozzles
(01) on the machine bed, opposite to each other at a particular distance which
depends upon the header diameter (normally in the range of 323 mm and 508
mm). The job is positioned in the machine bed (OS) and clamped by a plurality of
V blocks (04) and the tool holder with a tool (03) as shown, for machining the
required profile simultaneously in the two nozzles positioned in the opposite
directions. The profile machining is carried out in the two nozzles in a single set
up which reduces human fatigue and enhance comfort.
Figure 3.shows the finished product. formed according to the in.ventive method of
machining the profile. Because of the reduction in the thickness in the
chamfering portion of the configured profile, further edge preparation is carried
out without affecting the profile.
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Figure 4 shows positioning of the nozzle (01) in the chuck (06) with jaws (07) of
the machine. Here the job (01) is held vertically for making edge preparation.
The job is setup with offset setting. The offset distance is the summation of pipe
thickness plus 20 millimetre. Because of this inventive step of offset method, the
machining is carried out to complete the edge preparation on the opposite sides
of the nozzle (01) without difficulty and the nozzle is ready for welding with the
header pipe.
Figure 5 shows positioning of the nozzle (01) in the header pipe which is ready
for welding of Tee-joints and here the cycle time is reduced from 80 hours to 8
hours and the grinding time is eliminated 60% than that of conventional profile
machining and edge preparation with less pollution and more safe condition.

WE CLAIM:
1. a method of profile machining of high thickness pipe material to fabricate
Tee-joints in high pressure steam generators, the method comprising the steps
of:
placing horizontally at least two nozzles on the bed of a horizontal
boring machine spaced apart with the tube portions of the nozzles
facing each other, the intermediate distance between the nozzles
depending. on the diameter of the. header to be jointed with the
nozzles, and the nozzles clamped between at least two v-blocks and
the tool holder of the machine;
forming a profile at a first stage simultaneously, on the tube portions
of the two nozzles to reduce the thickness in a c1ampable portion of
the profile;
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positioning at least one of the profiled nozzles vertically in a chuck of
the machine with jaws, and edge preparation of the tube portion being
carried out at a second stage through eccentric turning operation on
the profiled side of the tube without affecting the configured profile of
the nozzle,
characterized in that the nozzle with the tube portion in the second stage is
disposed with an offset setting, and in that the offset distance is determined
by summation of the tube thickness plus 20 mm.
2. The method as claimed in claim1, wherein the horizontal distance
between the nozzle is 323 mm to 508 mm.
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3. The method as claimed in claim 1, wherein the welding time and the
grinding time of the Tee-joint between the nozzleand the header pipe is reduced
by 900% and 60% respectively.