FIELD OF THE INVENTION
This invention generally relates to a process of bending reheater Bifurcated tube
used in Power Boilers. More particularly, the invention relates to a method of
making bifurcated tube bends for power boilers.
BACKGROUND OF THE INVENTION
Reheater tubes having outside diameter 63.5 mm with thickness 7.1 mm are
generally used in steam generator, to increase pressure and temperature of
steam after releasing from high pressure turbine. The header is connected by a
bifurcated bend to avoid more number of openings in the reheater header pipes.
These bifurcate bends are manufactured in three stages, namely, forming a
radius of R100 in the bend by cold forming at ambient temperature. Secondly,
putting the bifurcated bend in a furnace to heat to a temperature range of 950
to 1000°C for 30 minutes. Thirdly, the bifurcated bends are squeezed in a
squeezing machine to get the desired final radius of 76.2 mm.
As shown in figure 1, a top part of a bifurcated bend (2) is connected to the
reheater header (1), and a bottom portion of the bifurcated bend (2) is
connected to the reheater coils (3) which are used for power boilers to increase
power output.
The above known process is time consuming and more energy is required as 960
numbers of bends are required per boiler. Considering the huge quantity and the
time necessary in performing the said three stages of manufacturing, there is a
need to device an alternate method of making bifurcated bends in a single stage
at ambient temperature to a desired radius of 76.2 mm.

OBJECTS OF THE INVENTION
It's therefore an object of invention to propose a method of making bifurcated
tube bends for power boilers.
Another object of the invention is to propose a method of making bifurcated tube,
bends for power boilers, which allows making 180° bifurcated bend at ambient
condition.
A further object of the invention is to propose a method of making bifurcated
tube bends for power boilers, which enables bending of tube with outside
diameter of 63.5mm to a radius of 76.2mm at room temperature.
A still further object of the invention is to propose a method of making bifurcated
tube bends for power boilers, which eliminates prior art method steps of furnace,
heating and squeezing.
SUMMARY OF THE INVENTION
According to the present invention, the method of making a bifurcated bend
consists of the steps of :-
- loading a bifurcated bend in a bending former assembly;
- bending the bifurcated bend; and
- unloading the bifurcated bend from the bending former assembly.
A bottom former of said assembly is mounted on a bending machine by means of
a stay bolt. The bottom former has the bottom profile of the bifurcated bend.
Above the bottom former, a Top former is mounted, which has the top profile of
the bifurcated bend. During bending operation, the top former and the bottom

former are held together by means of said stay bolt which is fitted with the
bending machine. A drive pin is used to avoid eccentricity between the top
former and the bottom former and further ensures translational motion of the
top former. The up and down motion of the top former is caused by the stay
bolt. To hold the top former and the stay bolt together, a top plate is used. To
avoid escaping of the former assembly, from the stay bolt, a Nut is used.
Hexagonal socket head screw is used to hold the top former and the top plate
together. A grub screw is used to fix a drive pin in its position.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows a bifurcated bend in position in a reheater header including a
reheater coil.
Figure 2 shows a bending former assembly which is used to make the Bifurcated
bend.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The bending operation of bifurcate bend consists of the steps viz.,
1) Loading the bifurcate e bend in bending former.
2) Bending the bifurcate bend
3) Unloading the bifurcate bend from bending former.
A bottom former (4) is mounted on the bending machine by means of a stay bolt
(11), which has the bottom profile of the bifurcated bend. Above the Bottom

former, a Top former (5) is mounted, which has the top profile of the bifurcated
bend. During bending operation, the top former (5) and the bottom former (4)
are held together by means of the stay bolt (11) which is fitted with a bending
machine. A drive pin (6) is used to avoid eccentricity between the top former (5)
and the bottom former (4) which interalia ensures translattonal motion of the top
former (5). The up and down motion of the top former (5)'is provided by the
stay bolt (11). To hold the top former (5) and the stay bolt (11) together, a top
plate (7) is used. To avoid escaping of the former assembly (4,5) from the stay
bolt (11), a nut (8) is used. A hexagonal socket head screw (9) is used to hold
the top former (5) and the top plate (7) together. A grub screw (10) is used to
fix a drive pin in its position. The work piece (2), for example, the bifurcated
tube bend is held between the top former (5) and bottom former (4) and the
entire assembly is rotated to get the desired bend radius used in the reheater
tube.

WE CLAIM :
1. A method of making bifurcated tube bends for power boilers, comprising
the steps of :-
providing a straight bifurcated tube (2);
mounting a bottom former (4) on a bending machine through a stay bolt
(11) having a bottom profile of the bifurcated bend to be produced from
said straight tube (2);
placing a top former (5) having a top profile of the bifurcated bend over
the bottom former (4);
providing a drive Pin (6) to avoid eccentricity between the top former (5)
and the bottom former (4);
disposing a top plate (7) to hold the stay bolt (11) and the top former (5)
together;
locking the top former in the stay bolt by using a nut (8);
interposing a hexagonal socket head screw (9) to hold the top former (5)
and the top plate (7) together;
locking the drive pin (6) in its position by applying a grub screw (10); and
importing a simultaneous motion of the former assembly (4,5) to produce
a required bend radius of 76.2 mm in the reheater tube (2) initially having
an outside diameter 63.5 mm.