FIELD OF THE INVENTION
The field of invention generally relates to manufacturing of the return bend used
in Heat Recovery Steam Generators (HRSG). More particularly the invention
relates to a device for clamping the return bend for drilling without marking and
setting.
BACKGROUND OF THE INVENTION
In the Heat Recovery Steam Generators (HRSG) return bends are used for
transferring steam from one module to another and also to drain water from the
module. The return bend outside diameter is 88.9 mm with the thickness ranging
from 5.5mm to 11.13 mm. A stub of outside diameter 33.4 mm to be welded on
the top of the return bend at the shop floor. Prior to the welding the hole drilling
operation is to be carried out at the top of the return bend. The diameter of the
return bend is 230 mm.
Normally the marking is done manually by butting the try square at one end and
marking the distance by measuring tape as a point is marked at the place where
the centre of the drilling will come. Punching is done at the centre using center
punch tool after marking the work taken to the radial drilling machine and job
setting is done for drilling, now the drilling is completed. There are 300 to 400
return bends which are to be drilled per boiler. Hence there is a chance when
deviation may occur during marking and that takes more time to rectify the
same. Consequently the rate of production becomes low. Hence there is a need
to find out fool proof method for drilling the return bends.

OBJECT OF THE INVENTION
Therefore the objective of invention is to propose a new method of fixing the
return bend for drilling operation.
Another object of invention is to avoid marking in the drilling operation.
A still further object of invention is to avoid the setting time for drilling operation.
SUMMARY OF THE INVENTION
Accordingly there is provided a device for clamping the return bend (5) for
drilling in the machine without marking and setting.
The device is like an enclosure comprising a pair of side plates (3) mounted and
welded perpendicularly over a base plate (1), a bottom back plate (2) welded
over the base plate (1) from the rear side, a top back plate (4) is connected with
bottom back plates (2) by means of hinge assembly (12), a top positioning lock
nut assembly (10) disposed in the front side of the assembly, a positioning lock
nut (9) fixed on the left side of the assembly, a top cover plate (11) welded on
the top side which is provided with a bush guide (7), bush (8) and bush locking
nuts (6) at the center of the cover plate (11), thus when the return bend (5) is
placed on the device during drilling, the arrangement grips the job tightly and
perfectly preventing any unwanted movement of the job during drilling
operation.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1: shows the elevation of the device with work piece in position.
Fig. 2: shows the view of fig. 1 when seen in the direction Q.
Fig. 3: shows the view of fig.1 when seen in the direction P.
Fig. 4: side plate (Item No. 3)
Fig. 5: Top cover plate (Item No. 11)
DETAILED DESCRIPTION OF THE PREFERED EMBODIMENT OF THE
INVENTION:-
Referring to Fig 1, a base plate (1) is welded perpendicularly with a pair of side
plates (3) at the distance of 315 mm apart for positioning the return bend (5).
One side of the side plate (3) is drilled and threaded, and M8 bolt (9) is used for
fine adjustment in the horizontal axis adjust any the movement in left and right
side. The bottom back plate (2) is welded with the base plate (1) to rest the
return bend (5). The top back plate (4) is connected with bottom back plate (2)
by means of hinge assembly (12) for opening and closing. The top cover plate
(11) is connected with the top back plate (4) by welding. For every time loading
and unloading of the work piece (5) is carried out by opening the cover plate by
like a door by means of hinge mechanism (12) provided on the top cover plate
(11).
The top cover plate (11) is having a hole at the center and bush guide (7) is
welded concentrically. A drill bush (8) is inserted on the bush guide (7) and
locked by the means of bush locking nut (6) on either side. The top cover plate
(11) is welded in the front side with top positioning locking nut assembly (10)

and this will be used to lock the work piece (5) for arresting the perpendicular
movement of the work piece (5) while drilling operation is being performed.
There are two sub-assemblies in the device, the bottom sub assembly consisting
base plate(1), the bottom back plate (2) and two Nos of curved side plate (3)
whereas the top sub assembly consisting of the top back plate (4), top cover
plate (11), drill guide (7), drill bush (8) and lock nut assembly (10). These two
sub-assemblies are inter connected by hinge assembly (12).
The complete assembly is taken to the drilling machine and the base plate (1) is
clamped with machine bed by conventional ‘T’ bolt (Not shown). The return bend
(5) is placed by opening the top cover plate (11) and all the degrees of freedom
arrested by tightening the side positioning lock nut (9) and top positioning lock
nut assembly (12). Now, the drilling is done without marking and setting and the
cycle is repeated for another return bend.

WE CLAIM:
1. A device for clamping the return bend for drilling without marking and
setting comprising:
a base plate (1) on which a plurality of side plate (3) mounted
perpendicularly from either side with a distance of 315 mm and welded;
a bottom back plate (2) welded at 90° position with the base plate (1) on
the rear side that butt with the work piece ( 5 ) from the back;
a top back plate (4) connected with the bottom back plate (2) by means
of hinge assembly (12) for opening and closing;
a top plate (11) welded over the top back plate (4) which will acts like
a door because of hinge mechanism (12) plate for opening and closing for
loading and unloading purpose;
wherein the said top plate (11) provided with a centre hole on which a
bush guide (7) is welded, the said bush guide (7) accommodates a drill
bush (8) which can be locked by a pair of bush locking nuts (6) from
either side;
a top positioning locking nut assembly (10) welded with the top cover
plate (11) from the front side for the purpose of tightening the work
piece (5) in the another direction so that the vertical movement can be
arrested;
the whole set up is moved to the drilling machine and the base plate (1) is
clamped to the machine table (not shown) to do the drilling operation;
after completing one work piece (5) the locking nut assembly (10) and
side locking nut (9) are released and by using the hinge assembly (12) the
top cover plate (11) is opened like a door with hinge mechanism;
the cycle is repeated for another work piece (5) as above.

2. The device as claimed in claim 1 that eliminates the marking and setting
operation before performing the drilling operation for the next job for
drilling the return bends (work piece).