Claims:WE CLAIM:
1. A method of bending a three bend offset in a single press wherein
top rollers (02) are fixed according to the required diameter of the tube (5);
bottom rollers (01) are fixed according to the diameter of a tube (5) and the radius of the bend required;
left (3) and right (4) quadrant dies are fixed, into the holder;
pressure is applied on said left (3) and right (4) quadrant dies to form the three bend offset.

2. The method as claimed in claim 1, wherein said left (3) and right (4) quadrant dies can be changed according to the diameter of said tube (5) and the radius of the bend required.

3. The method as claimed in claim 1, wherein said left (3) and right (4) quadrant dies are moved downwards on said tube (5) using hydraulic cylinders for attaining the three bend offset.
, Description:FIELD OF THE INVENTION
[001] The present invention generally relates to manufacturing bends required for water wall panels for high pressure boilers. The present invention more particularly relates to bending operations in press. Still more particularly the present invention relates to method of bending a three bend offset in a single press.
BACKGROUND OF THE INVENTION
[002] The conventional method of bending two bends in a same tube is carried out by normal pressing using conventional die. In a high pressure high temperature steam generator, furnace roof tubes three bend offsets are envisaged according to the requirement. In super critical boilers, hanger tubes are envisaged at roof locations which passed through the offsets available in the roof panels, for the passage of these hanger tubes three bend offsets are introduced in the roof panels. As such there is no method available for the manufacturing such bends in a single press as there is no gap between bends. In the conventional method bends are done in bending machine using a clamp, former and a follower jaw, this type of bend cannot be done in steam generators as there is no gap for clamping the tube after the completion of the first bend. Hence there is a need to find out an alternate method for manufacturing of three bends in a single press.

OBJECTS OF THE INVENTION
[003] It is therefore an object of invention to propose a reliable and an effective method of bending the three bend offset on boiler tubes.

[004] Another object of invention is to propose a suitable die for manufacturing.

[005] A still further object of invention is to propose a suitable die for three bends in a single press.
SUMMARY OF THE INVENTION
[006] The present invention refers to the method of bending a three bend offset in a single press. Accordingly the work piece is fed in between top rollers and bottom roller of the single press. The bottom rollers are used to feed the work piece and it has an inbuilt curvature according to the diameter of the tube on which is going to bend and it is also machined equal to the radius of the bend required. The top rollers are used to hold the work piece in a single direction which also has an in built curvature according to the diameter of the tube. Now the die is having two parts namely left quadrant die and right quadrant die. These two quad dies can be assembled together and put it in the holder(not shown). The assembly of left and right quadrants is moved downward to touch the work piece. Now load is applied on the die to form a three bend in a single press. Depending upon the design requirement of the profile of the bend (radius and depth of the bend) the left and right quadrant dies can also be separated to the required distance by inserting a straight piece with an inbuilt curvature according to the diameter of the tube.
BRIEF DESCRIPTIONS OF THE ACCOMPANYING DRAWINGS
Figure 1 shows the developed quadrant dies along with work piece
Figure 2 shows the detailed quadrant dies
Figure 3 shows the perspective view of the developed quadrant dies along with work piece
DETAIL DESCRIPTION OF THE INVENTION
[007] The present invention will be described in detail below with reference to an embodiment as shown in the drawing.

[008] The present invention refers to the method of bending a three bend offset in a single press. Accordingly the work piece (05) is fed in between top rollers (02) and bottom rollers (01). The two numbers of bottom rollers (01) is used to feed the work piece and I has an inbuilt curvature according to the diameter of the tube (05) on which we are going to bend and it is also machined equal to the radius of the bend required. The top rollers (02) is used to hold the work piece (05) in the unit direction which also has an in built curvature according to the diameter of the tube (05). Now the die is having two parts namely left quadrant die (03) and right quadrant die (04). The left and right quadrants (03, 04) are machined according to the radius of the bend required with an inbuilt curvature according to the diameter of the tube (05). These two quad dies can be assembled together and put it in the holder (not shown). The assembly of left and right quadrants is moved downward using hydraulic cylinders to touch the work piece. Now load is applied on the die (03, 04) to form a three bend in a single press. Depending upon the requirement the left and right quadrant dies can also be separated to the required distance by inserting a straight piece (not shown) with an inbuilt curvature according to the diameter of the tube (05).

[009] The same setup can be modified and used for tube diameters ranging from 38mm to 76.1mm, radius of bend ranging from 105 mm to 225mm and thickness of tube ranging from 4mm to 15.7mm.