FIELD OF THE INVENTION

The present invention generally relates to water wall panel fabrication for high pressure boilers. In particular, the present invention relates to panel fabrication by butt joining a plurality of tubes followed by Ball testing of the tube butt joints. More particularly the invention relates to a process for correction of internal diameter of butt joints in water wall panels applicable to high pressure boilers.
BACKGROUND OF THE INVENTION
In water wall panels, the panels processing operation begins with the Ball test. Ball test that ensures each tubes in the panel is having at least 80% flow area. For this operation, firstly 80% of tube Inside Diameter is calculated, and then at least one ball of said size allows to pass through the tube by using compressed air to push the ball from one end to the other. If the ball passes to the other end the test is successful. If not and ball struck in the butt joint, then we have to go for a correction. If correction fails, then the joint has to be cut and we have to put a Piece of tube of required length. Then we have to weld two nos. of Tungsten Inert gas welding (TIG) joints manually in place of one and again we have to conduct the Ball test.
Figure 1 shows the ball testing of water wall panel tube (part 2).This tube is having a butt welded joint (part 1). A ball of 80% ID of the tube is calculated and it is taken (Part 3) as the test-parameter. During testing, if the ball is allowed to pass through the joint (1) with slow supply of compressed air (4), the joint is an allowable joint. If the ball gets struck in the joint, it is a defective joint.
From the figure 2 it is clear that the ball of 80% ID (3) is passing through the joint (1).So it is an allowable joint. From the figure .3 it is clear that the Butt joint (1) has excess penetration so it will not allow the steel ball of 80% ID (3) of the tube to pass. So it is considered as a defective joint.

The correction required for the ball test failed tubes (Fig 3). These tube Butt joint(1) area is allowed to heat at red hot condition with a blow torch(5) and from one end a rod set up inserted through the joint. The rod set up(OLD TOOL) which can reach up to the butt joint area(1) (Normally the butt joint in a tube varies from 2-13 meters from one end, sometimes double) having a bolt head(7) which will match the 80% ID of the required tube. This long tube (8) with a bolt head (7) welded with one end is allowed to hit the red hot Butt joint (1) from the other end. The force of hitting is gained by hammering by a hammer (9) the rod at its end portion.
The plastic deformation happens to the excess penetrated root portion at the inside diameter of the tube by hitting with the hammer (9) at one end. If bolt head portion (7) go through the tube butt joint area (1), then the correction is done successfully. If the excess root is more or it never allows the plastic deformation, then the joint correction fails and further processing is cutting the joint and proceeding further. Cutting and replacing the joint with another joint it required Radio graphic test for these joints. If radio graphic test finds some defects in joints then the rework of the joint has to be done. This increases the cycle time of panel fabrication of high pressure boilers.
This correction process (Ref.Table.1, 2, 3) requires acetylene cylinders, heating set/blow torch 3 manpower. During the tube Butt joint heating if the heating goes beyond the upper critical temperature, there are chances for the joint failure. At later stage there by ensuring the quality standards never meets. So this process had found that it is time consuming and increases the utilization of materials as well as manpower also chances for poor quality of Butt joints.

Table 1: We can have a clear idea that the cycle time is more for the old method.

Hence there is a need to design a new method for ID correction of water wall panels.
Prior Art
Extensive search has been made in internet and it has been found that no such relevant patents found.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a process for correction of internal diameter of butt joints in water wall panels applicable to high pressure boilers.
Another object of the invention is to propose a process for correction of internal diameter of butt joints in water wall panels applicable to high pressure boilers , which eliminates wastage of material and manpower and improves quality of the joints.

SUMMARY OF THE INVENTION
Accordingly, experiments were conducted to find a simplified and an effective method for Excess penetration correction of Butt joints in water wall panels. Since the earlier method was found to be time consuming and more wastage of resources, we have finally chosen an idea that the Excess root portion can be removed and the necessary ID dimension can be maintained that requires 80% ID of tube. The excess Penetrated material can be removed by drilling the Butt joint root portion with a suitable size drill bit which is having 80 % Id of the tubes butt joint to be corrected. The size of the drill bit only should have to meet the 80% Id of the tube. This tool can be inserted to the butt joint excess penetration area and can drill and there by removing the excess penetration to make it to meet the dimensional requirements for our water wall panel fabrication.
The process there by eliminates manpower material wastage also reduces the cycle time and 100% ensures the quality as well as the correction of the excess root in straight tube butt welding or tube to tube butt welding.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure.1 shows the ball testing method for water wall.
Figure.2 shows the steel ball passing through a perfect butt joint.
Figure.3 Shows the ball test rejected butt joint.(excess penetration present).
Figure .4 Shows the Ball test rejected tube Excess penetration correction process
Figure.5 Shows the Tool used for Excess penetration correction in old method.
Figure.6 Shows a tool for excess penetration correction according to the inventive process.

Figure.7 shows a process of excess penetration correction with the tool using a chamfering machine.
Figure.8 shows the steps of operation followed in prior art method.
Figure.9 shows the steps of operation for the new method of excess penetration correction operation.
Figure.10.Shows the tube butt joint with excess penetration.
Figure.11 shows the excess penetration correction operation.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
This New method invented for the water wall panel Butt joints ID excess penetration correction for ball test rejected tubes. Earlier method in which the Excess penetration joints which are identified while ball testing of the panel tubes, are taken and correcting process is done.
We can see from flow diagram 1. That the steps for correction of Id of the butt joints following old method. It is taking 4 steps to complete the process. Step 1.Heating the butt joint area with a heating set up. Step.2.The heated joint is allowed to hit by the old tool(fig.5) with the help of a hammer(Part.9).The excess penetration in the butt joint(Part.1) thus plastically deforms and allows the bolt ( Part.6) to go through the joint(part 1). First ensures the bolt portion is passing through the joint, if it is passing this joint is taken for ball testing again. While ball testing the ball passes through the Butt joint (part 1) area as shown in fig.2 then the joint is considered as OK joint. This Steps are followed to the other ball test rejected joints in the panel.
This method required heating set up, Acetylene cylinders, one manpower for heating, and 2 manpower for hitting the Tool end with hammer. This old method takes more time for correction. Hammer may slip at any time while operation since it is doing manually so safety is not ensured. And quality of the corrected joints may decrease. Sometimes it won’t pass through the butt joint (part 1) then we have to do cut and weld to replace the one joint with 2 nos. of butt joints. Once new butt joints are made

we have to take Radio graphic test for the joints. This will increase the additional cost. RT test always threat for environment. This will increase additional work and excess raw materials usage.
Due to the problems faced in the old method we planned to find an alternative method which is efficient and less time consuming for the correction of excess penetration in the butt joints of water wall panel tubes. So we invented a new tool As shown in fig.6. This new tool I shaving 3 parts. Part. 10 is a drill bit chosen according to the 80% Id of the tube size.Part.11 Is a long hollow shaft which is having a considerable diameter (1 mm less than the tube ID) to insert the rod to the tube which is to be corrected the excess penetration(Part.1).part 12 is a guide arrangement which is a flange provided for eliminating the rod deflection and to provide a smooth drilling operation at the joint area(part 1).This flange arrangement can ensure no oval shape at the Excess penetration area after drilling.
The New tool operation, is quite simple as it can be connected to a tool holder (part no. 13) of a chamfering machine shown in fig.7.The chamfering machine is a pneumatic machine. It is driven by compressed air. When the machine is allowed to operate, the drilling process starts and the excess penetration removal operation begins. Once the joint is passed the tool is taken back and the process is continued for the other ball test rejected joints.
This new method is having advantage over the old method since there is no requirement of heating of the joint. And it requires only one manpower for the completion of the operation. Since all the joints can be made OK There is no need of Cut and weld and RT hence the excess raw material usage eliminated and Environmental safety problems reduced. No safety issues. We can see from the Flow diagram 2 that there is no rejected joints after the correction. So the cycle tie of the panel processing operation improves by this invention.

Table 2. Shows The Cycle time comparison of Earlier and New methods.

ADVANTAGES OF THE INVENTION
The proposed excess penetration correction operation is quiet simple and there is a huge savings in material utilization, manpower engagement and in cycle time of panel fabrication. It ensures 100 % quality. Because of removal of excess penetration unplanned joints can be saved in panels for high pressure boiler.
. The detail of modification is as below.
1. Referring to Figure 1, the quality requirement of 80% flow area in a tube has been mentioned. If the mentioned size is reached, then the Ball test will be ok. Since the drill bit size is same as the 80 % ID of the tube, it will clear the excess penetration in tube butt joint area. It is clear by this new method an effort less good quality Excess penetration correction is ensured.

2. The Figure.6 shows the new modified tool. The Tool is made of 3 parts.
a) Drill bit (10) of 80% of ID of tube has been selected for Excess Penetration removal.
b) A long rigid hollow shaft (11) is taken which is having good toughness can reach till the Butt joint portion needs correction. It’s one end having provision for fixing the drill bit (10) and other end for fixing in Chamfering Tool holder (13).
c) The second end fixed to the chamfering holder (13) is being attached to chamfering machine (14) holding point. When we switch on pneumatic chamfering machine which rotates the chamfering holder (13), as we give feed to the machine it removes the excess penetration in the butt joint (1). The excess penetration correction process before needs the heating setup (5) and excess manpower required and totally it is a time consuming operation. Now within one hour the excess penetration correction of a panel with 30-48 tubes can be done effortlessly.
d) Figure .5 shows the tool that has been using for the operation (old method). It is clear that the corrected excess penetration will not have a good finished root. And chance of failure is more.


Table 2: Man, material wise savings shown in Table
The total system can be used for irrespective of ID of tubes since provisions made for changing each parts according to the operation.
Thus as disclosed in the new process, since no heating is required. we have saved of 900 production shifts, thereby there is a substantial saving in man power, energy and time.

WE CLAIM:

1. A method of excess penetration correcting of tubes rejected in a Ball test process, the method comprising the following steps.
i) measuring the internal diameter (ID) of the rejected by a Vernier calliper; ii) arithmetically calculate 80% ID of the tube; iii) selecting a drill bit of 80% ID of the tube;
iv) measuring the length of the tube end upto the defective butt joint; v) selecting a hollow shaft according to the length measured at step; vi) welding said Drill bit with the Selected Hollow Shaft;
vii) inserting the hollow shaft with the drill bit till the assembly reaches the
defective Butt joint which has to be corrected;
viii) connecting the hollow shaft to a chamfering machine. ix) activating the pneumatic air supply source to supply compressed air to the machine;
x) commencing operation of drilling of the root joint, and correcting the excess penetration of the defective joint.