FIELD OF THE INVENTION
The field of the invention generally relates to identification of punctured tube in heat treatment furnace. More particularly the invention relates to a method of leak test in the radiant tube assembly of a heat treatment furnace adapted to relieve internal stresses developed during manufacturing of seamless steel tubes.
BACKGROUND OF THE INVENTION
During the manufacturing of seamless steel tube are subjected to internal stresses during the cold drawing process. In order to relieve the internal stresses, the tube is fed to the furnace for conventional normalizing and annealing (heat treatment process). Heat treatment process is one of the important processes carried out after the tubes are drawn on the Draw Benches for the refinement of grain structures, stress relieving and the softening. Furnaces are equipped with W-Tube Radiant Tubes for the indirect heating via radiation from the outer surface of the tube to the drawn tubes.
But in the long run, radiant Tubes develop cracks and gets punctured inside, making the process of radiation in-efficient and the flue gas enters in the furnace which in turn results in the oxidation, forming huge scales on the drawn tube surfaces. Thus, such Radiant Tubes have to be replaced when damaged in order to have the req. inert atmosphere inside.
If a furnace has 30 nos. of radiant Tubes, then checking physically the radiant tubes one by one after complete dismantling and taking out from the furnace is a big task as it requires the crane handling also.
All the 30 tube assemblies are to be dismantled one by one to find out the damaged radiant tube. This is time consuming process and more manpower, crane assistance is required. Hence there is a need to find out and a simple method of leak detection without take out of the hole radiant tube assembly.

OBJECT OF THE INVENTION
It is therefore an object of the invention to propose a method of leak test in the radiant tube assembly of a heat treatment furnace adapted to relieve internal stresses developed during manufacturing of seamless steel tubes.
Another object of the invention is to propose a method of leak test in the radiant tube assembly of a heat treatment furnace adapted to relieve internal stresses developed during manufacturing of seamless steel tubes, which is capable to quickly identify the damaged radiant tubes.
A further object of the invention is to propose a method of leak test in the radiant tube assembly of a heat treatment furnace adapted to relieve internal stresses developed during manufacturing of seamless steel tubes, which is enabled to carry out inspection of the tubes without dismantling and taking out tubes from the furnace.
SUMMARY OF THE INVENTION
Accordingly, one end of the radiant tube assembly flange is connected to a source of compressed air supply having a control valve. A stub is connected duly welded with the flange. The other end of the radiant tube assembly flange is connected with a pressure gauge. The compressor air passed through one end of the tube to the another end, and the pressure gauge records the pressure of the air, keeping the gate valve closed. If the pressure gauge indicates a constant value, then there will be no puncture in this tube assembly. This procedure is repeated to other tube assembly till the puncture is detected. By this method the total radiant tube assembly need not be taken out from the furnace to find in which of the tubes the puncture has occurred. Since there are 30 tubes available in the furnace this method of testing can be effectively used to reduce the time for the replacement the punctured tube.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure – 1 Shows the schematic diagram of a furnace with radiant tube assembly in position.
Figure – 2 Shows one typical radiant tube assembly.

Figure – 3 Shows a pressure gauge with connecting flange.
Figure – 4 Shows the connecting flange with a control valve and stubs.
Figure – 5 Shows the schematic arrangement of the assembly to conduct leak test for identifying a punctured tube.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
According to the present invention, referring to figure 5 a compressor air inlet flange
(11) is fastened with a counter flange (03) of the radiant tube (02) by means of a first fastner (13). The outlet flange (08) is connected to a corresponding counter flange
(12) of the radiant tube (02) by means of a second fastner (12). A compressor air hose (07) is connected with a first stub (06) which is welded on one end of a control valve (05) and the other end of the control valve is linked with the inlet flange (11) by means of connecting stub (04). A pressure gauge (10) is linked with the outlet flange (12) by means of a third stub (09). The compressor air is admitted to the radiant tube (02) through the inlet hose (07). The pressure gauge records the increase in pressure of 6 bar. Once the required pressure of 6 bar is reached, the control valve (05) is closed. The position of the pressure indicator of the pressure gauge is checked and if there is no change in the position, it ensures the corresponding radiant tube is not ruptured. This process is repeated in series to all radiant tubes till the ruptured tube is found out and that tube alone can be taken out for repair welding.
Thus a damaged radiant tube can be replaced afterwards directly. The Invention not only saves the time but also the hard labour required for the complete removal and physical checking.

WE CLAIM:
1. A method of leak test in the radiant tube assembly of a heat treatment furnace adapted to relieve internal stresses developed during manufacturing of seamless steel tubes, comprising the steps of :
- attaching two flanges (11 and 12) having pitch circle diameter corresponding to that of the inlet and outlet flanges (03) of the Radiant Tube, assembling a first flange with a pressure gauge (10) at a first end of the radiant tube (02), and attaching an air inlet valve (05) on the other end of the first flange (11);
- allowing the furnace (01) to cool down and then dismantling the burner and recuperator assembly from both ends of the Radiant Tube (02); connecting the end flanges (03) to said two flanges (11 and 12), a plurality of fasteners (12 and 13) fastening the flanges (11,12,03) securely by gaskets (14);
- supplying compressed air at a pre-determined pressure through the radiant tube (02) assembly; cutting-off the air supply by closing a control valve (05); measuring the outlet pressure by a pressure gauge (10), wherein if the measured outlet pressure is below said pre-determined pressure, a leak inside the radiant tube (02) is established.