Claims:We claim:

1. A method for leakage testing of gas line leakage during Major Shut Down of reheating furnace, the method comprising:
closing all zone burner gas valves and zonal header end flanges;
cleaning of gas line;
sealing the gas line by closing safety shut-off valve (108) and control valve (102);
connecting mobile air compressor (106) to the sealed gas line;
pressuring the sealed gas line by supplying air through the mobile air compressor (106), wherein the air pressure is regulated to 1500 mm WC;
checking and identifying leakages in the joints of the sealed gas line with soap bubble test; and
sealing the identified leakages in the sealed gas line.

2. The method as claimed in claim 1, wherein the air pressure is regulated by the outlet valve (107) to 1500 mm WC.

3. The method as claimed in claim 1, wherein the mobile air compressor (106) is connected with sealed gas line via flow measurement line (104).

4. The method as claimed in claim 1, wherein normal air is used for checking and indentifying the leakages in the sealed gas line.

5. The method as claimed in claim 1, wherein nitrogen gas is blown into the gas line to purge out the applied air from the gas line before light up the furnace.

6. The method as claimed in claim 1, wherein the reheating furnace is light up in one hour after receiving the light up clearance.

7. The method as claimed in claim 1, wherein the pressure of the sealed gas line is measured by the pressure gauge (105).
, Description:A METHOD FOR TESTING OF GAS LINE LEAKAGE IN REHEATING FURNACE DURING MAJOR SHUT DOWN
FIELD OF INVENTION:
[001] The present subject matter described herein, relates to operation processes of reheating furnace and, in particularly, to a method for testing of gas line leakages in reheating furnace during major shut down.
BACKGROUND AND PRIOR ART AND PROBLEM IN PRIOR ART:
[002] HSM (Hot strip mill) is using mixed gas in the reheating furnace, a mixture of Coke Oven and Blast Furnace gas, which contains 22% CO. The mixture of gases is supplied to gas line burners through the pipelines of different diameters containing various joints and bends within it. Before the consuming point the gas holders are installed to maintain the gas pressure while boosting it with the pumps. The coke oven and mixed gases are very corrosive in nature. The pipeline is corroded due to this within a span of 4-5 years and starts leaking. There is a good common practice existing that the people are using the CO gas detector while moving in the gas hazardous area. These detectors are sensitive enough to detect even a small amount of leakage like 10 ppm. After sensing in the detector, the people evacuate the place and inform the concerned authority for taking further action. After detection the area is cordoned off and the people start searching the leakage with fear. It is important to find out the leakage point to fix it.
[003] The coke oven gases contain lot of dust and tar which deposits on the pipe wall during operation of furnace. Therefore, all the pipes are opened for cleaning during major shut down. Once the cleaning job is done, all the pipes are joined back with the new joint sheets in the flanges. Due to human error, many leakages exist in the lines and the furnace cannot be started without fixing the leakages.
[004] In order to fix the leakages in the pipe line, several methods are adopted which consume time. Fig. 2 illustrates a known method for identifying the leakage and fixing the same in the gas line. At block 200, the reheating furnace is closed during the shut down for cleaning purpose. At block 201, the complete gas line is opened for maintenance and cleaning. At block 202, the gas pipe lines are cleaned in each zone of the furnace. If any pipe is corroded and required replacement, the pipe is replaced with the fresh pipe. At block 203, new pipes are assembled in the gas line with new joint sheet in the flanges. At block 204, conduct the cleaning job process for all the zones and entire gas line of the reheating furnace. At the block 205, if clearance job is completed for one zone, clearance completed signal raised for the zone. Wait till the other furnace jobs are completed in the other zones. At the block 206, once the clearance is completed and all people engaged in the cleaning are out from the furnace, a clearance signal is given for the furnace. At the block 207, nitrogen N2 gas is purged in the gas line to check any leakage in the joints by soap bubble test. If there is any leakage found, the same is repaired using existing technologies. Nitrogen gas is purged in the gas line at 1500 mm WC pressure and all approximate 900 flange joints of different diameters are checked with soap bubble test which were opened during shut down for maintenance. At the block 208, the gas line is charge with fuel gas having CO and seal the further leakages found by CO detector. This process is repeated as long as all the leakages are not sealed. At the block 209, a signal for light up the furnace is given.
[005] In the existing method, there are several challenges and dis-advantages. The entire process is tiresome and tedious, especially, to cover the total gas line network of 900 joints at one go. In case of higher diameters line more than 20 inches, the entire perimeter cannot be covered by soap bubble test so easily in the stipulated time period. As nitrogen N2 gas is odorless, hardly any leakages are found in this process. Most of the leakages are found during the lit-up process of the furnace after charging the mix gas which has a specific pungent smell. Even after getting the smell or sensed by the CO detector (carbon monoxide detector), it is not easier to find out the exact leakage location in the gas line. The operator need to wear the heavy gas mask and climb up on the gas line pipe to check the joints with soap bubble. In the reheating furnace, many of the pipe lines are out of approach of human and located in the “hard to access area”. Further, the human can work in the reheating furnace during N2 purging with oxygen mask only. With the oxygen gas mask, one can work for half an hour only. Then the cylinder has to be changed. Further, the atmosphere is tremendously adverse due to heat, one sweat heavily to get tired and the chances of accidents are high. The overall leakage testing job takes around 18-20 hours for one furnace and HSM has three such furnaces. Therefore, huge time is wasted in this process.
[006] It would be desirable to develop a method for testing the leakages that is relatively easy to perform, and that provides a relatively fast manner for testing the leakages and fixing the same. The method that can minimize the technical problem exist in the prior method that is high operation time and requirement of gas mask. In order to cater all the above mentioned technical problems, a simple and easy to perform method is required for identifying leakages in the gas line of the reheating furnace during major shut down.
OBJECTS OF THE INVENTION:
[007] The principal objective of the present invention is to remove unsafe practices followed during lit-up the furnace after major shut down (MSD) in the reheating furnace of Host strip mill (HSM).
[008] Another object of the present invention is to reduce the startup time after the major shut down of the reheating furnace.
[009] Another objection of the present invention is to provide a method which is simple and fast and easy to perform.
[0010] Yet another object of the present invention is to utilize the manpower and shut down time effectively.
SUMMARY OF THE INVENTION:
[0011] The subject matter disclosed herein relates to a method for testing leakages in zonal gas line of reheating furnace. In the present method, each zone of the reheating furnace or Hot Strip Mill is taken up separately during Major Shut Down (MSD) and leakage testing is done comfortably during the shutdown period itself. During the leakage testing process, each zone can be isolated from the other zones in the network by safety shut off valve. Further, a mobile air compressor is connected with the isolated sealed gas line zone used for this purpose with a pressure output of 2000 mm WC instead of N2 and fuel gas. As the air is harmless in the present method, the complete leakage testing process is done safely without wearing the heavy gas mask. The present simple innovative method saves a considerable time of 15 hours for startup. By deploying the present method in the reheating furnace, a considerable production time is saved. The present method can be used other than the MSD also where the furnace gets shut down in emergency for gas line maintenance.
[0012] In order to further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit scope of the present subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods or structure in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
[0014] Fig. 1 illustrates system arrangement of testing process in the zonal gas line of the reheating furnace, in accordance with an embodiment of the present subject matter;
[0015] Fig. 2 illustrates known method for testing the leakages in the zonal gas pipe line;
[0016] Fig. 3 illustrate a method for testing leakages in the zonal gas pipe line, in accordance with an embodiment of the present subject matter;
[0017] Fig. 4 illustrates combustion gas line diagram of the furnace, in accordance with an embodiment of the present subject matter; and
[0018] Fig. 5 illustrates nitrogen gas flow line diagram of the furnace, in accordance with an embodiment of the present subject matter.
[0019] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DESCRIPTION OF THE PREFERRED EMBODIMENTS:
[0020] The subject matter disclosed herein relates to a method for testing leakages in zonal gas line of reheating furnace. In the present method, each zone of the reheating furnace or Hot Strip Mill is taken up separately during Major Shut Down (MSD) and leakage testing is done comfortably during the shutdown period itself. During the leakage testing process, each zone can be isolated from the other zones in the network by safety shut off valve. Further, a mobile air compressor is connected with the isolated sealed gas line zone used for this purpose with a pressure output of 2000 mm WC instead of N2 and fuel gas. As the air is harmless in the present method, the complete leakage testing process is done safely without wearing the heavy gas mask. The present simple innovative method saves a considerable time of 15 hours for startup. By deploying the present method in the reheating furnace, a considerable production time is saved. The present method can be used other than the MSD also where the furnace gets shut down in emergency for gas line maintenance.
[0021] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.
[0022] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.
[0023] Fig. 1 illustrates system diagram of the zonal gas line, in accordance with an embodiment of the present subject matter. The present system 100 comprises a gas line burner 100a, individual burner 101, control valve 102, orifice plate 103, flow measurement line 104, pressure gauge 105, outer valve 107, mobile air compressor 106, safety shut off valve 108, and main gas line 109. During the major shut down (MSD) of the Hot strip mill (HSM), each zone of the reheating furnace is cleared. Further each gas line zone is connected with the main gas line with a tapping on it. The gas flow in the zonal gas line is disconnected by the safety shut-off valve 108. Once the safety shut off valve 108 is tapped no fuel gas can enter in the zonal gas pipe line. The orifice plates 103 and flow measurement line 104 us used to measure the gas flow. Further, the zonal control valve 102 is located to control the gas flow. By closing the safety shut off valve 108 and the control valve 102, the gas line is sealed. The mobile air compressor 106 is connected with the sealed gas line to apply air pressure in the sealed gas line. Further, the orifice plates 103 measures the air flow inside the sealed gas line. The mobile air compressor 106 is connected in the flow measurement line 104 to supply air in the sealed zonal gas line with the regulated pressure of 1500 mm WC controlled by the control valve 107. The pressure of the sealed gas line is measured by the pressure gauge 106. The mobile air compressor 106 has capacity to generate pressure output of 2000 mm WC.
[0024] After applying the air pressure in the sealed zonal gas line, soap bubble test is applied on the joints to check the leakage in joints. Once the leakage is found, the same is repaired.
[0025] The furnace is using the by-product gases like Coke oven gas, Blast furnace gas, Mixed gas and LD gas as fuel for manufacturing steel. All these gases containing Carbon Monoxide (CO) gas ranging from 7- 70%. The typical composition of the Industrial gases is given below. HSM (Hot strip mill) is using mixed gas in the reheating furnace, a mixture of Coke Oven and Blast Furnace gas, which contains 22% CO.
Component Unit C.O.Gas L.D.Gas B.F.Gas
CO2 % v/v 2~4% 12~16% 14~18%
O2 % v/v 0.2~1.0% 0.8~1.2% 0.4~1.2%
CO % v/v 7~9% 50~70% 22~28%
H2 % v/v 52~58% 2~8% 3~5%
CH4 % v/v 21~27% - 0~3%
N2 % v/v 3~10% 15~30% 50~60%
CmHn % v/v 1~3% - -
NCV Kcal/Nm3 3,800~4,400 1,600~2,000 750~925

[0026] Figure 3 illustrates the method of testing leakages in the zonal gas line of the reheating furnace, in accordance with the present subject matter. The present method is started after the major shut down of the furnace at block 300. At the block 301, all the zonal burner gas valves are closed. After closing the zonal bruner valve, the gas line is cleaned. If some pipe line is found corroded, the pipe line is replaced with the new pipe line. At the step 302, the zonal header end flanges are closed. The gas line is sealed by closing the safety shut off valve 108 and the control valve 102. At the block 303, the mobile air compressor 106 is connected with the flow measurement line 104 of the zonal gas line. The mobile air compressor 106 supply air to the sealed zonal gas line with regulated pressure to 1500 mm WC with the help of outlet valve 107. At the block 304, each joint of the zonal sealed gas line is checked for the leakage with help of soap bubble test. Seal the found leakage and repeat the process for other joints in the sealed gas line. Further, the identification of the leakage is performed without any gas mask. The same process is adopted for cleaning the each zone and each zone confirms about the leakage without waiting for the completion of the entire furnace cleaning. Therefore, the waiting time period for testing the leakage is reduced.
[0027] At block 305, once the complete cleaning is performed and each zone is tested for the leakage, the light up signal is given to the furnace. The present method saves around 15 hours start up time after the MSD to light up the furnace. The present method is applied in parallel to the other continuing jobs in the furnace without any interference with them. After getting the light up clearance it takes the normal 1 hour time only for lighting up. Earlier it was taking 15-20 hours to ensure the sealing of all gas line leakages.
[0028] Fig. 4 illustrates the overall gas line circuit and the job location of the HSM. The job has to be repeated for all the zones similar to zone -5 as shown in the figure.
[0029] Figure 5 illustrates nitrogen purging circuit in the furnace, in accordance with the present subject matter. The nitrogen is used for purging out any air or gas form from the gas line before the light up the furnace.
Advantages of the Invention over prior art:
[0030] The present method can be done in running shut down. In the present method, no gas mask is required as it is done with the help of normal air. Hence safety hazard or gas poisoning to the human being. Further, the present method can do the testing of leakages comfortably along with other jobs in parallel. Furthermore, the entire leakage testing job can be covered during the furnace shut down only. No extra 15 – 20 hours are required for doing this job in hurry. This time is extended sometime when the number leakages are higher.
[0031] Considerable savings in avoiding production loss as follows:
HSM hourly production = 550 T (average)
NR (net realization) for 1 T production = Rs. 4000.
Hence, savings for 15 hrs production = 15 x 550 x 4000 = Rs. 3.3 Crores.
[0032] Effective utilization of the equipment down time and manpower.
[0033] Although implementations for the method and the system for size characterization of the plurality of green balls based by image acquisition system have been described in language specific to structural features and/or method, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/device/structure of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.