Claims:WE CLAIM:
1. A pre-heating system for stationary push through/moving tube type panel welding machine comprising liquefied petroleum gas bullet common distribution line for supplying liquefied petroleum gas (8), which flows through flashback arrester (6) connected thereto, wherein the arrester (6) is provided in connection with flow control valve (3) with pressure gauge (4), which is in flow communication with common manifold (9) connected to gas hose lines (2), in which the gas hose lines (2) is connected to common rail (10) LPG burners for preheating of water wall panels (5).

2. The pre-heating system for stationary push through/moving tube type panel welding machine as claimed in claim 1, wherein LPG flow is regulated and pressure is set around 2 bar before flowing through said arrester (6).

3. The pre-heating system for stationary push through/moving tube type panel welding machine as claimed in claim 1 or 2, wherein the manifold (9) accumulates LPG which gets distributed to multiple gas lines according to temperature requirement with control valves to open/close the gas line.

4. The pre-heating system for stationary push through/moving tube type panel welding machine as claimed in any of the preceding claims, wherein flame proof flexible gas hose lines (2) are connected to the manifold (9) for minimum flexible movements of LPG burner headers with control valves.

5. The pre-heating system for stationary push through/moving tube type panel welding machine as claimed in any of the preceding claims, wherein the common rail LPG burner (10) is atmospheric venturi type having LPG line inlet (11) connected with the hose lines (2) and welded with LPG burners (12).

6. The pre-heating system for stationary push through/moving tube type panel welding machine as claimed in claim 5, wherein atmospheric venturi type gas nozzle (13) is fitted over the burner and over the burner JET 45 (14) is fitted to provide required LPG in the each burner for improved uniform heating.

7. A method for preheating of water wall panels by atmospheric venturi type common rail LPG burners in 20 torch MPM for boiler water wall panel formation comprising steps of:-

- tapping of LPG (8) from the LPG bullet common distribution line in proximity to the machine column,
- controlling the LPG flow with flow control valve (3) and setting of pressure around 2 bar using pressure regulator,
- fixing the flashback arrester (6) to arrest return fire flash while LPG burning,
- setting proper flow and pressure in the line by means of flow control valve (3) with pressure gauge (4),
- accumulation of LPG in the common manifold (9) and distribution into multiple gas lines,
- Connection of flame proof flexible gas hose lines (2) in the manifold for minimum flexible movements of LPG burner headers with control valves,
- Opening of the control valves for entry of the pressurized LPG into the common rail (10) LPG burners,
- preheating of water wall panels (5).
, Description:Preheating system for stationary push through/moving tube type panel welding machine and a method thereof

FIELD OF INVENTION
[001] The present invention relates to preheating system for stationary push through/moving tube type panel welding machine. Further, the present invention relates to method of pre-heating water wall boiler panels in 20 Torch membrane panel welding machine (20 Torch MPM) by atmospheric venturi type common rail LPG burners.

BACKGROUND OF THE INVENTION

[002] 20 Torch MPM is special purpose machine for welding tubes with fins which are used for manufacturing of panels for high pressure boiler application. The machine is designed and constructed to make water wall panel by means of 20-Torch MIG/MAG (Metal Inert Gas/Metal Active Gas) stationary push through/moving tube type panel welding machine. The leading end of the assembled panel is tack-welded by manual welding. The pre-assembled panel is welded on both top and bottom sides simultaneously by 20-Torch stationary welding machine.
Machine Configuration is as follows:
1. Panel Transportation Line
2. Fin Calibration Line
3. 20-Torch Panel Welding Machine
4. Control Board and Operation Panels
1. Panel Transportation Line in the 20 Torch MPM is used for transportation and handling of tubes within the machine so as to convert the raw material into panels. It also facilitates inspection of formed water wall panels to ensure quality requirements. It consists of Tube Supply Device & Stock table, Panel End Tacking Device, Panel Infeed Conveyors, Panel Discharge Conveyor, Panel Return Conveyor, Panel Transverse Device for Infeed, Panel Transverse Device for Discharge, Inspection Table. Maximum Panel Weight handled by the machine is up to 10000kgf.
[003] Fin Calibration Line

The fin is welded in between two tubes to form membrane water wall tube panel. Fin Calibration Line in the 20 Torch MPM is used for calibrating the fins with required length (maximum 24 meter) within the tolerance so as to meet the required panel formation from the supplied fin raw material. It also facilitates movement of calibrated fins from the fin stock table into a pre tack welding unit with the help of the fin supplying device and surface preparation of fins for welding by fin shot blasting. It consists of Uncoiler unit, Fin Welding Bench, Fin Blast Machine, Fin Calibration Machine, Fin Cutting Machine, Fin Feeding Conveyor, Fin Stock Table and Fin Supplying Device.
Control Board and Operation Panel
[004] The Control Board and Operation Panel facilitate the control and operation of the entire 20 Torch MPM. MPM is controlled by Programmable Logic Controller (PLC) and welding is controlled by DAIHEN`s controller. It consists of the Control Board for Panel Welding Machine, Operation Panel for Panel Welding Machine, Remote Control Box for Panel Welding Machine, Control Board for Panel Transportation Line, Operation Panel of Infeed Side for Panel Transportation Line, Operation Panel of Discharge Side for Panel Transportation Line, Operation Panel for Tube & Fin Preset Device, Control Board for Fin Calibration Machine, Operation Panel for Fin Calibration Machine, Control/Operation Board for Fin Blast Machine.

[005] 20-Torch Panel Welding Line

This forms the kernel of the 20 Torch MPM as shown in the Figure 2.1, since the pre-assembled panel is welded both top and bottom sides simultaneously by 20-Torch stationary welding line. Welding torches are equipped at two zones. First zone has 12 torches, i.e., 6 torches at top and 6 torches at the bottom. Second zone has 8 torches, i.e., 4 torches at the top and 4 torches at the bottom. Operator working space for upper welding (bottom torches) is provided as pit on the floor. The panel is transferred by tube pressing and gantry rolls through the Inverter drive motor works by pneumatic actuator with maximum pressure load of 68000 Kgf at 0.5 MPa. Adjustable Fin guide shoes and fin pressing rollers are equipped to ensure alignment of fin to tube center. In order to measure the panel length it is fixed with measuring rollers/encoders at the front and rear end of the machine. While welding, the generated welding fumes are collected and sent outside the working space by fume collectors. It consists of Panel Welding Machine structure, Welding Power Supply (MIG/MAG) - 20 sets, Shield Gas Mixing Unit - 4 sets, Fume Collector. The top of the machine frame is fitted with platform. Control Boards for the machine, Fume Collectors & Welding Power Supply, Chiller units, Welding wire pack (Coil holder) are mounted on the machine platform.

[006] MEMBRANE WATER WALL TUBE PANEL FORMATION IN 20 TORCH MPM

Panel formation in 20 Torch MPM involves 3 stages
1. Pre assembly stage
2. Formation stage
3. Inspection stage
[007] Pre assembly stage

The required size and number of surface prepared tubes from High Bay A will be loaded on the Stock table using EOT (Electrically operated Overhead Travelling) Cranes. By Tube Supply Device the required number of tubes will be transferred to Panel End/Tack welding unit. Then the surface prepared and calibrated fins will be fed in between the already placed tubes on the Panel End/Tack welding unit by fin supply device. After aligning the tubes with the fins operator manually welds the leading ends of the tubes with fins. This forms the pre assembly stage in panel formation.

[008] Formation stage

By Panel Transverse Device for Infeed, the pre-assembled panel is placed on the Panel Infeed Conveyors. From Panel Infeed Conveyors it is fed into the panel welding chamber of the machine through drive rollers. The panel is transferred by tube pressing and gantry rolls through the Inverter drive motor works by pneumatic actuators with maximum pressure load of 68000 Kgf at 0.5 MPa. Adjustable Fin guide shoes and fin pressing rollers are equipped to ensure alignment of fin to tube center. To measure the panel length it is fixed with measuring rollers/encoders at the front and rear end of the machine. With the help of measuring encoders/rollers & PLC

control non-welding length/desired skip can be preset in this 20 Torch MPM.

The pre-assembled panel is welded both top and bottom sides simultaneously by 20-Torch stationary welding machine. Welding torches (Bernard make) are equipped at two zones. First zone has 12 torches, i.e., 6 torches at top/down hand and 6 torches at the bottom/overhead. Second zone has 8 torches, i.e., 4 torches at the top/ down hand and 4 torches at the bottom/overhead.

In 20 Torch MPM, GMAW 1.2mm solid wire with 80%: 20 % Argon & CO2 gases are used for welding through 20 numbers of OTC make wire feeder units which are placed 10 on the top & 10 on the bottom side of the machine. While welding, the generated welding fumes are collected and sent outside the working space by fume collectors. Maximum of 5 Tubes and 6 Fins or 6 tubes with 5 Fins can be welded at a time with 20 welding torches. Based on the requirement, from 4000mm to 24000mm panels can be formed with a maximum speed of 700mm/min as productivity.

[009] Inspection stage

The forming panels are now on the Panel Discharge Conveyor and with the use of Panel Transverse Device for discharge it can be transferred to Inspection Table to ensure quality requirements. Based on the panel width requirement with the support of Panel Return Conveyor, the formed panels can be brought back to infeed side for completion of panel’s width up to a maximum 2500mm.Thus the panel forming cycle continues again. Thus a maximum panel weight of 10000Kgf can be formed in this 20 Torch MPM (A High Productivity Machine).

Thus due to maximum tonnage (productivity) in panel formation in minimum lead time when compared with all other panel processing machines at TPN, it is identified as one of the most critical and important machines in Tubular production shop.
20 Torch MPM is one of the critical machines running in 3 shifts, productivity of which is around 100 pass meter per shift, for typical Carbon steel/Alloy steel.

[010] Now referring to the Figure 1 showing the schematic arrangement of the existing pre-heating system in the 20 Torch MPM, wherein the LPG cylinder (1) is connected to individual gas blow pipe burners (7) with flash back arrester (6). LPG Flow in the flame proof flexible gas hose lines (2) is controlled using control valve (3) and the pressure gauge (4) is used for checking/setting the LPG pressure in the hose line. With pre-set LPG pressure and flow, on ignition it preheats the water wall panel (5) in the preassembled conveyor infeed line for welding in the 20 Torch machine.

[011] For pre-heating, individual gas cylinders with gas blow pipe burners are used, for eg. To make Type E Tube/Fin combination minimum 5 number of individual gas cylinders with gas blow pipe burners are required as per Figure 3, which becomes uncertain and less effective when gas cylinders empties for pre-heating of Advance Ultra Super Critical (AUSC) Grade T91 materials for further welding process in the 20 Torch MPM to preheat up to 200 - 250 deg Celsius with productivity of 700 mm/min in time. Further accumulation of LPG hoses lines leads to unsafe working environment and pay way to fire hazard when there is gas leakage in the gas hose lines due to frequent movement of lines (i.e. On requirement it is fixed below the panel otherwise all the gas lines are moved to nearby location/removed). Thus due to individual gas cylinders with gas blow pipe burners at required tube/fin intervals which is not sufficient for preheating the Grade T91 material water wall panels to 200 – 250 deg celsius and further this individual LPG preheating arrangement forced user to change new gas cylinders each time when the gas cylinder empties. This leads to major pre-heating distribution problem and in certain cases it may lead to reheating of panel from the left out portion if preheating stops in between which adds time and overhead cost to the operational cost. This problem further leads to reduced productivity of the machine as well as reduced life of the hose lines & burners considerably. Hence there is need to devise safe, suitable and effective pre-heating method/system so as to avoid undesired movement in the LPG line and to ignite LPG line just in time when there is need for pre heating/production plan.

OBJECTS OF THE INVENTION

[012] An object of the invention is to develop preheating system for stationary push through/moving tube type panel welding machine and a method thereof which obviates shortcomings of prior art(s).

[013] An object of the invention is to develop preheating system for stationary push through/moving tube type panel welding machine and a method thereof, that provides continuous, reliable and effective heating.

[014] Another object of the invention is to develop preheating system for stationary push through/moving tube type panel welding machine and a method thereof, which uses common rail LPG burners for uniform heating.

[015] A still another object of the invention is to develop preheating system for stationary push through/moving tube type panel welding machine and a method thereof, that uses atmospheric and venturi type LPG with air firing burners with safe working environment by minimizing individual LPG lines.

[016] A further object of the invention is to develop preheating system for stationary push through/moving tube type panel welding machine and a method thereof, which improves machine productivity at reduced overhead cost with just in time ignition.

SUMMARY OF THE INVENTION

[017] According to the invention, firstly, the pressurized LPG (around 2 bar) from the main LPG bullet common distribution line is tapped, regulated and accumulated in the common manifold wherein it gets distributed to multiple gas lines through flame proof flexible gas hose lines. On opening the control valves, the pressurized LPG enters the common rail LPG burners and due to low pressure and venturi effect near the intersection of gas nozzles atmospheric air enters the nozzle openings and enables forced atomization of LPG which generates uniform heat on ignition for said preheating application. Further, common rail LPG burners at regular intervals provides continuous, reliable and uniform heating instead of existing individual gas cylinders with gas blow pipe burners. Thus, the present invention eliminates drawbacks in individual gas cylinders with gas blow pipe burners.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[018] Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings of the exemplary embodiments and wherein:-

Fig. 1 shows: The schematic arrangement of the existing pre-heating system in the 20 Torch MPM.
Fig. 2 Shows: The schematic arrangement of pre-heating system in the 20 Torch MPM according to present invention.
Fig. 3 Shows: Sectional view of Tube/Fin combination during water wall panel formation in accordance with present invention.
Fig. 4.1 & 4.2 shows: Sectional view of atmospheric venturi type common rail LPG burner of the present invention.
DETAIL DESCRIPTION OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS OF PREFERRED EMBODIMENTS
[019] The invention is pertinent to preheating system for stationary push through/moving tube type panel welding machine and a method thereof. Now, reference may be made to Figure 2 illustrating the schematic arrangement of the present invention of improved pre-heating system. Here, the Liquefied Petroleum Gas (LPG) (8) from the LPG bullet common distribution line is tapped near the machine column. Further LPG flow is regulated and pressure is set around 2 bar as per requirement. Then the same is supplied through flashback arrester (6) so as to ensure safe working environment. Again flow control valve (3) with pressure gauge (4) is provided in order to re-ensure/check proper flow and set pressure in the line.

[020] Thereafter, the LPG is accumulated in the common manifold (9) wherein it gets distributed to another 4 to 5 gas lines as per temperature requirement of 200-250°C with control valves to open/close the gas line. Flame proof flexible gas hose lines (2) are connected to the manifold (9) for minimum flexible movements of LPG burner headers with control valves. Upon opening the control valves the pressurized LPG enters the common rail (10) LPG burners. Due to low pressure and venturi effect near the intersection of gas nozzles, atmospheric air enters the nozzle openings and enables forced atomization of LPG which generates uniform heat on ignition for said preheating application of water wall panels (5) of for example: grade T91 material. Further common rail LPG burners at regular intervals provides continuous, reliable and uniform heating instead of existing individual gas cylinders with gas blow pipe burners, thereby improving the machine reliability for high productivity in the 20 torch machine.

[021] The Figure 4.1 & 4.2 shows sectional view of atmospheric venturi type common rail LPG burner (10) of the present invention. In this, LPG line inlet (11) is connected with flame proof flexible gas hose lines (2) by threaded fittings BSP. Further common rail (10) can be made of Grade C steel material from pipe of required thickness without restricting scope of the invention to the same. A plurality of LPG burners (12) are welded on the common rail (10) at regular intervals. Atmospheric venturi type gas nozzle (13) which can be made of FG220 material is fitted over the burner by threaded fittings BSP. Over the burner JET 45 (14) of FRHC material can be fitted to provide the required LPG in the each burner for improved uniform heating. The materials hereinabove are given as example. Thus, other materials readily apparent to a person skilled in the art are understood to be within scope of the invention.

[022] Over and above the panel there is a detachable flame proof cover to protect machine/ cables from radiation heats during operation.

[023] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particulars claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogues to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances, where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B”.

[024] It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims:-