FIELD OF THE INVENTION:

The present invention relates to an apparatus and a method of purging reactive gases during welding. Particularly, the present invention relates to an apparatus and a method of purging reactive gases during welding of tubes/pipes.

BACKGROUND OF THE INVENTION:
Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

Generally, manufacturing of welded joints with reactive materials like alloy steel, stainless steel and nickel based alloys requires protection from reactive gases at the weld area in order to minimize oxidation of the reactive materials during welding. Welding performed in the presence of reactive gases can cause metallurgic changes which will adversely affect the strength and corrosion resistance of the reactive materials. For this reason, various efforts have been made to provide systems and methods for purging reactive gases from the weld area during fabrication.

The conventional method of purging with constant flow will affect the reactive materials which has more fluidity and may lead to positive pressure inside the tube/pipe. This positive pressure can create a suck back at the weld area with lack of fusion inside the tube and ultimately resulting in a defective joint.

Several techniques have been disclosed in the prior art for purging of reactive gases from the wed area.

US Patent no. 2819517 filed on July 30, 1953 discloses a method of welding of pipe ends together by inserting a baffle in each tube/pipe and thereby providing a chamber in between therein. A purging gas is allowed to flow into the chamber to prevent oxidation in the weldment area. The pressure inside the chamber of purging gas is controlled by a pressure regulator. The granted patent is completely silent on inflatable sealing rings and specialized directional flows.
US Patent no. 2802092 filed on Feb 1, 1954 discloses a method for preventing weld metal compounds from forming with gaseous elements of the atmosphere in the welding of abutting pipe ends or the like, the said method comprising the steps of providing a closed chamber traversing abutting ends of adjoining pipe, positioning oppositely disposed substantially sphere-like expansible members within the pipe and effecting the inflation of said sphere-like expansible members, each of the said expansible members being disposed on opposite sides of the said pipe abutting ends and thereby forming when inflated the end limits of the closed chamber, and venting the closed chamber before welding by allowing an inert gas through a survey hole. Survey holes taught by the granted patent are banned by the modern safety standards. Further, the granted patent is completely silent on pressure sensors and specialized directional flows.

US Patent no. 4916281 discloses an improvement in the process of gas back purging the root section of the weld during open-butt welding of pipe. The rates of gas flow in back-purging and in torch shielding are controlled and a ratio between the flow rates is established. The invention teaches a gas back-purging flow rate of about 40 CFH and a torch shielding flow rate of about 10 CFH under typical conditions to maintain a required 4 to 1 ratio of the flow rates. The granted patent does not teach about specialized bidirectional flows.

SU Patent no. 1323318 discloses a weld protection device provided with a pressure sensor to assure constant gas pressure.

JP Patent no. 0215375 discloses an apparatus and a method for purging reactive gases from the vicinity of a molten weld during the welding process, having particular application to the welding of industrial process piping systems and pipelines, especially stainless steel and other alloy pipelines. A system is disclosed for boosting purging speed and efficiency by providing a multidirectional flow of purging gas adjacent to the interior walls of the pipe sections being joined. The rate of purge gas flow is automatically adjusted in response to changing gas pressures in the vicinity of the progressing weld. The invention discloses a constant gas discharge through a valve.
Therefore, there is felt a need for development of an apparatus and a method for purging of reactive gases from the weld area during welding of pipes/tubes ends.

OBJECTS OF THE INVENTION:
Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed here in below.

An object of the present invention is to provide a simple apparatus for purging of reactive gases from the weld area during welding of pipes/tubes ends.

Another object of the present invention is to provide a simple method to prevent oxidation of reactive materials of pipes/tubes ends during welding.

One more object of the present invention is to control the pressure of reactive gases inside the chamber of pipes/tubes ends during welding.

Still another object of the present invention is to perform purging during welding operation using inert gases.

Further another object of the present invention is to improve the strength of the weld and eliminate weld defects during welding of pipes/tubes ends.

These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.
SUMMARY OF THE INVENTION:
In accordance with the present invention a purging apparatus for welding of tubes/pipes is provided, the purging apparatus comprises a pipe, a pressure sensor, a variable flow controller. The variable flow controller includes a timer. The pipe carrying the purging gas (argon) is adapted to pass through a sealing plate closing the distal end of the tube/pipe and one hole provided in a sealing plate closing the distal end of the tube/ pipe purges out the reactive gas (oxygen) from a chamber formed in between the sealing plates of the tubes/pipes. A pressure sensor is installed on the pipe to continuously monitor the pressure inside the chamber and transmit the same to a variable flow controller including a timer installed on the pipe to vary the flow rate of the purging gas (argon) entering the chamber.

In an aspect, the timer set for a fixed time allows the purging gas into the chamber at a fixed flow rate.

In accordance with the present invention, a method of purging reactive gases in a welding operation of tubes/pipes is provided, the method comprising the steps of:
a) setting a fixed time in a timer of a variable flow controller to allow the purging gas at a fixed flow rate into a chamber formed between sealing plates of the tubes/pipes;
b) flushing out reactive gases from the chamber;
c) continuously monitoring the pressure inside the chamber through a pressure sensor and transmitting the same to the variable flow controller; and
d) varying the flow rate of the purging gas entering the chamber through the variable flow controller depending on the input from the pressure sensor and adjusting the pressure inside the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS:
The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles. In the figures, the left-most digit(s) of 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 and/or methods in accordance with embodiments of the present subject matter are now described, by way of example only, and with reference to the accompanying figures, in which:

Figure 1 illustrates a perspective view of tubes/pipes ends placed against each other for welding purposes, in accordance with an embodiment of the present invention; and

Figure 2 illustrates a perspective view of tubes/pipes ends of figure 1 placed against each other and provided with process control mechanisms.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
A preferred embodiment will now be described in detail with reference to accompanying drawings. The preferred embodiment does not limit the scope and ambit of the invention. The description provided is purely by way of example and illustration.

Referring to fig 1, in accordance with the present invention, there is provided a plurality of tubes (202 and 204) placed against each other defining a space in between therein to perform welding. The distal ends of each of the tubes (202 and 204) from the weld zone are closed by sealing plates (not shown in the figure) adapting to mate with the inner circumference of the tubes (202 and 204). A hole is made in the sealing plate of the tube 202 for passage of a pipe 202(a) to carry out inert gases like argon, helium etc., The inert gas, argon is allowed to fill in a chamber created between the sealing plates of each of the tubes (202 and 204) and thereby purging the reactive gases like oxygen through a hole 206 provided in the sealing plate of the tube 204.

As shown in fig 2, a pressure sensor 208 is installed on the pipe 202(a) to monitor the pressure inside the chamber between the sealing plates and transmit the same to a variable flow controller 210 installed on the pipe 202(a). The variable flow controller 210 includes a timer 210(a).

The timer 210(a) is set for first pass of welding operation between the tubes (202 and 204) allowing the inert gas or purging gas (argon) into the chamber between the sealing plates and simultaneously monitoring the pressure inside the chamber between the sealing plates through the pressure sensor 208. Depending on the input from the pressure sensor 208 to the variable flow controller 210, the inert gas or purging gas (argon) at variable flow rate is allowed inside the chamber between the sealing plates and thereby adjusting the pressure inside the chamber to prevent suck back at the weld area caused by the constant pressure of the inert or purging gas (argon).

Although the invention has been described herein above with reference to the embodiments of the invention, the invention is not limited to the embodiments described herein above. It is to be understood that modifications and variations of the embodiments can be made without departing from the spirit and scope of the invention.

We claim:

1) A purging apparatus for welding of tubes/pipes (202 and 204) comprising:
a pipe (202(a)) carrying the purging gas (argon) adapted to pass through a sealing plate closing the distal end of the tube/pipe (202) and one hole (206) provided in a sealing plate closing the distal end of the tube/ pipe (204) for purging out reactive gas (oxygen) from a chamber created in between the sealing plates of the tubes/pipes (202 and 204),

wherein, a pressure sensor (208) installed on said pipe (202(a)) to continuously monitor the pressure inside the chamber and transmit the same to a variable flow controller (210) including a timer (210(a)) installed on said pipe (202(a)) to vary the flow rate of the purging gas (argon) entering said chamber.

2) The purging apparatus as claimed in claim 1, wherein said timer (210(a)) set for first pass of welding operation between said tubes (202 and 204) facilitates said variable flow controller (210) to allow the purging gas into said chamber at a fixed flow rate.

3) A method of purging reactive gases in a welding operation of tubes/pipes (202 and 204), said method comprising the steps of:

a) setting a fixed time in a timer (210(a)) of a variable flow controller (210) to allow the purging gas at a fixed flow rate into a chamber formed between sealing plates of said tubes/pipes (202 and 204);
b) flushing out reactive gases from said chamber;
c) continuously monitoring the pressure inside said chamber through a pressure sensor (208) and transmitting the same to said variable flow controller (210); and
d) varying the flow rate of the purging gas entering said chamber through said variable flow controller (210) depending on the input from said pressure sensor (208) and adjusting the pressure inside said chamber.