Apparatus and method for supplying inert gas to a welding location

In combination, a pair of pipes having butt ends spaced from one another to define a root-gap therebetween, and having respective substantially circular cylindrical interior surfaces defining predetermined diameters thereof, and an apparatus for concentrating an inert gas at a localized region along the root gap between the spaced butt ends of the pipes to be welded, the combination comprising:

• a gas feed line extending substantially axially and centrally through one of the pipes to be welded directing an inert gas from an inert gas source axially along the length of said one of said pipes to said spaced butt ends with said gas feed line extending a predetermined distance in and along the length of said one pipe, the predetermined distance being much greater than the predetermined pipe diameter;
• a locating member including a central aperture therethrough mounted in the pipe axially spaced from the joint to be welded, said locating member engaging said interior surface of said one pipe at a plurality of locations about said interior to maintain said feed line spaced from said interior surface;
• a shaft and bearing assembly extending through the locating member central aperture with the gas feed line extending through the shaft of the assembly and journalled for rotation therein by the bearings of the assembly so that the feed line remains fixed as the pipes are rotated during welding with the locating member and shaft rotating with the pipes about the feed line;
• and
• pendulum means attached to the gas feed line for directing inert gas from the feed line in a predetermined radial direction at the butt end of the pipe toward the joint to be welded as the pipe is rotated during a welding operation,
• wherein the pendulum means includes an elongate member having spaced ends including a hollow tube portion connected to the gas feed line extending substantially perpendicular thereto and having a single gas outlet port at one end of the elongate member and an enlarged weighted counterbalance portion at the other end of the elongate member to maintain the ends of the member substantially vertically aligned with each other with the hollow tube portion in an upright position for directing inert gas from the feed line therethrough out from the gas outlet portion thereof toward the space between the pipe butt ends as the pipe is rotated during a welding operation, and
• a small trailing shield at the single gas outlet port of the hollow tube portion to define the small localized region in which inert gas flowing through the gas feed line and elongate member tube portion is concentrated for providing an almost instantaneous purge of oxygen from the localized region defined by the trailing shield.

A method of supplying inert gas to a localized zone adjacent a pipe joint to be welded, the method comprising the steps of:

• directing inert gas through an inert gas feed tube having a delivery end along the length of a pipe to the butt end thereof toward a joint to be welded;
• causing the inert gas to accumulate in a localized region at the joint to be welded to purge the region of other gases before a welding operation begins;
• and
• maintaining the delivery end at a predetermined substantially fixed location which remains adjacent the top of the pipe interior after the welding operation begins and as the pipe is rotated during the welding operation.

A method of supplying inert gas to a localized zone adjacent a pipe joint to be welded, the method comprising the steps of:

• providing two pipe sections to be welded with their open butt ends in adjacent spaced relation to each other to form an unsealed root gap between the butt ends to be connected;
• directing inert gas through an inert gas feed tube having a delivery end along the length of one of the pipes to the open butt end thereof aligned with the root gap formed between the adjacent butt ends to be connected by welding;
• causing the inert gas to rapidly accumulate in a localized region at the joint to be welded to rapidly purge the region of other gases before a welding operation begins;
• welding the pipe butt ends together by rotating the pipes without having to remove sealing tape from between the unsealed pipe butt ends over the root-gap formed therebetween;
• and
• maintaining the delivery end at a predetermined substantially fixed location which remains adjacent the top of the pipe interior after the welding operation begins and as the pipe is rotated during the welding operation.