Pipe Welding Information 2

8/13/2019 Pipe Welding Information 2

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SUPPLEMENTAL INFORMATION 2

PIPE WELDING

Welding pipe is like welding any other structural shape and welding can take place in any of thenormal positions for welding. When welding pipe flanges and some joints configurations the weldapplied may be a fillet weld. When welding pipe to pipe the joint is similar to a vee groove and isoften open root. Welding pipe to pipe requires a higher degree of skill and is the topic of thissupplement.

The pipe welding positions covered are the 1G flat and rolled position, the 2G horizontal position,

the 5G vertical position and the 6G fixed position as shown below.

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12/25/2011http://deltaschooloftrades.com/supplemental_information_2.htm


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PIPE WELDING EDGE PREPERATION

The pipe coupons for welding are cut using the pipe beveling machine. The slag is removed and

the edges are ground smooth for welding a 1/8 landing or flat is applied to the pipe. The picturesbelow show the pipe beveling machine and the edge preparation.




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PIPE ASSEMBLY




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The pipe is assembled for welding by placing one piece on top of the other with a 1/8 electrodeithout flux on it between the pipe.

It is extremely important to set up and tack weld the pipe properly, if the pipe is not aligned on theinside it is difficult to obtain the proper penetration through the pipe.

The root gap around the pipe must be consistent. If part of the root gap is too wide the key holeill open up too much while welding and instead of penetration you may have burn through(more than 1/8 reinforcement) on the inside. If part of the root gap is too narrow you may not beable to penetrate through the pipe in those areas.

At least 4 tack welds should be placed around the pipe at 12 oclock 6 oclock 3 oclock and 9oclock.

The tacks must be strong enough to hold alignment while welding the root pass and shouldpenetrate enough to become a part of the root pass. When testing the tack may be removed using acutting wheel to get a consistent root weld around the joint.

The picture below shows the tacks in a flat position pipe.




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Chill ring

For some applications a chill ring may be used instead of an open root. The chill ring works like abacking bar in groove welding and becomes a part of the welded joint. When the chill ring is usedthe root opening is determined by the pins on the chill ring. After tacking the chill ring on theinside of the pipe, the pins are removed. If a chill ring is used the root pass may be made using E-7018 since it is not necessary to penetrate through the pipe.




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PIPE WELDING IN THE FLAT 1G POSITION

Pipe Welding in the flat position requires that the Welder make some adjustments to the normalangles and length of the welds during welding. In the flat position with the pipe being rolled orrotated the push travel angle works best. Shorter lengths of weld are used so that you do notchange your travel angle by stretching out of position. The pipe is then rotated before continuing.Stringer beads are used to weld the root, fill passes and cover pass on six inch schedule 80 pipe.

Technique for welding the 1 G Rolled Pipe

The root pass is made using the E-6010 Electrode to penetrate through the open root pipe. Makesure the amperage (heat) is set correctly to open and maintain the keyhole where the root is s goodfit. Use scrap metal and weld in the flat position with the amperage on approximately 100 and




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adjust the heat as necessary.

The root pass should be flat to convex in appearance on the groove side of the pipe with no holesand should be flush to 1/8 maximum reinforcement on the inside of the pipe.

After completing the root pass and evaluating the penetration, grind the groove side of the weld in




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preparation for the fill passes.

Set the amperage for the E-7018 1/8 Electrode at approximately 120-150 amps to weld the fillpasses and the cover passes. Use the stringer bead technique for welding the fill passes and coverpasses.

PIPE WELDING IN THE 2G HORIZONTAL POSITION

When welding in the 2g pipe position the pipe is vertical and the weld is horizontal. The pipe is notmoved during welding and the welder must move around the fixed position pipe. The preparationand amperage setting should be the same as for the flat position pipe with E-6010 Electrodes used

for the root and E-7018 Electrodes used for the fill and cover passes. It is important to layer thefill passes and cover passes from the bottom pipe up to the top pipe, while keeping the weld beadsstraight and properly overlapped.




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PIPE WELDING IN THE VERTICAL 5G POSITION

In the 5G pipe position the pipe is horizontal and the weld axis is vertical so that the welding isessentially a vertical weld. When welding some pipes for low pressure applications or smalldiameter pipe it may be acceptable to weld vertical downward with an electrodes like the E6010

however; most pipes are welded vertical upward with an E-6010 root pass and E-7018 fill and cap.

When welding in the 5G pipe position the weld beads may be either stringers or weaves dependingon the job requirements.

At the Delta School Of Trades we use the E-6010 electrode for the open root pass and E-7018 forthe fill and cover passes using the vertical upward weave technique.




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TECHNIQUE FOR VERTICAL 5G PIPE WELDING

AS always make sure the correct amperage is set for tacking the pieces and the root pass using E-6010 electrodes. Check the machine setting and use an amperage from 90-110.

Use E-7018 for the fill passes and cover pass set at approximately 120-150 Amps.

Use a slight U shape technique with the E-6010 electrode to open and maintain the keyhole. It maybe necessary to ride up very slightly on the inside edge of the groove to chill the keyhole if it opensup too much. If the keyhole is too tight, slow down and force it open with the electrode while

elding or stop and increase the amperage (heat).

Use a Z motion weave with the E-7018 Electrode keeping the ripples close together and the weldprofile flat for the fill and cover passes.




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VERTICAL UPWARD WEAVES FOR 5G PIPE

Stringer Weaves may also be used to weld the fill passes and cover passes. This is an importanttechnique to learn in preparation for welding in the 6G position

PIPE WELDING IN THE 6G FIXED POSITION

In the 6G Pipe welding position the pipe is set on a 45 degree inclined angle. Theweld in this position covers all position welding because the bottom of the pipe is anoverhead weld; the top of the pipe is a flat weld and the front and back sides are avertical upward weld. The pipe is welded using stringer beads except that a slight

weave motion must be used to prevent the sides or vertical upward part fromsagging and lumping up in the middle of the weld bead.




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The Electrode angle should remain the same for all passes. Use a slight push angle from bottom totop.

CRITICAL ELEMENTS FOR WELDING THE 6G FIXED PIPE

As for all pipe welding take the time to set up the pipe properly with a consistent root gap and 4evenly spaced tacks.

Make sure you have set the correct amperage for the electrode type and size as mentioned earlier.

After running the root, grind the root pass lightly before starting with the E-7018 Electrode.

Remember to use a slight weave motion with the E-7018 to prevent the weld lumping in the middleand to get proper fusion.

Each filler pass should overlap the prior pass without leaving a depression (called wagon tracks)and should show good fusion.




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The 6G pipe position is the one used extensively for testing, since it qualifies the welder for allposition welding of pipe, grooves, and fillets.

When testing; it is advisable to remove the tacks instead of weld over them to ensure penetration

at the root. A wire wheel brush and grinder may be used to keep each pass clean and prevent slaginclusions.

Although there are many Codes and Standards that govern the welding and testing of Pipe, theone most widely used and recommended at the school is the AWS D1.1 Structural Welding Code.

The test for SMAW is usually a 6 inch schedule 80 pipe with an open root, and is welded in the 6Gposition. This test qualifies the welder for welding fillets grooves and pipe in all positions. Alsoqualifies the welder for pipe sizes from 4 inches to unlimited and wall thickness from 3/16 inch to

unlimited.

An optional SMAW test on 4 inch schedule 40 pipe in the 6G position qualifies the welder for allpositions welding and pipe sizes from 3/4 to 4 inch with wall thickness from 1/8 to 3/4.

The pipe size recommended for GTAW Certification is the 4 inch sch 40 pipe.


Pipe Welding Information 2

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