6G pipe welding test is one of the chief concern in welding industry and primarily utilized in fabrication of pressure equipment like; piping, boilers, pressure vessels, etc. in petrochemicals, refineries and nuclear plants. Its main purpose is, to test a welder for piping which involves the welding of pipe joint, assembled at an angle of 45 degree. If a welder qualifies 6G position, he will pre-qualify to all weld types in all positions. It is to be noted that 6G pipe test varies from material to material; for say if you are going to test carbon steel then you are limited to carbon steel.In other words a welder who qualifies 6G in carbon steel, may not be pre-qualified for stainless steel or duplex stainless steels.
What are the Welding Positions in Piping?
There are five positions which are being used in pipe welding. For the ease of understanding, numeric digits 1,2,5,6 and alphabetic letter ‘G’ are designated to these positions. Digits represent the type of position while letter ‘G’ represents the type of weld which is groove in this case.
1G – Rolled pipe at horizontal position with flat welding at or near to the top of joint assembly.
2G – Pipe is fixed and at vertical position. Direction of welding is horizontal in this case.
5G – Pipe is fixed at horizontal position. Direction of welding is vertical either with upward or downward progression.
6G – Fixed pipe inclined at 45 degree either with upward or downward welding progression.
6GR – Same as 6G position with the exception of installed restriction ring on one pipe near to the joint.
Tips to pass Pipe 6G test using SMAW process
Here is the step by step demonstration on how to perform a 6G pipe test using the shield metal arc (SMAW) process. It includes the following steps;
At first the edges of both pipe pieces are prepared by beveling using a suitable grinding process. For this Codes and standards recommend 35 degree beveling. Not to forget, a sound edge preparation plays a vital role in making sound weld run. After this pipe pieces are ready for joint assembly.
2. Joint Preparation and Assembly
Pieces are brought together in such a way that the joint gap between them should be the size of filler rod to be fed. Welder can check it by placing the rod inside the gap. In order to keep the joint intact make the three tack welds at 12, 2 and 10 o’clock positions leaving the bottom side open. Also use some sort of metal pieces to insert into the gap to avoid any shrinkage during welding. Incline the assembly at an angle of 45 degree in suitable place where welding associates feel comfortable to perform the test.
Some people used to weld fourth tack at 6 o’clock position but to be honest if you weld three tacks just mentioned above, you will be more comfortable to move and see while making the weld run.
3. Technique Variations
Side to Side
Back and fourth
Both techniques can be used depending on the capability of welder. Some use side to side technique for root pass but some use back and forth, for their ease because they feel comfortable for travel speed. After making a root pass with back and forth technique, it will be good to make a next hot pass using side to side manner. As we know the main objective of hot pass is to add more metal, thickness and even reinforcement to the root pass without disturbing its mechanical properties. Another function of hot pass is to melt unremoved slag from root that may cause defects like lack of fusion, cracks, cold regions etc.
4. Test Weld Run
Start making weld run from the left side of joint assembly with uphill progression that is from 6 o’clock to 12 o’clock position.
Ensure slag removal after each bead.
When approaching to a tack weld, melt it, add some more filler metal and then blend them together.
Again start welding with uphill progression from right side of the assembly with the same technique.
In case of uphill pipe welding, the above mentioned practice gives a smooth uniform weld having an amazing level of consistency and completely fusion of edges. However, for downhill welding same procedure is exercised with the progression of top to bottom run that is from 12 o’clock to 6 o’clock position in a pipe joint. The later progression is widely used for the installation of pipelines where two way welding can be employed with the help of two welders. Watch Pipeline Installation with downhill progression using a SMAW process.