6G pipe welding test is one of the chief concern in welding industries and primarily utilized in fabrication of petrochemicals, nuclear plants, pressure vessels, boilers and many more. Its main purpose is, to test a welder for piping which involves the welding of pipe joint, assemble 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 shield metal arc (SMAW) process. It includes the following
steps;
1. Beveling
At first the edges of both pipe pieces are prepared by
beveling using the 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 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 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 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 the pipe joint. The later progression is widely used for
installation pipelines where two way welding is employed with the help of two welders.
Watch Pipeline Installation with downhill progression using SMAW process.