What does 6GR means?
6GR Stands for:
The number 6 here stands for the positions.
The letter G stands for Groove.
The letter R means restriction.
6GR Welding test Position is in accordance with AWS D1.1 Structural Welding Code – Steel. It is also called restriction welding, so the “R” in the 6GR term referring to restriction ring, while 6G in the term 6GR is the same as in 6G position. The changes with the 6G and 6GR position is the restriction ring and the bevel preparation as shown in below picture. 6G is prepared as double bevel or let’s say single ‘V’ at 45 degrees position with the horizontal plane, while the 6GR bevel preparation is single bevel and the two connecting pipe has different thicknesses, one is thicker of at least 4-6mm.
The thicker tubular member (pipe) is without weld bevel preparation, and the thinner member (pipe) is prepared in single bevel as visible in below sketch. while in 6G test piece, weld bevel is prepared on both sides.
So, what is T, K & Y joints?
Here, Т, К and Y letters serve only for the estimated type of joints description. This configuration of the control joint is intended to reproduce the conditions of the complicated access, which arise when welding the Т-, К- and Y- shaped connections of the tubular constructions in structural welding. It is reached by the lock ring installation at distance no more than ½ inches from the cutting line.
If you look from bottom you will find T shape, side way look like K shape ( when two tubular joints occurs) and from top you will find Y shape. Hence it’s called TKY joint.
It is most difficult welding in offshore modules. Since dihedral angle is less than 30deg and very difficult to pass root run welding.
Only 6GR qualified welders can weld and clear these strict welding & inspection requirements.
Difference between 6G and 6GR weld test position
If you notice, you will find difference between 6G & 6GR is the R in the 6GR. The letter R specifies that 6GR welding consists of a restricting ring where R literally mean Restriction.
Another difference between the 6G and 6GR is the bevel preparation. Normal 6G test piece have both side bevel or lets say full V groove preparation while in 6GR, the bevel is only one side as shown in below figure.
Additionally, in the 6G certification test, the welder has to weld in all positions while the 6GR position is for TKY joints.
Both positions are for welder qualification. 6GR is as per AWS D1.1 while 6G is followed in ASME as well as AWS.
6GR qualified welders are not readily available as it require extensive welding skills to produce a sound weld. A very high level of welder skill (as demonstrated by the 6GR test) is required for 6G weld test. So 6G test tends to be the most difficult test in a welder test certification.
6GR- Important Welding Test Position
This is the hardest welding test position in Shielded Metal Arc Welding welder qualification for welder testing. This position is mainly used in the welding of Offshore platform structure such as offshore jacket, beams, decks, boat landing, underside and other parts of the offshore platform as per AWS D1.1 code. This position qualifies a welder to weld TKY joints.