The 6G position will in general serve to qualify the welder for all six positions. In some cases the 2G and 5G tests can be combined to certify the welder in all positions as well. In the 2G position, the pipe is vertical and cannot be rotated, which requires a horizontal weld. The 5G test places the pipe in a horizontal position from which it cannot be moved. This requires the welder to transition from vertical to horizontal and overhead positions. These are similar to the welds required in the 6G position.
The Weld Procedure Spec (WPS) generally specifies filler material, number of passes, backing and heat ranges. Certifying organizations generally only specify the written procedures for the test and how sample welds will be tested. Since welding certification does not necessary transfer from company-to-company, the ASME designee is generally a company representative who has the authority to specify the WPS.
The 2G, 5G and 6G tests can be given with a restricting ring, restricted boiler plate tube or a box type restriction. These tasks are designed to test the welder in unusual positions, and in some cases welding with either hand. The box type restriction is additionally designed to test the welder in shipyard applications where access and vision is difficult.