Qualification of the Welding Procedure and the Welder
On many welding jobs, the fabricator is required to separately qualify the welding procedure to be used and the welder who is actually to weld the pipe. How this is done is specified by a code. One code frequently encountered in pipe welding is the ASME Boiler and Pressure Vessel Code, Section IX. While this code is not reproduced here in detail, the discussion in this chapter is based largely on the code.
Qualifying a Procedure
To qualify a procedure, the fabricator must prove the adequacy of his procedure with consideration given to the service conditions, particularly to the consequences should the piping system fail. A pipe weld is made according to the procedure to be qualified. Samples are cut from the weld; the positions from which they are cut are shown in Fig. 15-1. Figure 15-1 also specifies the dimensions of the test samples and the type of test to which they are to be subjected. After the weld specimens have proven to be acceptable, the procedure is considered to be valid.
Qualifying the Welder
In order to qualify the welder, the fabricator must have him weld a pipe joint in both the horizontal (2G), and the vertical (5G), positions, using the procedure that has been qualified for doing the job. Four samples, Fig. 15-2, are cut from each of the welds and bend test samples are prepared. As shown in Fig. 15-2, two face - bend tests and two root-bend tests are made from each weld.
The fabricator must maintain a record of the tests made by each welder, who is assigned an identification number for use as a reference. No welder is allowed to perform on the job unless he has been successfully qualified by passing the bend tests.
Passing one particular procedure will not qualify the welder for welding all different pipe sizes and wall thicknesses, but will restrict the operator to welding within a specific range of wall thickness. If
MACHINE ГНЕ MINIMUM AMOUNT
Ail CORNERS ALL CORNERS
Fig. 15-і. Specification of test specimens for qualifying the pipe welding procedure.
tests are conducted on pipe with %-inch wall thickness, the operator is then qualified to weld wall thicknesses one-half the size of the sample, or twice the sample size. Therefore, before attempting to weld heavier wall pipe, the welder, and procedure, must have new qualification.
A welder shall be requalified when there are one or more changes made, which differ from that of the already established procedure. The following changes are responsible for new qualifications:
A. A change from a base metal listed under one letter subgroup to one listed under another subgroup.
B. A change from one diameter wall-thickness range to another.
C. The addition of any welding position in which a large number of welds is made.
D. If the direction of welding is changed from bottom to top, or top to bottom.
There are other changes which are not quite related to this process:
E. An operator who is qualified with an E-6010 is not necessarily permitted to use a low-hydrogen electrode. If he is qualified with a low-hydrogen electrode, it is possible for him to use an E-6010 if the job permits.
FACE BEND ROOT BEND ROOT BEND FACE BEND
HORIZONTAL (2G} WELD
VERTICAL Ш WELD
Fig. ) 5-2. Bend test specimens for qualifying the pipe welder. The weld must bend ISO degrees without breaking.
Qualifying welders according to a procedure is the responsibility of a qualified inspector. An inspector not only inspects the completed weld samples, but also conducts this test in a systematic manner. There are three basic steps in testing;
2. Acceptance quality
3. Final result.