Hi Roadhogary,
For your example, X70 to X42, your WPS will need to be qualified on X70 material.
API 1104 5.4.2.2 reference follows: “
When welding materials of two separate material groups, the procedure for the higher strength group shall be used”.
However, for you to be completely covered for all combinations from Grade B to X70, with respect to materials alone,the following qualification tests will be necessary:
X42 to X42 [Specified minimum yield strength less than or equal to 42,000 psi (290 MPa)].
X60 to X60 [Specified minimum yield strength greater than 42,000 psi (290 MPa) but less than 65,000 psi (448 MPa)].
X65 to X65 *
X70 to X70 *
* [API 1104 5.4.2.2…For materials with a specified minimum yield strength greater than or equal to 65,000 psi (448 MPa), each grade shall receive a separate qualification test].
With respect to diameter and wall thickness, for
WPS qualification, API 1104 gives suggested groupings, but does not dictate the testing program. For the lower grade materials such as X42, you could somewhat easily find pipe thicknesses less than 3/16”. Not generally so for X60 or certainly above. Accordingly, the thickness you select should have an engineering basis you can rely on should the regulator question how you selected these thicknesses for PQR testing. As a suggestion, you could consider using a thickness near 0.500” as this somewhat represents the mid-point of the 3/16” to ¾” suggested grouping. With respect to OD, some companies qualified on NPS 10 or 12 while some qualified on a variety of diameters.
There is finally the comment from API 1104 5.4.2.2 that should be examined by your Engineering Group prior to commencing on a WPS qualification program:
"
The groupings specified in 5.4.2.2 do not imply that base materials or filler metals of different analyses within a group may be
indiscriminately substituted for a material that was used in the qualification test without consideration of the compatibility of the base materials and filler metals from the standpoint of metallurgical and mechanical properties and requirements for pre- and post-heat treatment".
The same comments apply to the qualification of fillet weld procedures.
Be aware that the suggested OD and thickness ranges for WPS qualification are just that: suggested groupings...see excerpt below:
5.3.2.3 Diameters and Wall Thicknesses
The ranges of outside diameters and wall thicknesses over which the procedure is applicable shall be identified. Example of suggested groupings are shown in 6.2.2, items d and e.
For welder qualification, thickness and OD groupings shown for single qualification are mandatory.
Finally, I recommend that you obtain a copy of the PRCI document “Guidelines for Interpretation and Application of API 1104 –Twenty-first Edition” [Catalog No. PR-186-124502-R01] as it provides excellent information regarding anything related to API 1104.
Although PHMSA has not yet incorporated the 21st edition of API 1104 by reference into either Part 192 or 195, this document provides the framework your company could use to establish welding procedure qualification, in particular, to the use of dual or triple stenciled materials on different thicknesses.
(No…I don’t work for PRCI)
Hope this helps...
