WPS chaper 3 or 4 2

AWS D1.1, Clause 3, Prequalification, is for WPS that meet all the requirements of clause 3 and can be used without further testing. The prequalified WPS must be written, but no testing is required prior to implementation for production welding. Again, all the conditions of prequalification must be met.

Clause 4 covers qualification of both WPSs that do not meet the conditions of prequalification as well as welders, tack welders, and welding operators. There are numerous reasons why a WPS may not meet all the conditions of prequalification, for example (not all inclusive):
1)The base metal is not listed in Table 3.1 or 3.2.
2)The weld is CJP from one side and deposited without steel backing.
3)The weld is CJP, welded from both sides of the joint without back gouging.
4)The contractor wants to specify a larger weld size than permitted for a PJP groove weld (assumed greater joint penetration).
5)The contractor wants to use a groove detail that is not listed as a prequalified groove detail, for instance - narrow groove welding.
6)The contractor wants to use a welding process that is not prequalified, i.e., GMAW using short circuiting transfer.
7)The contractor wants to use downhill vertical progression
8)The contractor wants to weld plug welds with a diameter smaller or larger than that permitted by Clause 2.

The list goes on, but space permitting does not.

Best regards - Al

Great help gtaw, thanks. This confirms my understaning