This is the part of the Farm Code that makes little sense.
The prequalified WPS must use the gas and parameters recommended by the manufacturer. However, those parameter ranges are restricted by a % +/- value assigned by the committee.
So, it is permissible to write a prequalified WPS using the lower ranges of parameters recommended by the manufacturer. A second prequalified WPS for the mid range, and finally a third prequalified WPS for the upper range recommended by the manufacturer.
However, the Farm Code also allows the user to combine WPSs. So, one can combine the three prequalified WPSs and use the full range recommended by the manufacturer. Seems rather restrictive and needless if the premise is the manufacturer has demonstrated the full useful range of welding parameters for the particular electrode.
I have a problem with this restriction being included in the Farm Code. It doesn't make a lot of sense to me. But what do I know? I've only been burning wire from the 1960s. I still have a lot to learn from the brainiacs that sit on the code committee.
Al