D1.1-2010, look at Clause 1.3.1. Engineer is defined. He is the representative of the owner of the project and is the only one with authority to accept/reject, modify designs and/or intentions of codes, etc. As this is also in D1.4, I don't have D1.6 with me, I am presuming it is in D1.6 as well. Even if not, to answer your question, NO, the owner of the shop cannot take that designation. Neither can the owner of the project. And, NO, the weld engineer cannot take that designation either.
All WPS's, welder's certs, and any variations of joint design, and many other items are to be submitted to the Engineer of Record (the customer/project owner's representative and Registered Design Professional) for approval before work begins.
Your people can submit those changes for approval but they are not the ones responsible, nor qualified, to approve them.
Have a Great Day, Brent
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