I would check on this with your client.
The intent of the training requirement is to ensure your welders are familiar with the requirements of all the fabrication documents applicable to the welding being performed.
My training program covers the requirements of NAVSEA TP278, MIL-STD-22D, MIL-STD-2035A, and the applicable in-house documents such as welding procedure specifications and visual inspection procedures used on the work to be performed. I also include NAVSEA TP1688 when any welding is performed to that standard. With the knowledge that many welders have never been involved with classroom training that covered the fundamentals of welding theory, I also cover welding processes (those that apply), welding symbols, basic metallurgy, weld discontinuities, etc.
This training also requires written examinations and your training program has to be reviewed and approved by your customer. Eventially, your training programs may find its way to SupShips or NAVSEA depending on your client and the purchase order requirements.
Also note that the welder training program requires involvement of a NDT Level III. The credentials of the instructor may also be subject to review and approval.
I doubt you will be permitted to hire a welder "off-the-street" that has received training from another company unless they took the training and examinations from your client, i.e., perhaps they got laid off from your client (a shipyard perhaps)and they were trained within the previous 36 months.
Best regards - Al