Article 130.7.12 of NFPA alludes to application of additional layers to achieve required protection level.
Also, NESC refers to the effective arc rating of a "clothing system", which can be made up of multiple layers.
Field test results can be extremely valuable for diagnosing transformer condition, and are relatively inexpensive, comparibly. As mentioned, saving the costs of shipping a unit unnecessarily.
However, generally, acetylene=bad. So you may be in need of some major repairs.
