A.
UN3363 Dangerous Goods in Apparatus or Dangerous Goods in Machinery are such item that contains dangerous goods as a residue or as an integral element of the machinery or apparatus. I am assuming that you are asking whether it is okay to extensively clean the equipment and forward it as “non-dangerous article”.

Above all, if it contains magnetic material, it must be shipped as UN 2807.

If the residue falls under other dangerous goods category, you will need to take steps such as cleaning, purging of vapors or refilling with non-dangerous goods to nullify any hazard. Thence, it can be shipped as “non-dangerous article”.
However, I wish to add that to the best of my knowledge, all airlines are returning UN3363 as dangerous goods. From safety precautions, they are being returned as UN3363 and not as non-dangerous article.