Is there a public repository of labeled sound files coming from an industrial area?
Freesound is a repository of sound files categorised by user-defined tags. Through those, you can spot what other users have labeled industrial sounds but be prepared that some of those might be artificially created (so, not really a recording of an engine but something that sounds like an engine).

In the same category is also Soundsnap.

The other popular choice would of course be Soundcloud but there, you will have to do a bit of digging to find sounds that suit your use case because the majority of sound clips there are about music (so, "industrial rock" for example).

In all of these, you can curate a subset of samples that seem to have a strong relationship between their content and the tags, to then use the tag as your class variable if you are looking to download a large dataset.

Hope this helps.