French to English Tech/Engineering Engineering: Industrial Part of a chemical process installation

URGENT, please!

This term occurs in a document dealing with safety aspects of work on a chemical plant during shut-downs.

They talk a lot about the 'boundaries' of different production units, which are points where isloation may need to take place in order to work on one unit while its neighbour remains in production, for example; so these are notional boundaries, albeit represented at soem point by a physical object (valve, blind flange, etc.)

I have found a previous FR > DE KudoZ where it occurs with the same meaning, but no conclusive answer seems to have been forthcoming there even in DE.

I have also found surprisingly few occurrences on the 'Net — many of them directly relevant, but so far without an explanation, let alone a translation!

The existing (highly dubious!) diocument from my customer calls it a 'battery limit' (?!), but I think if anything the word order would suggest it ought to be a 'limit battery' —which sort of makes sense, if we can imagine this battery in the non-electrical sense. But I would be really happy to have confirmation of this (or not). As far as I can tell from the context, it must be referring to the physical 'battery' of devices that are installed at this important boundary point between units.