Does CADWorx have a way to lock piping lines within a model, as when the iso is issued and we don't want anyone modifying the piping?

Not as such.

Maybe add a custom status property to components. I've also done a few things with the ISOGEN pipeline data, so if that line number is run a big ol'
DO NOT USE
text gets added across the face of the iso.

We just lock the layer the line is on, to prevent any changes.

Layer by line number, I take it?

The problem is that anyone can unlock the layer, change, and then lock the layer again.

True, I guess it prevents unintentional changes, but if someone really wants to make an edit they're always going to try and find a workaround.

So we have since discovered, that having locked layers prevents the model from syncronising with the database, so we're no longer going to lock layers.

Another option is you could change the properties of the piping model file to read only with admin rights. If all structural/civil/piping/etc. were x-ref into a "master" model.

We used the locked layer way as well. We have progress code included in Custom Fields so once a line or model reaches say code 4 then they have been issued for isometric. I know people can work around that but if you issue a Work note on it to designers explaining why they are being locked then generally people will abide by it. In the note you could also explain procedure for unlocking lines (go to admin to do it). We also did a change colour in Navisworks review model for any line that have reached code 4 progress code so you can see what has been issued to date in the model.