We have Woodward 505 installed for a compressor turbide drive control where it switches back to local control from remote. Can anybody explain under what conditions the control switches to local mode?

 

Only from key pad you changed its control, remote to local or local to remote. There is only one more reason that there is some break in your signal from DCS to governor.

 

Maybe, there are any input contact configured like Remote SetPoint enable. Verify this information trough the IHM. Normally, there are anu CCC or other controller send the set point to W505, then verify this interconections...