We are process tar sands crudes at this refinery. The issue is with our vacuum unit steam educators in the VDU, the primary inlet screens are plugging up. We inject a amine neutralizer into the steam to protect the vacuum condensers piping from corrosion. The steam flowrates have reduced drastically. If you have experienced similar issues please let us know. even though we have redundant eductors (3 in parallel) we would like to understand the root cause of the fouling. the deposit analysis have shown major components as C & O. N is also present in addition to Zn.