A rotary apparatus comprises a housing, a rotor, and a face seal. The rotor is mounted for rotation relative to the housing. The housing and the rotor cooperate to provide an annular clearance passage therebetween. The face seal is positioned in communication with the clearance passage and establishes a sealed connection between the housing and the rotor to block ingress of debris from the clearance passage. The housing or the rotor comprises a knife partially defining the clearance passage to cut debris that may enter the clearance passage. The rotary apparatus may be used, for example, in a shaft assembly or a final drive.