A surgical instrument has an ultrasonic blade that connects to a distal end of an ultrasonic waveguide. A clamp arm assembly is moveable from an opened position for receiving a tissue, toward a closed position for clamping the tissue. A clamp arm actuator connected to the clamp arm assembly directs the clamp arm assembly from the opened position toward the closed position. An outer sheath surrounds at least a portion of the ultrasonic waveguide. The outer sheath includes a cover removably received against a sheath body, and a sheath securement feature able to detachably couple the cover to the sheath body such that the cover can be detached from the sheath body for accessing the ultrasonic waveguide within the outer sheath. A device for forming a seal comprising a proximal form portion (9314) and a distal form portion (9310) is also disclosed.
