Accessory for disc refiner

An accessory for a disc refiner that is for refining lignocellulosic material and comprises at least two refiner discs, at least one of which is a rotor refiner disc, a motor, and a rotation shaft assembly that comprises (i) a rotation shaft that connects the motor and the rotor refiner disc for driving rotation of the rotor refiner disc from the motor, (ii) a shaft housing, which at least partly encloses the rotation shaft, (iii) at least one bearing between the shaft housing and the rotation shaft for allowing rotation of the rotation shaft within the shaft housing, and (iv) at least one ring-shaped locknut that encircles the rotation shaft, is configured for holding the at least one bearing in place on the rotation shaft, and comprises notches for a tool to grip when attaching the locknut in the rotation shaft assembly, wherein:

• the accessory is configured to be attached to the locknut and comprises at least one covering part configured to at least partly cover the notches of the locknut when attached to the locknut.