A hydraulic apparatus (1) for the receiving and returning to pressure circulation of overflow oil of a hydraulic motor comprises: a tank section (26), which comprises an air-tight liquid space (23) that is in connection with at least one connector (21), the volume of which liquid space (23) is restricted by at least one movable wall (19), and a drainage section (25), which has been configured in the first operating stage (I) to accomplish a reduction in the volume of the liquid space (23) by moving the wall (19) and in the second operating stage (II) to release the wall (19) to enable an increase in the volume of the liquid space (23). Moreover, the hydraulic apparatus (1) has been arranged in the first operating stage (I) to return overflow oil to the hydraulic circulation (55) through a non-return valve (45) and in the second operating stage (II) to receive overflow oil from the hydraulic motor (49) through a second non-return valve (46). Also includes a parallel independent claim concerning a work device usable with pressure circulation and equipped with a hydraulic motor.
