A work device usable with pressure circulation and equipped with a hydraulic motor, comprising: - a hydraulic circulation, which has a first pressure line and a second pressure line; - a hydraulic motor connected between the first pressure line and the second pressure line and which has an overflow connection; and characterised in that the work device further comprises - a hydraulic apparatus for the receiving and returning to pressure circulation of overflow oil of the hydraulic motor, wherein the hydraulic apparatus comprises: - a tank section, which comprises an air-tight liquid space that is in connection with at least one connector, the volume of which liquid space is restricted by at least one movable wall; and - a drainage section, which has been configured in a first operating stage to accomplish a reduction in the volume of the liquid space by moving the wall and in a second operating stage to release the wall to enable an increase in the volume of the liquid space; and wherein: - the hydraulic apparatus has been arranged in the first operating stage to return overflow oil to the hydraulic circulation through a non-return valve and in the second operating stage to receive overflow oil from the hydraulic motor through a second non-return valve; whereby the hydraulic apparatus has been configured to receive overflow oil from the hydraulic motor through a non-return valve and return overflow oil to the pressure circulation through a second non-return valve. - a hydraulic circulation, which has a first pressure line and a second pressure line; - a hydraulic motor connected between the first pressure line and the second pressure line and which has an overflow connection; and - a hydraulic apparatus for the receiving and returning to pressure circulation of overflow oil of the hydraulic motor, wherein the hydraulic apparatus comprises: - a tank section, which comprises an air-tight liquid space that is in connection with at least one connector, the volume of which liquid space is restricted by at least one movable wall; and - a drainage section, which has been configured in a first operating stage to accomplish a reduction in the volume of the liquid space by moving the wall and in a second operating stage to release the wall to enable an increase in the volume of the liquid space; and wherein: - the hydraulic apparatus has been arranged in the first operating stage to return overflow oil to the hydraulic circulation through a non-return valve and in the second operating stage to receive overflow oil from the hydraulic motor through a second non-return valve; - a tank section, which comprises an air-tight liquid space that is in connection with at least one connector, the volume of which liquid space is restricted by at least one movable wall; and - a drainage section, which has been configured in a first operating stage to accomplish a reduction in the volume of the liquid space by moving the wall and in a second operating stage to release the wall to enable an increase in the volume of the liquid space; and wherein: - the hydraulic apparatus has been arranged in the first operating stage to return overflow oil to the hydraulic circulation through a non-return valve and in the second operating stage to receive overflow oil from the hydraulic motor through a second non-return valve; - the hydraulic apparatus has been arranged in the first operating stage to return overflow oil to the hydraulic circulation through a non-return valve and in the second operating stage to receive overflow oil from the hydraulic motor through a second non-return valve;