Power wrench comprising a motor, an output shaft , and a hydraulic pulse unit including an inertia drive member connected to the motor and rotatable about a rotation axis (A-A), an oil chamber enclosed in the inertia drive member and an impulse generating means arranged to transfer intermittently kinetic energy to the output shaft , wherein the inertia drive member further comprises an end piece having a transverse wall , wherein a separating arrangement is provided for extracting air from oil, said separating arrangement comprising a disc shaped separator element and a sealing arrangement arranged to provide a seal between said disc shaped separator element and said transverse end wall , thereby partly delimiting a receiving space there between in fluid communication with said oil chamber , said disc shaped separator element further arranged to provide a passageway between said oil chamber and said receiving space by means of a fluid opening located at a first radial distance (a1) from the rotation axis (A-A), wherein said separating arrangement further comprises a partitioning element arranged in said receiving space , such that a first partial volume is formed on a first side of said partitioning element and a second partial volume is formed on the other side, wherein said first and second partial volume are in fluid communication and wherein said opening is arranged on said first side, wherein said fluid communication is provided by means of a fluid passageway at least partly formed by said partitioning element , characterized in that said sealing arrangement comprises an outer seal and an inner seal, and wherein said inner seal form said partitioning element such that said fluid passageway is provided by means of a channel (C) delimited by said outer seal and said inner seal. wherein a separating arrangement is provided for extracting air from oil, said separating arrangement comprising a disc shaped separator element and a sealing arrangement arranged to provide a seal between said disc shaped separator element and said transverse end wall , thereby partly delimiting a receiving space there between in fluid communication with said oil chamber , said disc shaped separator element further arranged to provide a passageway between said oil chamber and said receiving space by means of a fluid opening located at a first radial distance (a1) from the rotation axis (A-A), wherein said separating arrangement further comprises a partitioning element arranged in said receiving space , such that a first partial volume is formed on a first side of said partitioning element and a second partial volume is formed on the other side, wherein said first and second partial volume are in fluid communication and wherein said opening is arranged on said first side, wherein said fluid communication is provided by means of a fluid passageway at least partly formed by said partitioning element , characterized in that said sealing arrangement comprises an outer seal and an inner seal, and wherein said inner seal form said partitioning element such that said fluid passageway is provided by means of a channel (C) delimited by said outer seal and said inner seal. <EOS>