Well tool device comprising a housing having an axial through bore , where the well tool device is comprising: - a sleeve section connected to the housing in the through bore , where the sleeve section comprises an axial bore ; - a disc provided in the bore of the sleeve section in sealing engagement with the sleeve section ; where the sleeve section is axially displaceable within the bore between a first position (P1) and a second position (P2); where the housing comprises an axial bypass fluid passage provided axially between a first location (L1) above the sleeve section and a second location (L2) below the sleeve section when the sleeve section is in the first position (P1), where the axial bypass fluid passage is provided radially between the sleeve section and the housing when the sleeve section is in the first position (P1); where the well tool device comprises a sealing device provided radially between the sleeve section and the housing when the sleeve section is in the second position (P2); characterized in that - the disc is a frangible disc; - the sleeve section is releasably connected to the housing in the through bore when the sleeve section is in the first position (P1); - the well tool device comprises a pre-compressed locking ring provided in a recess in an outer surface of the sleeve section , and where the locking ring is configured to be engaged in a recess in the bore in the second position (P2). - a sleeve section connected to the housing in the through bore , where the sleeve section comprises an axial bore ; - a disc provided in the bore of the sleeve section in sealing engagement with the sleeve section ; where the sleeve section is axially displaceable within the bore between a first position (P1) and a second position (P2); where the housing comprises an axial bypass fluid passage provided axially between a first location (L1) above the sleeve section and a second location (L2) below the sleeve section when the sleeve section is in the first position (P1), where the axial bypass fluid passage is provided radially between the sleeve section and the housing when the sleeve section is in the first position (P1); where the well tool device comprises a sealing device provided radially between the sleeve section and the housing when the sleeve section is in the second position (P2); characterized in that where the sleeve section is axially displaceable within the bore between a first position (P1) and a second position (P2); where the housing comprises an axial bypass fluid passage provided axially between a first location (L1) above the sleeve section and a second location (L2) below the sleeve section when the sleeve section is in the first position (P1), where the axial bypass fluid passage is provided radially between the sleeve section and the housing when the sleeve section is in the first position (P1); where the well tool device comprises a sealing device provided radially between the sleeve section and the housing when the sleeve section is in the second position (P2); characterized in that - the disc is a frangible disc; - the sleeve section is releasably connected to the housing in the through bore when the sleeve section is in the first position (P1); - the well tool device comprises a pre-compressed locking ring provided in a recess in an outer surface of the sleeve section , and where the locking ring is configured to be engaged in a recess in the bore in the second position (P2). <EOS>