The present invention relates to a well tool device (1) comprising a housing (10) having an axial through bore (11). A sleeve section (20) is releasably connected to the housing (10) in the through bore (11). The sleeve section (20) comprises an axial bore (21) and a frangible disc (30) provided in the bore (21) of the sleeve section (20) in sealing engagement with the sleeve section (20). The sleeve section (20) is axially displaceable within the bore (11) between a first position (P1) and a second position (P2). The housing (10) comprises an axial bypass fluid passage (12) provided axially between a first location (L1) above the sleeve section (20) to a second location (L2) below the sleeve section (20) when the sleeve section (20) is in the first position (P1). The axial bypass fluid passage (12) is provided radially between the sleeve section (20) and the housing (10) when the sleeve section (20) is in the first position (P1). The well tool device (1) comprises a sealing device (36) provided radially between the sleeve section (20) and the housing (10) when the sleeve section (20) is in the second position (P2).