Pressure relief valve

A pressure relief valve to balance the pressure between a cargo tank and the ambient atmosphere, the pressure relief valve being arranged so that the velocity of the out flowing gas jet at no time is under a preset value when the valve is in an open position, the pressure relief valve comprising:

• a valve body designed to act against a valve seat located in an outlet opening structure through which an opening extends from the cargo tank, the valve body is connected to a rod extending into the opening the rod being supported and guided by a frame structure extending into the opening, the frame structure being fixed to the outlet opening structure;
• wherein the rod extends into the valve body, the valve body being moveable in respect of the rod and adapted to be retained in a first position by a spring, the spring counteracting motion of the valve body from the valve seat until a predetermined first pressure level within the cargo tank is reached,
• first and second magnetic structures connected to the valve body and the frame structure respectively, the magnetic structures being configured to attract each other by a preset magnetic force acting in the closing direction the preset magnetic force is suspended when the magnetic structures are brought apart when the pressure in the cargo reaches the predetermined first pressure level, the predetermined first pressure level being a threshold value initiating a first opening modus;
• wherein the central rod comprises a third magnetic structure configured to act against a fourth magnetic structure fixedly attached to the frame structure, the third and fourth magnetic structure are configured to attract each other by a preset magnetic force acting in the closing direction and is suspended when the magnetic structures are brought apart when the pressure in the cargo reaches a predetermined second pressure level, the predetermined second pressure level being a threshold value initiating a second valve opening modus;
• and
• wherein the predetermined second pressure level is higher than the predetermined first pressure level.