A junction part (2; 2') for an undersea fluid transport pipe, the junction part comprising: - a sleeve (4; 4') for connecting to the ends of two unit pipe elements; - a buckle arrestor flange (14; 14') projecting radially outwards from the sleeve; and - at least three differential pressure valves positioned radially within the flange, each differential pressure valve comprising: - a valve body having arranged therein an internal chamber open at one end to the pipe within which there exists an internal pressure Pi, and open at another end to the outside of the unit pipe element where there exists an outside pressure Pe; - a piston arranged in the internal chamber so as to subdivide the internal chamber into an admission chamber communicating with the inside of the pipe and a discharge chamber communicating with the outside, the piston being movable between an open position in which the admission chamber and the discharge chamber communicate with each other, and a closed position in which the admission chamber and the discharge chamber are sealed from each other; - a rating screw screwed into the valve body and including a bore within which there slides a rod of the piston together with at least one hole opening out into the discharge chamber and open to the outside; and - a spring positioned between the piston and the rating screw, said spring being rated so as to keep the piston in the closed position below a predetermined threshold pressure inside the admission chamber. - a sleeve (4; 4') for connecting to the ends of two unit pipe elements; - a buckle arrestor flange (14; 14') projecting radially outwards from the sleeve; and - at least three differential pressure valves positioned radially within the flange, each differential pressure valve comprising: - a valve body having arranged therein an internal chamber open at one end to the pipe within which there exists an internal pressure Pi, and open at another end to the outside of the unit pipe element where there exists an outside pressure Pe; - a piston arranged in the internal chamber so as to subdivide the internal chamber into an admission chamber communicating with the inside of the pipe and a discharge chamber communicating with the outside, the piston being movable between an open position in which the admission chamber and the discharge chamber communicate with each other, and a closed position in which the admission chamber and the discharge chamber are sealed from each other; - a rating screw screwed into the valve body and including a bore within which there slides a rod of the piston together with at least one hole opening out into the discharge chamber and open to the outside; and - a spring positioned between the piston and the rating screw, said spring being rated so as to keep the piston in the closed position below a predetermined threshold pressure inside the admission chamber. - a valve body having arranged therein an internal chamber open at one end to the pipe within which there exists an internal pressure Pi, and open at another end to the outside of the unit pipe element where there exists an outside pressure Pe; - a piston arranged in the internal chamber so as to subdivide the internal chamber into an admission chamber communicating with the inside of the pipe and a discharge chamber communicating with the outside, the piston being movable between an open position in which the admission chamber and the discharge chamber communicate with each other, and a closed position in which the admission chamber and the discharge chamber are sealed from each other; - a rating screw screwed into the valve body and including a bore within which there slides a rod of the piston together with at least one hole opening out into the discharge chamber and open to the outside; and - a spring positioned between the piston and the rating screw, said spring being rated so as to keep the piston in the closed position below a predetermined threshold pressure inside the admission chamber.