Abstract: This invention relates to a circuit breaker for an installation handling pressurized fluid comprising an internal valve, at least one joint of substanially toroidal shape being disposed in an accommodating housing around said valve and/or a member for maneuvering the valve, characterized in that the housing is connected, via at least one fluid-circulation channel, to a counter-pressure zone formed downstream of the joint around the valve or the maneuvering member. During a transitory phase of opening of the valve, a preferential flow circuit of the fluid is arranged between the housing and the counter-pressure zone through the channel. Thanks to the counter-pressure exerted on the seal, the latter does risk being dislocated with respect to its housing.