Safety fracture diaphragm with an active fracture knife on the pressure side

摘要

A safety device for limiting the pressure of a fluid to a predetermined value comprises a preshaped diaphragm having a downstream convex face and an upstream convex face mounted as a closing or sealing device in a pipe. A first knife faces the convex face of the diaphragm at such a distance that a predetermined pressure exerted by the fluid on the concave face of the diaphragm brings the latter into contact with the knife which then causes a bursting of the diaphragm. A second knife is fitted to face the concave face of the diaphragm and a mechanism is provided for making the second knife strike against the diaphragm in order to bring about the tearing thereof when the concave face of the diaphragm is exposed by the fluid to a pressure below said predetermined pressure. The first knife has a passive operating mode, but the second knife has an active operating mode. With this latter mode, it is possible to burst the diaphragm at a pressure value which is well below that at which the diaphragm is burst by the first knife.