pressure and the second pressure is not below the pressure threshold the flap moves to a second position preventing the gaseous fuel from flowing from the first portion to the second portion application_number US 201113234048 A description apparatus systems and methods that implement the embodiments of the various features of the present invention will now be described with reference to the drawings the drawings and the associated descriptions are provided to illustrate some embodiments of the present invention and not to limit the scope of the present invention throughout the drawings reference numbers are re used to indicate correspondence between referenced elements fig1 and 2 are side views of mechanical fuses within a pipe according to an embodiment of the present invention as seen in fig1 and 2 a mechanical fuse 2 is positioned within a pipe 4 and includes a first hinge 10 a second hinge 12 a first spring 14 a second spring 16 a first flap 18 and a second flap 20 even though first flap 18 and second flap 20 are shown mechanical fuse 2 preferably has 3 or 4 curved triangular shaped flaps that partially overlap to seal the pipe 4 therefore mechanical fuse 2 can have 3 or 4 hinges and 3 or 4 springs the flaps may also be referred to as foils when closed the.