Slam shut safety device

A slam-shut safety valve for a gas distribution system, the slam-shut safety valve comprising:

• a valve body;
• an upper case mounted to the valve body;
• a diaphragm disposed between the valve body and the upper case, at least part of the diaphragm being displaceable into an interior portion of the valve body and into an interior portion of the upper case, the diaphragm having a first side being exposed to gas system pressure, an outer o-ring, an outer planar portion, an outer convolution, a middle planar portion, an inner convolution, and an inner planar portion;
• a first spring and a second spring disposed within the interior of the upper case, the first spring and the second spring exerting spring forces on a second side of the diaphragm opposite the gas system pressure;
• and
• a plunger connected to the first side of the diaphragm, the plunger being adapted to activate a cam to release a slam shut plug,
• wherein the outer and inner convolutions are co-centered and a plate is connected to the diaphragm, the plate covering the outer convolution and the middle planar portion while leaving the inner convolution, the outer planar portion and the inner planar portion uncovered.