Valves not return of safety, certified EN 15089/2009 against the propagation of the explosion in the suction's line. A suitable counterweight allows the balancing of the 2 diaphragms for a regular opening and closing, equipped with safety's anti opening block. The high and efficiency of closure permit to fit at a very short distance from the point f possible explosion (silos, filter, container) 3 meters. Built in carbon steel painte Blue RAL 5010 welded in all the unions and reinforced structure to sustain an high pressure, standard production with flanges and counter flanges our standard. A seal ensures held in closed position.