Abstract: A valve for intercepting a fluid in a duct is provided. The valve has a valve body, a ball shutter, and a sealing device for forming a fluid seal with an external surface of the ball shutter. The sealing device has a polymeric sealing ring located in contact with the external surface, and a metal support ring coupled to the sealing ring. The support ring has an annular coupling portion having an annular contact portion formed by a frustoconical wall, and an elastically bendable influencing portion, so as to form an elastic lever. In an emergency condition in which the sealing ring is absent the annular contact portion is in contact with the external surface of the ball shutter due to at least fluid pressure, forming the fluid seal even in the emergency condition.