| 摘要 |
<p>A safety valve for a pressure vessel, e.g. a marine boiler, comprises a piston-operated valve mounted on the pressure vessel and provided with a cylinder which is connected to a pressure detector. According to the invention, a pair of juxtaposed control valves are provided for selectively opening and blocking communication between the cylinder and the pressure vessel and between the cylinder and the atmosphere, respectively, these control valves being actuated by an element disposed between them and connected by a rod to a control piston which is displaced by the pressure in the vessel against the force of an adjustable spring.</p> |
