Nuclear power plant double cut=off valve for steam or air - has second valve unaffected by pressure surges which could trigger unintentional opening

摘要

A shut-off valve assembly for compressed steam, air or gas comprises two main valves (16,17) connected in series; each main valve is preceded by a magnetically actuated precontrol valve (33); this control valve controls the loading of a piston (28), connected to the valve plate (25) of the main valve, by a gas in such a way as to hold the main valve plate closed by the medium and, when the piston is relieved of gas pressure, to move it into the open position. The second main valve (17) in the flow direction has a precontrol valve (33) with a 3-way function; in addition to relieving the piston (28) it also controls its loading with gas pressure in such a way that, when the precontrol valve (33) is in the position where pressure relief is blocked, there is a larger flow cross-section (35) acting upon the piston (28) than in the pressure relieving position. The effect of the 3 way precontrol valve is that pressure changes act with very little delay upon both sides of the piston (28), with the result that the piston is actuated only intentionally, and the opening of the second main valves does not take place or is limited to only a few milliseconds.