Any leakage steam arising while the valve is closed is led away into a leakage-steam line (K) located near the rear guide bush. The hydraulic section, which is also bolted to the connection part, is the active component of the emergency stop valve. It is a piston consisting of two parts, one disc-shaped, one bell-shaped. The disc-shaped section is fixed to the valve spindle while the bell-shaped section moves in a surrounding cylinder. A compression spring (11) which acts at one end on the inside of the bell-shaped part and at the other on the valve spindle via a spring cap (9) provides the connection between the two piston parts. The two parts are pressed against each other when trip oil (start-up oil F) acts on the bellshaped pushing it towards the disc.