| 摘要 |
<p>A control circuit for controlling a combined emergency shutdown and process protection (safety) system, especially on board platforms and vessels. There are two separate signal generators which, each by means of a control line (10, 17) of its own, can give release or control signals for operating a control valve (21) for the supply of hydraulic or pneumatic pressure medium for coupling a main valve (23) by means of an actuator (22). In order to, that one of the two control signal circuits should be capable of being operated independently on the operating condition and possible error conditions in the other, the control circuit comprises at least two separate connection branches (11, 18) for coupling to a common control line (12) to the control valve (21). The other of the two separate connection branches (18) includes an activating member (20), such as a relay, for a switch (14) adapted to connect the first connection branch (11) to the outgoing control line (12). An input signal on the first connection branch is coupled as an output signal to the control line (12) when a voltage is forced on the activating member (20).</p> |
