| 摘要 |
<p>An emergency shutdown system for a process control system includes an emergency shutdown (ESD) valve (12) and an associated valve actuator (18). An emergency shutdown (ESD) controller (46) provides output signals to the ESD valve in the event of a failure in the process control system. A solenoid valve responds to the ESD controller to vent the actuator to a fail state. A digital valve controller (DVC) (36) test strokes the ESD valve. An impedance booster device (52) enables the dc powering of the solenoid valve and the DVC over a two wire line (28, 30) while still permitting digital communication over the same two wire line.</p> |
