Abstract: In a safety system for controlling the closing of a primary valve in response to an indication of an undesirable condition from a monitoring device, the system including a valve arrangement which supplies operating fluid to the primary valve and an operator connected between the monitoring device and the valve arrangement for controlling the operation of the latter in response to the indication produced by the monitoring device, the speed and reliability of the system is improved by providing a direct fluid connection between the output of the monitoring device and the operator, whereby the system is directly controlled by the fluid pressure variations at the output of the monitoring device. Preferably, the system includes an hydraulic subsystem and a pneumatic subsystem.

Abstract: In a safety system for controlling the closing of a primary valve in response to an indication of an undesirable condition from a monitoring device, the system including a valve arrangement which supplies operating fluid to the primary valve and an operator connected between the monitoring device and the valve arrangement for controlling the operation of the latter in response to the indication produced by the monitoring device, the speed and reliability of the system is improved by providing a direct fluid connection between the output of the monitoring device and the operator, whereby the system is directly controlled by the fluid pressure variations at the output of the monitoring device. Preferably, the system includes an hydraulic subsystem and a pneumatic subsystem.