HYDRAULIC OR PNEUMATIC DRIVE FOR ACTUATING A FITTING COMPRISING A CONTROL VALVE OR SELECTOR VALVE

摘要

A safety circuit for valves actuated hydraulically via a positioning cylinder. The positioning cylinder in one embodiment is configured to be hydraulically or pneumatically depressurized in an emergency. The positioning cylinder has two cylinder chambers configured to be fluidically connected via a working line. A first and a second series-connected shut-off valve are provided in the working line. The positioning cylinder in another embodiment is configured to be hydraulically or pneumatically actuated in an emergency. The positioning cylinder has at least one first cylinder chamber configured, in an emergency, to be supplied with pressurized fluid via a first pressure medium flow path. A first and a second series-connected shut-off valve are provided in the first pressure medium flow path.