Can pneumatic double-acting shut-off valves meet the requirements for fail-safe operation?
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Can pneumatic double-acting shut-off valves meet the requirements of a fail-safe design?
No problem. First, use a double-acting positioner or solenoid valve; note that the air circuit can be configured in a fail-safe manner. Additionally, regarding the purge air, accessories such as air path switching devices, check valves, and air storage tanks are added during restart. When the pressure of the purge air is low, the switch changes the air path, and the purge air from the air storage tank is used to move the actuator to a safe position.
Reply to 2# wangyongan: The cylinder does not have a spring; will it still be able to meet the requirements in case of a power outage?
Reply to 3# oatobnus: It’s possible. In the event of a power outage in the grid, the ventilation system will stop, but gas storage tanks and safety devices ensure that the actuators move to a safe position. For DCS systems, a UPS power supply should be installed to provide coverage for a certain period of time. Additionally, double-acting positioners or solenoid valves should be configured to move the actuator to a safe position in the event of a signal interruption.
A manual valve can be added to manually control the air circuit in case of power loss, and to operate the control valve in order to maintain a safe condition
The gas circuit design is fine; there are no issues. A check valve is installed at the outlet of the cylinder and at the inlet, and pressure sampling for control is done before the check valve. The size of the steam tank is designed with valves that can operate at least three times.
It’s possible to do it according to the process requirements. A position holding valve can be used to maintain the valve position. Power or gas interruption can also serve as protection. The key is to see if it’s worth investing in.