【Daily Question 20090317】What safety protection measures should be considered for control systems?
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Discuss what safety measures should be considered when designing a control system to ensure its safe operation Summary: The safety measures to be considered when designing a control system include: 1. The system should have the capability for seamless switching between manual and automatic modes. 2. The system should have alarm functions, such as parameter out-of-limit alarms and instrument failure alarms. For critical parameters, dual or triple transmitters can be used. 3. The system should take into account functions such as regulator output limiting and anti-integration saturation. 4. The system should have the capability to detect power loss or signal loss and trigger alarms, while also maintaining the position of the actuator unchanged. When possible, it is best to enable the regulator to automatically switch to manual operation mode. For pneumatic systems, protections such as a gas cut-off source and a gas cut-off signal should be provided. If pneumatic position control valves (valve positioners) are used, control valves of the air-open or air-close type should be selected appropriately based on the requirements of the process system. 5. For some critical systems, it is also necessary to consider limits on the regulation speed (such as using rate limiters, magnitude selectors, etc.) ； At the same time, protection and alarm systems are considered together to form a complete system. 6. Additionally, for more complex systems such as unit power control systems (coordination control systems), in addition to the control loops, considerations must also be given to mutual tracking during mode switching, disturbance-free switching, and rigorous logical control. This post was last edited by Mobei Yihai on 2009-3-17 20:51.]
To ensure the safe and stable operation of the equipment, two-out-of-three or three-out-of-four interlocks are installed in areas with a high risk of accidents, to prevent erroneous operations caused by instrument failures.
For important control points, it is possible to install additional power and gas cut-off protection devices. Power failure protection devices typically use relays, while air failure protection devices use air lock valves.
Safety measures to be considered when designing a control system include: 1. The system should have the capability for seamless switching between manual and automatic modes. 2. The system should have alarm functions, such as parameter out-of-limit alarms and instrument failure alarms. For critical parameters, dual or triple transmitters can be used. 3. The system should take into account functions such as regulator output limiting and anti-integration saturation. 4. The system should have the capability to detect power loss or signal loss and trigger alarms, while also maintaining the position of the actuator unchanged. When possible, it is best to enable the regulator to automatically switch to manual operation mode. For pneumatic systems, protections such as a gas cut-off source and a gas cut-off signal should be provided. If pneumatic position control valves (valve positioners) are used, control valves of the air-open or air-close type should be selected appropriately based on the requirements of the process system. 5. For some critical systems, it is also necessary to consider limits on the regulation speed (such as using rate limiters, magnitude selectors, etc.) ； At the same time, protection and alarm systems are considered together to form a complete system. 6. Additionally, for more complex systems such as unit power control systems (coordination control systems), in addition to the control loops, considerations must also be given to mutual tracking during mode switching, disturbance-free switching, and rigorous logical control. This post was last edited by Mobei Yihai on 2009-3-17 11:25.]