On the card redundancy issue in DCS control systems
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Dear Haihao friends, the DCS system features redundant configurations for its power supply, controllers, and communication systems. But is it necessary to have redundancy in the analog control loops as well? Considering factors such as cost, is it possible to avoid redundancy, or are there any mandatory standards in this regard? ? ? ?
IO modules generally do not require redundancy; for particularly critical IOs, redundant modules can be considered.
Whether card redundancy is necessary depends on the importance of the device connected to the card, the reliability required for that device, and the risks associated with potential failures. Generally, for critical components and high-risk equipment, control requirements must be redundant in order to enhance the reliability of the entire system. If the equipment connected to the card could face serious consequences due to a failure of the card itself, such as system shutdowns that lead to major safety incidents, severe production problems, or significant economic losses, then redundancy for the card is necessary. For ordinary equipment, even if a failure occurs, there will be no serious consequences, so redundancy is not necessary due to cost considerations. Therefore, whether card redundancy is necessary or not depends on the importance of the associated devices, rather than the cards themselves; this holds true for any type of card. Based on factors such as process, safety, and equipment, a decision is made regarding whether redundancy is necessary.
Analog quantities with control and interlock functions require redundancy, while ordinary AI analog quantities (used only for indication) do not require redundancy.
Analog signals generally seem to have little redundancy; what was said above is correct – important control points that involve interlocks require redundancy. For analog signals, an alarm value is set, and if this value is exceeded, the system stops, thereby turning the analog signal into a digital one in effect
It is determined by the requirements. For example, in terms of temperature difference control in distillation towers, manual control is simply not sufficient; in such cases redundancy is necessary.