DCS safety barrier issues
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Under what circumstances do DCS cabinets require safety barriers for their components? Are intrinsically safe instruments necessarily required to have safety barriers, and why?
Intrinsic safety instruments must be equipped with a safety barrier
A safety barrier is used to reduce voltage and prevent short circuits that could damage controllers (such as PLC cards). The wires coming out of the safety barrier are then energized, allowing instruments to transmit signals as well. Intrinsic safety instruments require a safety barrier and intrinsic safety cables to form an intrinsic safety system. An intrinsically safe system refers not to a single instrument, but to the entire circuit system. To achieve the intrinsically safe explosion-proof level, it is required that the instruments in that circuit be intrinsically safe, that the cables used meet intrinsically safe requirements, and that a safety barrier be installed in the circuit. All three of the above are essential
Wires carrying instruments (that are not intrinsically safe instruments) of intrinsically safe explosion-proof systems into and out of the control room must be equipped with safety barriers. When a safety barrier is required, some DCS cards come with built-in safety barrier functionality, in which case no additional safety barrier is needed; otherwise, one must be installed. In practical applications, DCS cards with safety gate functions may not be sufficient to handle all types of signals, meaning that some signals still require a safety gate. Additionally, the performance and price of such DCS cards with safety gate functions might not be satisfactory, which is why in most cases an additional safety gate is used.