Issues regarding SIS settings
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In SIS systems, it is generally required that controllers and IO cards be configured in a redundant manner. However, a certain manufacturer’s controllers and cards are designed to be used without redundancy – does this comply with the specifications? In my opinion, card redundancy and triple redundancy for IO card channels are two different concepts; isn’t it possible for a single card to fail without any redundant cards available? If a single-card system is acceptable, then how could so many single-card systems in use across the country pass the approval process?
A triple-card setup can be considered a redundant configuration.
SIS system, triple control redundancy, with each IO card providing three outputs. Surge protection is added at the lower end, along with a safety barrier, relays, diodes for power supply, system power, and separate terminal power supply. With this configuration, the probability of a single card burning out, as you mentioned, is very low. During TUV certification, German certification bodies conduct failure probability tests, and the failure probability for products that pass these tests is extremely low, fully meeting German TUV standards. Too many people in China have fixed mindsets; they tend to apply the standards of DCS to SIS systems. The SIS systems available in China have all passed SIL3 certification. As long as proper isolation is provided in the circuit, it is entirely possible to ensure stable operation over long periods of time.