Which signals require redundancy?
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In the DCS I/O tables for the instruments in statistical projects, I need to determine which signals require redundant connections. As far as I know, signals that are part of interlocks need to be connected redundantly; for example, when controlling the opening degree of a control valve based on liquid level, both the liquid level input signal and the control signal for the valve need to have redundant connections. Senior colleagues, are there any specific regulations regarding which signals need to be included in the redundant signals?
In a nutshell, use redundancy for data that’s considered important. Those generally involved in control are redundant, while only the indicators are not redundant.
This post was last edited by sun_fm on 2022-11-7 at 09:25. It depends on the situation: for aspects related to safety (IPL) or **requirements (the “two key points and one major requirement”)**, redundancy is necessary; otherwise, redundancy is not recommended. After all, today’s component technology (reliability) has improved significantly compared to the past. In HGT20573, the I/O cards for control loops and critical monitoring points specified in 6.3.4.1 should be configured redundantly. In SHT3092, the multi-channel AO cards used for control functions shall adopt synchronous redundancy, while the other multi-channel analog I/O modules used for control and interlock protection functions should use hot standby or synchronous redundancy. 7.2.12.2 specifies that for multi-channel I/O modules that cannot be configured in a redundant manner but are used for control or interlock protection, it is advisable to provide I/O modules in a quantity equal to twice the number of channels. 7.2.12.3 It is not advisable to use additional signal conversion modules connected in series to achieve redundant configuration of I/O modules. (This item can be considered in conjunction with the question ‘Should a signal distributor be used?’) GBT50770 (similar to HGT20511) does not specify I/O redundancy, but requires that 8.5.2: Multiple transmitters measuring the same process variable should be connected to different input cards. 8.5.3 Redundant final elements should be connected to different output cards, with each output signal channel having only one final element connected to it. According to GBT50823, section 4.5.4, the control rooms, communication interfaces, and power supplies in important stations (plants) shall be equipped with 1:1 redundancy. The redundant configuration of the I/O template should be determined based on the system’s availability and actual requirements.
I/O signals involved in control (interlock, sequential control, automatic control feedback, etc.)
It’s needed for interlocked control as well as for emergency shutoff