Issues with combustible gas alarm specifications
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Dear colleagues: In the past, design institutes would integrate flammable and toxic gas alarms into the DCS for monitoring, using separate cards and dedicated operator stations. However, experts from the safety supervision agency have now suggested that such monitoring should not take place within the DCS, but rather in a separate system independent of it. What are everyone’s thoughts on this? How does your company implement new projects? Thank you!
We were also studying this issue some time ago. In fact, the experts simply said that monitoring cannot be carried out within the DCS; it is necessary to use a separate system that is independent of the DCS. By setting up a system that is not connected to the DCS, we meet the experts’ requirements. The software and hardware of this system are identical to those of the DCS, but we name it a flammable and toxic gas alarm monitoring system, and we provide a separate control station and display screens for it. In short: it does not connect to the DCS and is given a separate name.
Why not use it with DCS? Out of concern about potential impacts, interference, or other reasons, I think it’s better to install them together for easier management.
Enter the GDS system, which operates independently from the DCS system; the amount of data in the DCS system is too large.
In principle, that’s the case. But it’s not necessarily necessary to do this. It depends on the nature of the industry. Of course, our designs are all independently developed these days. Today, secondary displays for combustible gas detectors and toxic gas detectors are capable of performing functions such as independent alarm activation and data storage. Communicating with DCS is just more intuitive. And I think there’s nothing to operate with the alarm; why is an operation station needed? Operate what?
I believe GDS systems can be completely replaced by DCS. It independently powers the combustible and toxic alarms, as well as the primary and secondary sensors; the secondary sensors have functions such as storage and alarm capabilities, and are able to output both analog and digital signals. Communicating with the DCS is just an added bonus. However, if functions such as automatic spraying are required, only an FGS system can be used.
Our company uses a SIS system.
The combustible and toxic gas detection system GDS is installed independently (separate from the DCS system), and is implemented using a PLC system with SIL certification
I just checked the national standard: GB50493-2009. Flammable and toxic substances can enter the DCS system, provided that the I/O cards are configured separately.
This understanding is correct; it is necessary to have it separate, whether you use DCS cards or a separate alarm controller – as long as it is not integrated into the production process control system. Strictly speaking, combustible gas alarm systems are part of the SIS system and are required to be independent of the production process control system