Flammable and toxic gas alarm system and SIS
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In the LNG area, the design institute requires that the signals from four combustible gas alarms be fed into the SIS to participate in safety interlocks. Could it be considered that these four combustible gas detectors are the SIS instruments? Only SIS is needed; there’s no need to use GDS anymore! Alternatively, the signals from these four combustible gas detectors are fed into the GDS, while the high-alarm output signals go to the SIS to participate in the safety interlock system. Of these two options, which one is more in line with current safety standards and regulations?
Four combustible gas detectors are connected directly to the SIS system
Now it is required to be separated, entering SIS individually instead of being allowed to enter GDS.
The gas probe features a 4–20mA signal and high/low alarm outputs; the analog signal is sent to GDS, while the digital signal is sent to SIS. Is it feasible?
All the probes that a GDS should have are required; if it is to be integrated into the SIS, it will be part of the SIS as well – it’s a separate entity. Put simply, it’s two sets
Instruments entering the SIS system must be configured separately
It depends on your SIL rating; level 1 allows for two inputs via instruments. It’s a matter of a safety barrier with one inlet and two outlets; it’s not possible to estimate this at the first level – you’ll need to install two sets of instruments on-site, because the SIS system follows certain standards, while the requirements for toxic and harmful gases follow other standards
Do combustible gas detectors connected to the SIS require SIL certification?
I would like to ask what brands of detectors you have. I feel that gas detectors give a lot of false alarms, and if that happens in a SIS system, it could lead to problems.