GDS is independent of the DCS system; how to control equipment and valves?
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Since GDS now requires to be independent of the DCS system, it is necessary for on-site detectors to open the valves and fans for emergency ventilation once toxic or flammable gases are detected. How should the interlock logic be configured? Should the interlock logic for emergency ventilation be connected to the DCS, or can this logic be handled using GDS: handshake
Isn’t this the responsibility of the fire department? How can a standalone host be connected to DCS?
This DCS is quite comprehensive, covering the entire control layer. Including enterprise-level management, SIS, video, etc. In my opinion, it depends on the integration of the enterprise’s overall management system.
Since there is a GDS independent of the DCS, such gas protection interlocking should be implemented by the GDS. Typically, axial flow fans are controlled by electrical power on/off, so the GDS outputs a switch signal to achieve control. As for the reliability of GDS, it must undergo a SIL assessment; based on the level of hazard posed by flammable and toxic gases at the site, the configuration level of the GDS is determined, as well as whether a redundant design or higher reliability for individual devices is necessary.
In other words, can the combustible gas alarm signal be used to interlock and control valves via the DCS system, or can it only be connected to the GDS system for valve control? The 2020 version of the standards states that the GDS system is independent of the DCS system and cannot be directly connected to it
Current regulations state that the GDS system is independent of the SIS system, and therefore no SIL certification is required
……Our factory routes the detection signals from the toxic sensors to both the DCS and GDS systems.:)
For combustible gases, air valves and fans are required; is a fire alarm controller needed to enable fire protection interconnection? Toxic gases require interlock actions; whether to integrate them with a SIS to enable such actions… GB/T 50394-2019, Appendix C: Configuration diagrams for combustible gas and toxic gas detection and alarm systems
GDS and SIS are not entirely independent concepts; if combustible and toxic gases are linked to gas protection and fire suppression actuators, a complete control loop is formed, and in that case it becomes a combustible gas detection and protection system. According to Document No. 3116 issued by the Ministry of Work Safety, such a system should be classified as an SIS system, and a SIL assessment must be conducted to ensure its reliable operation. The signals from the GDS can be transmitted to the DCS system to enable redundant monitoring.
Those involving interlock actions belong to the process control system, and can be integrated into the DCS/SIS system as required； The GDS system is primarily used for on-site alarms; its response level is determined by the OEL, with the main purpose being to protect the safety of personnel on site ； Their purposes, functions, and modes of operation are all different; therefore, to achieve both interlocking and on-site alarm functions simultaneously, two sets of alarms need to be installed.