Interlocking issues between GDS system and SIS system

The signal enters the SIS cabinet; a 1-to-2 safety barrier is used to send the signal to the GDS

The GDS system (Gas Detection System) and the SIS system (Safety Instrumented System) are two distinct systems, each performing different functions: The GDS system is primarily responsible for monitoring the concentration of gases in the working environment, such as flammable gases and toxic gases, and it alerts operators or other systems in a timely manner to prevent harm caused by gas leaks. - The SIS system is designed to achieve a specific level of safety integrity; it carries out the necessary safety protection functions through highly reliable safety features, such as emergency shutdown (ESD), as well as flame and smoke detection and alarm systems. For combustible or toxic gas detectors that are part of the interlock system in the SIS, their signals are typically fed into the SIS system to trigger the corresponding safety measures. Since the GDS system also needs to monitor these signals for environmental monitoring and personnel alarm purposes, in practical applications, the signals from these detectors are sometimes fed into both the GDS and SIS systems simultaneously. When these signals are fed into the GDS system, it can monitor them in real time and display the status of the gas detectors on the control room or relevant display interfaces, allowing operators to understand the gas concentration levels in the working area. In actual engineering design, whether to connect the signals from gas detectors to both the GDS and SIS systems is determined by the following factors: 1. Safety design requirements: in accordance with the factory’s safety design philosophy and the safety needs of the actual process flow. 2. Standards and regulations: Local laws, industry standards, or best practice guidelines that must be followed. 3. System interoperability: Whether the technical capabilities of the two systems support interlocking and data exchange. 4. Cost and benefit analysis: Consider additional maintenance and operating costs, as well as the potential return on investment for safety measures. Therefore, whether to connect the detector signals involved in the interlock of the SIS system to the GDS system for status display should be decided after a comprehensive evaluation based on the factors mentioned above. Typically, engineering teams develop a set of standard operating procedures and system integration plans that meet the project’s requirements, by taking into account various technical and security standards during the early planning stages of the project. .

This post was last edited by zhouds on 2023-12-11 at 13:39. SIS and GDS should be equipped with separate combustible or toxic gas detectors; they cannot share the same detector, nor can a two-input one-output safety barrier be used to separate them. For interlock signals DO, they should not be communicated from SIS to GDS.

Flammable and toxic alarm instruments must be integrated into the GDS system for unified management; an advanced SIS system can be considered for use in this context, with the SIS then sending out alarms and indications to the GDS.

Since this table meets SIL3 certification, why not communicate directly to the DCS interface for detection?