Which department decides whether to use SIS control or DCS control?

For safety reasons, certain types of reactions must be fed into the SIS system. And which point to control is determined based on suggestions from process and safety considerations.

It can’t be determined by a single major. A HAZOP analysis is carried out by a multidisciplinary team, involving instrumentation/electrical/process/safety/environmental aspects as well as the patent holders of process packages.

DCS is different from SISI; it is relatively independent! Now it’s required that everyone must join, right?

Multiple specialties and departments, including the owner, design institutes, manufacturers, etc., participate in discussions to make a decision; specialized meetings are required to use the HAZOP analysis method (which is commonly employed) for this purpose. It is not determined solely by a particular specialty.

DCS is different from SIS; DCS is a distributed control system, while SIS is a safety instrumented system. DCS focuses on control, which refers to things like the adjustment of valves, while SIS focuses on safety and is mainly used for interlock switches.

The question of which discipline determines whether to use SIS control or DCS control is a bit vague. For example, it’s like asking whether you need to buy a car or a set of surveillance cameras – they are two concepts that have little overlap at all. DCS is used for production control; it’s like when you go on a road trip by car – a car is essential, and to prevent your car from being deliberately damaged, surveillance is necessary. SIS is used for safety control; its only purpose is to enable safe shutdowns. It cannot be used for production purposes, and its control components are separate from the production control system, so they cannot be used together. If your DCS system is powerful enough, you can do without a SIS. However, no matter how advanced your SIS is, you still need to use a DCS (or a control system with similar functions such as a PLC). However, due to the improved safety status, SIS systems are often used as a scapegoat by leaders to shift responsibility after an incident; as long as there is sufficient funding, no leader will refuse to install a SIS.

HAZOP and SIL analyses are required; the SIL analysis is used to determine whether a SIS is necessary... Relevant standards can be referred to: AQ/T 3049 Guidelines for the Application of Hazard and Operability Analysis (HAZOP Analysis), GB/T 21109 Functional Safety of Safety Instrumented Systems in the Process Industry

A few people from HaiChuan upstairs explained it very clearly. DCS systems and SIS systems are essential installations in every chemical plant; they also relate to safety and environmental protection issues. If such systems are not installed, the safety and environmental protection requirements cannot be met. The DCS system is primarily used for control; modern chemical plants tend to be highly automated in order to save labor as much as possible ； The SIS system ensures safety; in the event of operational errors during production, it can trigger a chain reaction, thereby safeguarding both the equipment and the personnel.

Refer to Document No. An Jian Zong Guan San [2009] 116 and Document No. An Jian Zong Guan San [2014] 116”

It should be decided by the process engineers, with the instrumentation staff responsible for implementing it