A question regarding the emergency shut-off valve
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I would like to ask everyone: is there no fundamental difference between the emergency shutdown methods used in DCS and those of the emergency shutdown valves connected to SIS? Is the difference merely in terms of signal feedback?
Yes, the shut-off valves on site are the same
They’re different; SIS shut-off valves generally require to be certified to a SIL rating. Although they may look the same on the outside, strictly speaking, the manufacturing and installation requirements for SIS valves are higher than those for ordinary valves
There are differences in the required performance levels for valves.
Certification issues – but are there any manufacturers in China capable of handling this?
What was said on the third floor is correct – all hardware in a safety instrumented system must have SIL certification, and cut-off valves are included in this category; DCS, on the other hand, does not require such certification； To save money, some projects combine DCS and SIS systems, using the same device for both purposes; this does not comply with the standards ； There is now a requirement to re-evaluate the SIS system, to be completed by the end of 2019; this is a key inspection item.
The SIS system has stricter requirements for equipment reliability than DCS； The valves used in the two systems can be the same; that is, valves that meet the requirements of the SIS can be used in the DCS, but valves that satisfy the requirements of the DCS may not be suitable for use in the SIS. That said, the valve claimed to provide an “emergency shut-off” function should be available in both systems.
It’s used to make money – reaching a certain level can earn you a few thousand extra dollars
Everyone should learn more*. See the reply on floor 8. It has been made clear. One more thing: SIS is an overall concept that includes control systems, detection instruments, and actuation instruments.