Can a electric valve be controlled by both the SIS and DCS systems?
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There is no requirement in safety instrumented systems that electric valves cannot be used in SIS systems; this has led to the following problem: If an electric valve is to be controlled simultaneously by both the SIS and DCS, how should the wiring be arranged?
Standardly, it is advisable to use pneumatic valves. Even if you say there are no mandatory requirements, are there actually electric valves that have passed SIL certification? If so, will things like travel time meet the operational requirements?
How to ensure that SIS actions take precedence over DCS, and how to guarantee power supply
For independence, it’s better to control the valves separately using SIS and DCS
Check Denso’s terminal blocks: in addition to the forward/reverse/stop terminals (in blue frames), which are used by the DCS, there are also emergency terminals (in red frames) that can be connected to the SIS; these allow the valves to be closed forcibly, giving priority to the SIS signals over those from the DCS. I have used Denso with SIS certification.
For the SIS valve, the required response time is 0.1 milliseconds; electric valves cannot meet this requirement, right?
GB50770-2013 7.1.2 Pneumatic control valves are preferred for final components, while electric control valves are not recommended.
Indeed. However, individual tank areas may not have instrument air (such as refined oil), and electrical actuators can only be used. If there are circuits rated as SIL, reliance can only be placed on Denso.
SIS systems that are handled as safety shutdowns are unlikely to have control valves.
It can be said that the vast majority are pneumatic quick-cut valves, but I have indeed seen designs that function both as control valves and as interlock valves.
This post was last edited by hfrs on 2021-1-12 at 13:44. It’s a bit ridiculous – things that aren’t strict enough wouldn’t be included in SIS, and since they’re on SIS, the standards must be quite strict. Can’t a sis use an electric valve, right? Leaving the regulations aside, how can fault-safe interlocking be achieved? Do you really need to equip the electric valve with a UPS as well? Furthermore, the closing time of the electric valve is generally around 30 seconds; then what is the purpose of feeding it into the SIS? Connecting an electric valve to SIS is nonsense.