I think the best people to answer that would be AB or Siemens guys. Just give them a call, vendors are always more than happy to help.

Electro-hydraulic. Because you will definitely not be using conventional electrical-only motorized valves for safety applications.

And yeah, there is nothing in the standards against using EH valves, because SIL-3 certified valve actuators are available on the market. But application of those is ...

Okay, well, yes volume isolation needs to be enforced for pipeline applications.

MOV's MAY be used for shutdown applications, there is a variety of SIL-3 certified EH valves available on the market with spring return (enabling fail-safe position). You just have to take notice of your process ...

No, there shouldn't be an impact when you're using the PLC in FULL REDUNDANT configuration. Depends up to what level you are enforcing the redundancy. If you're using redundant I/O modules but a single processor, then obviously there's going to be an impact on the scan time. But if you use full ...

What do you mean by RBV?

That would be the SIL rating of that particular loop, not specifically of the SYSTEM HARDWARE. I just presumed we were talking about the system hardware.

Just a thought - first, the level of redundancy does not imply a safer system. Even a simple redundant system can be safer than a QMR system (as proven by many FMEDA reports that can be viewed from websites of system vendors, including Invensys). If a system in rated for the particular SIL level ...

Ali, having redundant SOVs on the same shutdown valve will not enhance the safety factor of the valve in any way. Even the idea of eliminating the 'single point of failure' is a little abstract. Your SOVs on a shutdown line will be Fail-Close, and so will the SDVs, so by adding another SOV, you're ...