Timeline for What is the actual difference between a control function with Securtiy Integritiy Level (SIL) II and one without?
Current License: CC BY-SA 4.0
5 events
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| Jul 4, 2019 at 2:18 | answer | added | Ohio ChemE | timeline score: 1 | |
| Jan 25, 2019 at 19:23 | comment | added | alephzero | You don't know what reliability you need from the components till AFTER you have assessed the complete system. For example, consider what happens if the only purpose of the sensor and controller is the stop the tank filling, and there is an adequate overflow system. So far as the water level is concerned, the reliability of the sensor and controller is now irrelevant. Their only function is to prevent wasting water. | |
| Jan 25, 2019 at 12:21 | comment | added | mart | This is of course correct. I'm mostly asking about control systems because that's the part I understand the least. | |
| Jan 25, 2019 at 11:40 | comment | added | alephzero | The SIL risk assessment should apply to the complete system, not to individual components (ref: IEC 61508) Also "SIL" strictly speaking only applies to electrical components. As a trivial (but not unrealistic) example, if your system could be exposed to temperatures below 0C, your "SIl II certified PLC" etc won't prevent failure from burst pipes when the temperature rises again! IEC62061 may be more relevant than IEC 61508 for the complete system. | |
| Jan 25, 2019 at 8:59 | history | asked | mart | CC BY-SA 4.0 |