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| 8/6/2021 8:57 AM | |
Joined: 1/1/2017 Last visit: 7/22/2024 Posts: 331 Rating:
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Hi Physme, Yes it will affect the functionality effect as all Standard modules has some defined basic SIL standards. Now you will have to categorise at what process level are you using the modules? Refer the link: https://en.wikipedia.org/wiki/Safety_integrity_level PFD (probability of dangerous failure on demand) and RRF (risk reduction factor) of low demand operation for different SILs as defined in IEC EN 61508 are as follows: SIL PFH PFH (power) RRF 1 0.1–0.01 10ᶺ-1 – 10ᶺ-2 10–100 2 0.01–0.001 10ᶺ-2 – 10ᶺ-3 100–1000 3 0.001–0.0001 10ᶺ-3 – 10ᶺ-4 1000–10,000 4 0.0001–0.00001 10ᶺ−4 – 10ᶺ−5 10,000–100,000 For continuous operation, these change to the following. (Probability of dangerous failure per hour) SIL PFH PFH (power) RRF 1 0. 00001-0.000001 10ᶺ−5 – 10ᶺ−6 100,000–1,000,000 2 0. 000001-0.0000001 10ᶺ−6 – 10ᶺ−7 1,000,000–10,000,000 3 0. 0000001-0.00000001 10ᶺ−7 – 10ᶺ−8 10,000,000–100,000,000 4 0. 00000001-0.000000001 10ᶺ−8 – 10ᶺ−9 100,000,000–1,000,000,000 Hazards of a control system must be identified then analysed through risk analysis. Mitigation of these risks continues until their overall contribution to the hazard are considered acceptable. The tolerable level of these risks is specified as a safety requirement in the form of a target 'probability of a dangerous failure' in a given period of time, stated as a discrete SIL. Regards OmKris |
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