Safety Integrity Levels (SIL) - a basic introduction
10th Nov 2011
BES South Eastern
Allianz Engineering’s principal engineer, Glyn Amphlett, spoke about SIL
Delegates welcomed back to the region Allianz Engineering’s principal engineer, Glyn Amphlett, who this time delivered a presentation on SIL Levels.
Amphlett offered an overview on SIL, beginning with the principles of a guarding system as a basis for its introduction. He then went on to explain the meaning of SIS (Safety Instrumented Systems), SIF (Safety Instrumented Functions) and PFD (Probability of Failure on Demand), before highlighting the standard, IEC 61508 Functional Safety of Electrical/Electronic/Programmable safety related systems.
Practical examples were discussed, with regards to both older mechanical safety systems and newer electronically monitored safety systems, with the example of over speed governors being used for lifts and water level gauges, with regards to steam raising boilers.
Amphlett then went through some examples of how to establish a SIL, using HAZOP (Hazard & Operational Study) and LoPA, a methodology that was developed to assess SIL requirements of SIF.
The presentation was closed with detailed guidance on SIL, which can be found within BS EN81, the build standard for lifts, and SAFed BG01 Guidance on Safe Operation of Boilers. Finally, the speaker concluded with considerations for this evolving subject.