Vega VEGAFLEX 82 Operating Instructions Manual

Also see for VEGAFLEX 82: Safety manual Supplementary instructions Quick setup guide Operating instructions Operating instructions

Contents

Vega VEGAFLEX 82 Operating Instructions Manual Manual pdf 27 page image

276 Functional safety (SIL)VEGAFLEX 82 • 4 … 20 mA/HART - two-wire44222-EN-1702206 Functional safety (SIL)6.1 ObjectiveIn case of dangerous failures, processing facilities and machines cancause risks for persons, environment and property. The risk of suchfailures must be judged by the plant operator. Dependent thereon aremeasures for risk reduction through error prevention, error detectionand fault control.The part of plant safety depending on the correct functioning ofsafety-related components for risk reduction is called functionalsafety. Components used in such safety-instrumented systems (SIS)must therefore execute their intended function (safety function) with adefined high probability.The safety requirements for such components are described in theinternational standards IEC 61508 and 61511, which set the standardfor uniform and comparable judgement of instrument and plant (ormachine) safety and hence contribute to worldwide legal certainty.We distinguish between four safety levels, from SIL1 for low risk toSIL4 for very high risk (SIL = Safety Integrity Level), depending on therequired degree of risk reduction.6.2 SIL qualificationWhen developing instruments that can be used in safety-instrument-ed systems, the focus is on avoiding systematical errors as well asdetermining and controlling random errors.Here are the most important characteristics and requirements fromthe perspective of functional safety according to IEC 61508 (Edi-tion 2):• Internal monitoring of safety-relevant circuit parts• Extended standardization of the software development• In case of failure, switching of the safety-relevant outputs to adefined safe state• Determination of the failure probability of the defined safety func-tion• Reliable parameterization with non-safe user environment• Proof testThe SIL qualification of components is specified in a manual on func-tional safety (Safety Manual). Here, you can find all safety-relevantcharacteristics and information the user and the planner need forplanning and operating the safety-instrumented system. This docu-ment is attached to each instrument with SIL rating and can be alsofound on our homepage via the instrument search.6.3 Application areaThe instrument can be used for point level detection or level measure-ment of liquids and bulk solids in safety-instrumented systems (SIS)according to IEC 61508 and IEC 61511. Take note of the specifica-tions in the Safety Manual.Additional characteristicsand requirements