Vega VEGAFLEX 86 Operating Instructions Manual

Also see for VEGAFLEX 81: Mounting instructions Operating instructions Quick setup guide Operating instructions Operating instructions

Contents

Vega VEGAFLEX 86 Operating Instructions Manual Manual pdf 27 page image

276 Functional safety (SIL)VEGAFLEX 86 • 4 … 20 mA/HART two-wire44231-EN-1404306 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 (IEC 61062 - Ma-chines), which set the standard for uniform and comparable judge-ment of instrument and plant or machine safety and hence contributeto worldwide legal certainty. Depending on the degree of required riskreduction, we distinguish between four safety levels, from SIL1 for lowrisk to SIL4 for very high risk (SIL = Safety Integrity Level).6.2 SIL qualificationWhen developing instruments which can be used in safety-instru-mented systems, the focus is on avoiding systematical as well asdetermining and controlling random errors.Here the most important characteristics and requirements from theperspective of functional safety according to IEC 61508 (Edition 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 for func-tional safety (Safety Manual). Here, you can find all safety-relevantcharacteristics and information required by the user and planner forplanning and operating the safety-relevant system. This document isattached to each instrument with SIL rating and can be also retrievedvia the serial number search on our homepage.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, IEC 61511 and IEC 61062. Take note of thespecifications in the Safety Manual.The following inputs/outputs are permitted:Additional characteristicsand requirements