VEGA VEGAFLEX 81 4 … 20 mA_HART two-wire Coax probe With SIL qualification - Manual (Page 27)

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6 Functional safety (SIL)
VEGAFLEX 81 • 4 … 20 mA/HART two-wire
44216-EN-130823
6 Functional safety (SIL)
6.1 Objective
In case of dangerous outages, processing facilities and machines can
cause risks for persons, environment and property. The risk of such
outages must be judged by the plant operator. Dependent thereon are
measures for risk reduction through error prevention, error detection
and fault control.
The part of plant security depending on the correct functioning of
safety-related components for risk reduction is called functional
safety. Components used in such safety-instrumented systems (SIS)
must therefore execute their intended function (safety function) with a
defined high probability.
The safety requirements for such components are described in the
international 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 contribute
to worldwide legal certainty. Depending on the degree of required risk
reduction, we distinguish between four safety levels, from SIL1 for low
risk to SIL4 for very high risk (SIL = Safety Integrity Level).
6.2 SIL qualification
When developing instruments which can be used in safety-instru-
mented systems, the focus is on avoiding systematical as well as
determining and controlling random errors.
Here the most important characteristics and requirements from the
perspective 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 a
defined safe status
•
Determination of the failure probability of the defined safety func-
tion
•
Reliable parameterization with non-safe user environment
•
Proof test
The SIL qualification of components is specified in a manual for func-
tional safety (Safety Manual). Here, you can find all safety-relevant
characteristics and information required by the user and planner for
planning and operating the safety-relevant system. This document is
attached to each instrument with SIL rating and can be also retrieved
via the serial number search on our homepage.
6.3 Application area
The 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 the
specifications in the Safety Manual.
The following inputs/outputs are permitted:
Additional characteristics
and requirements