SIL 2/3
Functional safety is a crucial part of plant safety in the process industry. In order to ensure plant safety, most plant operators follow IEC 61508/61511. These rules and standards provide normative guidelines for ensuring the safe operation of process equipment. KROHNE supports its customers with measuring solutions and advice on plant safety. Below is a brief description of the key basic principles for safety loops.
Below is a brief description of the key basic principles for safety loops and what exactly the SIL 2/3 safety integrity level stands for.
Definition of Safety Integrity Levels
SIL stands for Safety Integrity Level and indicates the safety level on a device. The standards set out four safety integrity levels for minimising the risks of equipment. For example, a safety function designed in accordance with SIL 1 reduces the plant risk by a factor of 10-100, a function designed in accordance with SIL 2 reduces the plant risk by a factor of 100 – 1000, etc
A safety function (SIS – Safety Integrated Function) as per IEC 61508 essentially consists of three components:
sensor technology that has to identify a critical state in a plant component
(e.g. pressure or temperature sensors to identify overpressure or a critical temperature).a safety system, which uses the sensor technology to identify and assess the critical plant state, and if necessary trigger safety measures to render the plant safe.
actuator technology which allows the plant to achieve a safe state
(e.g. gates to shut down plant components, or shut-off valves to stop the flow of material).
What the SIL logos mean
This means that the hardware of the field instrument is certified in SIL 2, whereas the software is certified in SIL 3. Thus these devices can be used in a single channel (1oo1) in SIL 2 and in two channels (1oo2) in SIL 3 applications.