Safety Integrity Level (Sil) - Siemens SITRANS P DS III Operating Instructions Manual

Functional safety

8.2 Safety Integrity Level (SIL)

Disregarding conditions for fulfilling the safety function
Disregard can result in a malfunction of the process plant or application, e.g. process
pressure too high, maximum level exceeded.
The mandatory settings and conditions are listed in chapters "Settings (Page 132)" and
"Safety-related characteristics (Page 132)".
Please observe the applicable conditions to ensure the safety function.
Safety-instrumented system in single-channel operation (SIL 2)
Image 8-1
The combination of pressure transmitter, automation system and final controlling element
forms a safety-instrumented system that performs a safety function. The emphasis of this
description is on the pressure transmitter. For information on requirements for the
automation system or final controlling element, please refer to the corresponding standards.
The pressure transmitter generates a process-related measured value that is transferred to
the automation system. The automation system monitors this measured value. If the
measured value violates the high or low limit, the automation system generates a shutdown
signal for the connected final controlling element, which switches the corresponding valve to
the specified safety position.
Only one SITRANS P DS III device is required for single-channel operation for SIL 2.
8.2 Safety Integrity Level (SIL)
The international standard IEC 61508 defines four discrete Safety Integrity Levels (SIL) from
SIL 1 to SIL 4. Every level corresponds to a probability range for the failure of a safety
function.
130
WARNING
Safety-related system for pressure transmitters in single-channel operation
SITRANS P DS III/P410 with PROFIBUS PA
Operating Instructions, 02/2016, A5E00053276-08