Functional safety
8.2 Safety Integrity Level (SIL)
SITRANS P DS III with PROFIBUS PA
130 Operating Instructions, 06/2013, A5E00053276-07
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 133)".
Please observe the applicable conditions to ensure the safety function.
Safety-instrumented system in single-channel operation (SIL 2)
Figure 8-1 Safety-related system for pressure transmitters in single-channel operation
The combination of 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 transmitter. For information on requirements for the automation system or final
controlling element, please refer to the corresponding standards.
The 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.
Certificates (http://www.siemens.com/processinstrumentation/certificates)
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.
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