Safety Integrity Level (Sil) - Siemens Sitrans P500 Operating Instructions Manual

Functional safety

7.2 Safety Integrity Level (SIL)

1.2 % of 10 meters is 12 centimeters. If process monitoring is set to 9.88 meters, safe
shutdown is guaranteed even in the event of a random individual error within the safety
accuracy.
Note
Use of remote seals
If remote seals are used, the application-specific measurement error is the product of the
pressure transmitter and remote seal measurement errors.
Disregarding conditions for fulfilling the safety function
Disregarding conditions can result in a malfunction of the process system or application, for
example, process pressure too high, maximum level exceeded.
The mandatory settings and conditions are listed in chapters "Settings (Page 172)" and
"Safety characteristics (Page 174)".
Please observe the applicable conditions to ensure the safety function.
Safety-instrumented system in single-channel operation (SIL 2)
Figure 7-1
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 and the lower and
upper fault currents (≤ 3.6 mA/≥ 21 mA) . 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.
7.2 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.
170
WARNING
Safety-instrumented system in single-channel operation
SITRANS P500 with HART
Operating Instructions, 12/2014, A5E02344528-09