Siemens SITRANS P500, Руководство по эксплуатации, Страница: 174 / 238

Functional safety
7.5 Safety characteristics
SITRANS P500 with HART
174
Operating Instructions, 12/2014, A5E02344528-09
See also
Simulation (Page 158)
7.5 Safety characteristics
The safety characteristics necessary for using the system are listed in the "SIL declaration of
conformity". These values apply under the following conditions:
● The SITRANS P pressure transmitter is only used in applications with a low demand for
the safety function (low demand mode).
● Communication with the HART protocol is used only for the following:
–
Device configuration
– Reading diagnostics values
– However, it is not used for operations critical to safety. In particular, the simulation
function must not be activated in safety-related operation.
● The safety-related parameters/settings have been entered by local operation or HART
communication before commencing safety-related operation. Check the
parameters/settings on the device display. See Settings (Page 172).
● The safety function test has been concluded successfully.
● The pressure transmitter is blocked against unwanted and unauthorized
changes/operation.
● The current signal of 4 to 20 mA of the pressure transmitter is evaluated by a safe
system. The lower and upper fault currents ( ≤ 3.6 mA/≥ 21 mA) are monitored.
● Fault rates are calculated on the basis of a mean time to repair (MTTR) of eight hours
(order option C20).
7.6 Maintenance/Checking
Interval
We recommend that the functioning of the pressure transmitters be checked at regular
intervals of one year.
Checking the safety function
Check the safety function as detailed in the chapter Settings (Page 172).
Checking safety
You should regularly check the safety function of the entire safety circuit in line with IEC
61508. The testing intervals are determined during the calculation for each individual safety
circuit in a system (PFD
AVG
).