4.5. Application example
Safe CLOSING of a tank farm using the Safe ESD function
Standard PLC controls the overall system for filling the tank. A system fault occurs
if the filling level or the tank pressure exceed the permissible specified level. In this
case, the safety PLC immediately closes the valve for tank filling.
Figure 5: Application example: Overflow protection in a tank farm
4.6. System representation
The representation below shows the simplified design of fail safe unit in SIL version.
Figure 6: Simplified system representation
4.7. Diagnostic function by the operator
In addition to the already available internal diagnostics within the fail safe unit, further
diagnostic features are required by the safety PLC. Once a fault has been detected,
the system has to be checked immediately and the installation has to be put in a
safe state, if required.
14
Safety instrumented system and safety functions with non safety-related actuators
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