Allen-Bradley FlexLogix 1794, Reference Manual

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Publication 1794-RM001G-EN-P - December 2011
SIL Policy 1-3
Proof Tests
IEC 61508 requires the user to perform various proof tests of the equipment
used in the system. Proof tests are performed at user-defined times (for
example, proof test intervals can be once a year, once every two years or
whatever timeframe is appropriate) and include some of the following tests:
•
Testing of all fault routines to verify that process parameters are
monitored properly and the system reacts properly when a fault
condition arises.
•
Testing of digital input or output channels to verify that they are not
stuck in the ON or OFF state.
IMPORTANT
Important Note related to published PFDs.
•
The user must choose the appropriate PFD depending
on combinations and the appropriate 1oo1 or 1oo2
configuration.
•
Descrete and analog inputs must be used in a 1oo2
configuration for SIL 2.
•
Adapters must be used in a 1oo2.
•
Outputs may be 1oo2 in series or 1oo1 monitored by
an input with an external relay as a secondary device to
remove power.
•
Some specialized inputs can only be wired to a single
sensor such as thermocuples and two 1oo1 PFDs must
be used for each.
•
The total PFD for two 1oo1s is the sum of both.
IMPORTANT
The system user is responsible for:
•
the set-up, SIL rating and validation of any sensors or
actuators connected to the ControlLogix/FLEX I/O
control system.
•
project management and functional testing.
programming the application software and the module
configuration according to the description in the
following chapters.
The SIL2 portion of the certified system excludes the
development tools and display/human machine interface
(HMI) devices; these tools and devices are not part of the
run time control loop.
AB Drives