HIMatrix Appendix
HI 800 023 E Rev. 1.01 Page 67 of 72
Appendix
Increasing the SIL of Sensors and Actuators
Safety-related HIMatrix controllers are used in safety applications up to SIL 3. This
requires that the sensors and actuators (signalers and actuating elements) in use also
achieve the required SIL.
In some cases, sensors or actuators may not be available for the requirements defined in
the application, such as process value, range of value, SIL, etc. If this is the case, proceed
as follows:
For inputs: Use any of the available sensors that meet all of the requirements with the
exception of the SIL value. Use enough of them such that their combination provide an
input signal with the required SIL.
For outputs: Use any of the available actuators that meet all of the requirements with the
exception of the SIL. Use enough of them such that their combination affects the
process with the required SIL.
With inputs, associate the values of the individual sensors and their status information with
a part of the user program such that a global variable with the required SIL results from this
combination.
With outputs, distribute the value of a global variable among multiple outputs such that the
process adopts the safe state if a fault occurs. Further, the combination of actuators must
be able to affect the process in the required manner (for example, the serial or parallel
connection of valves).
For both inputs and outputs, design the system to have the required number of sensors and
actuators for a given process variable until the greatest possible degree of safety is
achieved for the process. Use a calculation tool to determine the SIL.
i
The use of multiple sensors and actuators for inputting or outputting a single
signal as
described here is only intended as a means of increasing the SIL. Do not confuse this with
the use of redundant inputs or outputs for improving availability.
For information on how to achieve the required SIL for sensors and actuators, see IEC
61511-1, Section 11.4.
To Next Page
Loading...
Need help?
General
