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Safety concept
4 Safety
Instruction book, IQAN-MC3
The IQAN-MC3 provides some diagnostic features related to the interface with sensors
and actuators (valves). However, sensors, actuators, and wiring must be analyzed
separately for their suitability to be used in safety functions.
The internal diagnostics of the IQAN-MC3 as well as built in diagnostics on I/O are
dependent on the system cycle time, a longer system cycle will in some cases delay the
diagnostics.
Architecture for a complete safety function
When analyzing a safety function, the IQAN-MC3 can be modeled as a safety related
sub-system. With this approach, there would also be at least one safety related input
subsystem (e.g. sensors), and a safety related output subsystem (e.g. valves).
The IQAN-MC3 module as subsystem.
Input subsystem
The input subsystem consists of the sensors or operator controls that initiate the safety
function.
To get sufficient diagnostics on the inputs on the MC3, the requirements of that input
type must be satisfied, see section I/O functionality, on page 28. For most input types,
there is a requirement to always use the signal in pair with a secondary redundant
signal.
The IQAN-MC3 is suitable for connection to input subsystems of category 2, 3 or 4 in
accordance with EN ISO13849-1, up to PLd. If inputs are connected as a Category B
subystem, that will restrict the overall PL to a lower level.
A category 1 subsystem is excluded because the unit is requiring simple electrical
inputs (connected to DIN) to be used in pair with a diagnostic signal.
MC3-SMR-004:A System cycle time
The application shall be designed so that the system cycle time is < 50% of the
maximum allowable error detection time.
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