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Machinery and Plant Safety
Fail Safe
The evolution of safety standards, with the introduction of UNI EN 13849-1 (PL) and CEI EN 62061 (SIL) in the machinery regulations, has determined a new approach to the design of the fail-safe functionalities both at the construction stage of new plants as well as updating of existing plans.
Righi Elettroservizi SpA has followed this development with particular interest, together with the implications that followed.
The design method proposed by the new standards runs through an interactive process shared with the parties involved, be they machine builders or end users of plans.
Step 1
Identify the dangers existing on the machine: in this phase the characteristics must be established for each safety function.
Step 2
Determine the required Performance Level (PLr). The PLr parameter represents the performance level required for a given safety function, the greater the risk the higher the safety requirement of the control system must be.
Step 3
Define the methods of implementation of the individual safety functions: once the PLr has been estimated, the control system must be designed following criteria that require compliance with this evaluation, then calculate the resulting PL and verify that it is greater than or equal to the PLr.