Mitsubishi Electric MELSEC iQ-R Series - Page 33

4 PRECAUTIONS FOR USE OF SAFETY PROGRAMMABLE CONTROLLER
4.1 Precautions for Designing Safety Application
31
4
■Using two Safety CPUs and two safety remote I/O modules (connecting extension module to
both modules)
Connect the emergency stop switch to the main module of the safety remote I/O module. Connect the safety relay to both of
the extension modules of the safety remote I/O module. Safety CPU controls safety communications between Safety CPUs
and safety relay on/off according to the input from the emergency stop switch.
• PFDavg/PFH of A: Sum total of the PFDavg/PFH values of two Safety CPUs (paired with the safety function module) (A1
and A2) on the safety path.
• PFDavg/PFH of B: PFDavg/PFH value when connecting the extension module (B2) to the main module (B1)
• PFDavg/PFH of C: The safety relay is connected to the safety programmable controller (1) and (2), so that add PFDavg/
PFH value of the safety remote I/O module that the safety relays are connected to. Note, however, that the safety relay
connected to the safety programmable controller (1) is connected to the safety remote I/O module that is same as B.
Therefore, adding the PFDavg/PFH of the safety programmable controller (1) safety remote I/O module to the PFDavg/PFH
of C is unnecessary (A safety device can be added for only once per safety path). Therefore, the value becomes PFDavg/
PFH value of the safety remote I/O module of the safety programmable controller (2). The PFDavg/PFH value of the safety
remote I/O module of the safety programmable controller (2) becomes the PFDavg/PFH value when connecting the
extension module (C2) to the main module (C1).
• PFDavg/PFH of D: PFDavg/PFH value of the emergency stop switch
• PFDavg/PFH of E: sum total of PFDavg/PFH value of two safety relays (E1 and E2) in safety application
PFDavg = (PFDavg of A1) + (PFDavg of A2) + (PFDavg of B1 and B2) + (PFDavg of C1 and C2) + (PFDavg of D) + (PFDavg
of E1) + (PFDavg of E2)
= (1.02  10
-5
) + (1.02  10
-5
) + (4.66  10
-5
) + (4.66  10
-5
) + (PFDavg of D) + (PFDavg of E1) + (PFDavg of E2)
= (1.14  10
-4
) + (PFDavg of D) + (PFDavg of E1) + (PFDavg of E2)
PFH = (PFH of A1) + (PFH of A2) + (PFH of B1 and B2) + (PFH of C1 and C2) + (PFH of D) + (PFH of E1) + (PFH of E2)
= (5.50  10
-9
) + (5.50  10
-9
) + (4.78  10
-9
) + (4.78  10
-9
) + (PFH of D) + (PFH of E1) + (PFH of E2)
= (2.06  10
-8
) + (PFH of D) + (PFH of E1) + (PFH of E2)
C2B2
A1
A2
E2E1
D
B1 C1
Input Output
Emergency
stop switch
Safety
relay
Safety
relay
Output