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2 Product description
2.5.5
Safety response time SFB
The overall response time of a safety function is made up of the following
individual times:
−
Response time of connected safety switchgear
(see operating instructions safety switchgear)
−
Delay Time Safety fieldbox SFB
−
PROFINET / PROFIsafe transmission time
−
Cycle time F runtime group F-PLC
−
Response time of safety shut-off element (actuator)
For all components installed in the system, the difference between the reaction
time and the watchdog time must also be calculated.
The longest difference time calculated must be added to the sum of all response
times to calculate the "Safety Function Response Time" (SFRT).
WARNING
In addition to the maximum response time of the SFB-PN, the response times of
the connected safety switchgear, the transmission time from PROFINET and the
response times of additional PROFIsafe components (if applicable) must be taken
into consideration.
WARNING
The maximum acceptable response times of the safety functions are defined in
the risk analysis of the machine!
The safety field box (SFB) has the following specifications:
Worst Case Delay Time SFB:
20 ms / 50 ms
(Delay time Input / Output)
Device Watchdog Time SFB:
10 ms
(Device_WD)
General information about the "Safety Function Response Time" (SFRT)
The "Safety Function Response Time" (SFRT) is the maximum time in which the
safety system responds to changes in input signals or to module errors.
In order to calculate the response time of a safety function, the overall system from
the safety switching device to the actuator must always be considered.
(see also DIN EN IEC 61784-3-3)
Worst Case
Delay Time
(Bus)
Worst Case
Delay Time
(Input)
Worst Case
Delay Time
(Process)
Worst Case
Delay Time
(Bus)
Worst Case
Delay Time
(Output)
Device_WD
F_WD_Time1
F_Host_WD
F_WD_Time2
Device_WD
Total Worst Case Delay Time = TWCDT
Longest
∆
T_WD
Safety Function Response Time = SFRT = TWCDT +
∆
T of the longest „Watchdog Time“
Safe state
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