S5-95F
S5-95F Failsafe Mini PLC
•
Danger prevention
G1: Possible under certain conditions
G2: Hardly possible
•
Probability of undesired events arising
W1: Very low
W2: Low
W3: Relatively high
Example:
Power plant burner control
The protection equipment of a power plant burner control must avoid gathering of an
explosive gas-air mixture in the combustion chamber.
The undesired event is the ignition of the gas-air mixture resulting in the explosion of the firing plant.
The death of several persons must be reckoned with if persons stay in the hazardous area (S3).
In our case, we assume that persons stay only seldom in the hazardous area (A1).
Without protection equipment, the probability of the undesired event arising is relatively high (W3).
According to the risk graph, this results in quality level 6.
Figure 1-2. Burner Control of a Power Plant
G2
G1
A1
A2
A2
A1
S1
S3
S2
S4
2
3
4
5
6
7
8
W3
1
Quality level
G2
G1
EWA 4NEB 812 6210-02
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