Pilz PSS SB FT, Basic license - Manual (Page 61)

Modular Block System: Burner Management 6-17
• SB158: IGNITION for deciding about pilot flame monitoring.
• SB159: RUN for decision about monitoring the main flame.
• SB255: To call up the operating system.
Programming guidelines
• ENBL
The enables for all SB150 blocks must be AND-connected in the
application program after being called up. The result of this bit operation
must be supplied to the input parameter
FLAs of SB152 “Burner: Start
and operator elements”.
The enables of the active SB150 blocks for pilot flame monitoring must
be supplied and additionally AND-connected to the input parameter
FLAs of SB157 “Ignition attempts”, if SB157 is used.
A programming example can be found in Chapter 8 under “Managing
enables”.
• Main flame monitoring after an error
If the main flame is in the operating position and the plant is shutdown
because an error occurs (e.g. monitor sequence broken), the flame
monitor receives the command to check the flame for “flame established”
in the next cycle. On some plants, the flame does not extinguish
immediately after switch-off i.e. within a cycle. In these cases, a fault will
result. To avoid this, a time
D_V can be started via step (SB149) when a
negative edge at the plant enable ( ENBL of SB152) is detected. During
this time, the flame monitor will not be evaluated ( MONI = 0). After this
time cycle SB159 “Run” assumes control of flame monitoring.
Programming example:
LN M74.00 .ENBL SB 152
U M73.01 .Auxiliary flag, negative edge ENBL
= M73.02 .Pulse flag
R M73.01 .Auxiliary flag, negative edge ENBL
L M74.00 .ENBL SB 152
S M73.01 .Auxiliary flag, negative edge ENBL
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