Pilz PSS SB FT, Basic license - Manual (Page 124)

6-80 Modular Block System: Burner Management
Standard Function Blocks
Timing diagrams
Counting ignition attempts where time is not exceeded
Setting input parameters
•
ITRY = 3: three ignition attempts
• T_V = 150s: time monitoring
SB157
When Bit0 = 1 SB157 is informed that the ignition
transformer was activated. The STEP pulse is created
with each burner start from SB152.
2nd ignition
attempt enabled
(1st ignition set)
A positive edge at SyOK creates a RDY pulse which jumps/loops
back in the cycle control (exists from SB149) and starts the second
ignition sequence.
The
SyOK enable is granted from SB152 after a reset and start.
The RDY and FLAs pulses are set or reset for one program cycle
only.
For a clearer display this has been technically-enhanced and
increased. The
FLAs drop out is detected within one program cycle.
3rd ignition
attempt enabled
(1st ignition set) 2nd ignition
attempt enabled
(2nd ign. set) 3rd ignition
attempt enabled
(2nd ign. set)
When Bit3 = 1 SB157 evaluates the flame monitoring. If the
input FLAs detects a “0” signal, this will be interpreted as an
ignition failure and stored internally.
First ingition failure in
the 2nd set
FLAs = 0, i.e. Flame
monitor responded/
energised.
After the 3rd ignition attempt, no
RDY pulse is created.
The sequence must be started
from the beginning with the initial
step (reset + start of SB152).