Pilz PSS SB FT, Basic license - Manual (Page 170)

8-6
Examples
Modular Block System: Burner Management
Using step monitoring time W_E of SB149
W_E as ignition ready time
In burner management the step monitoring time, for example, can be used
as ignition ready time. Within this time, manual ignition must be carried out
and the pilot flame be established. If this is not the case, an alarm is
triggered (
W_E = 1), which must be evaluated by the user.
The alarm signal can, for example, be inversely linked in the AND-operati-
on for the step enabling conditions
COND of the following step or it can be
integrated within the safety sequence.
If integrated within the safety sequence the positive edge
W_E must be
monitored in the application program. The positive edge should set a flag
to “0” for one PSS-cycle. This pulse flag must be supplied to the AND-
operation before the global input
CHAI from SB152 “Burner: Start and
operator elements”.
Example for programming:
L M 70.01 .W_E 1st step
O M 70.02 .W_E 2nd step
O M 70.03 .W_E 3rd step
= M 80.00 .W_E total
L M 80.00 .W_E total
UN M 80.01 .Auxiliary flag pos. edge W_E
=N M 80.02 .Pulse flagW_E
S M 80.01 .Auxiliary flag pos. edge W_E
LN M 80.00 .W_E total
R M 80.01 .Auxiliary flag pos. edge W_E
L M 85.00 .Limiter 1
U M 85.01 .Limiter 2
U M 80.02 .Pulse flag W_E
U M 85.31 .Limiter n
= M 90.00 .CHAI safety sequence
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