Pilz PSS SB FT, Basic license - Manual (Page 112)

6-68 Modular Block System: Burner Management
Standard Function Blocks
The cycle is enabled with the
SyOK input.
A 0 signal at this input sets
the outputs in a safe state
and the
RDY output to 0.
Exhaust valve present, V4?
must = 1.
With the control byte at the
NEXT input, the individual
steps are enabled.
During the whole cycle
SyOK must remain = to 1.
The RDY output in byte
format indicates the current
status of SB156.
The individual bits from this
byte must be linked with the
corresponding step block, so
that a timed cycle of the
outputs results. The length
of time of the individual
RDY
bits and as such the total
cycle will be determined
from the 0-1 edges of the
NEXT input bit.
Exhaust valve opened. The gas flues
will expand and the minimum
pressure monitor sets the
P- input.
The bit 1 from NEXT closes the valve
and the test time begins. Before bit 2
from
NEXT is set, the P- input must
have been a constant “1” for the
length of the first test time of
VAV1.
The corresponding test time must be
set by the user via setting the
parameters for an SB149 block.
The
GP- output signals: “seal check
for VAV1” is active.
VAV1 opens when bit 2 from the NEXT input is set, the
path between the safety valves
VAV1 and VAV3 will be
filled with gas and brought up to operating pressure P+.
After VAV1 is closed again via bit 3 from NEXT, the test
time for VAV3 and VAV4 begins. Before bit 4 from NEXT is
set, the P+ input must have been at a constant “1” for the
length of the test time of VAV3 and VAV4. The
corresponding test time must be set via parameters of a
SB149 block.
The
GP+ output signals: “seal check for VAV3 and VAV4” is
SB156