K-Patents DD-01 - Manual (Page 17)

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2. When both refractometers read dissolved solids content 58% (default) or below, an auto-
matic black liquor diversion must take place.
Either option is satisfactory.
The rules are listed in decreasing order of security. Only rule 1 satisfies the high safety requirements set by
BLRBAC, August, 1982. On the other hand, the probability of false trips decreases with decreasing safety. It
means that if false trips are too frequent, the rule 2 may be preferred at the cost of safety. The rule 2 has later
been accepted by BLRBAC.
A third conceivable alternative is to base the decision on only one refractometer (the master) and use the other
refractometer (the slave) for comparison only (and difference alarm). Concerning security and false trips, this
rule is a compromise between rules 1 and 2.
The divert decision rule is selected by the switch SW on the divert control board (Figure 3.13). ON position is
upwards.
Switch SW
SW1 SW2
Rule
OFF OFF One-of-two (BLRBAC) Rule 1
ON OFF A master, B slave -
OFF ON B master, A slave -
ON ON Two-of-Two Rule 2
Table 5.70 Divert decision rule selection.
ONLY ONE REFRACTOMETER IN OPERATION:
When only one instrument is IN OPERATION the divert action takes place if this instrument reads 58 % or
below. The status of SW (Table 5.70) has no influence on the divert decision in this case.
NO REFRACTOMETER IN OPERATION:
If both instruments are out of operation (due to malfunction or maintenance), then according to BLRBAC
divert action must take place. See also Section 8.7 about external DC supply.
REMOTE DIVERT SWITCH CONFIGURATION
Switch SW Rule
SW 3
OFF DD-01 normal operation
ON Remote divert card activated
See Section 8.8.
See Section 5.2 if you have on the screen the message DIVERT CONTROL FAULT.
INSTRUCTION MANUAL FOR DD-01 DOCUMENT/REVISION: IMD 1/5
Effective: June 20, 2005