ENFORCE32958

• Permit No: M1988112
• IBM Index Class Name: Enforcement
• Doc Date: 4/1/1992
• Doc Name: TAILINGS PH ADJUSTMENT SYSTEM OPERATIONS REVIEW
• Media Type: D
• Archive: No

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~y 7.2 INBTRIIMENTATION MALFUNCTION
I Correct functioning of the following instruments is critical
1 to the safe operation of the pH Adjustment System:
AE/AT 435 pH probe in pH Adjustment Tank discharge
AE/AT 405 pH probe in Fume Scrubber
AE/AT 900/10 HCN detector in scrubber stalk
Failure of either of the pH meters will resul# in loss of
control of the process. Allowing the probes to $ry out will
cause failure. Although the probes are norm{ ly immersed
in solution or slurry, they will be exposed wh~n the plant
is shut down. If a protracted shutdown is expected, the pH
probes should be removed and immersed in water,
Failure of the stack HCN detector will prevent khe operator
from diagnosing faults in the operation of tKe scrubbing
system.
7.3 OPERATOR ERROR
Operator errors leading to potentially hazardou~ situations
include the following:
^ Bypassing interlocks in the control systemiso that the
1 fail-safe design of the system is negated{
J ^ Opening of access hatches or inspection ~orts during
operation, allowing possible escape of HC .
Other operator errors, which may cause shutdown of the
system, but which do not create a hazardous situation,
include:
^ Closing manual valves in the sodium hydrox de delivery
line. This will eventually result in a decease in the
scrubber solution pH to the low-low lev 1, shutting
down the Sulfuric Acid Metering Pump.
^ Closing manual valves in the process waterline to the
scrubber solution reservoir. The solutio~ level will
eventually fall to the low-low point, shutting down the
Sulfuric Acid Metering Pump.
^ Closing manual valves in the sulfuric a id delivery
line to the pH Adjustment Tank. The pH wi~ 1 increase,
and slurry will be discharged to t e tailings
impoundment with higher than normal levels,of cyanide.
pj/1504rp 012591 7-3