
70 Control for Aluminum Production
TABLE5.1 (Continued)
Common Process Disturbances, Signs, and Responses in Smelting Potlines
Issue/
Mechanism Possible Causes Earliest Signs
Triggers—Stop
Now
Consequences of
Loss of Control
Response to Avoid
the Event
Response (Damage
Limitation)
Low Superheat
(6°C or less)
High metal
height, or shifts
to higher metal
Low bath, hard
crust at anode set.
Swings in
T/AlF3%,
highalumina
feed (cusum)
Not holding bath
level, despite
additions.
Anode ‘bath’
spikes or
deforms
High instability and
power input, with
pots at high
superheat
Detect T/AlF3%
abnormality,
increase power,
reduce metal level.
Reduce alumina
feed ...