Specifications

OPERATING INSTRUCTIONS Document No. DER04097
Effective Date 27 Nov 07 Page 3 of 7
OPERATION
Monitor the liquid and solids discharges continually to determine operating status of the
centrifuge. Take corrective action if any anomaly is detected such as insufficient solids discharge
and/or repetitive tripping of the overload release assembly. Note that any change in feed rate or
adjustment of pond depth will not produce an immediate response from the centrifuge. It may take
one or more hours of continuous operation before a change appears in the liquid and/or solids
discharges. Continuously monitor the feed condition and liquid and solids discharges to detect
any trend toward conveyor overloading, which may cause tripping of the overload release
assembly.
The following parameters affect centrifuge operation:
• Feed rate
• Pond depth
• Bowl speed
• Conveyor speed
The feed rate and pond depth should be adjusted, as required, to optimize centrifuge operation
and prevent tripping of the overload release assembly. Tripping indicates that the conveyor is
becoming overburdened in moving solids. The conveyor speed is fixed by the gearbox reduction
ratio and varies directly with bowl speed. Consequently, changing the motor sheave diameter
alters both the bowl speed and corresponding conveyor speed. A larger diameter sheave will
increase speed, and a smaller sheave reduces speed. The motor sheave should be replaced only
after feed rate and pond depth adjustments have been unsuccessful in achieving satisfactory
performance of the centrifuge.
Changing the feed rate and/or pond depth should produce the desired clarity of liquid effluent and
solids dryness. Feed rate may be changed while the centrifuge is operating, but pond depth can
be adjusted only with the centrifuge shut down and locked out and tagged out.
The differential speed between the liquid bowl and conveyor can be changed only by replacing
the gearbox. Two gearbox ratios are available: 52:1 and 125:1. Changing the gearbox to the
alternate ratio should be done only after all other options have been unsuccessful in achieving
satisfactory centrifuge operation and after consulting with the Derrick Service Department.
Adjustments
The following paragraphs discuss the effects of changing feed rate, pond depth, bowl and
conveyor speed, and gearbox ratio.
Feed Rate
If slurry is thin, increasing the feed rate may permit a higher processing rate. However, as feed
rate is increased, the operator must check that the conveyor is moving the increased solids
volume. The feed rate should be reduced if the overload release assembly trips repetitively.