Page 162 - Root Cause Failure Analysis
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150 Root Cause Failure Analysis
Figure 11-4 Batch-type mixer uses single or dual screws to mix product (Thomas Register
Z995).
PERFORMANCE
Unlike centrifugal pumps and compressors, few criteria can be used directly to deter-
mine mixer effectiveness and efficiency. However, the product quality and brake
horsepower are indices that can be used to indirectly gauge performance.
Product Quality
The primary indicator of acceptable performance is the quality of the product deliv-
ered by the mixer. Although there is no direct way to measure this indicator, feedback
from the quality assurance group should be used to verify that acceptable perfor-
mance levels are attained.
Brake Horsepower
Variation in the actual brake horsepower required to operate a mixer is the primary
indicator of its performance envelope. Mixer design, whether propeller or screw type,
is based on the viscosity of both the incoming and finished product. These variables
determine the brake horsepower required to drive the mixer, which will follow varia-
Figure 11-5 Combination mixer-extruder (Thomas Register 1995).
