TL;DR
Low blend uniformity means ingredients are not homogenized. Check mixing time, fill level, paddle condition, and the ingredient addition sequence before increasing mixing time.
What you might see
- coefficient of variation above 10% on mixer uniformity test
- ingredient segregation visible in mixer discharge samples
- pellet quality inconsistency from batch to batch
- nutritional analysis varying significantly between samples from the same batch
Likely causes
Mixing time too short for the ingredient density and fill level combination
Mixer overfilled, reducing paddle sweep effectiveness
Worn paddles reducing the intensity of the mixing action
Dense or liquid ingredients added too late in the mixing cycle
Required tools
- Mixer uniformity test kit (tracer method)
- LOTO kit
- Ruler for paddle wear measurement
Safety first
- Lock out the mixer drive before opening any access door or reaching inside the mixer.
- Grain dust inside mixers can reach explosive concentrations. Avoid ignition sources during inspection and do not use pneumatic tools that can create sparks.
Procedure
- 1
Run a mixer uniformity test using tracer analysis (typically salt or methylene blue dye). Sample 10 locations across the batch at end of mixing and measure CV.[1]
- 2
Check the current fill level against the mixer specification. Fill level above 80% of rated capacity significantly reduces uniformity.
- 3
Increase the mixing time by 30 seconds and repeat the uniformity test. Continue until CV drops below 10%.
- 4
Lock out the mixer and inspect paddle condition through the inspection access. Paddles worn below 50% of original dimension should be replaced.
Warning: Lock out the mixer drive before opening any access door or reaching inside the mixer housing. Mixer paddles rotate at moderate speed and cause serious injury. - 5
Review the ingredient addition sequence. Dense micro-ingredients should be added with a carrier grain early in the mixing cycle, not last.[1]
- 6
Check liquid addition spray nozzles for blockage. Blocked nozzles cause liquid to pool rather than spray, reducing dispersion.
- 7
After all corrections, run a final uniformity test and document the results before returning to production.
Sources
Bühler Bühler MWBA Feed Mixer / Blender general technical documentation, Bühler
Feed mixer uniformity testing and paddle maintenance, general feed manufacturing practice (general)
More guides for Bühler Bühler MWBA
How to fix a discharge gate that will not seal on a Buhler MWBA Feed Mixer
A leaking discharge gate wastes ingredient and cross-contaminates batches. Inspect the gate seal and pneumatic actuator, and clean the gate seat before replacing the seal.
How to diagnose mixer drive overload on a Buhler MWBA Feed Mixer
Drive overload means the mixer motor is drawing above rated current. Check fill level, ingredient bulk density, and paddle condition before increasing the motor size.
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