TL;DR
Worn or broken screens pass oversize particles and reduce throughput. Measure hole diameter and screen thickness, then replace when beyond the wear limit.
What you might see
- particle size increasing beyond specification
- throughput dropping for the same motor load
- screen holes enlarged or torn visible on inspection
- oversize particles passing through to the next process step
Likely causes
Normal wear from grain abrasion enlarging screen holes over service hours
Screen fracture from metal contamination or foreign object impact
Incorrect screen material for the abrasive ingredient being processed
Screen fastening loose, allowing screen to vibrate and wear at the edge
Required tools
- Pin gauge or calipers for hole measurement
- Micrometer for web thickness
- LOTO kit
- Replacement screens (correct hole size and material)
- Torque wrench for screen fasteners
Safety first
- Hammer mill hammers are extremely dangerous. Lock out and confirm full stop before reaching inside. Hammer mills coast for a long time after shutdown.
- Grain dust in the hammer mill housing reaches explosive concentration during operation. Do not use open flame or generate sparks near the mill.
Procedure
- 1
Lock out the hammer mill and remove the screen access cover.
Warning: Hammer mill hammers are heavy and sharp. Lock out and confirm zero rotation before reaching inside. Hammer mills coast for an extended time after shutdown. Grain dust inside is a fire and explosion hazard. - 2
Remove the screen half-sections and inspect each for cracks, torn holes, or visible thinning.[1]
- 3
Measure hole diameter at 10 locations per screen section using a calibrated pin gauge or calipers. Compare to the nominal hole diameter. Holes enlarged beyond 10% of nominal should trigger replacement.
- 4
Measure screen web thickness at the thinnest areas. Replace screens at or below the minimum web thickness for the material.[1]
- 5
Inspect the screen retaining hardware. Loose clamps allow screen movement and accelerate edge wear. Tighten or replace as needed.
- 6
Install replacement screens of the correct hole size and screen material. Secure all retaining hardware to specification torque.
- 7
Run the mill on a short test batch and confirm particle size distribution meets specification before returning to full production.
Sources
Bliss Industries Bliss Eliminator Hammer Mill general technical documentation, Bliss Industries
Hammer mill screen inspection and replacement, general feed ingredient grinding practice (general)
More guides for Bliss Industries Bliss Eliminator
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How to recover throughput on a Bliss Eliminator Hammer Mill
Throughput drops when screens are worn, hammers are flipped past their service limit, or the feed rate exceeds the mill's rated capacity. Inspect screens and hammers, and verify the feed rate against the mill nameplate.
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