TL;DR
Worn rollers reduce pelleting efficiency and pellet durability. Measure roller-to-die gap and inspect roller surface. Replace when gap exceeds the maximum or surface is deeply grooved.
What you might see
- pellet durability index declining
- motor current dropping without throughput change
- die-to-roller gap increasing on the gap gauge
- fines increasing in the pellet discharge
Likely causes
Normal progressive wear on the roller surface from die-contact friction over service hours
Abrasive ingredients (minerals, sand-contaminated grain) accelerating roller wear
Roller operating with insufficient lubrication, increasing wear rate
Incorrect roller-to-die gap setting allowing metal-to-metal contact
Required tools
- Gap gauge for roller-to-die measurement
- Grease gun
- Pellet durability tester
- LOTO kit
Safety first
- Lock out before opening the die access or reaching near the rollers.
- Die and rollers are hot during operation. Confirm cool-down before any contact.
Procedure
- 1
Measure pellet durability index on current production and compare to the baseline for this formula. A declining durability trend indicates reduced compaction from roller wear.[1]
- 2
Lock out the pellet mill and open the die access door after allowing the die to cool below 60 deg C.
- 3
Measure the roller-to-die gap with the gap gauge at four positions around each roller. Compare to the recommended gap range.[1]
- 4
Inspect the roller surface for deep circumferential grooves. Grooves deeper than 3 mm reduce the effective gripping surface and require roller replacement.
- 5
Check roller bearing lubrication through the grease fittings. Add grease per the lubrication schedule if overdue.
- 6
If gap is beyond the adjustment range and surface wear is advanced, replace rollers in matched pairs to maintain balanced die loading.
- 7
After roller replacement, set the gap per the recipe specification and run a pellet quality check before full production.
Sources
CPM California Pellet Mill CPM 7900 / 7700 Pellet Mill (Feed) general technical documentation, CPM California Pellet Mill
Pellet mill roller wear assessment and replacement, general feed pelleting practice (general)
More guides for CPM California Pellet Mill CPM 7900 / 7700
How to clear die hole plugging on a CPM 7900 Pellet Mill
Plugged die holes stop pellet extrusion and back-pressure the die. Clear the holes immediately with a die punch, and investigate moisture or temperature conditions that caused plugging.
How to diagnose main shaft bearing wear on a CPM 7900 Pellet Mill
Main shaft bearing wear causes excessive vibration and can lead to die-to-roller misalignment. Measure vibration and check bearing temperature at each scheduled inspection.
Stop fixing the same fault twice.
Dovient turns guides like this into your team's shared playbook, with AI that catches recurring issues before they break the line.