Build-up that isn't cleared compounds: it raises torque, unbalances the bowl, and eventually packs off into a hard stop and a manual dig-out. Almost every “bowl packed” call-out traces back to a missed or rushed flush.
Inadequate or skipped flush at shutdown — cake left to harden. The classic cause.
Pool too deep / feed too high, packing the bowl during the run.
Long runs on sticky feed without a clean-out cycle.
Sticky, high-LGS or gelled feed that adheres to the bowl wall.
Solids in faster than the scroll conveys out, accumulating on the bowl wall.
How to diagnose it
Compare current empty-bowl torque / vibration baseline against the clean reference.
Inspect flush records — was clean-out logged each shutdown?
Open and inspect the bowl interior at the next opportunity for hardened cake.
Check scroll clearance and flight condition.
The fix — step by step
Flush the bowl to clean at every shutdown — make it a logged step, not an optional one.
Keep feed within conveying capacity and pool no deeper than the duty needs.
On sticky feed, schedule periodic clean-out cycles within long runs.
Repair or replace worn scroll components that prevent a clean sweep.
Confirm it's fixed
✓ Verify: Empty-bowl torque and vibration back to the clean baseline after a full flush; the flush is logged every shutdown.
Field note. The flush log is the cheapest insurance on the rig. A two-minute flush at shutdown prevents the four-hour dig-out — yet it is the first step that gets skipped on a busy tour. If the flush isn't logged, assume it didn't happen.