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DPFs: the ash regeneration leaves behind, and the second bath that removes it

Why single-bath DPF cleaning returns filters that still gauge down — and the documented two-chemistry process that restores flow.

6 min readBy Misonics application engineers

A diesel particulate filter is a ceramic honeycomb with thousands of blind channels — soot burns off in regeneration, but the ash never leaves. This study documents the two-bath ultrasonic process developed from a filter specialist’s enquiry: carbon stage, ash stage, flow-tested result.

Industry
Transport · diesel service · filtration
Components
DPFs and DOCs, ceramic substrate
Contamination
Soot · lubricant ash · oil contamination
Machine
Industrial ultrasonic tank
Chemistry
Carbon stage + RegeniK ash stage
Verification
Flow test vs baseline

The contamination

Soot and unburnt carbon

The combustion load — heavy in filters off failed-regen vehicles, oil-soaked where a turbo or injector let go. Alkaline carbon chemistry territory.

Lubricant ash

The one regeneration cannot touch: mineral ash from burned oil packs the channel ends and blinds the substrate permanently. This is what the second bath exists for.

The blind-channel geometry

Alternately plugged channels mean every flow path is a blind hole. Only a process that works inside blind geometry — cavitation — cleans it without cutting the can open.

The process

Process diagram
LOADparts in basketSTAGE 1 · CARBONUltrasonic carbon stripalkaline carbon chemistrysoot & oil load removedSTAGE 2 · ASHRegeniK ash stageash chemistry attackspacked mineral residuein channel endsSTAGE 3 · FLUSHDirectional flush rinsefreed ash driven outof blind channelsSTAGE 4 · DRY + FLOW TESTDry & verifycontrolled dryflow vs clean baselinedocumented per filterRESULTverified & loggedTwo chemistries because two soils: carbon strips in the alkaline stage, but ash needs its own chemistry — one bath cannot do both jobs.
ParameterValue
Stage 1 chemistryAlkaline carbon formulation
Stage 2 chemistryRegeniK — the ash-stage product
Temperature / cycleEstablished per application
VerificationFlow test against clean-filter baseline; result recorded per filter serial
Substrate carePower and exposure limited for ceramic substrate; no caustic attack on washcoat

The results

Flow restored and proven. Every filter leaves with a flow-test number against baseline — not a visual opinion.
Ash out, not just soot. The two-bath sequence removes what regeneration and single-bath processes leave behind.
Substrate intact. No cutting, no burnout thermal shock, no rodding damage — the filter that arrives is the filter that returns.
A service product with a certificate. The flow sheet per serial is the customer deliverable — and the reorder reason.

Hardware and chemistry

Industrial ultrasonic tank for DPF service

Two-bath DPF cell

Paired industrial tanks — carbon stage and ash stage — with flush and drying, sized to the largest truck filter in the program.

Ask about DPF cell sizing →
RegeniK ash-stage chemistry, 5 litre

RegeniK

The ash-stage product: formulated for the mineral residue regeneration leaves behind, safe on ceramic substrates.

View the product, SDS and TDS →
Why two baths win: shops running a single carbon bath return filters that still gauge down on flow — the ash never left. The second bath is the difference between "cleaned" and "restored", and the flow test proves it to the customer.
FAQ

Questions about this process

Why do single-bath cleaned DPFs still gauge down?
Regeneration burns soot but never removes lubricant ash. Ash packs the channel ends and blinds the substrate. A carbon bath alone leaves it there.
What does the second bath do?
RegeniK attacks the packed mineral residue in the channel ends. A directional flush then drives the freed ash out of the blind channels, and a flow test against baseline proves the result per filter.
Why ultrasonics for a DPF?
Every flow path in the honeycomb is a blind hole. Cavitation works inside blind geometry, so the filter is cleaned without cutting the can open.

To run this process in your own workshop, see DPF cleaning machines for workshops.

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Tell us what the part is, what comes off it, and what it has to pass. Technical sales will tell you whether ultrasonics is the right answer for that part and what it takes to run it on your own floor.

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