Refuse-derived fuel changes from one delivery to the next, and moisture is one of the biggest reasons. A wet batch lowers the heat each tonne delivers, bridges in bunkers, and can foul feeders and conveying lines before the calciner shows any change. This checklist shows how teams can detect a spike, verify it, protect equipment, and record what happened in Oxmaint maintenance management software.
Cement RDF Moisture Spike Response Workflow
A practical response sequence for alternative fuel teams in cement plants, from first warning to close-out, with equipment checks and escalation rules for wet RDF.
NormalWithin the plant moisture band
WatchTrend rising, verify
SpikeAct on feed and equipment
CriticalReduce firing and escalate
RDF Moisture Spike Response Checklist
Work through the sections in order during a confirmed spike, and use the shift items as routine rounds when no spike is active.
SShiftWWeeklyMMonthlyXShutdown
Detection and verification
Moisture analyser reading, feeder torque, and weight trend compared for agreementSOperator
Sample taken from the suspect load, tagged with time, source, and vehicleSOperator
Response level set and recorded: normal, watch, spike, or criticalSSupervisor
Analyser lens cleaned and alignment checked; reading compared with a lab sampleWInstrument tech
Receiving and storage
Wet or suspect load diverted or segregated and not mixed into dry storageSOperator
Bunker walls, floor, and extraction area free of caking and bridgingSOperator
Roof, doors, and drains of the storage area checked for leaksWTechnician
Bunker liners, wear plates, and walking floor or extraction devices inspectedMTechnician
Extraction, metering, and airlocks
Screw or belt feeder torque and load within normal bandSOperator
Rotary airlock inspected for packing, wrapping, or sticking after a wet batchSTechnician
Weighing system zero checked and contact points cleanedWTechnician
Screw liners, rotor tips, and clearances measured for wearMTechnician
Conveying line and firing point
Conveying line pressure normal; bends and chutes free of damp build-upSOperator
Calciner outlet temperature trend reviewed; approved process adjustments loggedSControl room
Feed point and burner entry inspected for build-up near the injection zoneWTechnician
Blower and filter condition checkedMTechnician
Close-out and records
Handover note written with level, open work orders, and sample statusSSupervisor
Blockage events linked to the delivery record and likely causeWReliability engineer
Supplier feedback sent with delivery details and moisture readingWFuel manager
Monthly review of moisture events, downtime, and preventive tasks to addMReliability engineer
Inspection sign-off
All items above completed or marked not applicable, with inspector name, date, and shift recorded
Every failed item has a photo, a grade, and a work order number
Supervisor has reviewed open RDF findings and confirmed owners and due dates
Why Moisture Swings Matter in a Cement Kiln System
Process effects
- Part of the fuel energy goes to evaporating water instead of heating meal.
- Calciner outlet temperature can fall, which affects calcination.
- Flame behaviour and combustion can become less stable.
- Operators may raise primary fuel to compensate, which adds cost.
Equipment effects
- Wet, sticky material bridges in bunkers and hoppers.
- Feeders and screws load up and trip on torque.
- Rotary airlocks and chutes plug.
- Conveying lines and screens can blind or choke.
Where Moisture Comes From
- 1
Source material
Household and commercial waste contains organics, paper, and textiles that hold water, and moisture content shifts with weather and collection routes.
- 2
Weather and storage
Rain on open piles, leaking roofs, or damp trailers raise the moisture of a delivery after it leaves the processing site.
- 3
Processing variation
Shredding, screening, and drying at the supplier site change the final moisture, and any upset there reaches your plant a day or two later.
- 4
Plant handling
Mixing wet and dry batches, long storage, or condensation in covered bunkers can create local wet zones.
The Response Workflow in Six Stages
Stage 1DetectAn analyser, weighing change, supplier note, or operator observation raises a flag.
Stage 2VerifyTake a sample, check source, and compare with delivery and weather records.
Stage 3ContainDivert or segregate the wet load and avoid mixing it into dry storage.
Stage 4ProtectCheck feeders, airlocks, chutes, and conveying lines for loading and blockage.
Stage 5AdjustProcess team changes firing rate, blend, or feed rate based on plant rules.
Stage 6Close outRecord cause, actions, equipment findings, and supplier feedback.
Notes on each stage
- Detection works best when two signals agree, such as an analyser reading and a rising feeder torque.
- Verification should not be skipped. A faulty sensor can look like a moisture event.
- Containment depends on the layout. Some plants can divert to a separate bunker, others must slow intake.
- Adjustment decisions belong to the process team and must follow approved limits.
Response Levels and Who Acts
| Level | Typical signs | Maintenance action | Escalate to |
|---|---|---|---|
| Normal | Readings in the agreed band | Routine rounds | No escalation |
| Watch | Upward trend, minor feeder load rise | Extra visual check of feeders and chutes | Shift supervisor |
| Spike | Confirmed wet batch, torque alarms, bridging | Inspect and clear equipment, raise work orders | Alternative fuel lead and process engineer |
| Critical | Repeated blockages, unstable calciner temperature | Support controlled reduction or stop of fuel feed | Plant management and production lead |
Standardise the Spike Response Across Shifts
Put each stage into a checklist with owners and times, so every shift responds the same way.
Equipment Checks Along the RDF Path
Receiving and storage
- Bunker walls and floors for caking
- Walking floor or extraction devices
- Roof, doors, and drains for leaks
Extraction and metering
- Screw or belt loading and torque
- Weighing system zero and calibration
- Wear on screws, liners, and gates
Airlocks and conveying
- Rotary airlock clearance and sticking
- Pipe and chute for build-up
- Blower and filter condition
Firing point
- Feed point and burner entry
- Calciner temperature trend
- Build-up near the injection zone
Before and After a Formal Response Workflow
Without a workflow
- Operators react differently on each shift
- Blockages are cleared but not recorded
- Supplier issues are discussed from memory
- Same wet batch causes repeat trouble
With a workflow
- Clear signs, levels, and owners
- Every blockage becomes a work order with a cause
- Delivery, moisture reading, and equipment event linked
- Supplier discussions backed by records
Measurement Options for Moisture
- Laboratory sampling: Reliable reference, but results arrive after the material is already in the plant.
- Online near-infrared analysers: Give continuous readings, and need calibration against lab results and regular lens cleaning.
- Indirect indicators: Feeder torque, weight change, and calciner temperature trends hint at moisture, but are not a direct measure.
- Visual checks: Quick and useful, but subjective, so they should supplement and not replace measurement.
Maintaining the measurement itself
- Schedule analyser cleaning, alignment, and calibration as recurring tasks.
- Compare online readings with lab samples at a regular interval and log differences.
- Treat a drifting sensor as a maintenance finding, not an operator problem.
Shift Timeline During a Confirmed Spike
First 15 minutesConfirm the signal, take a sample, notify supervisor, and check feeder and airlock status.
First hourSegregate the wet batch, clear early blockages, and agree on process adjustments with the control room.
End of shiftHand over open work orders, equipment status, and sample results to the next shift.
Within the weekReview cause, update supplier feedback, and adjust inspection frequency if needed.
Feeder and Airlock Troubleshooting During a Wet Batch
| Symptom | Likely link to moisture | First response | Follow-up |
|---|---|---|---|
| Rising screw feeder torque | Sticky material packing the screw and trough | Reduce load if allowed, then inspect for build-up | Check liner wear and clearances at the next stop |
| Airlock tripping or jamming | Wet fibres wrapping or packing the rotor | Isolate safely, clear, and inspect rotor tips | Review clearances and seal condition |
| Bridging in the bunker or hopper | Wet material forming arches and rat-holes | Use approved clearing methods, never enter unsafely | Inspect walls, liners, and extraction devices |
| Weighing signal unstable | Build-up on belts, hoppers, or load cells | Clean contact points and verify the zero | Schedule calibration check |
| Conveying line pressure rise | Damp material sticking in pipe bends | Reduce feed and inspect line | Record location and cleaning method used |
| Calciner temperature dips after feed change | Extra evaporation load from wet fuel | Inform the control room immediately | Log the delivery and moisture reading together |
Safety Points During Moisture Events
Before clearing a blockage
- Isolate and lock out the equipment, then confirm zero energy.
- Use the site procedure for confined spaces and bunkers.
- Wear dust protection and suitable gloves and eye protection.
- Keep communication open with the control room.
Fire and gas awareness
- Wet and decaying material can produce heat and gas in storage.
- Watch for odour, steam, or hot spots in the bunker area.
- Know the location of detection, suppression, and emergency stops.
- Report any heating event to the supervisor straight away.
Supplier Feedback: Turning Events Into Evidence
Supplier discussions go better when the plant can show what arrived, when, and what happened afterward. Keep the evidence simple and consistent.
- 1
Delivery details
Record supplier, date, time, vehicle, and source if known.
- 2
Sample and reading
Link the lab or analyser result to the delivery record.
- 3
Plant impact
Note feeder events, blockages, and any process change that followed.
- 4
Agreed action
Record what the supplier committed to and the date for review.
Seasonal and Site Factors to Plan For
- Rainy periods: Expect more wet deliveries and more leakage from storage. Increase inspection of roofs, doors, and drains beforehand.
- Cold weather: Moisture can freeze and form lumps that jam extraction and feeders when it thaws.
- Hot weather: Stored material can heat up. Watch bunker temperature and odour.
- Delivery peaks: Busy periods push storage and mixing beyond normal practice, which raises the risk of wet pockets.
- Shutdown restarts: Material that has sat in lines and hoppers can be damp. Check and clear before restart.
Handover Notes Worth Writing at Every Shift Change
Current response level and the reason for it.
Equipment that has been cleared, and equipment still at risk.
Open work orders, owners, and due times.
Latest moisture reading, sample status, and where the sample is stored.
Process adjustments in place and who approved them.
Anything the next shift should check in the first hour.
Moisture Response Roles Across the Plant
| Role | Main responsibility | Records to keep |
|---|---|---|
| Alternative fuel operator | Spots early signs at receiving, storage, and feeders | Observations, sample tags, and delivery details |
| Control room operator | Watches calciner temperature and feed signals and applies approved adjustments | Setpoint changes and the time of each action |
| Maintenance technician | Inspects and clears equipment, repairs wear damage, and checks instruments | Work orders, photos, parts used, and findings |
| Process engineer | Reviews effect on calcination and fuel substitution rate | Analysis notes and recommended limits |
| Supervisor | Decides level changes and escalates to management | Level log and handover notes |
| Procurement or fuel manager | Raises supplier feedback and tracks agreed actions | Supplier communications and review dates |
Why role clarity matters
- Operators know when to act and when to call for help.
- Maintenance is not asked to guess whether a blockage is a fuel issue or a mechanical issue.
- Supplier conversations rest on records, not recollection.
- Reviews can focus on fixing the cause instead of debating who did what.
Questions for the Monthly Review
How many moisture events occurred, and how many led to equipment downtime?
Which feeder, airlock, or chute failed most often during wet batches?
Did the response level match the actual impact on the process?
Were analyser readings in line with lab samples?
Which preventive tasks should be added before the next wet season?
Preventive Actions That Reduce Spike Impact
Inspect and repair roof, door, and drain leaks in the storage area.
Keep bunker liners, wear plates, and extraction devices in good condition.
Set agreed moisture limits in supplier contracts and inspect incoming loads.
Schedule cleaning of feeders, airlocks, and chutes before wet seasons.
Keep spare screws, liners, and airlock parts for the most affected equipment.
Train operators on warning signs and the response levels in this workflow.
KPIs for RDF Moisture Response
Moisture events per monthShows frequency of problem batches
Time from detection to containmentMeasures response speed
Blockage events linked to moistureShows equipment impact
Feeder downtime hoursCost to alternative fuel throughput
Analyser calibration complianceConfidence in readings
Signs a wet batch is still in the system
Feeder torque stays above the normal band after the first clearing.
Calciner outlet temperature recovers slowly or oscillates after feed adjustment.
Material in the conveying line looks clumped or leaves a damp residue on inspection.
Weighing readings drift between cleaning cycles.
Operators report repeated small blockages in the same chute or airlock.
Training Operators on Moisture Warning Signs
Show crews what a normal feeder load, normal material appearance, and normal calciner trend look like, so changes stand out.
Practise the response levels in a short drill, so the first real event is not the first time anyone uses the workflow.
Explain why a verified reading matters before a process change is made, and who has authority to make one.
Teach safe blockage clearing, including isolation, permits, and what must never be done by hand.
Review one recent event each month and ask the crew what they would do differently.
Keep a short guide at the feeder area with the response levels, contacts, and first checks.
Rotate drill scenarios between night and day shifts so every crew practises the workflow under real conditions.
Ask new starters to shadow a moisture event response before they take a feeder round alone.
What to capture after every drill or event
Time from first sign to a confirmed reading.
Time from confirmation to containing the wet material.
Equipment that needed attention, and whether the checklist covered it.
Gaps in spare parts, tools, access, or communication.
Changes to the checklist or response levels agreed afterwards.
How Oxmaint Supports the Workflow
- Inspection checklists for bunkers, feeders, airlocks, and conveying lines on mobile devices.
- Work orders raised from a blockage or alarm, with cause and photo attached.
- Preventive maintenance for analysers, weighing systems, and wear parts.
- Asset history that links repeat events to specific equipment.
- Inventory tracking for screws, liners, airlock parts, and filters.
- Dashboards and reports that show repeat failures, response times, and overdue tasks.
Frequently Asked Questions
What counts as a moisture spike?
A reading or trend outside the band your plant has agreed with process and fuel teams for stable operation.
Who decides to change firing rate?
The process and control room team, following approved limits. Maintenance supports with equipment status and findings.
Can maintenance prevent moisture issues?
Not the source, but it can reduce impact by keeping storage, feeders, and sensors reliable. Schedule those tasks in Oxmaint.
How should blockages be recorded?
As a work order with location, likely cause, photos, and the related fuel delivery for later review.
Can this workflow be built into a CMMS?
Yes, as a checklist with levels and owners. Book a demo to see how.
Be Ready Before the Next Wet Batch Arrives
Give every shift the same signs, steps, and records, and learn from each moisture event.
