A cement-mill water-injection system can show normal pump activity while cooling performance collapses because the lance or nozzle is partially blocked, the spray is poorly atomized, purge air is ineffective, or cement has agglomerated on the nozzle tip. Diagnose the complete chain: compare commanded and actual water flow, inspect water and atomizing-air pressure, test valve and lance response, clean the nozzle, verify purge-air operation when water is off, and confirm the spray reaches the intended mill zone. Do not increase water blindly; the objective is controlled evaporation and temperature response without wetting cement or creating coating.
Restore reliable mill cooling when the temperature rises despite a water-injection command or the nozzle repeatedly blocks.
Use mill outlet temperature trend, commanded/actual water flow, water and air pressure, spray condition, nozzle deposits, purge-air function and process ventilation.
Separate blocked nozzle, failed atomization/purge, instrumentation error and insufficient cooling capacity before changing the setpoint or flow.
Capture the cooling response before dismantling the lance
Record: mill feed and clinker temperature; mill outlet material and vent-air temperature indications used by the plant; commanded and measured water flow; water-pump pressure; atomizing or purge-air pressure; control-valve output; mill ventilation/fan condition; recent nozzle-cleaning history; and whether the temperature responds at all when injection starts.
Trend response is important. A stable water-flow signal with no temperature response can indicate a false flow measurement, a blocked/poor spray, or water not reaching the intended zone.
1. Verify actual water delivery, not only the PLC command
Check tank level, suction condition, pump operation, strainer/filter, control valve and flow measurement. Compare indicated flow with an independent maintenance check where the system design permits it. A stuck control valve, blocked strainer or slipping pump can give the appearance of an active control loop without the required water reaching the lance.
2. Inspect the nozzle for cement agglomeration and mineral deposits
After safe isolation, remove and inspect the nozzle. Cement can agglomerate around the tip, especially where fine dust and moisture meet. Water quality can also leave scale that changes the orifice and spray cone. Document the deposit location before cleaning because repeated buildup on the same side can indicate an unfavorable air/material flow around the lance rather than a water-quality issue alone.
3. Test atomizing and purge air
Many systems use air to atomize the water and/or keep the nozzle clear while water is off. Verify the air supply, regulator, solenoid/check valves and lance passages. A purge-air system that is nominally enabled but restricted cannot protect the tip from cement deposition. Confirm air quality as well; wet or dirty air can worsen fouling. Use the injection-system supplier’s pressure and sequence settings rather than generic values.
4. Check spray pattern and droplet quality outside the mill when the OEM procedure allows
The cooling effect depends on water being dispersed into fine droplets that evaporate in the intended zone. A partially blocked nozzle may still pass water but produce a jet or asymmetric spray. Test the nozzle in a safe approved setup. Check spray cone symmetry, pulsation and response to flow changes. Replace worn nozzle components if cleaning does not restore the specified pattern.
5. Verify lance position and orientation
A good nozzle installed in the wrong position can become rapidly coated or can spray onto liners, diaphragm or a poorly ventilated zone. Compare insertion depth, angle and orientation with the mill/injection-system drawing. If deposits form preferentially on the upstream face of the nozzle, review local material and air direction. Do not relocate the lance without an engineering review because injection location affects evaporation and mill internals.
6. Correlate water injection with mill ventilation and heat load
Water injection complements, rather than replaces, proper mill ventilation and process heat balance. If the ventilation path is restricted, outlet temperature can remain high and moisture removal can deteriorate. Check mill fan/damper condition, filter DP and gas path. Also review clinker/feed temperature and production rate: a large change in heat input may exceed the system’s previous cooling duty even when the nozzle is healthy.
7. Protect product quality and mill internals from over-injection
The aim is for injected water to evaporate and remove heat, not to wet the cement bed. Watch for coating, diaphragm blockage, altered flowability or quality concerns. If operators compensate for a poor nozzle by increasing flow, local wetting can become worse while useful cooling remains poor. Restore atomization and distribution first, then tune the control loop to the plant’s established process and quality limits.
Water-injection diagnostic matrix
| Evidence pattern | Likely direction | Next check |
|---|---|---|
| Flow command rises but measured flow stays low | Pump/valve/filter restriction | Strainer, pump, control valve, line blockage |
| Measured flow normal but spray is a jet/asymmetric | Nozzle fouling or wear | Nozzle tip/orifice, atomizing air and scale |
| Nozzle blocks after water stops | Ineffective purge / tip agglomeration | Purge-air sequence, solenoid, air path and lance location |
| Injection healthy but temperature response weaker at higher production | Higher heat load / ventilation limit | Heat input, mill ventilation and system design capacity |
| More water causes coating without useful cooling | Poor atomization/distribution or excess water | Spray pattern, lance position and control tuning |
Common mistakes
- Increasing water because outlet temperature is high without proving the nozzle is spraying correctly.
- Cleaning the nozzle while ignoring a failed purge-air solenoid.
- Trusting a flow transmitter without comparing process response.
- Relocating the lance without checking the mill supplier’s design.
- Ignoring ventilation and clinker/feed heat load.
Return-to-service verification
After cleaning or repair, verify water and atomizing/purge-air paths, then run a controlled injection test under a stable mill load. Acceptance means actual water flow follows the control demand, the temperature trend responds predictably, there is no evidence of local wetting or new coating, and the nozzle remains clear through start/stop cycles. Inspect the tip after an initial production interval if recurring agglomeration was the original failure.
Related Infinity technical guides
References
Christian Pfeiffer and Lechler technical guidance describes mill water injection as controlled fine-droplet cooling, with system design depending on the mill and process. Cement-industry troubleshooting experience also identifies cement agglomeration on nozzle tips and purge/atomizing air as important nozzle-blockage factors. Final injection limits, temperatures, lance position and flow must follow the mill, cement-quality and injection-system specifications.