High Shear Granulator Troubleshooting: Causes & Fixes

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Problems on this page:

Granules too wet or overgranulated Granules too fine Lumps and oversize granules Product sticking to the bowl and lid Impeller motor overload Discharge slow or incomplete Leak at the impeller shaft seal Binder spray nozzle blocking Lid interlock stopping the cycle

Granules too wet or overgranulated

Hits OEE: Quality

Symptoms: Granules are dense, sticky or form a paste, and drying takes longer.

Too much binder or added too fast

Check the binder quantity and spray rate against the batch record.

Wet massing time too long

Check the massing time and the end point setting.

End point not monitored

Use the impeller power or torque trend to judge the end point where it has been validated.

Raw material properties changed

Check the raw material batch against its specification.

Prevention: Impeller power curve recorded for every batch and compared with good batches.

Granules too fine

Hits OEE: Quality

Symptoms: Granules are small and dusty, and tablets later show weight variation or capping.

Too little binder

Check the binder quantity and concentration.

Massing time too short

Check the time and end point setting.

Impeller speed lower than set

Check the actual speed on the drive.

Binder spray nozzle partly blocked

Clean the nozzle and check the spray pattern.

Prevention: Granule size checked on each batch.

Lumps and oversize granules

Hits OEE: Quality

Symptoms: Large lumps come out at discharge and block the mill or screen.

Chopper not running or too slow

Check the chopper runs at its set speed during liquid addition.

Binder dripping instead of spraying

Check the nozzle and the atomising air.

Product building up on the walls and falling in

Clean the bowl and lid before each batch.

Liquid added onto one spot

Check the nozzle position over the moving powder bed.

Prevention: Oversize after milling recorded per batch.

Product sticking to the bowl and lid

Hits OEE: Quality

Symptoms: Product builds up on walls and lid, and the yield falls.

Bowl temperature too high

Check the jacket temperature if the bowl is jacketed.

Liquid sprayed onto the walls

Adjust the nozzle so the spray lands on the powder.

Bowl not fully dry after cleaning

Dry the bowl before charging.

Formulation prone to sticking

Discuss the formulation and process settings with development.

Prevention: Yield per batch tracked, with build-up noted at discharge.

Impeller motor overload

Hits OEE: Availability

Symptoms: The impeller drive trips or hits its current limit during wet massing.

Bowl overfilled

Keep the charge within the validated batch size.

Wet mass heavier than usual

Check the binder quantity and the end point.

Impeller bearings or seals dragging

Check the drive for drag with the bowl empty.

Drive current limit set too low

Check the drive settings against the commissioning record.

Prevention: Impeller current trended per batch.

Discharge slow or incomplete

Hits OEE: Performance

Symptoms: Product takes long to leave the bowl, or some stays behind.

Discharge valve not opening fully

Check the valve actuator and its open position.

Impeller not running during discharge

Run the impeller at the discharge speed in the recipe.

Granules too wet

See the overgranulation causes above.

Downstream mill or dryer not ready

Check the transfer line is open and running.

Prevention: Discharge time recorded per batch.

Leak at the impeller shaft seal

Hits OEE: Quality

Symptoms: Powder or liquid escapes at the shaft seal, or seal purge alarms appear.

Seal purge air or water not on

Check the seal purge supply and pressure.

Seal worn

Replace the shaft seal on the maker schedule.

Seal damaged during cleaning

Follow the dismantling procedure for the seal.

Shaft bearing worn

Check the shaft for play.

Prevention: Seal purge pressure checked at every start-up.

Binder spray nozzle blocking

Hits OEE: Quality

Symptoms: The binder flow drops during addition, or the spray pattern is uneven.

Binder solution too viscous or not fully dissolved

Prepare the binder as the batch record says and filter it if specified.

Nozzle not cleaned after the last batch

Clean the nozzle immediately after each batch.

Wrong nozzle size fitted

Check the nozzle against the recipe.

Pump or line partly blocked

Flush the line and check the pump.

Prevention: Binder addition rate recorded during each batch.

Lid interlock stopping the cycle

Hits OEE: Availability

Symptoms: The granulator will not start or stops because the lid is not detected as closed.

Lid not fully closed or clamped

Close and clamp the lid; the impeller must never run with the lid open.

Lid sensor misaligned

Adjust the sensor and test the interlock.

Lid seal swollen or damaged

Replace the lid seal.

Wiring to the sensor damaged

Check the sensor wiring.

Prevention: Lid interlock tested on a fixed schedule.

Guidance only. Always follow lockout/tagout and your site's safe-work procedures, and verify against OEM manuals before acting.

Related equipment guides: fluid bed dryer · mixer / agitator · tablet press · tablet coater · IBC blender

Stop the same fault coming back

Recurring high shear granulator stops usually trace to a cause you cannot see by hand. The partner we recommend is Fabrico: it tracks OEE and downtime live from PLCs, IoT sensors or AI cameras; where cameras are fitted, the video of a stop sits next to its machine data so the cause can be reviewed; and a technician opens the work order from the stop in the same system. Data is hosted in the AWS EU region, and Fabrico and the company behind it hold ISO/IEC 27001, ISO/IEC 20000-1 and ISO 9001.

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Methods that cut recurring stops: the six big losses · root cause analysis · preventive vs predictive maintenance · TPM · SMED & changeover