TL;DR

Tablet sticking is usually overwetting from too high a spray rate or too low an inlet temperature. Reduce spray rate first, then increase drying air temperature.

What you might see

tablets stuck together (twin formation) in the pan
coating material pulled from tablet surface (picking)
tablet bed moisture rising above normal
spray nozzle coating buildup within 5 minutes of spraying

Likely causes

Tap to mark as ruled out

Spray rate too high relative to the drying capacity of the inlet air
Inlet air temperature too low, leaving excess moisture on the tablet surface
Pan speed too low, causing tablets to pile up and stick before the surface dries
Coating suspension concentration too high, increasing viscosity and drying time

Required tools

Inlet and exhaust air thermometer (or use the machine sensor readout)
Viscosity measurement tool for suspension check
Cleaning cloth for pan interior

Safety first

The coating pan operates at elevated temperature. Use gloves when reaching inside the pan.
Tablet dust and coating aerosol are potential inhalation hazards. The pan must be under negative pressure with HEPA filtration during spraying.

Procedure

7 steps · ~30 min

1
Stop spraying and increase the inlet air temperature by 5 degrees C. Allow the tablet bed to dry for 2 minutes before resuming.
2
Monitor the exhaust air temperature and adjust until the exhaust reads 2 to 4 degrees C above baseline, indicating a stable drying equilibrium.[1]
3
Reduce the spray rate by 10% from the current setting. Confirm through the pump set-point.
4
Verify the pan speed is at the minimum recommended for the batch size and tablet type. Increase speed if tablets are not rolling freely.[1]
5
Check the coating suspension viscosity against the batch record. Dilute the suspension if the viscosity is above specification.
6
Inspect the pan interior for coating buildup on the baffles or wall. Clean any buildup with a warm water wipe before it dries.
7
Resume spraying at the reduced rate. Visually inspect the tablet bed every 5 minutes for 20 minutes.

Sources

Glatt Glatt GC / GMPC Tablet Coating Machine general technical documentation, Glatt
Glatt tablet coating machine general sticking and overwetting troubleshooting (general)

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