TL;DR
A blocked cyclone reduces yield and increases chamber powder accumulation. Stop the dryer, isolate the cyclone, and clear the blockage using a soft tool.
What you might see
- product yield dropping below normal
- differential pressure across cyclone rising
- audible pulsing from the cyclone body
- fine powder accumulating in chamber instead of cyclone
Likely causes
Hygroscopic product absorbing moisture and caking at the cyclone cone
Static charge causing fine particles to cling to cyclone walls
Product collection valve sticking closed allowing cyclone to fill
High product feed concentration exceeding cyclone capacity
Required tools
- Inspection flashlight
- Non-metal probe or soft brush
- LOTO kit
- Respiratory PPE (pharmaceutical powder)
Safety first
- Spray-dried pharmaceutical powder can be potent. Wear respiratory PPE rated for the specific product when clearing cyclone blockages.
- If the product is hygroscopic, opening the cyclone in high-humidity conditions will worsen blockage. Time maintenance for dry conditions.
- Cyclone interiors can have accumulated static charge. Bond the cyclone body to ground before reaching inside.
Procedure
- 1
Stop the feed pump. Allow the dryer to purge for 2 minutes before shutting down the heater and fan.
- 2
Lock out and tag out the heater, fan, and feed pump.
- 3
Wait for the cyclone body to cool to a safe handling temperature.
- 4
Open the cyclone clean-out port or cone valve. Inspect the interior using an inspection flashlight.[1]
- 5
Remove blockage with a soft non-metal probe or by gentle vibration of the cyclone body. Do not use metal scrapers on the interior surface.[1]
- 6
Check the product collection valve at the cyclone outlet for sticking or fouling. Clean or replace the valve actuator if it does not fully open.
- 7
Inspect the cyclone gaskets and flanges for air in-leakage that could disrupt the vortex pattern.
- 8
Restart and monitor differential pressure across the cyclone for the first 30 minutes of operation.
Sources
GEA Niro GEA Niro PSD / Mobile Minor Spray Dryer general technical documentation, GEA Niro
GEA Niro PSD / Mobile Minor spray dryer general cyclone maintenance and blockage procedures (general)
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