In a solid dosage plant, the powder that causes trouble is the powder that leaves the process. It settles on equipment that will run the next product. It could be inhaled in by the operator at the sifter. Extraction is one of the controls that keeps powder where it belongs, and this post explains where it fits and how it is specified.
Where powder escapes
Almost every step in tablet and capsule manufacturing opens the powder to the room at some point.
- Dispensing and weighing. Scooping and pouring from drums and bags releases a cloud at the weighing point.
- Sifting. Vibratory sifters shake powder across an open screen, and the discharge chute releases more.
- Granulation and drying. Dust escapes when the granulator or dryer is charged and discharged.
- Blending. Charging a blender and emptying it into containers both release powder.
- Tablet compression. The die table, the deduster and the tablet chute all produce fine dust.
- Coating and capsule filling. Loading, unloading and filling stations shed powder throughout the shift.
Some of this dust is an active ingredient and it can end up somewhere it should not be.
What dust extraction does in a pharma plant
Extraction in a pharma plant has five jobs. Missing any one of them weakens the others.
1. Capture at the source. Dust has to be taken where it is released, before it spreads into the room air. Once powder is in the room, the room’s ventilation can only dilute it, and it settles on every surface on the way. Capture at the source means a hood, arm or direct connection at each point listed above, sized so the air moves fast enough at the opening to pull the dust in.
2. Work with the room’s air balance, not against it. Pharma production rooms are held at set pressures relative to the corridor and to each other, so air flows from clean areas towards dustier ones. The revised Schedule M (India’s updated manufacturing rules for drug makers) sets requirements for this pressure cascade between manufacturing zones. Every extraction point removes air from the room. If the extraction removes more air than the heating, ventilation and air conditioning system supplies, the room becomes more negative than designed and pulls air in from the corridor. The extraction design and the air conditioning design have to be done together.
3. Keep the dust inside the collector during service. Operators are most exposed when a filter is changed or a dust bin is emptied. The collector should discharge into a closed container, and the filter should signal when it needs attention, so service is planned rather than forced by a blocked unit. NAF’s Dust Extractor discharges into round containers from 16 to 160 litres, drawers or big bag stations. It monitors the pressure drop across the filter and signals when service is due.
4. Treat the powder as combustible until tested. Pharmaceutical powders can burn and explode. A study by Patheon, published in Pharmaceutical Technology, says it is common for active ingredients to be capable of releasing explosion pressures of 8 to 10 bar, and named electrostatic discharge as the usual ignition source. Most excipients such as lactose and starch are less sensitive, but magnesium stearate, a common tablet lubricant, can be ignited by very little energy. The same study lists fluid bed drying, milling, sieving, micronising and pneumatic transfer as the higher risk operations. A collector serving these steps should be built in an explosion protected configuration, with pressure relief and electrical parts rated for the dust zone. NAF offers this build on its Dust Extractor.
5. Keep products apart. A central system that connects rooms making different products also connects them through its ductwork. Where cross-contamination between products is a concern, separate collectors for separate rooms or product lines may be the safer layout, even if a single central unit would cost less. Our post on central or standalone extraction covers the trade-off.
Where general extraction stops
Extraction around an open process reduces exposure. It does not seal the process. Highly potent drugs, hormones, cytotoxic compounds and penicillin type antibiotics are handled in closed systems such as isolators, where the powder never meets room air at all. For these products, containing the process comes first. Extraction then serves the rest of the plant, including the general solid dosage areas, the warehouse dispensing booth and the packing hall.
We say this plainly because a plant that relies on extraction where a closed system is needed is taking a risk that no collector can remove.
Matching extraction to each step
| Process | Where powder escapes | How it is captured | NAF equipment |
| Dispensing and weighing | Scooping and pouring at the scale | Arm or hood at the weighing point | Articulated arm (250 to 3,000 m³/h) or hood, connected to a Dust Extractor |
| Sifting | Open screen and discharge chute | Hood over the sifter and a connection at the chute | Hood or arm, Dust Extractor |
| Granulation and drying | Charging and discharge | Connection at the charging and discharge points | Dust Extractor in explosion protected build |
| Blending | Charging and emptying | Hood at the charging port and discharge | Hood, Dust Extractor |
| Tablet compression | Die table, deduster, tablet chute | Direct connection to the press and deduster | Dust Extractor with HEPA after filter |
| Coating and capsule filling | Loading, unloading, filling | Hood or arm at the station | Arm or hood, Dust Extractor |
How the NAF Dust Extractor is configured for powder
The NAF Dust Extractor is built from seven modules (exhaust air, fan, filter cleaning, controls, filter, discharge and mobility) in seven size classes, from XS to XXL. For powder handling, the choices that matter are these.
- Filter. The filter media is matched to the powder, with a HEPA after filter available for the finest fraction.
- Cleaning. Compressed air pulses or vibration clear the filter while the unit runs, so airflow at the capture points stays steady through the shift.
- Discharge. Closed containers, drawers or big bag stations, chosen to suit how the powder is disposed of.
- Explosion protection. Pressure relief and rated components for steps that handle combustible powder.
- Monitoring. Pressure drop across the filter is tracked, and an optional connected control reports filter condition.
NAF has supplied a dust extractor to a pharmaceutical plant in Karnataka. The equipment is designed and built in Chennai, with design input from NAF’s German partners ULMATEC GmbH [See the Pharma and Chemical section of our industries page for product information]
Start with a site survey
Powder extraction is specified point by point, so the design starts on your floor. A NAF site survey covers the following.
- Every point where powder is handled, with the material and batch size at each one.
- Which points run at the same time, and which rooms make which products.
- The room pressure scheme and the air conditioning supply to each room.
- Any combustibility test data for your active ingredients and excipients.
- How collected powder is disposed of today.
Book a site survey and we will come back with a capture point for each step and a collector configuration to match.