Dome-Shaped Dust Capture Bags for Dryer Outlets and Spray Systems

Skytech Ultrafab Bonnet Bags are dome-shaped (bonnet-style) fabric filter elements fitted over the exhaust outlets of fluid bed dryers, spray dryers, and pneumatic conveying systems to capture fine product dust before it reaches the fan and atmosphere. The large dome surface area provides low-resistance filtration at high air volumes, ensuring maximum product recovery, equipment protection, and environmental compliance across pharmaceutical, food, and chemical processing facilities.

What Is a Bonnet Bag?

A Bonnet Bag (also called a dome bag or umbrella bag) is a hemispherical or domed fabric filter element that fits over the outlet of a dryer or conveyor system to act as a final-stage dust barrier. Unlike cylindrical bags that hang downward, bonnet bags wrap over the top of the outlet connection, held in place by a drawstring, elastic, or clamping ring. The dome geometry presents the full fabric surface to the outgoing airstream, maximising filtration area within a compact installation envelope.

Features and Benefits

• Large Dome Filtration Area: Hemispherical construction presents maximum fabric area to outgoing airstream — lower face velocity per unit area means lower pressure drop and longer service intervals
• Antistatic Fabric: Needle-punched polyester felt with conductive fibre treatment prevents static charge build-up during high-velocity powder-laden airflow — essential for flammable and explosive dust applications
• Secure Closure System: Drawstring, elastic band, or snap-fit SS ring closure ensures the bonnet remains sealed at the outlet connection during dryer operation and cleaning pulses
• Multiple Material Options: PP, PES, and nylon needle-felt options cover the temperature, chemical, and food-safety requirements of pharmaceutical, food, and chemical dryer applications
• FDA-Compliant Grades: Food-grade PP and PES felts available for spray dryer and fluid bed dryer applications in food ingredient, dairy, and pharmaceutical manufacturing
• Custom Dome Geometry: Dome diameter and depth fabricated to fit any outlet flange diameter — all standard spray dryer and FBD outlet sizes accommodated with custom options on request

Technical Specifications

Applications

• Fluid Bed Dryers: Outlet dust capture in pharmaceutical, nutraceutical, and food ingredient FBD granulators — recovers product fines and prevents fan contamination
• Spray Dryers: Secondary dust recovery at spray dryer exhaust outlets for dairy, infant formula, instant coffee, and pharmaceutical spray-dried powder production
• Pneumatic Conveying: Dust capture at silo vents, transfer points, and pneumatic line terminals in food, chemical, and mineral powder conveying systems
• Rotary Dryers: Outlet particulate capture on rotary drum dryers in fertiliser, mineral, and chemical processing applications
• Cyclone Overflow: Polishing filter over cyclone overflow outlet — captures sub-micron particles that pass through the cyclone primary separation stage

Why Choose Skytech Ultrafab for Bonnet Bag?

• Antistatic as Standard: Conductive fibre felt standard for pharmaceutical applications — eliminates static ignition risk from API and excipient fine powder without additional antistatic treatment cost
• FDA Documentation: Material certificates and FDA 21 CFR declarations for food and pharmaceutical dryer applications — essential for GMP equipment qualification
• Exact Outlet Fit: Custom dome diameter and closure type matched to any outlet flange — correct fit eliminates air bypass around the bag perimeter
• Rapid Replacement Supply: Standard outlet diameters in 5–7 working days — bonnet bags are a fast-wearing consumable in high-volume production, so fast reorder is critical
• Complete FBD Programme: Order bonnet bags together with Skytech FBD bags, combo bags, and finger bags — one source for all fluid bed dryer filtration consumables