Powder hopper valves · Butterfly, slide-gate and rotary valves at hopper outlets, rotary valve capacity by size and speed, pocket fill, shaft seals and air purge, sanitary and hazardous-area options
A powder hopper valve is fitted at the outlet of a hopper, bin or silo to shut off, release or meter the flow of powder or granules into a feeder, conveyor or process, using a butterfly disc, a slide gate, or a rotary airlock or dosing rotor that also seals between different pressures. Ask three things first: whether the valve must only isolate or also meter and seal, what volume of material per hour it must pass at the material's bulk density, and what hygiene, temperature, pressure and hazardous-area conditions it faces.
Valves at hopper, bin and silo outlets handling powders and granules: manual and actuated powder butterfly valves, inflatable-seal butterfly valves, slide gates, rotary airlocks and rotary dosing valves. Liquid valves, dispensing valves for fluids, complete pneumatic conveying systems and screw feeders are outside this page.
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AVM lists sanitary powder valves for pharmaceutical, biotechnology and food processing, including manual and actuated powder butterfly valves, inflatable-seal butterfly valves, powder discharge valves, powder sampling valves, rotary dosing valves and double-rotor metering valves. [2]
Cyclonaire's rotary airlock and feeder sheet describes valves for metering powders, granules or pellets and controlling flow into dilute-phase pressure or vacuum conveying, with a maintenance slide gate above the feeder in its example layout. Its standard design is carbon steel with 6–16 in round flanges, adjustable packing-gland seals and a worm-gear reducer, described as NFPA compliant; options include 304 or 316 stainless steel, 6–26 in square flanges, air-purge shaft seals using 3–5 SCFM of compressed air, sanitary CIP, high-temperature and hazardous-location controls, a vented body and a zero-speed switch. [1]
Editorial note: a butterfly valve or slide gate only opens and closes the outlet; when the valve must set the feed rate or hold back conveying air, specify a rotary valve and state the pressure difference across it.
Give the supplier the material, bulk density, particle size and flow behaviour, required rate (kg/h or m³/h), duty (isolation, metering, airlock), pressure difference, temperature, outlet size and flange standard, materials of construction, seal type, hygiene or CIP needs, hazardous-area classification, actuator and supply, position or speed monitoring, and quantities.
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Cyclonaire's capacity chart, based on 100% pocket fill, gives 6, 12, 24, 45, 66, 84, 162, 276, 384 and 540 ft³/h at 1 rpm for 6, 8, 10, 12, 14, 16, 18, 22, 24 and 26 in valves, rising in proportion to speed up to 20 rpm, where a 10 in valve gives 480 ft³/h and a 26 in valve 10,800 ft³/h. [1]
Editorial calculation: 2,000 kg/h of a powder with an assumed bulk density of 500 kg/m³ is 4.0 m³/h, about 141 ft³/h. A 10 in valve at 10 rpm gives 240 ft³/h at 100% fill; at an assumed 70% pocket fill that is about 168 ft³/h, enough for 141 ft³/h, while an 8 in valve at 10 rpm would give about 84 ft³/h. Ask the supplier for the fill factor they use for your material and pressure difference. [1]
Editorial note: real fill depends on the material, inlet feed, rotor speed and air leakage up through the valve; confirm capacity with the supplier's data for a similar material.
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Coperion's rotary valve page gives flange sizes from 80 mm to 1,000 mm and rotor speeds of 1 to 70 rpm, depending on valve size, throughput and any ATEX requirement. It states that standard designs suit pressures from a few millibars up to 3.5 bar, reinforced or special versions handle system pressures up to 6 bar, and custom-engineered valves are available above 20 bar. [3]
Coperion defines leakage gas as the air that flows through the clearances between housing and rotor from the higher- to the lower-pressure side, and notes that it reduces the air volume available for pneumatic conveying and can raise energy use; it also mentions scoop gas carried back by the empty rotor pockets. It states a rotary valve may be installed in an Ex zone only if it is shown not to be an ignition source (surface temperature, mechanical sparks, electrostatic discharge), and that to act as an explosion isolation device it must show sufficient pressure resistance and that flame cannot pass through, with certification by a notified body under the ATEX Directive. [3] Size the pocket volume and speed with the capacity chart above. [1] [2]
Editorial calculation: Cyclonaire's 26 in valve is about 660 mm, inside Coperion's 80–1,000 mm range; Cyclonaire's 20 rpm chart limit is inside the 1–70 rpm range Coperion gives.
| Coperion point | Value |
|---|---|
| Flange size range | 80–1,000 mm |
| Rotor speed | 1–70 rpm |
| Standard design pressure | A few mbar up to 3.5 bar |
| Reinforced or special versions | Up to 6 bar |
| Custom-engineered | Above 20 bar |
| Hygienic designs | Referenced to FDA, EHEDG or GMP guidelines |
For a valve feeding a pneumatic line, ask for the leakage air at your differential pressure, the pressure class, and whether the valve is ATEX-certified as a non-ignition source or as an explosion isolation device.
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Slide gate maker Vortex describes its Roller Gate for dry material in gravity flow or low-pressure service above or below gravity-fed hoppers and silos, mixers and screw conveyors, and as an air shut-off gate in vacuum dust collection. It uses live-loaded, wear-compensating hard polymer bonnet and side seals that can be replaced while the valve stays in line. Its Quick Clean Gate is a round, sanitary slide gate for non-abrasive powders, pellets and granules where regular sanitation is required. [4] [5]
Vortex lists position confirmation by magnetic reed, proximity or mechanical limit switches on the Roller Gate, and says Quick Clean Gate seals should be hand-cleaned in solutions not above 180 °F (80 °C). Both are listed for gravity flow, so a valve that must hold a conveying-line pressure difference is a rotary valve question (see the Coperion pressure classes above), not a slide gate one. [4] [5] [3]
Editorial calculation: the Roller Gate's 6–30 in standard range spans a 25:1 ratio in opening area for square gates (6 × 6 in = 36 in² against 30 × 30 in = 900 in²). Give the supplier the outlet size and shape, material temperature, cleaning regime, actuator air or power supply and the ATEX zone at the hopper. [4]
| Vortex tech spec | Roller Gate | Quick Clean Gate |
|---|---|---|
| Conveyance type | Gravity flow only; low pressure or vacuum on enquiry [4] | Gravity flow only; low pressure or vacuum on enquiry [5] |
| Standard sizes | 6–30 in (150–760 mm), square or rectangular [4] | 2–10 in (50–255 mm), round; schedule 10, 20 or 40 pipe sizes [5] |
| Overall height | 3–4 in (75–100 mm) [4] | 4 3/8 in (111 mm) [5] |
| Weight | 30–200 lb (15–90 kg) [4] | 30–110 lb (15–50 kg) [5] |
| Material temperature, standard | 180 °F (80 °C); modified to 400 °F (205 °C) [4] | 180 °F (82 °C) [5] |
| Body and contact materials | 6061-T6 aluminium, 304 or 316L stainless body; 304 or 316L contact [4] | 304 stainless body; 304 or 316L contact [5] |
| Seals | Nylon, PET, 25% glass-filled PTFE or felt bonnet and side seals; silicone rubber load seal [4] | PET and silicone rubber pressure plate; silicone rubber load seal [5] |
| Actuation | Double-acting air cylinder, hand wheel, chain wheel or electric actuator [4] | Double-acting air cylinder [5] |
| Compliance | ATEX Zone 20 (internal), Zone 21 (external), FDA [4] | ATEX Zone 20 (internal), Zone 21 (external), FDA, USDA Dairy Standard [5] |
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Suppliers linked to this page list powder hopper valves; each card links to the page reviewed.
Listings include sanitary powder butterfly valves, inflatable-seal butterfly valves, rotary dosing valves and double-rotor metering valves.
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This is a functional reference built from the sources cited; it is not one maker's design.
| Part | Role | Fix in the order |
|---|---|---|
| Body and flanges | Connect to the hopper outlet. [1] | Size, flange, material. |
| Disc, gate or rotor | Shuts off or meters flow. [2] [1] | Type, rotor pockets, tips. |
| Seat or seal | Stops leakage. [2] [1] | Inflatable seal, packing, air purge. |
| Drive | Turns rotor or disc. [1] | Motor, reducer, turndown. |
| Actuator | Opens and closes. [2] | Manual or pneumatic. |
| Monitoring | Confirms motion. [1] | Zero-speed or position switch. |
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A powder hopper valve quotation needs values for your material and outlet. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.
| Field | What it means and published values | Ask the supplier for |
|---|---|---|
| Nominal Diameter (mm) | 6–26 in rotary valve sizes in one range. [1] Slide gates: 6–30 in (150–760 mm) square or rectangular; 2–10 in (50–255 mm) round sanitary. [4] [5] | Outlet and flange size. |
| Operating Temperature (°C) | High-temperature option in one range. [1] Slide gate standard 80 °C, modified to 205 °C. [4] | Rated range. |
| Flow Coefficient (Cv) | For powders, capacity is volume per hour by size and rpm. [1] | Capacity at your fill factor. |
| Leakage Rate (%) | Seal and air leakage. | Leakage at your pressure difference. |
| Actuation Time (s) | Open and close time. | Time for your actuator. |
| Supply Voltage (V DC) | Actuator or motor supply. | Supply and controls. |
| Power Consumption (W) | Motor size set for the application. [1] | Motor rating. |
| Ingress Protection | Enclosure of motor and controls. | IP rating; hazardous-area rating. |
| Body Material | Carbon steel, 304 or 316 stainless steel. [1] | Grade and finish. |
| Seal Material | Packing gland, air purge or inflatable seal. [1] [2] | Seal type and compound. |
| Weight (kg) | Support at the outlet. E.g. 15–90 kg for 6–30 in slide gates. [4] | Weight with drive. |
| Pressure class | Standard up to 3.5 bar; reinforced to 6 bar; custom above 20 bar (Coperion). [3] | Differential pressure; leakage air. |
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Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Material: [name; bulk density; particle size; flow] Duty: [isolate; meter; airlock; pressure difference] Rate: [kg/h; m³/h] Outlet: [size; flange; temperature] Build: [material; seal; CIP; hazardous area] Supply: [actuator; drive; switches; quantity]
These companies list powder hopper valves.
Lists sanitary powder butterfly valves, inflatable-seal butterfly valves, powder discharge valves, rotary dosing valves and double-rotor metering valves.
Product scope checked 2026-10-11
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
Convert the required mass rate to volume using bulk density, then pick a size and speed whose capacity at the expected pocket fill exceeds it; one maker's chart lists capacity at 100% fill by size and rpm. [1]
One maker gives 3–5 SCFM of compressed air for its air-purge seals. [1]
One maker lists powder butterfly, inflatable-seal butterfly, rotary dosing and double-rotor metering valves. [2]
Coperion states standard rotary valve designs suit pressures from a few millibars up to 3.5 bar, reinforced versions up to 6 bar and custom designs above 20 bar. [3]
Sources checked 2026-10-12. Cyclonaire publishes its own rotary valve capacity chart and options; AVM lists its own powder valve range; Coperion and Vortex publish rotary valve and slide gate specifications for their own products. Capacity for your material must come from the supplier's data at your fill factor and pressure difference.
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