A rotary valve is a compact mechanical device broadly used in dry bulk materials handling applications to control the flow of dry bulk solids between two systems, upstream and downstream equipment. It is known by a variety of names, airlock valve, star valve, rotary feeder etc.
A rotary feeder a valve whose primary function is to feed or meter dry bulk solids from an upstream device to a downstream device without necessarily separating a pressure differential. An airlock feeder on the other hand is a valve that separates a pressure differential while feeding or metering dry bulk materials into a downstream system.
The blades of a rotary valve rotate inside the valves housing during operation. This rotation is driven by a motor. As the motor rotates, rotor pockets follow through. Dry bulk solids are supplied to the valve from upstream equipment through its inlet and settle in the pocket. The rotor continues to rotate and then discharges the dry bulk solids through its outlet port. Two types of rotation exist; load side rotation and return side rotation. The former is defined as the rotation of the rotor pockets from the inlet to the outlet, whereas the latter is the rotation of the rotor pockets from the outlet port to the inlet port.
Rotary valves are used in several industries for various industrial applications. It is used for several different reasons including; the control of dry bulk solids flows, feeding downstream systems, and maintaining a pressure differential between an upstream device and a downstream device.
Rotary valves are an essential part of any industry that processes dry bulk solids. Our experience within the industry of producing bulk handling systems allows us to design and produce cutting-edge airlock feeders used in various industries like cement, food, chemical, mining, plastics, agriculture etc., for numerous applications. We have the experience to design and supply our customers with the right rotary valves to meet their requirements.
Rotary airlock feeders are used to feed dry bulk materials to conveying lines from upstream devices such as storage silos or hoppers. They prevent air leakage while maintaining constant feeding of dry bulk materials.
Rotary valves are used to handle a wide range of dry bulk materials. Depending on the characteristics of dry bulk materials being processed, rotary feeders can be manufactured from stainless steel, carbon steel or hardox steel. Some of the bulk materials that can be handled using a rotary valve are sugar, salt, spices, wheat, rice, cornstarch, corn (maize), bran, coffee beans, broad beans, milk powder, coffee powder, wheat flour, cornstarch, plastic pellets, rubber powder, cement, fly ash, sand, alumina, copper oxide, sodium sulphate, calcium carbonate, limestone etc.
The processing of most food products is fairly easy hence the basic valve design can be used without compromising the product. Foods such as salt, sugar, baking soda, wheat, rolled oats, rice, dry beans, dried corn etc. that contain preserving or sterilizing agents and do not pose any corrosion risks can be processed by a standard constructed valve. On the other hand, foods such as fatty milk powder, and infant food products have a high degree of sensitivity and require the use of a properly configured valve. The configurations include stainless-steel with a polished internal surface. The dairy sector also makes use of the properly configured rotor valve significantly. The valve is responsible for material movement whilst maintaining sanitary surroundings. The valve is designed to keep away from bacteriological contamination.
This industry needs a valve that can simultaneously withstand the material’s hostility and maintain proper functionality. The valve serves two main purposes, (i) to behave like a lock – prevention of fire and gas reflux. (ii) to behave as a feeder – feeding the biomass to the pneumatic conveying line that conveys the biomass to the burning chamber. Thanks to the advanced geometry of the valve, large sized biomass particles of up to 50mm can be fed to the conveying line. The valves can be manufactured from carbon steel or cast iron. Further enhancements for durability are possible by means of coating.
Steel, aluminum, cast iron, bronze, and brass are some of the common raw materials used in many industries. Foundries are places that generate a high amount of dust. Metal melting and casting are the primary sources of dust emission. Dust collection systems are used to provide a safer environment. The dust is carried from the source by a suction tube attached to the dust collector with the hopper at the bottom. The hopper is fitted at the bottom with a rotary valve for continued release of dust. The dust enters the dust collector, and the heavy particles fall down to the hopper due to the baffle plates used in the system, then exits via the rotary valve into the bin.
Similar to the processing of infant foods in the food industry, the valve used in the chemical industry must be corrosion resistant, easy to clean, and able to withstand harsh environments. This industry involves the movement of delicate and pure chemicals whose purity cannot be imperiled. Hiccups must be avoided at all costs because of the nature of the industry.
Just as the name ‘aggregate’ entails, this industry is responsible for the manufacturing of building materials such as materials driven from the Earth’s core (sand, asphalt, cement, sandstone, garnet, ceramic, silicon carbide, slag etc.). Due to the nature of the industry, the valve must be solid to put up with the materials roughness and toughness. The prime function is to convey the material from an inlet down through its desired point of work. The valve must have the following characteristics; abrasion resistant, Hardox rotor and housing, and coated internal surface with tungsten carbide or hard chrome. This particular valve is not only used in this industry, but also in asphalt, cement, coal, and mining industries just to mention a few.
This is one of the industries that immensely makes use of the rotary feeder. The rotary valve is used mostly for handling grains. The grains are supplied to the valve, then the valve discharges the grains to the conveying pipeline. Properly selected rotary valves provide good service without harming handled product.
Other bulk materials handled include cement, calcite, ash, glass powder, marble powder, plastic pellets, sawdust, fly ash, coal, coal dust, wheat, flour, barley, feed, seed, corn, chickpea, bean, soybean, sesame, rice, rice flour, dried fruit, nuts, peanut, almond, sunflower seed, cotton seed, grain cereals, chestnut, coffee grain, coffee powder, sugar, salt, spice.
ATEX certified rotary valves play an important role in bulk material handling industries that process combustible dry bulk materials. They are used to help reduce or isolate explosion propagation in instances where a combustible cloud ignites. Polimak’s ATEX rotary valves are certified with 10 bar explosion tests.
An ATEX certified rotary valve does not cause a risk for explosion, hence it is an ideal choice for explosive zones. All rotary valve components such as rotary valve rotors, rotary valve endplates etc., comply with ATEX regulations and provide ex-proof characteristics. An ATEX certified airlock valve can be used in the food industry and many other industries that handle combustible dry bulk solids.
This is an explosive atmosphere with a combustible dust cloud that is likely to ignite frequently and extensively.
This is an explosive atmosphere containing a combustible cloud that ignites less frequently and less extensively compared to that of Zone 20.
In this zone, the explosive atmosphere contains a combustible dust cloud that ignites less frequently than in the aforementioned zones and occurs for a short period.
For the ones that involve hazardous gas, mist or vapor, the zones can be classified as follows.
This comprises areas where an explosive atmosphere containing dangerous gas, vapor or mist may combust frequently for an extended period.
This includes areas where the explosive atmosphere with hazardous vapor, mist or gas is likely to combust less frequently and less extensive compared to the effects in Zone 0.
An explosive atmosphere containing gas, vapor or mist that ignites less frequently and occurs for a short period compared to Zones 0 and 1.
Wide range of rotary valve models and configurations are available for different process conditions and physical properties of transferred bulk solids. According to process (silo, cyclone, jet filter, conveyor, pneumatic conveying system etc.); according to bulk material (fine powder, granule, abrasive, elastic, high temperature etc.)
Polimak provides its customers with state-of-the-art accessories that help improve the already existing bulk solid handling equipment. Most of our accessories are available in different shapes and sizes so that their functions can be adopted to a wide range of equipment.
Process and manufacturing industries such as cement, agriculture, food, chemicals, plastics and many others rely on rotary feeders to facilitate efficient bulk material flow. Facilitating efficient bulk material flow requires uninterrupted operations, unfortunately, operational issues can arise.
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