Pneumatic Conveyors

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Pneumatic conveying systems are attractive alternatives to mechanical conveyors, which use moving belts, spinning rollers or vibrating plates to move objects. Mechanical conveyors are excellent tools for the movement of large objects, but they are limited in their ability to safely and effectively move very small objects like fine silica, powders and granulated materials. Pneumatic conveyors are much better suited to powder handling than mechanical conveyors because the conveyance channels used in pneumatic conveyors are completely enclosed. Pneumatic powder conveyors feature no belts into which powders can be ground accidentally, nor are there any mechanical components between which they could become stuck. Bulk conveying processes like railcar unloading, bulk bag unloading and some food handling processes are tasks best suited to dense phase and dilute phase pneumatic conveying.

Pneumatic conveyors are used for materials handling and transportation in a wide range of industries. The transportation of materials like flour, grain, seeds, coffee, fly ash, alumina, talc, plastic pellets and many other small products would be very difficult on an unenclosed, mechanical conveyor. Mechanical conveyors present too many opportunities for small objects to become scattered, spilled, ground up or otherwise dispersed in an undesirable way. These risks are especially threatening for food processing, pharmaceutical and other operations, whose products must meet strict standards of cleanliness and safety. Pneumatic conveyors offer food products manufacturers, pharmaceutical products developers, petrochemical processors, mineral processors and an extensive range of other industrial operations a means by which materials can be transported without the risk of product loss or contamination. Pneumatic conveyors can be custom-designed to meet the specific needs of a given operation and installed in a way that maximizes the conveyor's efficiency without impeding a facility's operations. Unlike many mechanical conveyor designs, pneumatic conveyors can be designed to move products between floor levels and around difficult angles. They can also be used outdoors and can move products between buildings.

Manufacturers of pneumatic conveyors design conveyor systems to handle a broad range of materials with various properties. Most pneumatic conveyors are designed to handle specific materials. These include abrasive materials like silica sand, hazardous materials like sodium sulfate, materials that cake or clump together like fly ash, sticky or moist materials like sugar, non-free flowing materials like flour, friable materials like graphite flakes and heterogeneous mixtures like cereal. Most pneumatic conveyors and vacuum conveyors belong in one of two categories; their pressures and conveyance speeds distinguish them from each other. Dilute phase conveyors are the most common pneumatic conveyors. They are called "dilute phase conveyors" because they dilute materials in a conveyance channel with compressed air or with a powerful vacuum. The materials become suspended in the channel and don't make sustained contact with its surfaces. This allows for a continuous flow of materials between their source and destination. The other main pneumatic conveyor category is dense phase. Dense phase conveyors do not produce an air stream that suspends materials. Dense phase conveyors are mainly used for the transportation of larger materials compared to those transported by dilute phase conveyors. Objects moved through dense phase conveyors slide along the bottom of the conveyance channel. Different operations call for different pneumatic conveyor configurations, and all of a material's properties should be considered when choosing between dilute phase and dense phase conveyors.

Besides the large variety of materials pneumatic conveyors are able to handle, they also have the benefit of low product leakage. This remains particularly important in industrial applications involving the conveyance of hazardous materials where a leak can be dangerous as well as a threat to the operation. Other benefits of pneumatic conveyors include sanitary operation and a wide range of models to suit the varying needs of different industries and products. Product damage in pneumatic conveyors is minimal compared to occurrences of product damage or loss in screw conveyors and tubular drag conveyors. Flexible screw conveyors and tubular drag conveyors are used for bulk material handling applications similar to those of pneumatic and vacuum conveyors. Although screw conveyors and tubular drag conveyors tend to require less energy than pneumatic conveyor blowers and vacuums, screw conveying is more likely to cause product damage by caking, smearing, packing or grinding. Non-free flowing, friable and liquefiable products in particular are most efficiently and carefully handled by pneumatic conveyors.

Image provided by Flexicon	Image provided by Nol-Tec Systems, Inc.

Image provided by Vac-U-Max	Image provided by Whirl-Air-Flow Corp.

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Pneumatic Conveyors Types

• Abrasive materials conveyors move coarse, rough materials at a slow pace. Abrasive materials conveyors often use compressed air to move the material through the system efficiently.
  
• Air conveyors use pneumatic power to transport materials.
• Bulk bag unloaders provide efficient discharging of powders or other dry bulk materials from bags, which were used to provide storage or easy transport for otherwise difficult-to-handle materials.
• Bulk conveyors handle a variety of materials for a wide and ever-increasing range of industries. These conveyors fill bags with bulk materials and transport them.
  
• Dense phase conveying is the process of transporting abrasive, friable or heavy materials such as sands, soils, minerals and rocks. Dense phase conveyors use an air compressor to generate high pressure levels to move materials slowly through the system.
  
• Dilute phase conveying is the process of moving non-abrasive, light materials like powders and grains. Dilute phase conveyors use low pressure air levels during the quick transportation of materials through the system.
  
• Enclosed conveyers are conveyor systems that are completely covered. Enclosed conveyors protect against product contamination and are particularly useful in applications involving the conveyance of sensitive products for many industries including the pharmaceutical, chemical and medical industries.
  
• Food handling conveyors are used in the food processing industry to convey a variety of food products including beans, nuts, powders and formulas. Because food handling conveyors transfer products that will eventually be ingested, cleaning is very important to avoid product contamination
  
• Mobile conveyors are rolled to and positioned at a desired discharge point. Material can be drawn from a container, a feedbin or a pickup adapter under a bin or process vessel.
  
• Pneumatic conveying uses forced gas to transport solid goods.
• Pneumatic conveying systems consist of all of the components used in air-powered conveyors.
• Powder conveyors carefully and efficiently transport powders that could be potentially hazardous, like sodium sulfate. 
• Powder handling is the process of industrial mixing, conveying, measuring or packaging of delicate, friable, sticky or free-flowing powdered solids.
• Railcar unloading is the method of transferring materials or products from railcars to storage such as silos or bins
• Vacuum conveyors are generated by compressed air-driven vacuum pumps that can be controlled automatically. When the material container is full, the vacuum pump is stopped and the bottom valve opens so the material can be discharged.

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Pneumatic Conveyors Terms

Air Compressor - The piece of equipment that creates pressurized air above atmospheric level in a dense phase pneumatic conveyor system (http://www.iqsdirectory.com/air-compressors).
 
Air Receiver - A tank that holds compressed air obtained from the system's air compressor in a dense phase pneumatic conveyor system.
 
Atmospheric Pressure - The amount of force the atmosphere exerts upon the earth's surface. Air in a pneumatic conveyor with pressure greater than 14.7 psi is considered compressed, and pressure below 14.7 psi is considered a vacuum.
 
Bin Vent Filter - In a pneumatic conveyor, the mechanism that removes or filters dust from system components, such as silos.
 
Casters - Wheels that make the pneumatic conveyors portable.
 
Diverter Valve - A mechanism that changes/diverts material flow in pneumatic conveyors to a different direction.
 
End Receiver - The mechanism that transfers the conveyed material from the tubing to the receiving bin.
 
Footprint - The total space that pneumatic conveyors occupy on the production floor.
 
Horsepower (HP) - A measure of the time rate of doing work.
 
Piping - The tubes through which the conveyed material travels to reach the intended destination. Pneumatic conveyor piping is arranged in a network that travels through the facility, avoiding obstacles.
 
Pneumatic Piping System - The entire system of pneumatic conduits used to transfer air or other gases between various operating components of the pneumatic system such as pumps, valves and actuators of the pneumatic conveyors.
 
Pressure - Force per unit of area.
 
Psi (Pounds per Square Inch) - A unit that measures the amount of pressure applied to an object.
 
Receiving Bin - Pneumatic conveyor component that obtains or receives conveyed material.
 
Relief Valve - A mechanism attached to different pneumatic conveyors components that alleviates built up pressure created by the system.
 
Rotary Valve - A mechanism responsible for releasing pneumatic conveyors materials under gravitational pressure.
 
Silo - A large container in which material is stored prior to conveyance.
 
Tubing Bend - Sections of tubes containing various degrees of curvature to facilitate the efficient maneuvering of pneumatic conveyors pipes, through which conveyed materials are transported.
 
Transporter - A container in pneumatic conveyors that stores material to be conveyed at a certain rate. Dense phase pneumatic conveyor transporters often accept compressed air into the container to move or transport the material under pressure.

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