Pneumatic conveyors are ideal for moving small dry, objects like granular material, fine silica, and powdered substances. Examples include: plastic pellets, talc, alumina, fly ash, coffee, seeds, grain, and flour. Note that they are not suitable for use with slurries, cements or liquids. They give numerous industries the ability to transport materials without the risk of the products being contaminated or lost. They are used as a replacement for mechanical conveyors, which do not move small objects nearly as well or as safely as pneumatic conveyors. (Mechanical conveyors move large objects using spinning rollers, vibrating plates, and moving belts.)
A wide variety of industries use pneumatic conveyors for processes such as bulk bag unloading, railcar unloading, and food handling. Some of these industries include: food processing, pharmaceutical processing, mineral processing and petrochemical processing.
The earliest use of pneumatics for conveying was recorded around 1950 in Germany, when a man by the name of Gasterstadt experimented with 100 meter long horizontal pipes and developed the first pressure drop flow meter system. The next decade, professors Rumpf and Barth of Karlsruhe Institute of Technology (formerly Karlsruhe University) continued this work. Around this same time, at Nagoya University in Japan, a group of students was assigned to come up with a way to conduct solid material conveying throughout a multi-level facility. Their studies resulted in several advances in pneumatic conveying systems both then and later in their careers.
Meanwhile, in the USA, a number of large companies in the energy generation industry, and others, invested time and energy into developing pneumatic conveying systems for their various purposes. Through their efforts, and the efforts of researchers at Cambridge University, they came up with two major schools of pneumatic conveying: dilute phase and dense phase. These conveying types are still used today.
How It Works
Pneumatic conveyors use a combination of air/gas flow and pressure differential in order to force powder bulk and dry bulk materials through the pneumatic system. This pressure is a negative pressure that forces the material and the positive pressure inside the equipment to move inside the pipe.
Pneumatic conveyors work inside a fully enclosed pipe, which typically lacks a rubber conveyor belt. They work this way in order to prevent fine powdered materials from spilling or escaping into the air, and getting stuck between the mechanical components of a belt, respectively.
There are two main ways to categorize most pneumatic conveyors, depending on conveyance speeds and pressure. The first type is known as a dilute phase conveyor and the second type is known as a dense phase conveyor. A less known pneumatic conveying method is lean phase pneumatic conveying.
Dilute Phase Conveyor
This type of conveyor system is the most common. It gets its name from its ability to use compressed air or a vacuum to dilute materials by suspending them in a conveyance channel and preventing them from making prolonged contact with its surfaces. In turn, the materials can flow without obstruction from the source to the destination. Dilute phase conveyors use high pressure and they work best when transporting materials over long distances.
Dense Phase Conveyor
Dense phase conveyors are equipped to handle the transportation of larger materials, and thus do not feature a vacuum or compress air mechanisms. In a dense phase conveyor, objects slide along the bottom of the conveyance channel instead of being agitated and suspended inside it. This conveyor type works best with abrasive or fragile materials. The configuration of a pneumatic conveyor system greatly depends on its intended operation, and the properties of the materials the machine will work with.
Lean Phase Conveyor
During lean phase conveying, conveying is under one bar. Lean phase conveyors are very useful in the transportation of a wide range of materials, and they can be used in combination with both vacuum and pressure conveying.
Within these three categories are many other pneumatic conveyor types, such as pressure conveyors, food handling conveyors, mobile conveyors and vacuum conveyors.
This type of conveyor is a pressure vessel system. It can work on its own, or can be incorporated into existing equipment. Pressure conveying is best for strongly abrasive bulk materials and high capacities.
Food Handling Conveyor
Food handling conveyors are designed specifically to meet food industry standards. They must be cleaned meticulously in order to avoid cross-contamination. Typically, they carry food products like formulas, powders, beans and nuts.
These pneumatic conveyors are equipped with casters so that they can be moved around a workspace and positioned at discharge points as needed. Mobile conveyors can move materials drawn from a feed bin, container or pickup adaptor placed underneath a process vessel or bin. Mobile conveyors are perfect for environments in which you have to reposition your conveyor equipment a lot, as you do during grain collection.
Vacuum conveyors move material using compressed air-driven vacuum pumps. These are typically controlled automatically, and designed to stop and open up from the bottom when the container is full. They can move items a distance of more than 300 feet using pneumatic suction. Vacuum containers are ideal for moving materials from multiple sources to a single destination. They’re also important to environments that require sensitive material movement, because they greatly reduce the risk of occurrences such as: sparking, mechanical interruption or contamination.
Pneumatic conveyors have a few key components. These include: a feed system, a conveyor line, gaseous flow equipment (air mover) and solid gas separation equipment. The feed system feeds the solid material into the gaseous stream as it blocks the gas from continuing on into the storage systems. The conveyor line, sometimes called a conduct line, carries the items or material down the line and through the system. Usually, the solid gas separation equipment is a centrifugal separator, jet filters or bags. The gaseous flow equipment, or air mover, is often something like a stainless steel positive displacement blower. Other common conveyor components include: dust collection systems, chutes, diverter valves, rotary valves, bin vent filters, end receivers and termination vessels.
If you need to move dry bulk material, pneumatic converters offer many benefits that others, such as tubular drag and flexible screw conveyors, do not. First, free from components like a rubber belt, they create a much safer environment for products, ensuring that they will not be damaged or lost. Second, they keep product leakage to a minimum. This is especially beneficial for industrial applications that work with volatile or highly hazardous materials. Next, pneumatic conveyors allow for the operations to be more sanitary. In contrast to all these points, the use of a mechanical convey system can put smaller objects at risk of spilling, being scattered, or being dispersed. The risk of dispersion can be severely detrimental for applications used in the food processing and pharmaceutical industries, due to the strict and health and safety regulations implemented in all of their operations. Fourth, and finally, pneumatic conveyors come in a wide range of models and configurations to meet the various needs of multiple industries.
Design and Customization
When designing or customizing a pneumatic conveyor, manufacturers think about a few important factors. These include: conveying distance, material type, material bulk density and other material characteristics. These factors help them determine design details such as: air mover size, amount of compressed air to be used, power levels and general system pneumatic size.
Pneumatic conveying systems are easy to custom design and install. Manufacturers also think about structural design, and can build them to operate at maximum efficiency in your unique setting. For example, they can design them to move around complicated corners, between multiple floor levels, and between buildings.
Safety and Compliance Standards
Like all industrial equipment, pneumatic conveyors must first be built to meet OSHA standards. OSHA standards are in place to keep employees safe. Other important safety and compliance standards for your equipment, depending on your region, include: ASME B20.1-2015 (offers guidance regarding the design, construction, installation, operation and maintenance of both public and private sector conveyors and related equipment), ISO 7149:1982 (special safety rules), BS EN 1366-7:2004 (British standard detailing fire resistance tests for service installations of conveyors systems and closures; also available in DIN, ON or SS), BS EN 620:2002+A1:2010 (British safety and EMI shielding standards for continuous handling equipment and systems that move bulk materials), BS EN 618:2002+A1:2010 (British safety and EMI shielding standards for all continuous material handle equipment and systems that move bulk materials, except belt conveyors) and general ANSI standard guidance.
You will need to follow additional standards if you are working in the food and beverage industry, medical and/or pharmaceutical industry or military industry. To learn more about the standards you should or must follow, reach out to an industry leader.
Things to Consider
Choosing a conveyor of any type for your goods can be a daunting task. That’s why we recommend you work with a proven professional, who can guide you through the process and make sure you get the best system possible. To help you find such a professional, we’ve gathered a list of those pneumatic conveyor manufacturers and suppliers we know to be the best and most reliable. As you’ve undoubtedly noticed, we’ve placed their respective profiles and website links dispersed throughout this page. To find the right one for you, take the following steps: 1) Make a list of your specifications, requirements and questions. 2) Armed with this information, study the profiles of each of the companies listed here. Note which manufacturers offer the services for which you’re looking. 3) Make a list of three or four manufacturers to whom you’re most interested in talking. 4) Call each of those manufacturers, and discuss everything you have written down on your list. Make special note of their lead times, prices, delivery services, secondary services (including testing) and their overall attitude. 5) Compare and contrast their answers. Remember, your goal is to find a manufacturer that is willing and able to bring you the best product possible. Look for the manufacturer in whom you have the most confidence. Once you’ve determined what conveyor company that might be, reach back out to them and get started. Good luck!