Should I use aero mechanical conveyors or pneumatic conveyors? Which are better? If these are questions you’ve found yourself asking, you’ve come to the right place. We get asked these questions all the time about our various conveyors, and we love to help answer these questions for our clients.
Here at Spiroflow, we’ve been in the bulk material handling industry for more than 45 years and we have sold both types of conveyors over the years. Given our experience, we find that aero mechanical conveyors are often a better option in many different types of processes.
In this article, I’ll cover how each type of conveyor works, what their similarities are, how they’re different, and how you can best determine which is best for your particular application.
Which is which?
Before I go on, I want to define each type of conveyor. You’ll see that both conveyors have several similarities.
Aero Mechanical Conveyors
An aero mechanical conveyor or AMC is a tubular conveyor that utilizes a cable and disc assembly. The movement of the conveyor is so rapid it aerates the product. As a general rule, each pocket contains about 80% air and 20% material.
It is one of the most efficient methods of conveying materials. Its dust-free and clean handling properties make the conveyor a good fit for many applications across several industries.
In a pneumatic, the product is conveyed in a suspended stream of gas, usually air. When particulate materials are metered into an airstream, at an optimal solids-to-air ratio, the differential air pressure generated via a vacuum pump creates a high enough velocity to move the materials within the conveying tube.
Pneumatic conveying is a simple option to move material across challenging routes. The product is moved hygienically and is a good fit for several applications.
What are the differences?
Now, I’ll talk about what makes each stand out. One may be a better fit for your process than the other. Hopefully, this section will give you a clear understanding of what would work best for you.
Is power consumption a priority?
Aero mechanical conveyors can convey material at a rate from 9 ft3/min (11.8 m3/hr) to 36 ft3/min (51.9 m3/hr) depending on the diameter of the tube. These conveyors can pull this off by using a drive motor between 2-7.5 hp through a gearbox. Pneumatic conveyors require a 20-40 hp blower to reach comparable rates to an AMC.
Is noise a factor? Aero mechanical conveyors operate below 85 dBA. Pneumatic conveyors are much louder than AMCs. They must be remotely installed or have mufflers installed, adding to the cost of the system.
Does your process require multiple inlets or outlets?
Multiple inlets and outlets can easily be integrated with aero mechanical conveyors. When multiple outlets are used we recommend that the conveyor operates at half speed. This ensures that the material exits the conveyor properly. A tube valve at each outlet provides a smooth path for the ingredient to pass through.
Multiple outlets on vacuum conveyors require a separate receiver, its own pressurized air supply for filter cleaning as well as its own feed control valve and diverter valves. Additional piping is also needed to feed each individual usage point. Each receiving point requires venting of the motive air as well as filters, valves, diverters, and additional piping to direct product to each use point for pressure systems.
What about venting?
One of the major advantages of an aero mechanical conveyor is that it’s a balanced system. Ambient air is drawn into the conveyor along with the material and the material is discharged at the outlet of the conveyor. The displaced air is drawn back into the conveyor creating the balanced system. There are no special venting or filtering requirements because there is no pressurization at the discharge point.
Pneumatic systems handle venting differently. A receiver is utilized that requires venting off the motive air. Compressed air is also required for backwashing the filters and valves required for proper operation. Pressure systems require venting with filtration for the receiving vessel with exhaust entering into the surrounding area or vented outside the building.
Vacuum systems generally draw motive air from the surrounding area. It is important to determine if special air conditioning or additional climate control will be required in these areas. This could greatly increase the cost of heating or air conditioning and should be factored into your budget.
Aero mechanical conveyors are considered gentle conveyors. Pocket fill is typically 80% air and 20% material. The air stream carries the product around any corners in the system and mixtures are maintained throughout the conveying process.
Pneumatic conveyors use a similar air-to-material ratio. The entire length of the circuit is under the same pressure or vacuum. Because of centrifugal force, the product hits the walls of the tube hard. This can lead to degradation of the material and wear on the machine. Blends are more likely to separate while being conveyed over long distances.
Aero mechanical conveyors will transfer virtually all of the material introduced into the conveyor. Air purging is an option to clear out any residual material. Another option is dry cleaning, running a material like salt inside of the conveyor. Wash gates and drains are included when the application requires the system to be wet washed. When wet washing the AMC creates an agitation effect, like a dishwasher, that completely washes the inside of the conveyor. The conveyor can run while empty to dry out.
Pneumatic conveyors are also easily cleaned. They can be dry cleaned using salt to scour the conveyor. For wet cleaning, a “pig” is pushed through the piping system using compressed air.
Still have questions?
It’s difficult to say which conveyor will truly work best for your process without an engineer knowing more about your operation. Not all processes are the same. At Spiroflow, we have a team of engineers in the United States and the United Kingdom that can help you. Feel free to contact us if you have any more questions.