3 Pneumatic Conveying Hassles that can push Engineers to use Screw Conveyors

Posted by Justin Dechene on Jun 13, 2017 2:30:00 PM

Positive Physical Control vs. Indirect Control

The two primary means of conveying bulk products are by pneumatic and mechanical conveying with the most common type of mechanical conveyor being the screw conveyor. Both methods have benefits in certain applications over others. In general, finer, more consistently sized materials as well as some granular and pelletized materials work well with pneumatic conveyors whereas larger, irregularly sized materials, as well as moist, doughy, and packable materials work better with screw conveyors. However, in the middle reside the majority of materials for which both systems could be appropriate. Screw Conveyor Vs Pneumatic Conveying

In cases where either system could be used, sometimes previous hassles or perceptions of pneumatic conveying problems may lead engineers to use a screw type system. Let’s review three of these and consider why engineers should not be hasty to rule out pneumatic conveying - in fact how to overcome these problems to make pneumatic conveying more reliable. 

3 Pneumatic Conveying Challenges:

1. Justifying Investment in “Complex” Pneumatic Systems

At first glance, many assume that screw conveyors are overall simpler and thus where possible “simplicity is best”. While this advice may prove true in most cases, its not strictly applicable here. True, for short, direct conveying routes a screw conveyor often proves to be the most effective solution. However, pneumatic conveyors can actually prove more cost effective to operate when all factors are considered. Additionally, some OEMs now make smaller, self-contained pneumatic solutions that have even closed the initial price difference with screws. Despite larger initial capital costs, on larger applications that move large quantities of bulk material over long distances and throughout factories, screws are simply not feasible and pneumatic conveyors cost far less than screws to operate and maintain.

2. Maintaining Adequate Flow and Preventing Blockages

Some worry about the perceived difficulty of maintaining adequate flow through pneumatic systems, mistakenly thinking that the mechanical screw has the advantage in positive physical control. Putting aside proper design, installation, and operation as contributing factors, the biggest challenge has traditionally been the inability to monitor actual particle velocity - instead pneumatic and vacuum systems have operated with theoretical calculations of particle speed or measurement of air/gas speed as a proxy. When blockages occurred, air speed was cranked up. That often leads to product damage and system wear and tear....and so engineers turned, understandably to alternatives.

Until now! In an interesting application of triboelectric particulate monitoring traditionally associated with emissions monitoring, instrumentation can now measure actual particle velocity within a pipe. This allows engineers to observe particle velocity and adjust air speed to optimize performance. This substantially reduces blockages (associated with low air speed) and product damage, wear & tear and excess energy costs (associated with higher speed.)

particle velocity monitoring improves pneumatic conveying as an alternative to screw conveyorsThe devices which help operators maintain adequate flow rates and prevent blockages include Flow/No Flow Detectors and More Flow/Less Flow Monitors along with particle velocity monitoring systems to help prevent blockages in dilute phase and dense phase pneumatic conveying systems. 

3. Managing Maintenance Requirements 

While screw conveyors don't require large vacuum or compressor systems they often actually have more moving parts than pneumatic systems.  Maintenance needs can be further reduced by making use of Auburn Systems’ monitoring technology for mechanical conveying systems as well as filter receivers/dust collection systems on pneumatic systems. This can result in lower maintenance burdens in many applications. 

Conclusion

Don’t be hasty to assume the only solution for your application is a screw conveyor. These points highlighted above and others show that incorrect assumptions about pneumatic conveying can cause engineers to prematurely default to screw systems. Why not contact Auburn Systems today for more information about how their customers across countless applications are able to improve their conveying processes? Click here to contact us. 

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Topics: Particulate Monitoring, Process Control, Flow Control