Superior Technology for Plastics Conveyance
ConTranTM by HorizonPSI has enjoyed immense success in the consumables market by protecting post extrusion product shape and reducing product degradation. ConTran is a continuous pneumatic transfer technology that utilizes dense-phase waveform conveying to gently handle materials.
But ConTran technology also provides “Best in Class” system design for reducing plastic pellet degradation, streamers and angel hair in the plastics industry. After commissioning a system, one customer asked “why doesn’t everyone switch from dilute phase to ConTran?” The answer is: it depends on whether a manufacturer wants to address degradation with upfront system design or fix the issues when they arise.
So, what are the notable physical differences of a ConTran Dense Phase System vs. a typical Dilute Phase system?
- The ConTran Air Controller – This component modifies the density of the air entering the blower to compensate for system fluctuations, such as material throughput and/or air loss, by increasing or decreasing the mass flow of air in the system. This maintains a constant pre-selected material-to-air ratio during conveyance thus creating and sustaining a low velocity, dense phase waveform flow pattern.
- Pressure Blower Flexibility – Due to the inherent efficiency and quick response time of the ConTran air controller, a positive displacement blower can be utilized versus expensive air compressor powered alternatives.
- High Performance Rotary Valve – This valve provides a repeatable air loss calculation as material is metered into the conveying system. This repeatability allows the ConTran air controller to consistently compensate for system air loss thereby maintaining a stable conveying condition.
- Control Package – The ConTran system includes a PLC-driven control package with pre-engineered logic to provide easy control and troubleshooting of the system parameters.
- Metal-to-Metal Couplings – We include machined metal-to-metal couplings to assure an even connection with no rough or sharp edges that may harm the pellets. Compression couplings are often misaligned or ill-fitted which causes gaps and edges that get worse over time. The metal-to-metal couplings also utilize an O-ring gasket, to avoid contamination concerns.
- Plug-Style Diverter – To ensure an even, ledge-free interior, we include plug-style diverter valves in lieu of wye-line or flapper diverters. Plug-style diverters have an internal plug with a bored hole that rotates to the correct position which assures an even, ledge-free interior.
These components help us build systems that deliver the following benefits for plastic manufacturers:
- Efficient Line Purging – Our ConTran system stops the flow of product in the convey stream the same way as a dilute phase system. However, since the blower includes a variable frequency controller, we slowly increase the blower speed, to gently push the residual material to the destination. ConTran systems are often designed to automatically purge the convey line after each cycle prior to shut down doing so with less damage to your pellets.
- Protective Conveying Velocity – A notable feature of dense phase conveying is the reduced product velocity during transfer. This reduced velocity lessens skins, streamers and angel hair formation and fines. In all pressure systems, air is compressed at the start of the system and then decompressed throughout the convey line. In our lab, the exit velocity for a ConTran system set-up was 1,932 FPM versus a
Dilute system setup of 4,443 FPM with each system running at 6PSIG. This 3,288 FPM reduction will result in a significant benefit to product integrity. - Beneficial Material-to-Air Ratio – Typical dilute phase systems are designed with up to a 10:1 material-to-air ratio. Therefore, dilute phase systems use a lot of air with minimal product in the convey stream which exposes the pellets to more contact with the convey pipe raising the probability of skins, angel hair formation and fines. Our ConTran dense phase system is designed with material-to-air ratios of 15:1 to 20:1 minimizing convey pipe contact and pellet damage.
- Reduced Heat Exposure – Our ConTran systems use much less air to convey product compared to dilute systems. The ConTran system is designed with 178 ICFM of inlet air flow compared to 462 ICFM in a 4 inch dilute phase pressure system with both running at 6 PSIG pressure. Typically, you will gain 13°F for every 1 PSIG of air pressure utilized by the system. So given a 90°F day, any pressure system running at 6 PSIG would have an increased temperature of 168°F ((6 PSIG x 13°F) + 90°F). We typically utilize air-to-air heat exchangers to reduce the air temperature to which the pellets are exposed, but a ConTran system exposes the pellets to a lower air temperature compared to dilute phase systems. Less air and more product in the convey stream reduces temperature gain in the plastic pellets as they reach their destination.
- Efficient Elbow Design – Dilute phase systems typically include long-radius elbows (12 x diameter of convey line) to reduce pressure drop in the convey line. Some dilute phase systems utilize deflection elbows which have a reduced radius and thereby reduce friction, however each of these have an expanded pocket causing a ball of material suspended in air to rotate. A ConTran system can utilize short radius elbows (6 x diameter of convey line) since there is less air at a lower velocity and is less susceptible to an increase in line pressure. Shorter radius elbows reduce friction between pellets and elbow lessening skins, streamers and angel hair formation and fines, while not allowing an expanded pocket that may harbor residual material preventing a full material purge from the convey line.
- Untreated Convey Pipe – Many dilute phase systems incorporate the use of expensive treated pipe (i.e. shot peened or spiral grooved) to deal with skin and angel hair. But treated pipe simply breaks the skins or angel hair into smaller fragments, which may appear to solve the issue, but in reality, creates dust in your finished product making it inconsistent. The ConTran system proactively reduces skins and angel hair and is therefore able to use smooth interior wall pipe which is a better way to reduce convey line friction and cost.
- Reduced Electrical Costs – By consuming less air, ConTran is able to utilize smaller motors with lower running horsepower (HP) to deliver material from less electricity. Depending on time, line size and distance, this can result in significant utility savings.
If you are building a new facility, increasing capacity within your existing system or encountering skins, fines, streamers or angel hair that are negatively impacting your finished product, give us a call at 800-842-1600 or contact us to talk with an in-house Plastic Systems Sales Engineer. Or learn more about HorizonPSI’s Plastics Industry capabilities.