Dust or no dust…. that’s the question!
The formation of
Dust in polyolefin resins is a fact but the concentration of dust can be minimised by careful handling of the material. Fibres, angel hair and streamers on the other hand should not be present. The occurrences of fibres, angel hair and/or streamers indicate transport problems somewhere between production of the pellets and arrival in the hopper of the extruder.
The formation of dust, fibres, angel hair and streamers is dependent upon several parameters like conveying air temperature, conveying speed and the layout of conveying systems (internal roughness of the pipes, conveying distance, number of bends and the radii of the bends).
Temperature of the conveying air and the conveying speed are the most important causes for the formation of dust, fibres, angel hair and streamers. Conveying air temperatures over 70° C and conveying speeds over 35 m/s are seen as dramatic promoters.
Influence of conveying air temperature and speed
Also the internal roughness of the pipeline system has a significant influence on the formation of dust, fibres, angel hair and streamers. Not only on the amount but also on the kind; a smooth pipe surface “produces” angel hair and streamers and a relatively rough pipe surface “produces” primarily dust.
As already mentioned the degree in which dust, fibres, angel hair and streamers are “produced” is depending on the conveying speed and the conveying air temperature.
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| Smooth pipe “producing” angel hair and streamers | Rough pipe “producing” dust and fibres |
We at SABIC make a maximum effort to avoid the presence of dust and angel hair in our material. Special cyclone screeners and de-dusters are used during the loading of bulk carriers and to bag the material. Also our silos are frequently rinsed with water to avoid accumulation of dust during storage. In this way we are able to supply material with a minimum level of dust and the absence of fibres, angel hair and streamers.
Unloading of bulk carriers
Another source for dust, fibres, angel hair and streamers can be the unloading of bulk carriers. This because bulk carriers use compressed air, produced by a compressor (blower), to transport the pellets from the truck into the silo at your plant. So inaccurate unloading of the bulk contributes to the formation of dust, angel hair and streamers.
The used air speed and temperature during unloading are influencing the extent in which dust, fibres, angel hair and streamers are “produced”. The ideal situation to unload a bulk carrier into a silo would be a single 4” hose (100mm) with a length of 5m connected to a 4” filling pipe using only two 90° bends with radii of 7 to 10-times the diameter.
The European Chemical Transport Association (ECTA) formulated a Guideline for Standardisation of Equipment in which not only the requirements for compressors, and bulk carrier are established but also the unloading conditions, regarding the maximum pressure of 0.9 bars and the maximum temperature of 70 °C are mentioned.
Our Technical Marketing Department designed a colourful sticker mentioning, in six languages, the maximum pressure and temperature during unloading of a bulk carrier. This sticker can be attached to your silo(s) or filling pipe(s) to point out these unloading requirements to the truck drivers.
Stickers are available on request for our customers. Please contact your local Sales Office or
the Technical Marketing Department.
From silo to extruder
After the material is unloaded into your silo it still has to be transported from the silo to the extrusion lines. The layout of your internal conveying system is also of major importance to avoid dust, angel hair and streamers. Conveying speed, diameter of pipes, type and number of bends influence the degree in which you are “producing” dust, angel hair and/or streamers.
Dust and fibres can clog up your filters of the feed hopper and angel hair and dust can clog up the dosing units frequently used on extrusion lines resulting in downtime of your production!
You can contact our Technical Marketing Department for additional information via the following e-mail link:
TCC.TM-PE@SABIC-europe.com
