Talking Tubing

Internal tube treatments

Experts say the initial design of your resin transfer tubing system is the most critical aspect to reducing the occurrence of streamers. However, if you’re the typical processor, your resin transfer system is already installed and was designed to meet your requirements at the time of installation, although those system requirements have probably since changed.

So, let’s say you’ve launched a new product made from a softer form of plastic and now, all of the sudden, you’re starting to see increased amounts of angel hair in your system and the resulting line blockages. What do you do?

Some of the potential solutions we’ve heard about at Pricefitters.com include treating the interior surface of the tube to reduce the amount of contact between the pellet and the tube wall or installing heat exchangers to lower the temperature inside the conveying tube. How effective have these treatments been for you?

Resin Line Problems

Many problems in the pneumatic conveying of resin centers around material build-up in the lines. Often times lines get contaminated from a shredded gasket (unless the Instalok coupling is used), long thin lines of resin, tiny particles of resin, dust, etc. These unwanted materials have been called many different things: fines, dust, tails, streamers, angel-hair, snakeskins, etc. But what exactly is the difference between these terms? Is there one?

From my understanding, streamers, angel-hair, and snakeskins are essentially the same thing. During conveying, heat develops due to friction between the resin pellets, the tubing wall and the conveying air. This friction heat in turn causes the resin pellets to soften. When the softened resin pellets come in contact with the tube wall, they smear and over time the smears become strands of material that fall into the air stream in the form of angelhair or snakeskins. This can result in line blockages that may ultimately reduce the efficiency of the resin transfer system.

Fines appear to be the catch-all phrase for material that isn’t an intact resin pellet, but isn’t as long as a streamer. Tails are a more specific form of a fine – when the pellets are cut, at times the cut isn’t clean and results in a little material left at the end of the cut. Tails and fines, in theory, seem to be less of a problem than streamers in terms of pipe blockage and material build-up because of their respective size.

What’s your experience with angel-hair or fines been? What solutions have worked for you if it’s a problem?