Talking Tubing

Wear Resistant (Porcelain-Lined) Elbows

For conveying today’s highly abrasive engineered resins, in particular glass fiber reinforced resins, PriceFitters offers wear resistant elbows. Known in the industry as "porcelain-lined," "ceramic-lined," or "glass-lined" elbows, these components are a proven solution to elbow wear.

Resin pellets generally travel at speeds between 3,500 and 5,500 feet per minute when conveyed pneumatically in dilute phase systems. As they travel, they come in contact with the inner wall of the conveying tube, especially when they reach an elbow. Highly abrasive materials conveyed in this manner can wear standard aluminum and stainless steel elbows prematurely.

For these types of applications, PriceFitters offers wear resistant elbows consisting of a steel elbow with a 0.004-0.007" thick coating of porcelain enamel on the inside surface of the tube. Our single coat, wear resistant elbows deliver approximately 12 times the service life of a standard stainless steel elbow, which can help eliminate downtime and maintenance costs.

Porcelain enamel is a borosilicate glass frit that is applied evenly to the tube wall at temperatures in excess of 900° F. Porcelain enamel provides a high resistance to abrasion due to its high surface hardness (6-7 on the MOHS Hardness Scale), resistance to gouging or crushing of its underlying enamel structure, and excellent lubricity which allows for pellets to slide along the wall with very little friction.

PriceFitters offers in-stock, wear resistant elbows in standard radius sizes from 1.5" OD through 4"OD. In addition, alternate radius bends, as well as fittings and transitions, may be ordered with either single (0.004-0.007") or double (0.008-0.012") enamel lining. Available base materials are limited to carbon or stainless steel due to the high temperature required when affixing the enamel.

SEE AVAILABLE WEAR RESISTANT PARTS HERE

Shot Peening

In a previous posting to this blog we requested that readers who have experienced issues with angel hair, streamers, or snakeskins write to us about their experiences and any solutions that they have applied.

One of the solutions that PriceFitters supplies is directional shot peening. The directional shot peening process is designed to roughen up the internal surface of conveying line tubing and fittings. During dilute phase pneumatic conveying, resin pellets travel at high rates of speed through the conveying lines. These high rates of speed result in heat developing from the friction between resin pellets, the tubing wall, and the conveying air. In turn, this heat causes the resin pellets to soften. When the softened pellets come in contact with the tube wall they slide leaving a smear of material behind, and over time the smears agglomerate or meld together to form strands of material that can fall into the air stream in the form of "angel hair" or "streamers". When the internal surface of the conveying tube is directionally shot peened, the interior surface of the tube becomes irregular and rough. As a result the resin pellet tends to tumble and bounce away from the tube wall instead of smearing against it. Ultimately, this reduces the occurrence of angel hair.

If you have had experience with directional shot peening or one of the alternative methods used to roughen up internal tube surfaces, we would love to hear about it.

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?

Welcome to “Talking Tubing!”

Pricefitters.com was created solely for the plastics processing industry and strives to provide all the tubing related components needed to install, maintain, and repair your material transfer lines. We designed this blog to discuss products, services, and related technology in the plastics industry. We hope “Talking Tubing” will be beneficial to all of us as we explore the products to the problems of plastic processing and its use of tubing related components.

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