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Extrusion Basics: Safe at Home, and at Work

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There is no place for risk in a factory. On the extrusion floor, it’s important to consider the potential hazards of heat, electricity, pressure, chemicals, and what’s above that could fall and what’s below that could trip you up.

Safety is on everyone’s mind and in the news these days, and rightly so. There are still many who see glory and strength in risk, a concept worth more consideration, but not here.

There is no place for risk in a factory, and it may take more courage to demand, follow, and encourage reasonable safety measures than it does to ignore them. Yes, it can be overdone, as can most everything else, but that doesn’t diminish the value of established practices, plus the “extra mile” now, to minimize the ravages of COVID-19 and keep the factory and workers in productive shape.

In extrusion, we must recognize the following areas of concern.

Heat. This mainly involves finger and hand protection, so wear insulating gloves where appropriate. The outsides of extruders may be warm, but they shouldn’t be so hot as to be dangerous. Know how to use a non-contact infrared thermometer, which are now used everywhere to spot COVID fevers. Keep burn remedies near the machines, as well as a pail of water (marked not to use on anything electrical). Make sure everyone, especially newbies and front-office people, knows that extruded plastic is dangerously hot even after it looks solid.

Electricity. This acts instantly, so we don’t get a warning. Electricians are aware of this — get yours to tell you how to be careful. Cover terminals, ground (earth) machinery, wear non-grounding shoes, mop and stop water leaks, and keep lockouts on high-power cabinets. An electrician should be on call, if not on the premises, at all times, along with a responsible authority to support a shutdown for safety reasons. In some lines, static electricity can build up and be a problem, but there are ways to avoid such buildup.

Pressure. Most extrusion lines have pressure gauges, but not all of them read correctly and very few are alarmed. Calibrate often. Insulate melt transfer tubes and be aware of danger of their breakage or separation when melt expands on reheating after full shutdown. And stay away from the die opening as much as possible.

Weight. Many extrusion dies are heavy and must be handled accordingly. This means using hoists and carts to move them, and thinking before taking a head apart. Can we avoid this and save time by using a purge? Should we replace a less streamlined internal component with a more streamlined one to reduce need for disassembly? And do we wear steel-tip safety shoes? These can look like ordinary shoes and feel remarkably light, and they may also come with nonskid soles.

Bags of resin or additives are typically 50 lb/25 kg. Not everyone can lift such a bag safely. Know your limits, and know how to lift with the legs and a straight back. As for drums and barrels, you can safely roll a drum weighing hundreds of pounds, but not everyone can do this. Get help — including a forklift — when needed.

Speed. Running faster may exceed safe limits for machinery such as pullers, winders, and cutters, as well as motor current (amps). Those limits should be known and respected. The common push to run faster may make more product and earn more money, but only if the increase can be profitably sold. Otherwise, the rush for speed may reduce dimensional precision and may require more resin to ensure thick enough product, maybe make more out-of-gauge scrap, and, thus, waste money. With products like pipe, dimensional variation may cause trouble with fittings, so too much focus on speed may even risk losing customers.

Fast-moving wire can also be a hazard, and its path must be guarded both before and after the die. Roll nips also need guards and an often-tested emergency cord to open them. And, in general, no neckties or loose clothing. Untucked shirts may be controversial, but rules should be clear and depend on what kind of equipment there is.

Height. Some extrusion, notably blown film, runs upward into a cooling tower. There may be places where tools or other loose objects can be left, and if they fall can injure people or damage machinery.

The floor. Look up to spot objects that could fall, but look down, too. Pellets, water, and oil are my main worries. Cleated shoes help avoid pellet slips; mopping oil leaks and drips isn’t so easy, as water won’t mix with the oil. In refineries, where petroleum leaks are common, they use special solvents. In an extrusion plant, cleaning the mop in detergent-rich water may work, and today’s cleaning specialists will know more. Don’t depend on me, except as the one who says, “Don’t forget about it.” 

Chemicals. Much noise is made about the “toxicity” of plastics — they aren’t — but when plastics are overheated some may degrade into compounds that are unhealthy to breathe. This is another reason to stay away from the die opening as much as possible. We all know what six-foot social distancing is now, and it applies here, too. And so do masks. I had to wear a 95% mask in some of my plant visits, and fortunately kept a few and use them now. (Tip: When you wash a mask, use detergent, and if you need fast drying, hang it over an ordinary table cooling fan.) Also, careless powder feed may put powder in the nearby air. If the area around your hopper looks like it just snowed, check where it’s coming from. Powder feed can be safely enclosed but seals and passages may need maintenance.  

Smoke at die lips. Masks don’t help much here but a vented blower (intake side) may. It may be harmless moisture, but that’s unlikely if the product looks OK, as too-moist feed (above 0.1%) makes pocks and dotted lines on the product. With some resins such as PET and nylon, it takes far less than 0.1% to weaken the product. These resins need to be super-dried before feeding or via a well-placed vent in the barrel (and high enough rpm). The smoke may be a volatile additive or even a residual monomer boiling off, especially if the melt temperature is too hot for too long. If it’s an additive, you may have less in your product than you think. In any case, find out what it is — condense and analyze. If left unknown, that contributes to fear.

Fire is rare but very serious. Most plastics are flammable but not explosive (except powders). Fire extinguishers should be visible, big enough, and the right type (i.e., not water-based). A melt leak in the head may spontaneously ignite in air, a signal that it needs to run cooler, or slower, if necessary.

Silence. This is a safety hazard if people are afraid to report a danger, or are just too busy to do anything about it. In my first industry job, we held a safety meeting every Monday morning at 8 a.m. We tech people took turns as presenters and the safety manager would provide us with plenty of material. He had lost an arm in a factory accident and just interacting with him reminded us to work safely. We covered outside dangers, too, such as drunk driving and hazards at home. It was a way of making sure we all showed up on time Monday morning after the weekend. But most important, it supported a culture of safety, which creates team spirit and suppresses the natural and otherwise glorious aspects of risk.

 

About the author

Allan Griff is a veteran extrusion engineer, starting out in tech service for a major resin supplier, and working on his own now for many years as a consultant, expert witness in law cases, and especially as an educator via webinars and seminars, both public and in-house, and now in his new audiovisual version. He wrote Plastics Extrusion Technology, the first practical extrusion book in the United States, as well as the Plastics Extrusion Operating Manual, updated almost every year, and available in Spanish and French as well as English. Find out more on his website, www.griffex.com, or e-mail him at algriff@griffex.com.

No live seminars planned in the near future, or maybe ever, as my virtual audiovisual seminar is even better than live, says Griff. No travel, no waiting for live dates, same PowerPoint slides but with my audio explanations and a written guide. Watch at your own pace; group attendance is offered for a single price, including the right to ask questions and get thorough answers by e-mail. Call 301/758-7788 or e-mail algriff@griffex.com for more info.

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