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August 1, 2012
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Send to KindleBest practices for specifying conveying and container handling equipment
Despite their importance, conveyors and container handling technologies don’t always receive sufficient consideration, and are often an after-thought. Here are nine reasons why they shouldn’t be.
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Despite their importance, conveyors and container handling technologies don’t always receive sufficient consideration, and are often an after-thought. They shouldn’t be. Things to consider:
1. Buy the conveyor pre-integrated. When considering a new line, it’s often smart to buy the conveyor as part of the machine. If you’re buying a packaging machine as a replacement, it might be tempting to retain the old conveyors, but be aware that the match might not be optimal, especially at transfer points. If the machinery builder supplies the conveyor already integrated, it reduces installation costs (versus purchasing a separate conveyor), installation time and line commissioning of I/O devices—especially since no standalone control cabinet is required and all VFDs, devices, power panel and PLC control panel are assembled onto the conveyor legs and frame. And all the information shows up on one screen—from motors, alarms and controllers—making things
simpler for the operator, technicians, and engineering staff.
2. Understanding how your containers behave is very important. You have to consider package geometry, center of gravity, and mass when specifying conveyors. For example, empty PET bottles act differently under pressure compared to filled bottles; hence the conveying and container handling has different requirements on different stages of the line. Fully understanding your package geometry can also help you avoid excessive backpressure. When you’re feeding a product, excessive backpressure can force a package into a machine before it’s ready. Whether you’re feeding, sorting or unscrambling, backpressure values are all dependent on the dimensional stability of the package; so, you need to completely understand your package or container specs when asking a vendor to design a starwheel or a timing screw around the package. Everything depends on form and shape. Starwheels are good for certain shaped containers, whereas timing screws are often better for rounded containers.
3. It’s all about control of the container. Conveying is rarely, if ever, just free-flowing product or containers. Proper spacing, position, orientation must be maintained. The goal is to ensure that product flow can take place within a given footprint. Conveying is not just a means to get something from one machine to the next. You must understand what the next machine can handle. You need to understand whether container control may best be achieved by single file or mass conveying, as well as how many lanes should be used. You must also determine the optimal speed. Different containers pose different questions: if you have an unstable container, how do you maintain control at the desired speeds? Do you need to control it by the neck, or the base? If something downstream breaks and conveying systems stop, can you control it? Is there adequate clearance and access to easily clear a conveyor of jams? Or will things slam into each other, lock up your machines, and stop your line? Slower speeds may mean a higher chance of success.
4. Consider unique features and options carefully. Some conveyor manufacturers offer a simplified change of direction, having integrated features into conveyors that turn packages at a 90 degree angle. It’s done with rollers in the conveyor mat top, and you can adjust the direction of the turn to your specific floor space. Similarly, some engineers prefer to have variable frequency drives (VFD) on every conveyor. Sometimes that extra hardware is an unnecessary expense; it’s a great feature, but you may not need VFDs on every conveyor. Depending on your product, some things will never need a change in speed. In those situations, VFDs may end up just adding unnecessary complexity, though some experts believe they’re worth it for future flexibility.
5. Pay close attention to friction, cleats, and inclines or declines in elevation. When conveying unpackaged foodstuffs with vibratory conveyors, ensure minimization of drops, with a general guideline being that no drop should ever exceed 6 inches. Similarly, when conveying delicate product, you need to seek out the most non-abrasive conveyors in a quest to reduce friction. If you bounce your product against redirecting plates, as opposed to a soft landing on other product, you will end up with less good product in the box. In terms of containers, timing screws can offer gentler handling compared to starwheels, and also tend to be more compact.
6. Features to look for. A valuable feature is modularity: sections designed to be quickly and easily combined and recombined. For energy efficiency, conveyors powered by direct current (DC) instead of alternating current (AC) can save energy. Beyond that, components (motors, drives, transmissions, gearboxes, controls, and an ever-widening array of bells and whistles) can be designed and matched with energy-efficiency in mind.
7. Ease of maintenance. The level of technology involved can directly affect the type of maintenance required and the skill level of maintenance personnel, and, therefore, should be a factor in evaluating the equipment’s total cost of ownership. A sometimes-overlooked component of good maintenance is spare parts inventory and equipment documentation. Determining which parts should be kept on-premises can be the difference between a short and extended stoppage.
8. Safety first. Conveyor accidents impact companies in lost productivity, workers’ compensation and even OSHA fines. Safety hazards should be designed out; however, there remains an inherent danger, owing to the fact that conveyors have moving parts. Use safeguards: conveyors should have lockouts, guardrails, and similar features. Pay attention to operator ergonomics such as easy and quick access to emergency stops and speed controls. Not every aspect of safety, however, can be factory-ordered. Your company should have safety policies that include employee training. There are federal government-compiled statistics on industrial accidents, categorized by type of equipment. It’s a good reference source to assure that employee training, at the very minimum, addresses the most common causes of conveyor accidents.
9. Sanitation. For food-contact applications, pay attention to sanitation and cleanability. If you’re trying to remove cross-contamination between product, make sure the conveyor belt design doesn’t trap particles. For food, beverage or pharma applications, look for conveyors with a minimum of nooks and crannies that can harbor bacteria and dirt. Verify that if the conveying chain is swabbed, that it removes 100% of the product. (That will be especially important for compliance with the Food Safety Modernization Act.)
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