- Created: 2018-02-06
To ensure products are properly secured when handling, storing and in transit, it’s helpful to understand the far-ranging options
by Donald Person, senior QA manager, and Paul E. Sowa, CPP manager, ADR/senior packaging research engineer, Signode Industrial Group LLC
Today, the U.S. Industrial Packaging market is nearly a $50 billion venture. A key part of this flourishing and ever-changing market is end-of-line packaging, which includes the materials, systems, equipment and methods used in the final stages of production before packages are shipped.
Although the packaging market continually progresses, some fundamentals remain constant: Customers require the best possible packaging, unitizing and loading methods that provide optimal product protection along with production efficiency, all at the lowest possible cost.
Safety has always been a consideration. Many factors go into properly securing a package, unit or load for handling, storage and shipment, including how a packaged product is stacked and how it is secured to the truck or rail car.
Strapping is used to contain a packaged product and must be done in a way that allows the product to be safely moved and stored. It is important to review all of your packaging, unitizing and loading requirements before deciding what strapping systems are appropriate.
For a detailed understanding of these factors, refer to ASTM D4675 Standard Guide for the Selection and Use of Flat Strapping Materials and consult your packaging suppliers for further information and best practices. Transportation regulatory agencies, such as the Association of American Railroads (AAR), also require compliance to specified packaging, unitizing and loading methods.
Packages, units and loads that have not been properly evaluated for safety considerations may present a potential hazard. The power of WCM. Not only is it the power of the engagement of the entire workforce, but by doing WCM you get that pride, quality, you get that entire workforce working in the same direction. It’s a very powerful tool. Customers also expect end-of-line packaging solutions to remain economical and reliable while factoring in the production process and sustainability requirements.
With many factors to consider, how does one begin to evaluate what end-of-line packaging solution is best? To do so, several factors should be taken into consideration, including packaged product characteristics, securement methods, storage methods and modes of transport.
Further considerations include the characteristics of the packaged product and the purpose of the packaging. Packaged products can be rigid, shrinking, expanding or have multiple characteristics. Packaging systems provide reinforcement, carton closure, edge protection, securement, unitization, baling, bundling, bracing, palletization, compression retention, product identification and pilferage reduction.
Strapping, shipping and storage
Several feet of steel or plastic strapping can replace bulky containers, cartons, bags, stuffing, foam and other methods of packaging. Product characteristics that influence strap selection include weight, stability, rigidity, integrity and sharpness of edges. Handling, shipping and storage considerations that affect the choice of strapping include: how far the package is shipped, how it’s handled by the shipper and receiver, and where and how it’s stored.
Steel strapping is offered in different finishes to suit various packaging methods along with the equipment used to apply the strap. Painted strapping offers corrosion resistance and is used mostly with notch-type seal systems to produce high joint strengths. Painted and waxed strapping also provides corrosion resistance and helps improve applied tension and tension transmission around load corners. Zinc finish strapping is waxed and has a zinc-enriched coating to provide rust resistance.
For some industries, steel is the only choice, but there are some disadvantages to its use, including high costs. It can also be dangerous to work with if not handled properly because of its sharp edges and ability to burst with the immense force of its stored energy when cut or damaged.
Alternatively, plastic (non-metallic) strapping is made of polyester, polypropylene, rayon and nylon. Generally, plastic strapping has controlled surface properties that minimize tensioning requirements, improve tension transmission around corners and enhance operating efficiency. All are split-resistant to increase reliability in tools and machines.
Polyester strapping can be tensioned to a higher percentage of its break strength than any other strapping material. It provides superior retained tension under hot, humid conditions and is more resistant to such environments than other plastic strapping. It provides greater package, unit and load stability during storage. It’s more tear and snag resistant than other plastic strapping.
Polypropylene strapping is used for light and medium-duty applications, mainly for bundling and carton closure and reinforcement. It has an “elastic” memory, which absorbs shock and keeps strapping tight. Although it’s unaffected by moisture and doesn’t rust, it can be sensitive to extreme heat, making it unreliable for hot environments. It’s especially suited to the food industry because of its ability to withstand cold, moisture-laden environments.
Nylon strapping is ideal for use in cold-room applications, such as food processing. It resists tension decay and provides better reinforcement over long storage periods. It conforms to changes in package, unit and load size as well as shape without sacrificing its reinforcement capabilities. Nylon features a smooth, lubricated finish that helps it run reliably in application equipment. And, it provides excellent transmission of tension around corners, for better reinforcement and protection.
Rayon cord strap is a bonded non-woven soft strapping product that can be easily knotted for securement. Compared to polyester bonded and woven cord strapping, rayon cord strapping has a lower tensile strength and a greater amount of elongation. Rayon strapping, however, is not water resistant and loses strength when subjected to moisture.
Conversely, polyester bonded and woven cord is more resistant to weathering and moisture. It also has high energy-to-break qualities for a given cross-section. Heavy duty and extra heavy-duty versions are suggested for applications where break strength, elongation recovery and high energy-to-break are overriding considerations.
Characteristics, physical properties
Whether plastic or steel, the correct strap has its own defined set of characteristics and physical properties that make it ideal for a given application. A few important characteristics and physical properties to understand include break strength, working range, applied and retained tension levels and elongation recovery.
A strap’s break strength is the tensional force, in pounds, required to break a strap. When selecting strapping, the strength of the strapping is a key property that contributes to protection and securement. Additionally, strapping does its work securing a package, unit or load within its working range. The working range is when the strap has been tensioned to its highest elongation without deformation and is still able to recover.
The ability of strap to retain its tension levels despite the shifting and settling that occurs during handling and transit is a critical factor in choosing a strapping for a specific application. Furthermore, elongation recovery is the ability of a strap to contract and remain tight when the package, unit or load settles or shrinks. As a package, unit or load is moved through the warehouse and in transit, it sustains shock, vibration and environmental conditions, all of which can cause shrinkage or settling.
Sealing and joining
The way the strap is joined together is dependent on the equipment being used to join it. Likewise, sealing methods are also influenced by the type of equipment selected to apply it.
A crimp joint seals the ends of strapping by pressing or crimping undulations into the seal and strapping ends. The strength of the crimp joint comes from the deformed seal creating high frictional forces. Crimp joints produce high static and dynamic joint strengths and are used for applications in which the strapped package, unit or load is subject to severe impact. Crimp type seals can be used to join steel and plastic strapping.
Another way to lock strap ends is to cut or notch the seal and the strapping it joins to form tabs at the edges. The strength of the notch joint comes from the mechanical interlock between the seal and strapping. Notch joints are typically used on waxed lubricated steel strapping in packaging and unitizing applications.
Sealless joints are made through interlocking key locks on steel strap and provide static joint strength similar to notch-type joints. The reverse lock sealless joint features a reversed interlocking key for added security in impact conditions.
Finally, buckles can serve as an economical option for low-volume manual applications and typically don’t require a special sealing tool. Buckles can be used with general-duty plastic and cord strapping.
Today, manual hand tools are ideal for environments where power sources aren’t available and speed isn’t a necessity. Manual sealers provide positive sealing action with minimal effort. Light and durable, they lock strap ends into a high-efficient joint, ensuring that packages, units and loads remain secure during transit, handling and storage. They are available in front action for light-duty applications as well as side action for heavier steel strapping applications.
Manual tensioners can strap a range of tension with minimal interruption, effort and strap waste. They are available in feedwheel models for general use or a push-type variation for round or irregular bundles. Windlass is another option, which is typically used with dry non-lubricated, thicker strapping. And finally, rack and pinion is available for heavy, round or irregular applications.
Combination tools function as tensioners, sealers and cutters, eliminating the handling of separate tools. Sealless combination tools require no seals, saving time and money. Production interruptions for reloading are eliminated along with the purchasing, inventorying and loading of seals.
Manual seal-feed tools are also available and can save time by eliminating the handling of separate tools. They do, however, require adding magazines of seals to the tool intermittently during production. It’s important to note that all tools should be cleaned and maintained regularly in accordance with safety, preventative maintenance and operation requirements.
Pneumatic tools are driven by compressed air and offer more speed and power than hand-held tools and can be lightweight and ergonomic. They require an ongoing clean, filtered and lubricated air supply plus ancillary parts and equipment to ensure that the tool is operating at its best.
Pneumatic tensioners minimize the effort to strap large or compressible packages. They provide consistent uniform tensioning through adjustment of an air pressure regulator. Similarly, pneumatic sealers are used to achieve high production on heavy strapping, especially when seals are in awkward positions or whenever productivity must be maximized.
Pneumatic combination tools have the tensioning, sealing and cutting functions combined in one tool. Combination tools eliminate the handling of separate tools. They are available in push-type, seal-feed and sealless models and perform well in harsh environments.
Some battery-operated tools now combine all the strapping functions into one tool, including tensioning, sealing and cutting. Battery-operated tools are lightweight, portable and faster than manual hand tools. Typically, battery-operated tools also require less maintenance than a pneumatic tool.
Recent designs feature an intuitive digital display that indicates characteristics of the tool’s operations from tension settings to speed. Battery-operated tools provide consistent performance. However, they often are not as durable as pneumatic tools. Portability can also be a downfall because movement from location to location can cause damage.
Regardless of the type of tool used, steel and plastic strapping can often replace bulky containers, cartons, bags, stuffing, foam, and other packaging and reinforcing materials while also increasing safety and performance with lower energy and maintenance costs.
Until recently, the latest tool innovations were limited to use with plastic strapping. In 2014, however, Signode revolutionized the market by developing the first-ever line of battery-operated steel strapping tools for the heaviest applications. As end-of-line packaging customers demand more by way of reliability, productivity and speed, suppliers continue to innovate to meet the challenge.