Induction sealing has gained wide use in the drug industry since 1982, when FDA began requiring tamper-evident packaging for most OTC drugs. Besides providing tamper evidence, hermetic foil seals also prevent moisture and oxygen transmission and eliminate leakage.
For addressing tamper evidence, FDA mandated that container mouth inner seals “must be torn or broken to open the container and remove the product. The seal cannot be removed and reapplied without leaving visible evidence of entry. Seals applied by heat induction to plastic containers appear to offer a higher degree of tamper resistance than those that depend on an adhesive to create the bond.”
Air-cooled systems have become the standard in induction sealers.
Today, air-cooled induction sealers have replaced their cumbersome water-cooled predecessors. The Unifoiler waterless induction sealer by Pillar Technologies (Hartland, WI) takes up one-third the space of water-cooled equipment. One pharmaceutical customer is replacing 11 water-cooled lines with Unifoiler sealers and may be adding six new lines, says Cheryl Miller, induction sealer marketing and sales, Pillar Technologies.
“Their equipment was only two years old. Waterless sealers are rapidly replacing the older-style, water-cooled systems. Only extremely unique applications still have a need for the water-cooled machines. We have eliminated filters, hoses, pumps, radiators, flow switches, water, and in some cases, a mess,” she says.
Bill Zito, induction sealer vice president sales for Enercon Industries (Menomonee Falls, WI) says he’s not surprised when companies make the switch to a waterless sealer. “Enercon pioneered air-cooled technology more than a decade ago. In the last five years, many companies have switched over to our line of Super Seal air-cooled cap sealers.”
Different cap and bottle configurations often require different induction sealing methods. The approach used is dictated by the location, during cap application, of the foil in relation to the top of the cap, and to the lip of the container.
Many two-piece cap-in-cap systems typically require tunnel-style induction coils, because the foil is too far away from the top of the cap to be effectively heated by a flat-coil configuration. “The foil may be as much as 1¼4 to 2¼3 of an inch below the top of the cap. With a flat coil, the electromagnetic field that heats the foil dissipates,” says Zito.
Tunnel styles support high-speed capping when package sizes are uniform. For contract packagers sealing a range of cap sizes, “all-in-one coils” may be called for.
Both Enercon Industries’ All-in-One sealing head and Pillar Technologies’ Universal flat coil support sizes from 20 to 120 mm. The sealing heads have some capabilities to seal child-resistant (CR) caps. “We don’t have to automatically jump customers into a tunnel coil,” says Pillar’s Miller.
“With child-resistant and click-lock closures, the foil is located a little further down from the top of the cap. People think they need a tunnel coil for this. Our Universal coil provides greater power on the top end for sealing these systems,” she says.
Zito says that Enercon has done a great deal of statistical analysis supported by field and laboratory data that shows it is possible to have some success sealing a CR container with a flat coil. “Packagers do need to understand that the geometry of the CR bottle and the physics of the induction process makes a tunnel sealing head more efficient, allowing the user to seal faster and use a smaller power supply,” he says.
Induction-sealed two-piece cap systems often require a tunnel-style coil configuration.
New one-piece cap-and-bottle configurations are also challenging induction sealer manufacturers to adapt their equipment for successful sealing. The advent of air-cooled induction technology has propelled the use of induction sealers as an alternative to conduction sealing, where seals are applied before capping.
Enercon is working with several pharmaceutical companies that are considering converting from a two-piece cap to a child-resistant, single-piece senior-friendly cap. The company has developed a pressure belt induction sealer for these types of applications. The pressure belt is required in this instance because the cap in the push-and-turn package raises up after it is screwed on, putting the foil at a distance from the lip of the bottle, says Zito.
“In order to get a good induction seal, the foil needs to be in contact with the lip of the container. This is easy to do with a standard cap. The application torque applies enough pressure to seal the container. This new closure is torqued on like a standard cap, but once engaged, it locks on and lifts up,” Zito says.
The pressure belt maintains contact with the cap throughout the sealing process, forcing the cap to hold the seal in place. The pressure belt eliminates the necessity of getting the correct application torque. And, there is no need for a second retorquing step after the caps have been seated.
“Those companies are planning to replace our standard induction sealers with our new pressure belt solution. Once these packages are introduced, we expect to see a lot more people going to one-piece caps. They are less expensive, and you are eliminating the need for retorquing,” says Zito.
Pillar Technologies is offering an induction seal detection system that is more cost effective and features easier setup and alignment than previous models. Features include a relay encoder working with multiple optical sensors that signals faulty bottle/cap combinations. The device warns the operator of any containers that are missing liners. A pneumatic reject mechanism is available to kick defective containers off the line. The device detects loose or crooked caps or mis-seated containers and shuts down the line if a bottle becomes stalled under the induction coil.
Many of Enercon’s pharmaceutical customers use its integrated detection/ inspection and rejection systems, however the industry is still searching for a way to achieve 100% seal verification. Says Zito, “There is no way you can measure the quality of the seal, or tell if the bottle is completely sealed, when the cap is on the bottle.”
Pharmaceutical firms looking to achieve 100% seal verification may be able to benefit from recent induction advancements developed for other industries. These new capless sealing systems that apply the seal prior to capping are attracting interest. Mechanically, they operate similarly to conduction sealing machines in that the seal is applied onto the container and then held in place during sealing.
Induction, however, is a much easier technology to work with. Platen management and monitoring as well as temperature ramp up and cool down times are avoided. And induction requires one-tenth the power of conduction, where platens are typically heated to 400°F, says Zito.
“Induction sealing is much safer and more efficient. The induction heating head is cool, and you are applying much less pressure. We can also apply a silicon rubber pad on the sealing element to make up for any irregularities in the container. Then you can perform a water bath or retort process to test the seal before the cap goes on,” he says.
For capless sealing, companies can easily retrofit existing conduction systems with Enercon’s induction power supply unit and sealing heads. And they can employ seal and container handling techniques already being used, in indexing, rotary, and pressure-belt configurations.
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Zito says that a capless induction system is significantly less costly than conduction. But companies might spend more for cap-less induction than they would for on-cap induction. The capless solution induction equipment is about five times the cost of Enercon’s induction technology for sealing capped containers. Zito said the technology is under test with a number of customers. “Forty percent of our inquiries at the Pack Expo Las Vegas show were about capless sealing,” he says.
Although new closure systems and the desire to ensure that seals are completely sealed are spurring the industry to investigate new foil seal solutions, traditional cap and bottle induction sealing has remained the industry-preferred method for many major pharmaceutical manufacturers, because of its cost and ease of use.