- Induction sealing
Induction sealing, otherwise known as cap sealing, is a non-contact method of heating a metallic disk to
hermetically sealthe top of plasticand glasscontainers. This sealing process takes place after the container has been filled and capped.
How it works
The closure is supplied to the bottler with foil liner already inserted. Although there are various liners to choose from, a typical induction liner is multi-layered. The top layer is a
paperpulp that is generally spot-glued to the cap. The next layer is wax that is used to bond the foil to the pulp. The bottom layer is a polymer film laminated to the foil. After the cap or closure is applied, the container passes under an induction coil, which emits a varying electromagnetic field. As the container passes under the induction coil (sealing head) the conductive aluminum foilliner begins to heat. The heat melts the wax, which absorbs into the pulp backing and releases the foil from the cap. The polymer film also heats and flows onto the lip of the container. When cooled, the polymer creates a bond with the container resulting in a hermetically sealed product. Neither the container nor its contents are affected, and this all happens in a matter of seconds.
It is possible to overheat the foil causing damage to the seal layer and to any protective barriers. This could result in faulty seals, even weeks after the initial sealing process, so proper sizing of the induction sealing is vital to determine the exact system necessary to run a particular product.
Sealing can be done with either a hand held unit or on a conveyor system.
A more recent development allows for induction sealing to be used to apply a foil seal to a container without the need for a closure. In this case, foil is supplied in a reel, it is die cut and transferred onto the container neck. When the foil is in place, it is pressed down by the seal head, the induction cycle is activated and the seal is bonded to the container. This process is known as capless induction sealing and has over recent years gained increasing popularity since it brings the benefits of induction sealing (clean, efficient, safe & reliable) but at the same time removes the requirement of a good cap/bottle fit, dispenses with cap torque requirements and also allows for bottle weight reductions since the thread can be reduced or removed.
Reasons that induction sealing may be useful
There are a variety of reasons companies choose to use induction sealing:
FDAregulations concerning tamper-resistant packaging, pharmaceutical packagers must find ways to comply as outlined in Sec. 450.500 Tamper-Resistant PackagingRequirements for Certain over-the-counter (OTC) Human Drug Products (CPG 7132a.17).
Induction sealing systems meet or exceed these government regulations. As stated in section 6 of Packaging Systems:
“…6. CONTAINER MOUTH INNER SEALS. Paper, thermal plastic, plastic film, foil, or a combination thereof, is sealed to the mouth of a container (e.g., bottle) under the cap. The seal 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…”
Some shipping companies require liquid chemical products to be sealed prior to shipping to prevent hazardous chemicals from spilling on other shipments.
Induction sealing keeps unwanted pollutants from seeping into food products, and may assist in extending
shelf lifeof certain products.
Induction-sealed containers help prevent the product from being broken into by leaving a noticeable residue from the liner itself. Pharmaceutical companies purchase liners that will purposely leave liner film/foil residue on bottles. Food companies that use induction seals do not want the liner residue as it could potentially interfere with the product itself upon dispensing. They, in turn, put a notice on the product that it has been induction-sealed for their protection; letting the consumer know there was a liner on the plastic bottle prior to purchase.
How to select the right sealer
When selecting the appropriate induction sealing for applications, there are a few factors to consider. What is the speed of the production line? What is the size and type of cap being used? What is the chemical makeup of the container or inner seal? What are the contents of the container?
There isn’t a direct relationship between the induction sealer’s power supply kilowatt rating and its sealing capability. The kilowatt rating is only part of the process. In addition, when induction sealer’s coil design is incorrect, the quality of the seal will be inconsistent.
Induction Sealer Metering Devices
Because it is important to have a consistent seal from one run to another there are meters available that measure the strength of the field produced by the induction sealers to assure a consistent seal. These meters are great for testing the machinery as well as setting up the machinery especially on an automatic line that will require certain strength variations from one bottle to another.
Benefits of induction vs. conduction sealing
Conduction sealing requires a hard metal plate to make perfect contact with the container being sealed. Conduction sealing systems delay production time because of required system warm-up time. They also have complex temperature sensors and heaters.
Unlike conduction sealing systems, induction sealing systems require very little power resources, delivers instant startup time, and its sealing head can conform to “out of specification” containers when sealing.
Variety of products that use induction sealing
Cosmetics, health & beauty
*Agricultural and ag chem.
*Animal care and medicines
*Children’s toys (clays, bubbles, etc.)
*Home remodeling products
*Musical instrument supplies (cleaners, resins, lubricants, polishes)
*Personal pleasure products
*Manufacturing shop supplies
*School supply products
dyes, carbon products….
* [http://www.automatetech.com/evolution.htm Evolution of Induction Sealers]
*1957-1958 - Original concept and method for Induction Sealing is conceived and proven by Jack Palmer (a process engineer at that time for the FR Corporation - Bronx, NY) as a means of solving liquid leakage from polyethylene bottles during shipment
*1960 - U.S. Patent (# 2,937,481) is awarded to Jack Palmer, in which his concept and process of Induction Sealing is made public
*Mid-1960s - Induction sealing is used worldwide
*1973 – First solid state cap sealer introduced
*1982 – Chicago Tylenol murders
*1983 – First
transistorized air-cooled power supply for induction cap sealing
*1985 – Universal coil technology debuted
*1992 – Water-cooled,
IGBT-based sealer introduced
*1997 – Waterless cap sealers introduced (half the size and relatively maintenance free)
*2004 – 6 kW system introduced
* [http://automatetech.com/evolution.htm The Evolution of the Waterless Cap Sealer]
* [http://automatetech.com/how.htm How Induction Sealing Works]
* [http://www.seligsealing.com Selig: Manufacturers of Induction Seal Cap Liners]
* [http://www.relco.co.uk/1inductionsealing/induction_cap.htm The Principles of Induction Cap Sealing]
* [http://www.pillartech.com/Sealers/hsw.htm Demonstration of How Capsealing Works]
* [http://www.fda.gov/ora/compliance_ref/cpg/cpgdrg/cpg450-500.html FDA’s regulations concerning tamper-resistant packaging]
* [http://www.seligsealing.com/pdf/brochure.pdf Overview of the various types of innerseals (liners), their uses and their construction. Page 7 specifically addresses the difference between a one-piece and two-piece innerseal.]
* [http://www.unipac.ca/fi_index.html More information/graphics]
* [http://www.enerconind.com/sealing/eLibrary/techArt/myths.pdf Myths & Mysteries of Induction Sealing]
* [http://www.pillartech.com/Sealers/Documents/2006-TC-Article.pdf How to Select an Induction Sealer]
* [http://www.automatetech.com Automate Technologies Induction Sealing Equipment - Manufacturer]
* [http://www.relco.co.uk Relco, Cap Sealing Equipment - Manufacturer]
* [http://www.enerconind.com/sealing/eLibrary/techArt/improveYourCapSealingIQ.html Improve your cap sealing IQ]
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