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A shrink tunnel or heat tunnel is a heated tunnel mounted over or around a
A shrink tunnel or heat tunnel is a heated tunnel mounted over or around a conveyor system
A conveyor system is a common piece of mechanical handling equipment that moves materials from one location to another. Conveyors are especially useful in applications involving the transport of heavy or bulky materials. Conveyor systems allow ...
. Items (such as packaging
Packaging is the science, art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of designing, evaluating, and producing packages. Packaging can be described as a coo ...
) have shrink film
Shrink wrap, also shrink film, is a material made up of polymer plastic film. When heat is applied, it shrinks tightly over whatever it is covering.
Heat can be applied with a handheld heat gun (electric or gas), or the product and film can p ...
loosely applied; with heat, the film shrinks to fit snugly around the wrapped object.
Uses
* Shrinklabel
A label (as distinct from signage) is a piece of paper, plastic film, cloth, metal, or other material affixed to a container or product. Labels are most often affixed to packaging and containers using an adhesive, or sewing when affix ...
s.
* Combining small items for sale and display (example: bottled water).
* Tamper resistant or Tamper-evident bands or seals.
* Form large unit loads for transport.
* Form primary barrier on foods such as cheese, meats and fish.
* Skin packs.
Types
Several types of shrink tunnels are available. The heat source can be based onheating element
A heating element is a device used for conversion of electric energy into heat, consisting of a heating resistor and accessories. Heat is generated by the passage of electric current through a resistor through a process known as Joule heating. He ...
(electrical resistance), infrared heater
An infrared heater or heat lamp is a heating appliance containing a high-temperature emitter that transfers energy to a cooler object through electromagnetic radiation. Depending on the temperature of the emitter, the wavelength of the peak of th ...
, steam, or gas flame. Often forced air is used to improve convection
Convection is single or Multiphase flow, multiphase fluid flow that occurs Spontaneous process, spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoy ...
, sometimes focusing the heat on one component of the item.
Tunnels are available with or without a conveyor system. Some are built into a production line or are integral with machinery that also applies the shrink film. Others are movable by hand or by castors. A shrink tunnel, referred to as an oven, may be equipped with an integrated conveyor of two different kinds: the roller conveyor or the belt conveyor. Roller conveyors can be used with polyolefin
A polyolefin is a type of polymer with the general formula (CH2CHR)n where R is an alkyl group. They are usually derived from a small set of simple olefins (alkenes). Dominant in a commercial sense are polyethylene and polypropylene. More speciali ...
, PVC
Polyvinyl chloride (alternatively: poly(vinyl chloride), colloquial: vinyl or polyvinyl; abbreviated: PVC) is the world's third-most widely produced synthetic polymer of plastic (after polyethylene and polypropylene). About 40 million tons o ...
, and shrink polyethylene
Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging (plastic bags, plastic films, geomembranes and containers including bott ...
films. The space in between the rollers is filled with hot air from the bottom of the tunnel to shrink the film layer around the object, creating a sealed package. When used with polyolefin and PVC based films the rollers are called "live" or spinning. When used with polyethylene films the rollers are called "dead" or not spinning. The tunnels with Teflon
Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a spin-off from ...
mesh belts and polymer
A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...
mesh belts are used for smaller packages, or when the package may have an instability and need a stable platform.
Some heat shrink tunnels have two or more zones for heating and controlled cooling.
See also
*Heat gun
A heat gun is a device used to emit a stream of hot air, usually at temperatures between , with some hotter models running around , which can be held by hand. Heat guns usually have the form of an elongated body pointing at what is to be hea ...
References
* Soroka, W, "Fundamentals of Packaging Technology", IoPP, 2002, * Yam, K. L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009, {{DEFAULTSORT:Shrink Tunnel Packaging machinery Plastics applications Industrial ovens