Unitizing Loads by Stretch Wrapping.

TM 38-400/NAVSUP PUB 572/AFMAN 23-210 MCO 4450.14/DLAM 4145.12

(1) Shrink films conform to odd shapes and

(9) Shrink ovens occupy more space than

sizes thereby offering greater versatility in package size

conventional strapping equipment.

reduction than conventional strapping.

(10) Some minor heat loss occurs in most

(2) Strapping impressions and product

convection-type shrink ovens. This must be considered

abrasion are eliminated.

if such units are to be used in refrigerated areas.

(3) The overwrap of shrink film shields the

(11) Shrink

equipment

for

high-speed

load from outside moisture conditions and also prevents

operation is more expensive than conventional

dust collection on the material. The load will frequently

equipment. (This can be offset by labor savings and

lend itself to temporary outside storage thereby easing

increased production.)

warehouse problems.

(12) Film envelope provides poor ventilation

(4) Shrink-film overwrap deters pilferage by

Remember, film use in not a method of packaging

making entry obvious when it has occurred.

protection, but a device to bond loads for movement

from shipper to customer. Condensation build-up must

Opaque film is also available which

be considered when selecting film, because certain

prevents ready identification of specific contents of the

commodities may be adversely affected.

pallet.

(13) Some types of film may pose disposal

(5) Shrink film is more safely removed from

problems.

However, polyethylene is the most

the pallet load than conventional metal strapping.

commonly used and can be easily recycled. If recycling

(6) Shrink wrapping is more economical than

is not feasible, incineration or disposal in sanitary

the standard combination of corrugated triple-wall

landfills is preferred.

containers and steel strapping.

h. Safety. Shrink-film operations will be inspected

g. Disadvantages.

at least every 3 months by installation fire prevention,

safety, or health personnel. Matters such as ventilation,

NOTE

use of protective equipment and clothing, and potential

Many of the disadvantages listed

fire conditions should be included in this inspection.

below also apply to conventional

i. Items not suitable for shrink-film application.

metal strapping methods.

Few products need to be eliminated from consideration

for shrink processes, even though they may be exposed

(1) Shrink wrap does not add stacking

to 500 . or higher, during the shrink process. Tests

strength.

Stacking strength of noncartoned loads

have shown that the temperature under the shrink film

depends upon the strength of the commodity.

normally rises only a few degrees above the room or

area temperature in which the packaging takes place.

(2) Shrink wrap provides no protection from

Products that are excluded from the shrink methods and

impact forces on sides or top of load.

procedures described because of their extreme heat

(3) Interlocking pallet patterns are particularly

sensitivity are ammunition, nuclear explosives, POL,

important in order to take advantage of the frictional

and other flammable materials.

forces of the package surfaces to provide load integrity.

(4) For best results, outside dimensions of the

3-91. Unitizing Loads by Stretch Wrapping.

load should be close to or slightly less than the size of

the pallet to allow the film to cling to the pallet. (Film

a. Definition of Stretch wrapping. A process of

will perform adequately, in most cases, even with a

enclosing a load by using a roll stock plastic film

material overhang.)

bonding to secure contents without the application of

heat to the film.

(5) Plastic film is elastic in varying degrees.

b. Methods of application.

Thickness and density of film must be

carefully selected to provide sufficient tension to

(1) Spiral. This method uses a film of a width

maintain load integrity.

less than the height of the load. A predetermined

number of film wraps are applied to the bottom of the

(6) When pallet loads are stacked, nailheads,

load, the film is spirally wrapped to the top of the load,

splinters, or a rough surface of the upper pallet can

and a predetermined number of film wraps are then

abrade or tear film. (Such abrasions or tears, however,

applied to the top of the load completing the wrapping

will not spread further by themselves.)

operation. (See figure 3-64)

(7) Most films are adversely affected by

sunlight. (Ultraviolet inhibitor film can be used where

this protection is desired.)

(8) Satisfactory application of film requires

precise control of temperature and time during the

shrinking process.

3-91