Strapping, also known as bundling and banding, is the process of applying a
strap
A strap, sometimes also called strop, is an elongated wikt:flap, flap or ribbon, usually of leather or other flexible materials.
Thin straps are used as part of clothing or baggage, or bedding such as a sleeping bag. See for example spaghetti s ...
to an item to combine, stabilize, hold, reinforce, or fasten it. The strap may also be referred to as ''strapping''. Strapping is most commonly used in the
packaging industry {{set category, first= industries (branches of an economy), alternative=industries, topic=Industry (economics)
For other meanings of "industries", see :Industries.
...
.
Types of strap
Strap is a flexible flat material, most commonly made from
steel
Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...
or various
plastic
Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...
s.
Steel
![FEMA - 37694 - FEMA Disaster relief supplies staged in Louisiana](https://upload.wikimedia.org/wikipedia/commons/b/bd/FEMA_-_37694_-_FEMA_Disaster_relief_supplies_staged_in_Louisiana.jpg)
Steel is the oldest and highest tensile strength strapping. It is available in a variety of widths and thicknesses as well as variations in the grade of steel. Steel is used for heavy duty holding where high strength and minimal stretch are desired.
Surface finish
Surface finish, also known as surface texture or surface topography, is the nature of a surface as defined by the three characteristics of lay, surface roughness, and waviness.. It comprises the small, local deviations of a surface from the perf ...
es for steel strap include:
paint
Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture. Paint can be made in many ...
, paint and
wax
Waxes are a diverse class of organic compounds that are lipophilic, malleable solids near ambient temperatures. They include higher alkanes and lipids, typically with melting points above about 40 °C (104 °F), melting to give low ...
,
bluing or
zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
and wax. The wax is used to better transmit the tension around the bundle and for use with certain types of tensioners. Common applications include steel coils, bundles of metal,
baling wire
Baling wire, otherwise known as bale wire, farm wire, haywire or soft wire, is a type of wire used in agriculture and industry for many uses such as mending fences or manually binding rectangular Hay#Small bales, bales of hay, straw bale, straw, ...
,
brick
A brick is a type of block used to build walls, pavements and other elements in masonry construction. Properly, the term ''brick'' denotes a block composed of dried clay, but is now also used informally to denote other chemically cured cons ...
s and
pavers, and roll end-binding. Steel Strapping is sold by weight rather than length, due to the natural expansion and contraction of steel in the manufacturing process. A 3/4 x .020 Steel Strapping Coil yields approximately 19.6 feet per pound.
Polypropylene
Polypropylene strap (oriented or ) is an economical material designed for light to medium duty unitizing, palletizing and bundling. It is available in various widths, thicknesses, and polymer variations (e.g., copolymers). Most polypropylene is embossed, some of which is also printed. This product offers higher elongation at break but tends to have irrecoverable dead stretch with constant stress.
What is not generally known to end users is that polypropylene strapping will lose about 50% of the applied tension within one hour, and that this tension loss is accelerated with increases in ambient temperature, consequently although suitable for packs with a degree of stored energy that will take up any relaxation that occurs in the strap, unacceptable strap slackness may occur after time if used on product that is 'Solid' such as bricks or concrete. Furthermore polypropylene strapping is susceptible to UV degradation and can quickly degrade if left outside exposed to the elements. The sensible choice of colour will retard the process, such as specifying black strap. Similarly, a UV inhibitor can be specified.
Polypropylene strapping may be printed, either during production and pre-embossing for the highest quality and precision, or post production over the embossing for a reduced quality. Both offer security and marketing advantages to the strapped product.
Polyester
Oriented or polyester and nylon are the strongest plastic strapping products and are used as a viable alternative to steel strapping in some industries. Polyester provides excellent retained tension on rigid loads. Its excellent recovery properties help a load absorb impact without strap breakage.
There are specialized types available for specific applications. For instance, in cold climates a strap bonded in hot melt glue is used because it is
weather-proof.
Nylon
Nylon strap has the greatest
specific strength
The specific strength is a material's (or muscle's) strength (force per unit area at failure) divided by its density. It is also known as the strength-to-weight ratio or strength/weight ratio or strength-to-mass ratio. In fiber or textile applic ...
of the three plastics, however it is rarely used due to its high price. In the past nylon strap used to be very popular, but over time polyester has replaced almost all of its use. One application that still uses this type of strap is cold room applications, because it does not
creep
Creep, Creeps or CREEP may refer to:
People
* Creep, a creepy person
Politics
* Committee for the Re-Election of the President (CRP), mockingly abbreviated as CREEP, an fundraising organization for Richard Nixon's 1972 re-election campaign
Art ...
as much as the other types of plastic.
Corded and woven
Corded and woven strapping are available in several constructions, primarily involving polyester and rayon. Some types are reusable. Because this system uses a buckle for a joint, corded and woven strapping can have a larger system strength than steel banding. Corded polyester strapping also has a higher elongation than other strapping systems, which gives it an ideal memory for sea and rail shipments. Because corded and woven polyester straps are light and soft, they are also a safer alternative to steel banding.
Paper
Paper
Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, rags, grasses or other vegetable sources in water, draining the water through fine mesh leaving the fibre evenly distributed ...
strap is used to strap paper products between
industrial processes
Industrial processes are procedures involving chemical, physical, electrical or mechanical steps to aid in the manufacturing of an item or items, usually carried out on a very large scale. Industrial processes are the key components of heavy ind ...
. This allows the bundle to be introduced into the process without the need to cut the straps, which can lead to the product falling apart prematurely.
Composite
Composite strapping has polyester filaments embedded longitudinally down the length of the strap that provides the tensile strength. These polyester yarn fibers are embedded within a polypropylene coating. The polypropylene provides foam to the strap but also improves the non-slip characteristic when combined with the wire buckle. In the load securing industry it is often referred to as “synthetic steel”. It is very
abrasion resistant and has the highest joint efficiency when used with a buckle. Both advantages are not affected by climate.
Uses of strapping
Examples include:
*Bundling items together for handling and shipment: newspapers, pipe, lumber, concrete block, etc.
*Attaching items to
pallet
A pallet (also called a skid) is a flat transport structure, which supports goods in a stable fashion while being lifted by a forklift, a pallet jack, a front loader, a jacking device, or an erect crane. A pallet is the structural foundat ...
s, skids, and
crate
A crate is a large shipping container, often made of wood, typically used to transport or store large, heavy items. Steel and aluminium crates are also used. Specialized crates were designed for specific products, and were often made to be reusa ...
s
*Reinforcing
wooden box
A wooden box is a container made of wood for storage or as a shipping container.
Construction may include several types of wood; lumber (timber), plywood, engineered woods, etc. For some purposes, decorative woods are used.
Boxes as ship ...
es, crates, and corrugated boxes, such as
gaylords
*Attaching items to flatcars, flatbed
semi-trailer
A semi-trailer is a trailer without a front axle. In the United States, the term is also used to refer to the combination of a truck and a semi-trailer; a tractor-trailer.
A large proportion of a semi-trailer's weight is supported by a tracto ...
s,
*Securing a
unit load
The term unit load refers to the size of an assemblage into which a number of individual items are combined for ease of storage and handling, for example a pallet load represents a unit load which can be moved easily with a pallet jack or forkli ...
of bricks, packaged glass, metal parts, etc.
*Closing corrugated boxes and
shipping container
A shipping container is a container with strength suitable to withstand shipment, storage, and handling. Shipping containers range from large reusable steel boxes used for intermodal shipments to the ubiquitous corrugated boxes. In the context of ...
s
*Securing coils of steel or paper
*Holding bales of agricultural products or textiles
*
Load securing
Load securing, also known as cargo securing, is the securing of cargo for transportation. According to the European Commission Transportation Department “it has been estimated that up to 25% of accidents involving trucks can be attributable to i ...
items within
intermodal container
An intermodal container, often called a shipping container, is a large standardized shipping container, designed and built for intermodal freight transport, meaning these containers can be used across different Mode of transport, modes of trans ...
s,
boxcar
A boxcar is the North American ( AAR) term for a railroad car that is enclosed and generally used to carry freight. The boxcar, while not the simplest freight car design, is considered one of the most versatile since it can carry most ...
s, and semi-trailers
Strapping is most often used in complete horizontal or vertical bands. ''Edge protectors'' are used to help spread the load at corners and reduce damage to the load by the tensioned strap. Strapping can also be used in loops attached to holding locations on rail cars, skids, etc.
Joining methods
After the strap is tensioned, the strap is often sealed to itself. Steel strap is sealed with a seal and notch joint, a seal and crimp, seal-less joint, or via
welding
Welding is a fabrication (metal), fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing Fusion welding, fusion. Welding is distinct from lower ...
. Seals come in various shapes depending on the application; some can be put on after the strap is tensioned, while others must be installed before tensioning. To create the seal, the seal and strap are notched on both sides; if one set of notches are created then it is called a ''single notch'' joint, if two sets of notches are created then it is called a ''double notch'' joint. Crimp joints also use a seal, but crimp undulations are used instead of formed notches. These crimps form great
frictional force
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding (motion), sliding against each other. There are several types of friction:
*Dry friction is a force that opposes the relative la ...
s which keep the joint from seeping. Seal-less joints are created by forming interlocking ''keys'' into the middle of the strap.
Plastic strap is most commonly joined by melting the straps together by adding heat to the joint. For lighter gauge strap, usually and narrower, heat is introduced with a hot knife system. First, the hot knife moves in between the straps. Then a
platen
A platen (or platten) is a flat platform with a variety of roles in printing or manufacturing. It can be a flat metal (or earlier, wooden) plate pressed against a medium (such as paper) to cause an impression in letterpress printing. Platen m ...
comes up and compresses the straps and hot knife against an anvil on the order of tens of milliseconds. The platen then drops and the hot knife is removed. After the hot knife is completely clear of the straps the platen comes back up and compresses the joint so that the melted portions of the strap mix and harden.
For thicker plastic strap, usually and thicker, friction is used to create heat within the joint. The process starts with the strap compressed between the platen and the anvil. There is a vibrator built into either the platen or the anvil, which has teeth; there are also teeth on the opposite component that does not move. The vibrator is quickly vibrated, which creates enough heat to melt the interface between the two strap, because of friction. To complete the weld the vibrator is stopped and the pressure held until the joint has solidified. Polypropylene and Polyester strapping can also be sealed in a similar manner with the heat being produced by sound in the form of Ultrasonic waves passing through the materials and exiting the molecular structure. They are then compressed as in a heat seal. In ultrasonic welding of plastics, high frequency (15 kHz to 40 kHz ) low amplitude vibration is used to create heat by way of friction between the materials to be joined. The interface of the two parts is specially designed to concentrate the energy for the maximum weld strength.
It may also be joined manually by crimping a seal or via a buckle.
The joint is the weakest part of the system, therefore the type of joining method used is very important if strength is an issue. The strength of a joint is defined as the force required to break the strap in uniaxial tension. This is then compared to the uniaxial strength of the strap and recorded as the percent difference (e.g., a sample of steel strap may have a break strength and the seal may fail at , so the seal is said to have a 60% strength). Hot knife welds have a minimum break strength of 55%. Friction welds have a minimum break strength of 65%. Well set up strapping machines or friction weld tools will aim for around 80% of break strength. Metal clips/seals are surprisingly low with circa 100 – 120 kg slip resistance.
For pallets strapping based on norm ASTM D3953 Standard Specification, the number of the strapping procedure is around 10 times for a minimal.
Equipment
![Strapping Saturn 2500](https://upload.wikimedia.org/wikipedia/commons/4/49/Strapping_Saturn_2500.jpg)
There are two major types of equipment available for strapping: hand tools and ''strapping machines'' or ''banding machines''. A dispenser is used with both types of equipment to dispense the strap. Some strapping machines have the dispenser built-in, others (typically those on large arch machines) have a separately powered dispenser, which can automatically load or thread new coils. Non-powered separated dispensers have a pulley which releases and activates a
brake
A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction.
Background ...
to stop the
inertia
Inertia is the idea that an object will continue its current motion until some force causes its speed or direction to change. The term is properly understood as shorthand for "the principle of inertia" as described by Newton in his first law ...
of the coil to keep the strap from over-running onto the floor. Typically dispensers used on large arch strapping machines have multiple pulleys to act as a way to store strap in a way that can be quickly dispensed. Smaller arch machines such as tabletop machines will feed strap into a pool box/accumulator instead. In both cases this is required otherwise the strapping machine will draw the strap faster than the dispenser can pay off.
Within hand tools, there are manual and automatic tools. Manual tensioners and crimping systems are available for low volume applications. Automatic hand tools are used for higher volume applications. Automatic tools are available using a
battery
Battery most often refers to:
* Electric battery, a device that provides electrical power
* Battery (crime), a crime involving unlawful physical contact
Battery may also refer to:
Energy source
*Automotive battery, a device to provide power t ...
power source or
compressed air
Compressed air is air kept under a pressure that is greater than atmospheric pressure. Compressed air is an important medium for transfer of energy in industrial processes, and is used for power tools such as air hammers, drills, wrenches, and o ...
. Both manual and automatic tools are available as combination tools, which perform the tensioning, sealing and cutting, or as separate tensioners, sealers, and cutters. Manual sealers for plastic strap always use a seal and a compression (serrated seals) or crimp joint (smooth-faced seals). Manual and automatic hand sealers for steel can use a seal or a seal-less joint. Automatic hand tools for plastic strap use a friction weld.
Strapping machines, also known as ''bundlers'' or ''banders'', are used for higher volume applications or special applications. They are available in horizontal and vertical orientations, however the vertical orientation is far more common. They are also available in bottom seal, side seal, and top seal orientations, which define where the joint is located on the bundle. They are available in semi-automatic and automatic varieties. The automatic versions can additionally to be used inline with
conveyor
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 ...
systems. A
photocell
Photodetectors, also called photosensors, are sensors of light or other electromagnetic radiation. There is a wide variety of photodetectors which may be classified by mechanism of detection, such as photoelectric or photochemical effects, or by ...
is used to detect when the bundle is in the correct location, stop the conveyors, and activate the strapping machine. Most however will be found in standalone applications.
Degree of automation
Strapping Machines
Semi-automatic and fully automatic strapping machines substantially improve efficiency in a warehouse and also the overall presentation of your packaged product. The labour-saving can often easily cover the relatively low cost of the strapping machine.
Both semi and fully automatic strapping machines can easily be included in a packing production line where packing tables and strapping machines are positioned at workable heights.
= Banding Machines
=
![ATS US-2000 Banding Machine](https://upload.wikimedia.org/wikipedia/commons/0/03/ATS_US-2000_Banding_Machine.jpg)
Banding machines like strapping machines allow the unitization and securing of products with a variety of different shapes and sizes.
Banding machines, however, are less damaging to the product being strapped, since the larger widths of bands available (20mm - 100mm) allow greater surface area that minimizes the harm on sensitive products. Banding machines can also run on paper straps for a more eco-friendly alternative to plastic strapping.
Banding Materials
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Operation is by photo-sensor, foot pedal, or a PLC, allowing these machines to be integrated into production lines or for standalone operation.
= Automatic Strapping Machines
=
Automatic strapping machines allow hands-free securing of parcels with automatically tensioned, sealed and cut polypropylene strapping.
Operation is either by a foot pedal or parcel sensor making these machines ideal for volume throughput.
= Semi-Automatic Strapping Machines
=
Semi-automatic strapping machines will allow one operator to automatically tension, seal and cut polypropylene strapping to give neat and secure fastening on any size box.
Adjustable strap tensioning to suit each package prevents strap damage to softer boxes.
See also
*Cable tie
A cable tie (also known as a hose tie, zip tie, or tie wrap) is a type of fastener for holding items together, primarily electrical cables and wires. Because of their low cost, ease of use, and binding strength, cable ties are ubiquitous, findi ...
References
Further reading
* Yam, K. L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009,
* Wulftec International
Wulftec International Inc. is a Canadian packaging company specialized in semi-automatic and automatic stretch wrapping machines, strapping systems and conveyor systems. It is a Duravant Operating Company; a global engineered equipment company. ...
Standards
*ASTM D3953 Standard Specification for Strapping, Flat Steel and Seals
*ASTM D3950 Standard Specification for Strapping, Nonmetallic (and Joining Methods)
*ASTM D4675 Standard Guide for Selection and Use of Flat Strapping Materials
*BS EN13891:2003 Tensional Strapping - Guide to selection and use of tensional strapping
*BS EN13394:2001 Packaging Specification for non-metallic strapping
{{packaging
Packaging materials