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 A pallet jack, also known as a pallet truck, pallet pump, pump truck, hand truck, scooter, dog, or jigger is a tool used to lift and move pallets. Pallet jacks are the most basic form of a forklift and are intended to move pallets within a ware ...

forklift truck A forklift (also called lift truck, jitney, hi-lo, fork truck, fork hoist, and forklift truck) is a powered industrial truck used to lift and move materials over short distances. The forklift was developed in the early 20th century by various ...

, or a container load represents a unit for shipping purposes. A unit load can be packed tightly into a

warehouse A warehouse is a building for storing goods. Warehouses are used by manufacturers, importers, exporters, wholesalers, transport businesses, customs, etc. They are usually large plain buildings in industrial parks on the outskirts of cities ...

rack,

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 modes of transport – from ship ...

truck A truck or lorry is a motor vehicle designed to transport cargo, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame constructi ...

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, yet can be easily broken apart at a distribution point, usually a

distribution center A distribution center for a set of products is a warehouse or other specialized building, often with refrigeration or air conditioning, which is stocked with products (goods) to be redistributed to retailers, to wholesalers, or directly to co ...

wholesale Wholesaling or distributing is the sale of goods or merchandise to retailers; to industrial, commercial, institutional or other professional business users; or to other wholesalers (wholesale businesses) and related subordinated services. In ...

r, or

retail store Retail is the sale of goods and services to consumers, in contrast to wholesaling, which is sale to business or institutional customers. A retailer purchases goods in large quantities from manufacturers, directly or through a wholesaler, and t ...

for sale to consumers or for use.

Function

Most consumer and industrial products move through the supply chain in unitized or unit load form for at least part of their distribution cycle. Unit loads make handling, storage, and distribution more efficient. They help reduce handling costs and damage by reducing individual handling. A typical unit load might consist of corrugated fiberboard boxes stacked on a pallet or

slip sheet Slip sheets are thin, pallet-sized sheets made of plastic, heavy laminated kraft paperboard, or corrugated fiberboard and are used in commercial shipping, replacing traditional wooden pallets. The unit load is usually stretch wrapped or shrink ...

and stabilized with

stretch wrap Stretch wrap or stretch film is a highly stretchable plastic film that is wrapped around items. The elastic recovery keeps the items tightly bound. In contrast, shrink wrap is applied loosely around an item and shrinks tightly with heat. While ...

pressure-sensitive tape Pressure-sensitive tape, known also in various countries as PSA tape, adhesive tape, self-stick tape, sticky tape, Sellotape, or just tape, is an adhesive tape that will stick with application of pressure, without the need for a solvent (such a ...

strapping Strapping, also known as bundling and banding, is the process of applying a strap 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 packag ...

shrink wrap Shrink may refer to: Common meanings *Miniaturization *Shrink, a slang term for: ** a psychiatrist ** a psychoanalyst ** a psychologist Arts, entertainment, and media * ''Shrink'' (album), album by German indie rock/electronica group The Notwist ...

. About 2 billion unit loads are in daily use in the United States.

Unit load design

There are three kinds of unit load design: component-based, systems-based, and standards-compliant. These have different applications.

Component-based design

Component-based design is the outmoded ''ad hoc'' method of unit load design. Components are sometimes over-specified to get assured performance, or tested to get inexpensive economic performance. Unit load storage and distribution systems consist of several interacting parts: *

Packaging and labeling 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 ...

(with product) * Pallet * Handling/storage equipment * The distribution environment (

shock Shock may refer to: Common uses Collective noun *Shock, a historic commercial term for a group of 60, see English numerals#Special names * Stook, or shock of grain, stacked sheaves Healthcare * Shock (circulatory), circulatory medical emergen ...

vibration Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic, such as the motion of a pendulum—or random, su ...

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity dep ...

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temp ...

, etc.) Considerable knowledge exists regarding the design of each of these components: their interactions have more recently been studied. When packaging, pallet, and handling systems are designed separately at different locations by different teams, the result might be inefficient unit load systems. The consequences of independent component-based design in the supply chain can include: *Unsafe workplaces *Product damage *High packaging costs *Reduced handling efficiency *Wasted natural resources *Reduction of environmental quality

Systems-based design

Systems-based design is a proven process of unit load component cost optimization based on an understanding of how the pallet, packaging and material handling equipment interact during product distribution and storage to design the unit load component parts. A systems-based approach to unit load design uses software tools and lab testing to create a package that uses just the right amount of material to protect the product, make for safe handling and transportation and minimize the use of non-recyclable materials.http://www.millwoodinc.com/resources/1/literature/Designing-The-Better-Unit-Load-From-The-Ground-Up.pdf Companies must now consider sustainability when determining how their packaging products will be reused or recycled at the end of their journey. By combining sustainability with unit load science, they not only create the optimal unit load, but also reduce the amount of packaging material used to transport that load, maximizing the materials that can be recycled and minimizing what goes into a landfill. Unit loads move via an unpredictable combination of many types of vehicles and storage areas, and the exact set is difficult to predict. Therefore, unit loads must be designed to travel by any such vehicles, and be stored in a wide variety of places. There are many similarities in the requirements for long-term storage and long-distance transportation of unit loads. Factors considered in unit load systems-based design include: *Distribution vibration and resonance *Load bridging and deformation *Unit load deflections *Interfacial friction and load stability *Compression stress and product protection *Vertical and horizontal stabilization Often a few inexpensive additions to the packaging can stabilize or stiffen a critical part and give good unit-load performance at a low cost.
Systems Based Design Eliminates Product Damage, Pallet Enterprise, pg. 90

Standards-compliant design

Technical standard, Standards permit a unit load to be designed and tested to meet a written

specification A specification often refers to a set of documented requirements to be satisfied by a material, design, product, or service. A specification is often a type of technical standard. There are different types of technical or engineering specificati ...

test method A test method is a method for a test in science or engineering, such as a physical test, chemical test, or statistical test. It is a definitive procedure that produces a test result. In order to ensure accurate and relevant test results, a test m ...

. A unit load can be verified to comply with a standard and validated to determine that the unit load is indeed effective. Standards provide institutional memory of the many conditions in real logistic trains, and collect the best practices for design and testing unit loads. Standards also describe load requirements, so that logistic providers can plan to meet them. * Material-based standards describe proven designs for particular circumstances. These are often used to describe unit load components such as pallets, strapping, seals, caps, retaining rings and battens. * Package testing, Performance testing standards describe needs and allow flexibility in the choice of materials. These are applied to particular unit load designs. ASTM International, ASTM D4169 has standard test protocols for unit loads. These vary based on the value of the load, the expected hazards, and the distribution environment. This is a performance-based standard. Another standard for unit loads is MIL-STD-1660, a standard for ammunition unit loads. DOD unit loads generally use pallets, which unfortunately do not pack efficiently into ISO containers. They weigh less than to limit the stresses on handling equipment. They are weatherproof, and stack high. They often use steel pallets, steel straps with notched seals, outdoor plywood, and plastic film. MIL-STD-1660 mandates that loads must never be less than the width of a pallet, while permitting some overhang. The markings are LOGMARS barcode, bar codes and standard inventory numbers. The standard describes major parts of the logistic path, including storage, ship, air, truck, forklift and sling (i.e. ship-to-ship and parachute). There are auxiliary standards for ship-to-ship transfers, and amphibious transfers. There are tests for stacking, transport, sling, forklift and pallet jack, impact, drop tests, tip, water-retention (i.e. weather), and safe disassembly. MIL-STD-1660 at first looks like overdesign to commercial unit-load designers. However, similar marking standards, safety, stability, volumetric efficiency, weight limits and impact resistance are routinely needed in commercial logistics. Sling handling is routine for small ports and noncontainer transports. Weatherproofness could be optional. It is sometimes valuable, and the baggies are cheap. High, standardized stacking could be optional as well. It is expensive, but sometimes valuable for rackless and military customers.

References

External links

Virginia Tech Center For Unit Load Design
{{Authority control Packaging Shipping containers