Unit load - AbsoluteAstronomy.com

A unit load combines individual items or items in shipping container

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...

s into a single "unit" that can be moved easily with pallet jack

Pallet jack

A pallet jack, also known as a pallet truck, pump truck, or jigger is a tool used to lift and move pallets.The front wheels are mounted inside the end of the forks, and as the hydraulic jack is raised, the forks are separated vertically from the front wheels, forcing the load upward until it clears...

or forklift truck

Forklift truck

A forklift is a powered industrial truck used to lift and transport materials. The modern forklift was developed in the 1920s by various companies including the transmission manufacturing company Clark and the hoist company Yale & Towne Manufacturing...

. A unit load packs tightly into warehouse

Warehouse

A warehouse is a commercial building for storage of goods. Warehouses are used by manufacturers, importers, exporters, wholesalers, transport businesses, customs, etc. They are usually large plain buildings in industrial areas of cities and towns. They usually have loading docks to load and unload...

racks, intermodal container

Intermodal container

An intermodal container is a standardized reusable steel box used for the safe, efficient and secure storage and movement of materials and products within a global containerized intermodal freight transport system...

s, truck

Truck

A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...

s, and boxcar

Boxcar

A boxcar is a railroad car that is enclosed and generally used to carry general freight. The boxcar, while not the simplest freight car design, is probably the most versatile, since it can carry most loads...

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

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 to be redistributed to retailers, to wholesalers, or directly to consumers. A distribution center is a principal part, the order...

, wholesale

Wholesale

Wholesaling, jobbing, or distributing is defined as the sale of goods or merchandise to retailers, to industrial, commercial, institutional, or other professional business users, or to other wholesalers and related subordinated services...

r, retail store

Retailing

Retail consists of the sale of physical goods or merchandise from a fixed location, such as a department store, boutique or kiosk, or by mail, in small or individual lots for direct consumption by the purchaser. Retailing may include subordinated services, such as delivery. Purchasers may be...

, etc.

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

Pallet

A pallet , sometimes called a skid, is a flat transport structure that supports goods in a stable fashion while being lifted by a forklift, pallet jack, front loader or other jacking device. A pallet is the structural foundation of a unit load which allows handling and storage efficiencies...

or slip sheet

Slip Sheet

Slip sheets are thin pallet-sized sheets made of plastic, heavy laminated kraft paperboard, or corrugated fiberboard used in commercial shipping. Often, these replace the use of traditional wooden pallets...

and stabilized with stretch wrap

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...

, pressure sensitive tape

Pressure sensitive tape

Pressure-sensitive tape, known also in various countries as PSA tape, adhesive tape, self-stick tape, sticky tape, or just tape, is an adhesive tape that will stick with application pressure, without the need for solvent, heat, or water for activation...

, strapping

Strapping

Strapping, also known as bundling and banding, is the process of applying a strap to an item to combine, hold, reinforce, or fasten it. The strap may also be referred to as strapping...

or shrink wrap

Shrink wrap

Shrink wrap, also shrinkwrap or 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 hand held heat gun or the product and film can pass through a heat tunnel on a conveyor.-Composition:The...

. About 2 billion unit loads are in daily use in the United States (Ward 1993).

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 (with product),
Pallet, and
Handling/Storage Equipment
The distribution environment (shock
Shock (mechanics)
A mechanical or physical shock is a sudden acceleration or deceleration caused, for example, by impact, drop, kick, earthquake, or explosion. Shock is a transient physical excitation....

, vibration
Vibration
Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.Vibration is occasionally "desirable"...

, humidity
Humidity
Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...

, temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

, 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.

Very 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.

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

Standards-compliant design

Standards permit a unit load to be designed and tested to meet a written specification

Specification (technical standard)

A specification is an explicit set of requirements to be satisfied by a material, product, or service. Should a material, product or service fail to meet one or more of the applicable specifications, it may be referred to as being out of specification;the abbreviation OOS may also be used...

or test method

Test method

A test method is a definitive procedure that produces a test result.A test can be considered as technical operation that consists of determination of one or more characteristics of a given product, process or service according to a specified procedure. Often a test is part of an experiment.The test...

. A unit load can be verified

Verification and Validation

In software project management, software testing, and software engineering, verification and validation is the process of checking that a software system meets specifications and that it fulfills its intended purpose...

to comply with a standard and validate

Validity

In logic, argument is valid if and only if its conclusion is entailed by its premises, a formula is valid if and only if it is true under every interpretation, and an argument form is valid if and only if every argument of that logical form is valid....

d to determine that the unit load is indeed effective.

Unit loads move by an unpredictable mix of many types of vehicles and storage areas, 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 therefore many similarities in the requirements for long term storage and long distance transportation of unit loads.

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.
Performance testing
Performance testing
In software engineering, performance testing is in general testing performed to determine how a system performs in terms of responsiveness and stability under a particular workload...

standards describe needs and allow flexibility in the choice of matierials. These are applied to particular unit load designs.

ASTM

ASTM International

ASTM International, known until 2001 as the American Society for Testing and Materials , is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, and services...

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 40 by 48 in (1,016 by 1,219.2 mm) pallets, which unfortunately do not pack efficiently into ISO containers. They weigh less than 4000 lb (1,814 kg) to limit the stresses on handling equipment. They are weatherproof, and stack 16 ft (4.877 m) high. They often use steel pallets, steel straps with notched seals, outdoor plywood, and plastic film. Interestingly, MIL-STD-1660 mandates that loads must never be less than the width of a pallet, while permitting some overhang. The markings are LOGMARS bar code

Barcode

A barcode is an optical machine-readable representation of data, which shows data about the object to which it attaches. Originally barcodes represented data by varying the widths and spacings of parallel lines, and may be referred to as linear or 1 dimensional . Later they evolved into rectangles,...

s 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 ridiculous 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's sometimes valuable, and the baggies are cheap. High, standardized stacking could be optional as well. It's expensive, but sometimes valuable for rackless and military customers.

External links

http://www.unitload.vt.edu Virginia Tech Center For Unit Load Design

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