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, [1] for example a pallet load represents a unit load which can be moved easily with a pallet jack or forklift truck, or a container load represents a unit for shipping purposes. A unit load can be packed tightly into a warehouse rack, intermodal container, truck or boxcars, yet can be easily broken apart at a distribution point, usually a distribution center, wholesaler, or retail store for sale to consumers or for use. [2]
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 and stabilized with stretch wrap, pressure-sensitive tape, strapping or shrink wrap. About 2 billion unit loads are in daily use in the United States. [3]
There are three kinds of unit load design: component-based, systems-based, and standards-compliant. These have different applications.
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:
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:
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. [4]
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. [4]
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:
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. [5]
Standards permit a unit load to be designed and tested to meet a written specification or test method. 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.
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. [1] DOD unit loads generally use 40 in × 48 in (1,016 mm × 1,219 mm) pallets, which unfortunately do not pack efficiently into ISO containers. They weigh less than 4,000 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. 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 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.
In mechanics and physics, shock is a sudden acceleration caused, for example, by impact, drop, kick, earthquake, or explosion. Shock is a transient physical excitation.
An intermodal container, often called a shipping container or ISO Container, is a large standardized container designed and built for intermodal freight transport, meaning these containers can be used across different modes of transport – such as from ships to trains to trucks – without unloading and reloading their cargo. Intermodal containers are primarily used to store and transport materials and products efficiently and securely in the global containerized intermodal freight transport system, but smaller numbers are in regional use as well. These containers are known under a number of names. Based on size alone, up to 95% of intermodal containers comply with ISO standards, and can officially be called ISO containers. Many other names are simply: container, cargo or freight container, shipping, sea or ocean container, container van or sea van, sea can or C can, or MILVAN, SEAVAN, or RO/RO. The also used term CONEX (Box) is a technically incorrect carry-over usage of the name of an important predecessor of the international ISO containers, namely the much smaller prior steel CONEX boxes used by the U.S. Army.
A forklift 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 companies, including Clark, which made transmissions, and Yale & Towne Manufacturing, which made hoists. Since World War II, the use and development of the forklift truck have greatly expanded worldwide. Forklifts have become an indispensable piece of equipment in manufacturing and warehousing. In 2013, the top 20 manufacturers worldwide posted sales of $30.4 billion, with 944,405 machines sold.
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 coordinated system of preparing goods for transport, warehousing, logistics, sale, and end use. Packaging contains, protects, preserves, transports, informs, and sells. In many countries it is fully integrated into government, business, institutional, industrial, and for personal use.
A pallet 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. Many pallets can handle a load of 1,000 kg (2,200 lb). While most pallets are wooden, pallets can also be made of plastic, metal, paper, and recycled materials.
A Slip sheet is “a corrugated, solid fiber, or plastic sheet onto which a unit load can be assembled. A protruding short panel can be grasped by the jaws of a pull-pack truck and the load pulled back onto the pull-pack platform.”
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 consumers. A distribution center is a principal part, the order processing element, of the entire order fulfillment process. Distribution centers are usually thought of as being demand driven. A distribution center can also be called a warehouse, a DC, a fulfillment center, a cross-dock facility, a bulk break center, and a package handling center. The name by which the distribution center is known is commonly based on the purpose of the operation. For example, a "retail distribution center" normally distributes goods to retail stores, an "order fulfillment center" commonly distributes goods directly to consumers, and a cross-dock facility stores little or no product but distributes goods to other destinations.
Intermediate bulk containers are industrial-grade containers engineered for the mass handling, transport, and storage of liquids, semi-solids, pastes, or solids. The two main categories of IBC tanks are flexible IBCs and rigid IBCs. Many IBCs are reused or repurposed.
An automated storage and retrieval system consists of a variety of computer-controlled systems for automatically placing and retrieving loads from defined storage locations. Automated storage and retrieval systems (AS/RS) are typically used in applications where:
Pallet rack is a material handling storage aid system designed to store materials on pallets. Although there are many varieties of pallet racking, all types allow for the storage of palletized materials in horizontal rows with multiple levels. Forklift trucks are usually required to place the loaded pallets onto the racks for storage. Since the Second World War, pallet racks have become a ubiquitous element of most modern warehouses, manufacturing facilities, retail centers, and other storage and distribution facilities. All types of pallet racking increase storage density of the stored goods. Costs associated with the racking increases with increasing storage density.
Material handling equipment (MHE) is mechanical equipment used for the movement, storage, control, and protection of materials, goods and products throughout the process of manufacturing, distribution, consumption, and disposal. The different types of equipment can be classified into four major categories: transport equipment, positioning equipment, unit load formation equipment, and storage equipment.
A bulk box, also known as a bulk bin, skid box, pallet box, bin box, gaylord, or octabin, is a pallet-size box used for storage and shipping of bulk quantities.
Insulated shipping containers are a type of packaging used to ship temperature sensitive products such as foods, pharmaceuticals, organs, blood, biologic materials, vaccines and chemicals. They are used as part of a cold chain to help maintain product freshness and efficacy. The term can also refer to insulated intermodal containers or insulated swap bodies.
A wooden box is a container made of wood for storage or as a 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 international shipping trade, "container" or "shipping container" is virtually synonymous with "intermodal freight container", a container designed to be moved from one mode of transport to another without unloading and reloading.
The container compression test measures the compressive strength of packages such as boxes, drums, and cans. It usually provides a plot of deformation vs compressive force.
Corrugated box design is the process of matching design factors for corrugated fiberboard or corrugated plastic boxes with the functional physical, processing and end-use requirements. Packaging engineers work to meet the performance requirements of a box while controlling total costs throughout the system. Corrugated boxes are shipping containers used for transport packaging and have important functional and economic considerations.
Package testing or packaging testing involves the measurement of a characteristic or property involved with packaging. This includes packaging materials, packaging components, primary packages, shipping containers, and unit loads, as well as the associated processes.
The EUR-pallet, also known as Euro-pallet or EPAL-pallet, is the standard European pallet as specified by the UIC pallet working group and the UIC 435-2 leaflet. Pallets conforming to the standardization are eligible for the European Pallet Pool (EPP), the system which allows for an exchange as "pallet for pallet".
Reusable packaging is manufactured of durable materials and is specifically designed for multiple trips and extended life. A reusable package or container is "designed for reuse without impairment of its protective function." The term returnable is sometimes used interchangeably but it can also include returning packages or components for other than reuse: recycling, disposal, incineration, etc. Typically, the materials used to make returnable packaging include steel, wood, polypropylene sheets or other plastic materials.