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Materials Handling - Unit Loads

Note: Additional information on unit loads as relating to the carriage of same by rail can be found in Vol. 1 in the section on Cargo and Wagon Loads (Unit Loads on the Railways). Photographs of container handling gantry cranes , straddle carriers and reach stackers have been added to the section on Freight Operations - Air Braked Freightliner Container Services

The modern Unit Load is a consignment of goods made up into a package which is too heavy for a man to move and for which mechanical lifting aids are provided. The advantage is that with mechanical handling aids the goods are moved more quickly, generally suffer less damage in transit, are easier to 'tally' and can be stacked to make better use of expensive storage space (which is rented out by the square foot of floor space not by volume).

The idea is not new, containers are the classic unit load and they have been in use since before the railways. The Bridgewater canal used wooden coal containers or 'skips' to carry coal in barges from the mines to the town wharf's. In Manchester one early destination was near the top of a hill so a tunnel was dug allowing the canal boats easy access and a crane was used to hoist the containers to the surface. Containers had been in use on the railways for over a hundred years but there was little standardisation in design until the 1930s. Various pre-ISO container types seen on railways are discussed in detail in Vol. 1 in the section on Unit Loads on the Railways. _Modern (International Standards Organisation) Containers. These were equipped with lifting rings that allowed a standard railway goods yard crane to handle them, albeit rather slowly.

The modern International Standards Organisation (ISO) standard container as used on railway Freightliner services first appeared in the early 1950s. The basic concept was developed by the US Department of Defence in the 1940s. The system was developed for supplying military units in the field but was soon adopted for shipping civilian goods. In the USA at the time some 50-70 percent of the cost of shipping goods by sea was accounted for in port labour costs, the container seemed a viable answer to this problem and they were first used on US domestic routes in 1957.

The container offered many advantages, container ships had faster turn-round in port, measured in days or even hours instead of weeks and there was some reduction in pilferage (although human ingenuity being what it is goods began to go missing by the container load instead of in pockets). The unit of measure of container traffic relates back to the original US Do scheme where units have a standard sized end, originally 8 foot by 8 foot, and come in multiples of ten foot lengths, giving the term TEU or Ten foot Equivalent Unit.

As a standard the container has proved somewhat flexible, the first variant to appear was 8 feet wide by 8 feet 6 inches high and these days 9 foot six inch high units are appearing in service. This causes problems for railways where clearances are tight, such as in the UK.

Containers began to appear on the transatlantic shipping routes in the early 1960s, then on the Europe-Australasia and US-Caribbean trades. Somewhere along the line the Geneva based International Standards Organisation became involved, laying down rules for the design of these containers. The control introduced by the ISO ensured that changes would be properly orchestrated and allowed the international trade in standardised containers to develop.

By 1970 the equivalent of 3.2 million 10 foot `boxes' (3.2 million TEU) were being moved annually, by 1986 this figure had increased to 30 million TEU. In 1970 containers accounted for about 60 percent of all non-bulk goods moved internationally by sea and by 1986 containers held over 70 percent of the market share, although the proportion of sea borne coastal traffic moved in boxes has declined of late and now accounts for some 30 percent of the total.

By the mid 1980s large purpose built 'cellular' container ships had appeared, equipped with vertical guides to allow the containers to be stacked easily on board, and the rapid loading facility of these ships gave the container another boost in international trades. The ISO has authorised a number of variants on the basic box of the 1950s, Fig ___ shows a number of variants which may be seen in UK trades.

The normal box is classed as a 'dry freight' container, these may have doors in the end only (the most common design) or they may have doors in the sides and/or ends, called side door or multi-door. Some of these containers are ventilated whilst others are insulated and some are refrigerated either using a clip-on cooling unit or a unit built-in the container itself, in either case these are electrically powered by the carrying vehicles or ship. Freightliners do not currently (mid 1980s) have the facilities for carrying powered cooling units of this type.

Quite early on someone thought of the open topped container, covered with a removable tarpaulin roof, used for a range of bulk goods such as grain. Modern versions have a mechanically operated roll-back canvass top. Curtain sided containers are useful for fork-lift loading as the whole of the side can be opened for access. Half-height containers are usually open topped, they are useful for carrying heavy items such as steel billets and some are fitted with drop-down planked sides to ease loading. A platform has no raised sides or ends, they often have sockets along the sides and ends into which steel posts can be inserted. Some of these are fitted with H shaped metal posts into which wooden panels can be dropped to form low sides and ends, these are used for a range of tasks such as shipping palletised bricks. Flats or flatrack containers have a floor and ends but no top or sides, they are used for large items such as tractors. Some of these have fold-down ends, producing a standard two foot high unit which can be shipped stacked on top of one another to save space. Finally there are tank containers of various designs. Early tanks were similar to railway tanks mounted in an open framework, the Peco ten foot wheelbase tank can be used for these. Later came standard looking boxes with a plastic liner, these are recognisable as they have filling hatches on the top, no doors on the end and usually a sliding panel covering the discharge point. Chemical tanks have been built with flat ends and an open framework (modelling these is discussed in Volume 1 under Cargo & Wagon Loads) and more recently a new design has appeared called a 'beam tank' container in which the tank itself is strong enough not to require any longitudinal support. The two ends are fitted with rectangular frames with standard container securing points.

The standard ISO full and half height containers have sockets on the top corners onto which a frame can be attached to lift it using oval 'twistlock'. Not all container have these lifting points however, some rely on attachments on the base and many containers have sockets in the base for fork-lift handling. The photos below show - Top- a half height container with top mounted lifting points, this type can be stacked. Below left - A half height container with no top lifiting points, this type cannot be stacked. Below right - close up of the H section metal side stanchions into which the side panels could be inserted.

Fig___ Stackable and non stackable half height containers

Photos of stackable and non stackable half height containers

ISO containers have been built for the carriage of livestock such as race horses, however these have not been used on the railways in the UK as the complications with the regulations regarding livestock make this traffic uneconomic.

Contains can also be handled using a conventional crane, although to lift a container longer than 10 foot a special frame must be used. In the case of the 20 foot container this might be a simple spreader bar with four lines fitted with hooks (which fasten into the bottom lifting lugs).

To transfer containers between ship and shore the original solution was to suspend some form of lifting frame from a conventialonal heavy lift dock crane, this approach is still used where the berth is not a dedicated container terminal or in ports where an unusual lift is likely. By the 1970s most dedicated container ports favoured a larger version of the travelling gantry crane, with an extension to reach out over the ship. The extension can be tilted upwards when not in use to clear the ships masts and superstructure as it manouvers alongside the berth. In specialised ports the lifting frame is equipped with automatic twistlocks (controlled by the crane operator) that engage in the sockets on the top corners of the box.

Once on shore the containers are often stacked in the dock area using mobile cranes. In the early days (60s and 70s) one commonly used machine was the 'straddle carrier', originally developed in America for carrying timber and steel sections about the place. The standard container straddle carrier consisted of two rectangles of square section steel, joined across the top. Wheels are mounted at each corner and a container lifting frame is suspended from the top. The carrier drives over the container to lift it and they are built so that they can stack containers one on top of another to save storage space. Some straddle carriers were wide enough to span two containers, allowing them to lift a container directly onto a lorry, but these were not common. The straddle carrier needs very little room between the adjacent stacks to manoeuvre, the drawbacks were that they could only stack containers two-high, which soon proved insufficient, and the hydraulic drive to the wheel motors was unreliable. The straddle carriers were mainly confined to sea ports, where large numbers of containers were routinely stored awaiting ships, although a few have been used at inland container depots. These vehicles were not widely used to load railway wagons as they need to travel the length of the rake to place them. They are comparatively easy to model and if you have a river-side container berth for small coastal ships one of these makes an interesting addition to the scene.

Fig___ Straddle Carrier

Sketch of a stradle carrier based on a photograph taken in the Far East - These machines are similar all over the world

Most railway container depots use travelling gantry cranes to lift the containers on and off the railway wagons, these are more fully discussed in Railway Company Goods Facilities - Container Handling and photographs have been added to the section on Freight Operations - Air Braked Freightliner Container Services .

For container handling in the depot machines resembling very large fork-lift trucks, technically described as 'mast lift trucks', became common in the early 1980s. These container trucks can stack containers three or four high and as these vehicles operate from the side they are used to load containers onto railway wagons at a number of rail connected depots (including the waste disposal container sites operated by various councils). A variation on this idea is the reach carrier, which has a telescopic arm, hinged at the rear of the vehicle. For illustrations of the mast truck and reach stacker see Railway Company Goods Facilities - Container handling and Freight Operations - Air Braked Freightliner Container Services.

Pallets and Fork Lift Trucks

The pallet is not as new an idea as you may think, the Lancashire cotton industry was using a simple wooden tray capable of being craned on and off railway trucks and road wagons in the nineteenth century. By the nineteen twenties the 'portable platform' was relatively common in industries involving large numbers of small packets such as breakfast cereals. The system worked but there was no standardisation so each industry, sometimes individual factories, had their own designs. During the Second World War the Americans made extensive use of the petrol or battery powered fork lift truck in their logistics and developed the pallet to go with it. The fork-lift idea had existed in essence since the 1930s but these were simple (usually three wheeler) vehicles equipped with hand-pumped hydraulic lifts under the cargo space at the rear. They were intended to elevate a load for stacking or to ease loading onto a lorry or trailer. The American powered fork lift truck was initially seen in British industry as a useful little crane; fitted with specialised claws and hooks they could handle rolls of paper, barrels and other heavy items and stack them in warehouses. The pallet was the real breakthrough, enabling standard loads to be stacked and manoeuvred with relative ease, but it took a long time to catch on with British industry. As recently as the early 1970s British Rail was having difficulty finding palletised loads for its new air braked vans and open wagons (which were built with pallets in mind). At first there was some doubt regarding the best design for the pallets, the original American idea used simple wooden plank designs but shipping experts believed that steel would be the eventual standard. In the early 1950s a Paris based branch of the International Standards Organisation (ISO) tested the strength of wooden pallets by the simple expedient of dropping some from a great height. No damage was sustained and the wooden pallet is now virtually standard. Steel pallets pressed from sheet metal can be nested, which reduces the room required to ship them, but as pallets are cheap and used world wide there is only a limited need to ship the empties. There has been a continuing struggle to standardise the pallet, not with a great deal of success.

The ISO has been the main driving force behind this but the `standard' has proved a rather flexible concept and currently agreed sizes include 1000mm x 800mm, 1,200mm x 800mm, 1,200mm x 1,000mm, 1,200mm x 1,600mm etc. The ISO put a lot of effort into rationalising the situation in the late 1980s, officially recognising only three standard sizes; 1200 x 800, 1140 x 1140 and one at 1290 x 1060mm (this latter size to be phased out at a later date). The depth of the pallet depends upon its construction, the simplest form (as supplied by Knightwing in their range) is the single faced pallet, consisting of three supporting strips with a plank `floor' on top, these are some four inches high. More recently the 'Europallet' has been developed for use within the European Union, this is not an ISO standard and it does not fit neatly into the ISO standard container, it does fit neatly into the EU standard 'swap body'. As a result there has been a new type of container developed, slightly larger than the ISO standard but based on the same technology, which is used within the EU for transporting Europallet loads.

Pallets with a deck top and bottom as supplied by Ratio are called double faced and generally they are about 6 inches deep. Note the Ratio pallet is really too big, they look better if you trim them down by cutting with a sharp knife close outboard of one of the inner cross timbers (reducing it from three to two bays). The Ratio pallets can have a strip of 20x20 thou added to each half, trimming the ends down to length and producing two single faced pallets. This generates more 'clutter' and introduces a little variation into a scene. One advantage of the pallet is that when empty it is a single small item and takes up less space than an empty container, metal pallets score well here, requiring only half as much room when stacked as the common wooden type.

It is now common practice to containerise loaded pallets. This means the goods can be shifted at either end by fork lift truck but receive the protection of containers in transit.

One final item worth mentioning is the 'pallet truck', introduced in the 1950s and used for man-handling loaded pallets. This resembles in principle the standard 'trolley jack' used by motor mechanics but the lifting arm is replaced by a set of forks and the wheels are set father apart to make the thing stable when being moved. The wheels at the non-forked end are mounted on a swivelling axle attached to which is a long handle which is used to manoeuvre the thing. The handle also serves to pump the hydraulics, the truck is pushed under the pallet and the hydraulic pump is engaged by pulling a lever. The handle is them pumped up and down to raise the two lifting arms until the pallet is clear of the floor.

Fig ___ Pallet truck

Pallet truck sketch

Usually there are roller type wheels at the end of the forks and a swivelling 'dolly' wheel at the handle end so that with the pallet lifted a man can pull the trolley about, steering with the aid of the dolly wheel. Once the pallet is in the required position a second lever on the handle releases the hydraulics, lowering the pallet in position. These little trucks are common in industries which make regular use of pallets although they do require a smooth floor surface.

Powered versions of the pallet truck appeared in the mid 1950s, fitted with a smal battery or petrol engine, allowing the operator torepeatedly move heavy pallets whilst walking along. These small powered trucks were used when loading the early BR centre-door pallet vans. Some of these were slightly different, effectively a small fork-lift truck able to lift the load a good six inches above the floor to clear the ramp arranged for access into the railway wagon. I have only seen one flim clip of these, I didnt have a pencil and paper to hand so I cannot attempt a sketch

Fig ___ Small trucks and pallet carriers

With the arrival of the pallet came the development of methods of fastening things to it. The original American wartime system appears to have relied on careful stacking of the boxes or cartons to form an interlocked load. Sacks, cardboard cartons and bricks can all be stacked in such a way that they 'interlock', forming a stable load. This was no worse than the hand stacked piles they replaced but where pallets were to be moved on the pot-holed floors of older factories, or stacked on top of one another, securing the load was an advantage. At first rope was used but very quickly someone invented a simple system for fitting steel strips (known by the trade name of `Band-it'), this in turn lead to plastic strapping and of late `shrink wrap' plastic has been used. Shrink-wrap is a plastic tube which is slipped over the load and pallet, heat is then applied which causes the plastic to shrink down and grip the load. The metal strapping is still used, the shrink wrap goes on over this. Depending on the load and how it is secured pallets can be stacked several levels high.

Intermediate Bulk Containers (IBC's)

Intermediate Bulk Containers (IBC's) are very large sacks, usually made of plastic fabric with webbing reinforcing straps. IBC's first appeared in the mid 1960s, they can hold a ton or more of dry or liquid goods and are designed for mechanical handling. IBC's are commonly used for materials such as powdered chemicals and agricultural fertilisers, although the farmer requires a specialised machine to discharge the contents. IBC's are referred to as `Minibulk' in current railway advertising but the term 'big bag' is widely used in shipping circles and in the 1960s and 70s they were sometimes referred to as 'balloons'.

The most common way of handling these was originally to fit them onto a standard pallet base but a fork-lift truck can lift them using its forks passed through loops sewn onto the bag. The fork lift type truck can be fitted with a short 'crane' type attachment, which allows it to lift and carry larger IBC's suspended from loops. The latter system has become more common in the 1990s and farmers use the fork lift attachment on their tractor to lift the bags onto the equipment using them. IBC's can be loaded onto standard curtain sided vans and are generally shipped in these in the UK, on the railways they are shipped sitting on the floor of the wagon.

Fig___ IBC being moved

Sketch of a fork lift shifting an IBC

Generally IBC's are disposable, or rather non-reusable, but in the early 1990s I saw used IBC's made for powdered chemicals being re-used by a builders merchant to supply sand. These were white or light brown bags, roughly four foot long, three foot wide and four foot high, with a lifting strop at each corner. They were marked in black stencilling about six inches high with the name and formula of the chemical powders they had originally been used to carry. Within a couple of years builders merchants had their own IBC's, marked with their name.

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