Loading and unloading large goods vehicles can be a complex, multi-stage process, with scope for error and risk at every point. Any delay that affects capital equipment like trucks and trailers costs real money – particularly if it is already under time constraints such as drivers’ hours. So, an automated system, with the possibility of loading an entire vehicle safely in a few minutes, is attractive.
Pallets are the obvious application for automated loading, but not the only one: firms such as FLSmidth offer systems for overhead loading of bagged goods such as cement, with either mechanical or vacuum lifting. More conventional trailers, such as the typical curtainsiders used by most transport companies, are loaded from the rear in loading docks, and there are a number of options for doing this.
As with any capital equipment, the first stage in specification is to establish whether it is likely to be cost-effective; naturally, a low-volume or highly diverse application is unlikely to provide savings. And any loading system is only as fast as the supply of loads to it, so it might be worth examining the flow of goods throughout the premises at the same time –indeed, it could become an integral part of the production cycle.
A well-known name in automated loading for trucks is Joloda. Other brands include Ancra Systems and A-Service. Joloda offers three machines for automatic loading of trailers: Slipchain, Trailerskate and moving-floor system.
Karen McBride, Joloda’s marketing and project manager, explains: “The Trailerskate and the Slipchain systems work effectively in the same way. Both move the same types of pallets, the same kind of weight – but the Slipchain system is for operators with frequent operations, including in some cases internal operations.”
An example is the Heinz site in Wigan: this has an internal shuttle using four 16m Slipchain trailers that travel some distance between docks, around 40 times per day. Up to 30 pallets can be loaded in under two minutes. The Slipchain system uses a pneumatically-actuated rise-and-fall chain and roller track which lifts and moves pallets directly: this is fitted to both the dock and the trailer.
The Trailerskate system, on the other hand, moves a pre-assembled load on a ‘skate’ which can be as long as the trailer bed. This is lifted by airbags within the skate and then pulled into the trailer using a drive chain. The skate slides on four steel channels mounted in the floor of the trailer; once the load is in place, the airbags are deflated and the load is secure. The skate system can handle loads such as paper reels, standing up or lying down.
DHL’s site at Cannock, Staffordshire uses a Trailerskate system with skates that take up to 30 tonnes on 26 pallets. Twenty trailers were fitted with Trailerskate track to transfer products from Unilever factories 70 miles away.
As McBride puts it: “The Trailerskate dock is more expensive, but the trailers only need four channels – no electrics, nothing else – so if a customer does only one run a day you don’t want to invest a lot in the trailer. And you can have infills in the channels, so you can carry backloads. With Slipchain, the dock is the lower cost and the trailers are more expensive.
“The moving floor is different; it’s for non-standard loads. Chains and skates wouldn’t pick up those sorts of loads.” Joloda’s Moving Floor System (MFS) is a low-profile slat (segmented) conveyor belt, fitted to both dock and trailer, which loads and unloads at up to 30m/minute, and handling payloads of up to 30 tonnes. It is suitable for pallets, drums, sheet products, automotive racks, paper reels and loose packages. The MFS should not be confused with the “walking floor” produced by firms such as Keith, which consists of moving metal floor slats used for unloading bulk products such as grains or aggregates.
Allied Distillers uses MFS to transfer whisky between maturation sites (pictured, inset, p26): the system loads 96 barrels, weighing approximately 23 tons, in one shot. The system is mounted directly on to the trailer decking, and fitted with plastic guide rails on both sides. A moving headboard and rear shoring poles provide an adjustable load area and additional restraint. Loaded pallets can be stacked two high; the system is loaded with a fork truck and each pallet load is indexed automatically using sensors inside the trailer. It is unloaded by fork truck at the delivery sites, again indexing positions.
A number of firms are offering automated forklift systems to load and unload trucks. While these are not as fast as a dedicated loading machine, they have the potential to be more flexible. They don’t seem to be at the production stage yet, although Spanish firm Duro Felguera has demonstrated prototypes of its Nalon N8 system (pictured above, and in https://is.gd/itopow. A transfer car positions the truck loading car (TLC) laterally, in line with the trailer to be loaded. The TLC – which looks like a driverless, double-width forklift – then picks up two or three pallets at a time (totalling up to 3,000kg) from a dedicated roller or conveyor system. The TLC can reach to the end of a 13.5m trailer, and its maximum loading rate is 150 pallets per hour.
Whatever the scale of the system, the process of installation is the same. “We carry out a risk assessment before we actually start the design of the project,” says McBride. The equipment itself complies with the Machinery Directive and is interlocked with limit switches and photocells controlled by a safety PLC.
The overall commissioning process takes around two weeks. “Before installation, we ask the customer to fit an electrical supply [400v, three-phase] for each dock,” says McBride. Joloda’s moving floor systems can be operated hydraulically if no suitable electrical supply exists. They will also operate from the 24V DC batteries of a truck and have a manually-operated fail-safe option.
Obviously, any previous dock leveller needs to have been removed. The loading machinery itself is mounted (usually by crane) on a level concrete slab (concrete specification C25, 200mm thick) with as little reinforcing steel as possible, to allow holes to be drilled for the floor anchors.
There are alternative methods for keeping the trailer in place as it is loaded or unloaded. McBride says that ideally the trailer is fitted with a central kingpin at the rear, which engages in a fifth wheel (as on a tractor unit) fitted to the dock. “The trailer is physically locked on,” McBride explains. However, the kingpin requires significant trailer modification so “if you have a fleet of 20 or 30, that’s a lot to modify”. The more common installation is a simpler setup of approach ramp noses and ‘teardrop’ guides fitted to the trailer.
The firm trains operators on site: this takes only a few hours because it is carried out from a control panel, and it’s automatic. Signals follow a traffic light code:
● Green: the system is ready to accept a trailer or the trailer is OK to leave
● Red: trailer docked, locking hitch closed
● Red (flash): slipchains to move or moving
“The main training is what needs to be done if a fault happens. They might need to manually move the dock to reset it,” says McBride.
The operator should check the machinery on a weekly basis, McBride adds. “The chains run in channels, so check those – debris from pallets does get in the rollers and can damage the airbags – and blow out any debris. Check that air fittings are secure, grease the chains, check the sprocket tensioners and wipe the sensors clean – it’s all stuff that engineers can easily do. We also do a quarterly service for most of our customers – we’ll spend a full day doing an in-depth clean and an inspection. Our engineers can spot problems before they arise.”
CASE STUDY: Great Bear Distribution
Third-party logistics firm Great Bear Distribution has a long-established contract with cereal manufacturer Cereal Partners Worldwide: the firm recently installed Joloda’s Slipchain automatic loading system, fitted to docks at the client’s South West factory and distribution centre and to two new Don Bur 13.6-metre curtainsided trailers, which replace the four trailers previously used.
The loading or unloading process now takes as little as 90 seconds. Each trailer covers around 52,000km a year and makes 12 collections and deliveries per day. Joloda claims that the increased efficiency of the system has saved around 35,000 hours of labour, equating to £250,000, while Great Bear transport operations manager Colin Keegan says that deliveries can now be loaded and unloaded “quickly and safely”.