DOCK LEVELLERS – A BRIEF GUIDE
Andy Georgiou, General Manager of Stertil Dock Products examines a number of options to consider when deciding upon the most appropriate dock leveller for your application.
Modern warehouses and distribution centres need to be supremely efficient to ensure maximum space utilisation, accurate order picking and fast vehicle turn rounds. However, none of this would be possible if the loading and unloading of vehicles within well equipped loading bays is not supported by the correct type of dock levellers.
As a minimum, the length of the dock leveller is closely connected to the difference in height between the vehicle floor and the loading dock, while not exceeding the maximum gradients identified in the European norm (EN1398). Gradients can be a determining factor when considering what kind of internal materials handling equipment would be most suitable. The width of the leveller depends not only on the internal width of the loading space of the vehicle as well as the accuracy of the driver as he positions his vehicle in front of the dock, but also the track width of the materials handling equipment and its load.
The standard for operating a dock leveller is the actual working range which, on an average leveller, is about 300mm above and 300mm below loading dock height. A dock leveller installed in a loading dock 1250mm high is suitable for loading and unloading vehicles with a deck height of 950 to 1550mm. When, for example, a 2000mm long leveller has a working range gradient of 300mm above platform level, or exceeds the permissible range of the internal materials handling equipment, a longer leveller will be required. The max gradient identified in EN1398 should not exceed 12.5% (1:8).
Standard, multiple leveller widths are available between 1750 and 2250mm. It’s generally advisable to select a width as big as possible because it simplifies the placing of loads. Do not however, choose a leveller width that is too close to the internal vehicle width. If a vehicle is not parked perfectly central it could make loading/unloading difficult. Of course, the installation of wheel guides makes it easier to park straight and allows the use of the widest leveller possible.
Dock levellers were originally conceived to solve the problem of bridging the gap between the deck of a vehicle and the loading dock. Early models featured swing lips to not only achieve the necessary ‘gap bridging’ but also to overcome any height differences between the two. The swing lip design remains the most common type of dock leveller although the introduction of telescopic lip models has seen something of a revolution in the global logistics industry. There is now also a choice of a parallelogram lip which is unique to Stertil and is especially advantageous when dealing with fragile loads.
Swing lip leveller
Swing lip dock levellers may be manually or electro-hydraulically operated although, today, the latter is the most popular. Control panels, incorporating simple push buttons ensure safe and easy operation. The operating cycle begins with the platform rising to its highest position at which point the swing lip hinges automatically. The platform then lowers until the lip comes into contact with the vehicle deck to provide an effective bridge and the platform will follow the up and down movement of the trailer as loads are transferred. Upon completion of loading/unloading, the operator can use the push buttons to return the platform to its original position.
Telescopic lip leveller
Telescopic lip levellers are electro-hydraulically operated and, again, are controlled using push buttons to achieve raising and lowering plus the extension and retraction of the lip. In operation, the platform is raised above the height of the vehicle deck and the lip is extended. The platform is then lowered until the lip forms a bridge with the vehicle deck and the platform will follow the up and down movement of the trailer as loads are transferred. Loading/unloading can then commence.
Importantly, the extension of the lip is infinitely variable which means that the leveller can be safely used to serve vehicles that have not reversed sufficiently far enough to make contact with the dock’s bumpers. Also, if a vehicle’s position is not absolutely aligned with the dock, the telescopic lip can safely accommodate this situation without difficulty. Finally, and most importantly, the telescopic lip can allow loading of vehicles almost right up to the edge of the vehicle’s deck thereby ensuring maximum space utilisation for optimum efficiency.
It’s worth noting that the design of all quality dock levellers ensures that both the lip and platform automatically adjust to allow for the rise and fall as goods are transferred between the vehicle deck and the loading dock. All major designs of dock levellers also incorporate a number of safety features to protect against malfunction including emergency stop buttons.
On inferior dock levellers, stability can be a problem. However, most models will incorporate legs or struts that support the front edge to prevent the levellers from ‘sinking’ when heavily laden fork trucks are being driven over them. Also, the combination of special rear hinges and immensely strong tensile steel in the construction of the platforms allows them to twist by up to 125mm on each side. This feature not only ensures that cross traffic is safely accommodated but also that an uneven vehicle deck will not create a potentially dangerous gap beneath the platform lip.
Stertil Dock & Door Products
Tel: 0870 770 0471