In part two of our guide to fork-lift trucks, Robin
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Meczes looks at the role played by two specialist categories of lift truck and considers how best to manage your fleet of fork-lifts, whatever its make-up. CONVENTIONAL FORK-LIFTS —like pallet trucks, stacker trucks, counterbalanced and reach trucks—will suit many first-time and experienced warehouse operators (see CM 22-28 July) but those who want to squeeze maximum use out of a given area would be well advised to consider VNA (very narrow aisle) equipment
A VNA truck is a fork-lift that can pick up or deposit loads in racking laterally, without the need for a 90° turn towards the racking bay—it never needs to turn within the aisle. This has a number of knock-on benefits, by far the most important of which is that VNA trucks can operate in much smaller aisles than conventional equipment—as little as 1.3m. Compare this with the 3.5m aisle widths associated with most counterbalanced trucks and you can appreciate why there are those prepared to pay the premium VNA equipment usually commands.
Mike Mellor, VNA product manager at Boss Group, says that even compared with a reach truck, -you should get about 30%
more pallet positions with VNA, depending on the shape and size of the building".
Space saving is a top priority in storage—but there is more. VNA trucks can safely be used to raise or lower loads at the same time as moving down an aisle (not a safe practice with conventional trucks). This means a significant reduction in pallet cycle times which anyone looking at efficiency will find hard to ignore— Mellor estimates an improvement in productivity of typically 10-15%.
There are basically two types of VNA truck—man-up and mandown. The operator in a mandown truck remains at ground
level while the forks are raised to the load in the racking; in a manup truck, the forks and cab are raised together to the load.
This makes for a much better view of the picking operation— important when you're trying to guide the forks into the small recesses of a pallet several metres above the ground without damaging the load or the carrier. According to Mellor, anything over 7nri is considered to be a man-up application, as well as any operation in which bar-codes are used. "You'll need to scan the barcodes on individual pallet positions and that's almost impossible to do from the ground,' he explains.
As for the fork carriages, there are two main types. Some trucks have a turret which can transfer the forks from one side of the aisle to another; others have a slide-through telescopic fork mechanism.
VNA trucks are generally used for capacities of i tonne and to lift heights ofco-tam. Those operating above 5-6m are usually fitted with some sort of guidance sys tern as driving these vehicles in a straight line at height is not easy.
Guidance comes in two basic forms—rail and wire. Rail guidance usually has twin rails fixed to the bottom of the racking bays with rollers on the truck body to run along them. Wire guidance is usually embedded in the floor.
Rail guidance
usually means blocking access to the ground level racking positions along the aisle. However, a lowprofile rail (5omm high, not roomm) will allow the forks of a conventional pallet truck over the top while still giving practical guidance to the VNA unit.
Wire guidance, which used to be a more expensive option, is now roughly compara ble in price and Mellor says about 70% of Boss's manup VNA trucks have wire guidance. "Rail guidance is economic where you have lots of trucks and few aisles. If you have lots of aisles and few trucks, the cost of wire is a fraction of rail costs."
The downside of VNA equipment is price—typically L3o,000-7o,000 a unit—and its lack of flexibility compared with conventional fork-lifts. VNA trucks are excellent at space-saving pallet operations in the aisle, but not so good outside it, because of their lateral forks. They wouldn't be much use at picking up pallets blockstacked on the floor, and you wouldn't want to use them for lorry loading.
Order picking
Some industries, particularly retailing, require storage operators to deliver mixed loads built
by picking small quantities of goods from individual pallets in the racking.
You can simply bring down a pallet load of goods, take a couple of cartons from it for your new pallet load or roll cage, and return the first pallet. But this is timeconsuming and can be avoided by using a breed of trucks known as order pickers.
These take an operator up to the pallets to be picked from, along with the pallet or roll cage to be picked to. The operator can then move from position to position down an aisle, picking product from any number of pallets to make up the mixed load.
This saves huge amounts of time compared with removing pallets, driving them to the end of the aisle, getting them taken to a picking station by another truck, waiting for an operator to pick from them, and then replacing them.
There are few situations where order pickers cannot be justified for order picking.