Handling and storage represents a vast area of potential cost saving for manufacturers and some of the greatest economies can result from effective management of the forklift truck fleet. By specifying the right truck for the job, you can create an efficient and cost-effective operation. One of the major points to consider before making a purchasing decision is the power behind the trucks.
Industrial trucks come in as many shapes and sizes as they have uses, but they're generally driven in one of three ways – electrically, via diesel or with liquefied petroleum gas (lpg). The first uses a battery and the latter two employ internal combustion (ic) engines.
Comparison between power sources
The traditional argument insists that a direct comparison between the three power sources is pointless since fuel type is dictated mainly by the use to which the truck will be put. It would, for example, be silly to use an electric truck on very steep slopes or long, uninterrupted runs because the battery would quickly run down. By the same token, using an unmodified diesel-engined truck inside or in confined spaces is potentially dangerous because of the poisonous emissions from its engine.
However, the times they are a-changin' and in the wake of new truck designs has come more freedom for the truck specifier Diesel and lpg are getting cleaner, and electric trucks more powerful. The result of technological improvement is a greater crossover between the uses to which the different truck types can be put.
Dave Rylance, counterbalance product manager for Toyota Material Handling UK, says: "There are various areas customers need to consider when choosing a forklift including the initial investment, charging opportunities, service and maintenance costs, type of operation and environmental impact, but the changing market and technology has provided customers with a choice of power type."
If you opt to buy rather than rent, the purchasing decision will, in the main, revolve around seven factors: safety; quality and reliability; availability of spare parts; service life; noise levels; capital cost; and running costs.
? Safety: Modern trucks with any of the three power sources are safe provided they are made by a reputable manufacturer and properly maintained and used. Safety considerations are best identified by the truck manufacturer or fuel supplier, but will include:
– The batteries on electric trucks must be charged in well-ventilated areas since the hydrogen gas given off during charging can, in sufficient concentration, form an explosive mixture.
– Using standard diesel-powered trucks in confined spaces can be dangerous since the noxious fumes emitted can lead to errors of judgment by forklift drivers.
– LPG is an explosive gas which must be taken into account when siting and operating an lpg fuelling area.
? Quality and reliability: These should be a given and are more or less comparable across the three power sources, although, arguably, electrics have the edge on reliability because they have fewer moving parts than ic engines.
? Spare parts: Spare parts availability shouldn't cause a problem with any of the power sources, although a replacement battery in an electric truck is relatively expensive – around £3,000 on an average-sized counterbalanced truck.
? Service life: The service life of a truck will depend on the way it's treated and how much it is used. An electric truck battery will typically last for around 16,000 to 20,000 hours. An engine-driven truck should last for around 25,000 hours depending on how hard it's worked. All things being equal, lpg trucks will not last as long as their diesel-engined cousins because the latter must be physically strong to withstand the high compression pressures and heavy internal components.
? Noise levels: Electric trucks are quieter than ic models. However, provided they are properly adjusted and sufficiently insulated, none of the three truck types is excessively noisy. Some estimates put sound levels at 68dB for electric trucks and 79dB for diesel.
? Capital cost: Electric trucks are typically the most expensive to buy. However, you shouldn't take the purchase price as a guide to cost effectiveness. The cost of running the truck and its service life have a more significant impact on the overall cost of the truck.
? Running costs: On the face of it, lpg is the most expensive in terms of running costs; diesel is next, and then battery electric. It costs about £2.80 to recharge the average battery. "However," cautions Trevor Clifton, technical manager of Briggs Equipment, "the true running cost depends on how you measure it. For example, a battery will only give between 2,000 and 2,500 charge/discharge cycles. So you have to decide whether you're going to count that as a capital cost, or you count the cost of the battery over each individual charge cycle. If you do the latter, that narrows the gap between battery electric and diesel, but battery electric is still the cheapest."
Electric power provides clean, quiet operation and the facility for precision handling or inching required by delicate loads. The electric truck also has fewer moving parts than diesel or lpg, leading to lower maintenance and servicing costs. And, the fact that ic engine trucks are capable of higher performance can, ironically, lead to more abuse in their operation. However, most electrics are complex and require specialist knowledge and test equipment in order to carry out maintenance properly.
The electric truck's main disadvantage is its initial capital cost, often the highest of the three power sources because of the price of the battery.
Maintenance-free batteries are now available from the major manufacturers. They are sealed and offer freedom from topping up the electrolyte.
Battery charging normally takes six to 10 hours depending on the type of charger used and the end of shift discharge level. If you are working a multi-shift operation, then you will probably need an eight-hour charger. However, if shifts aren't a consideration, or if you have spare batteries, then a 12-hour charger (which will increase battery life) can be used. A fully charged battery will last for a single shift, eight to 10 hours, depending on its workload.
The reason for diesel's continuing popularity, meanwhile, can largely be put down to the fact that it is generally the cheapest to buy. On top of this, it has been proved over many years to give reliable and long service. It's the best truck for rugged conditions on steep gradients – up to one in five – and for long, uninterrupted runs. A diesel engine has the power to overcome some of the difficulties associated with electric trucks and, although it has a more complex transmission system and a higher regular maintenance requirement than electric, engine maintenance is relatively simple.
Halfway house between electric and diesel
LPG trucks have been described as a halfway house between electric and diesel. They have the power advantages of diesel without the carbon emissions. Exhaust purifiers can increase clean operation further by reducing the emission of noxious fumes so that they can be used inside. LPG trucks tend to be used in operations that require a clean environment, but where a multi-shift working pattern makes electric power too expensive. The more trucks you operate, the more economical lpg becomes.
There is also a new kid on the block – the fuel-cell powered truck (see the box below for more details). Fuel cells have, according to some, about half the power efficiency (40-50%) of lithium-ion batteries (80-90%), but they have a higher 'energy density' which could allow forklifts to run longer.
The market has become particularly sensitive to running costs and, in particular, to fuel consumption – fuel cells offer one potential answer to this.
However, for Briggs Equipment's Clifton the future trend will be towards ic/electric hybrid trucks. These incorporate a small capacity engine running at optimum efficiency driving a generator which charges the battery powering the truck (similar in operation to hybrid cars like the Toyota Prius).
Clifton says: "Their complexity increases the maintenance cost on hybrid-powered trucks, but, by 2018, I think you will find that most manufacturers will go down this route because of the environmental and energy-saving benefits. Hybrid is 20% more fuel efficient than conventional power sources."
He ends with this warning: "Be careful. Because the UK forklift truck business is predominantly rental, once you sign into a contract, it can be hellishly expensive to get out. If you make a mistake when selecting the power source, there are massive cost implications."
The power source you choose to drive your forklift fleet is one of the most important specifying decisions you will make. Get it right and the management of your fleet will be made much easier. Get it wrong and you will incur unnecessary costs and a continuing headache for many years to come.
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The maintenance of power
? Electric: Probably the most reliable power source and the easiest to maintain as long as nothing goes wrong with the motor. Most electrics are complex and require specialised test equipment in supporting skills to do the job properly.
And, warns Bill Goodwin, sales director of Jungheinrich UK: "Operators naturally select the most conveniently-located battery when it comes to changeover time.
"This often means that batteries placed nearest the entrance to the charging bay are most frequently picked.
"Unfortunately, overused and insufficiently cooled batteries have a dramatically reduced capacity and life."
? Diesel: Oil must be changed regularly, but otherwise, with no spark plugs and no complicated electrical circuitry, diesel-powered vehicles are fairly simple to maintain and fix when they go wrong. Their relatively low technology and the fact that many fitters have been brought up on these engines – and therefore understand them – is an advantage in maintenance terms.
? Liquefied petroleum gas: These trucks are prone to going out of tune and, as a consequence, not performing at their optimum level. Tuning is quite a complex operation and, with more serviceable parts, these machines are generally more expensive to operate and maintain in the longer term. A lack of familiarity with these engines could create a lack of confidence in maintaining and fixing them.
? Fuel cells: Briggs Equipment has supplied two Yale fuel cell-powered forklift trucks to the Honda manufacturing plant in Swindon. These use hydrogen gas which is produced on site and supplied to a refuelling station within the factory 300m away. The trucks typically last for just over five hours before needing to be refuelled.
Meanwhile, Linde Material Handling has supplied tow trucks and industrial trucks with fuel cell hybrid drive to the BMW plant in Leipzig, as part of a research project funded by the German Federal Ministry of Transport.
These vehicles are powered by green-certified hydrogen and are used to supply parts in body production of BMW cars. Munich Technical University is evaluating the field trial, which is taking place under realistic production conditions.
Linde believes the fuel cell will prevail as a key propulsion technology in materials handling: "Recharging cycles, battery replacement and the maintenance of lead/acid batteries require relatively long downtimes for conventional trucks and thus reduce their productivity. By contrast, the fuel cell hybrid system used in these Linde vehicles can be refuelled within just a few minutes and requires relatively little maintenance.
"The resulting higher availability of the industrial trucks and tractors is particularly advantageous in multi-shift operation. Moreover, the energy recovered during braking is stored in the lithium-ion battery of the hybrid system and released once again during load peaks, while the fuel cell provides the basic power."
