Fork lift trucks powered by LPG (liquified petroleum gas) have long been popular, due to their competitive pricing and suitability for inside/outside usage and convenience for round the clock working.
The engines are usually derivatives of car engines, and consequently parts are readily available at keen prices. “Compact” gas trucks are more manoeuvrable than “yard design” diesel fork lifts, due to the solid cushion tyres and compact chassis compared with larger diameter tyres and increased clearances around the wheel arches of diesel trucks. LPG powered trucks are quieter in use (dba levels at the drivers ear) than diesel alternatives and their exhaust fumes are less offensive than diesel fumes. Exhaust catalytic converters work more efficiently on higher temperature LPG spark ignition engines, than on diesel compression ignition engines. The performance characteristics of LPG powered trucks are usually superior to electric and diesel powered equivalents. Travel speeds, rates of acceleration, and lift speeds usually outperform their electric/diesel rivals because of better power to weight ratios and more responsive engines. The service weight of gas trucks is generally less than their electric and diesel stable mates. Vibration levels of LPG trucks at the driver’s seat are lower than diesel trucks but higher than electrics.
Disadvantages. Whilst they are the cheapest to buy new, their maintenance and fuel costs are the highest of the three types. As with diesel trucks, they need to be given a “winter service” with antifreeze.
***Of the three types of propulsion, the residual values of LPG trucks is probably lowest compared with electric and diesel. Gas trucks have an annoying tendency to run out of gas without notice, and sometimes a long way away from the gas bottle store. There is not normally a fuel gauge to give the operator an indication of how much gas is in the bottle. When gauges are provided, they are usually in the bottle and not on the instrument display. Pressure switches, indicating that the bottle is nearly empty, only give between 5 and 20 seconds warning. On larger capacity trucks, dual bottles overcome this problem. As with diesel forklifts, LPG machines are more prone to leaks from the engine and transmission and may not be acceptable internally in some applications e.g. pharmaceutical industry, food industry, etc. The exhaust fumes can leave an oily film of hydrocarbon particles on surrounding surfaces in extreme cases, where there is no ventilation.
Gas trucks and diesel forklifts require from the driver a higher level of skill compared with an electric counterbalance truck. The use of the “inching” pedal or clutch, when loading/off-loading vehicles, to enable slow traction speed and high lift speed is not necessary when operating an electric machine. Because they will still run when the engine is out of tune, LPG and diesel machines are mistakenly sometimes thought to be more reliable than electrics, but this makes them much more prone to abuse if they continue to be used and more serious problems then arise, due to lack of regular maintenance.