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 of working round the clock. The engines are usually derivatives of car engines, and consequently parts are readily available at reasonable prices. Gas powered trucks are quieter than diesel alternatives and their exhaust fumes are less offensive than diesel fumes. Exhaust catalytic converters work more efficiently on gas engines, than on diesel engines. The performance characteristics of gas powered trucks are usually superior to electric powered equivalents. Travel speeds, rates of acceleration, and lift speeds usually outperform their electric rivals because of a better power to weight ratio. The overall weight of gas trucks is generally less than their electric and diesel stable mates. Vibration levels of gas trucks are lower than diesel trucks but higher than electric trucks.
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 regular servicing including topping up of coolant/antifreeze and regular engine oil changes.
Gas trucks have an annoying tendency to run out of gas without notice, and sometimes a long way 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 on 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 can help to overcome this problem. As with diesel fork lifts, gas trucks are more prone to leaks from the engine and transmission and may not be acceptable in clean environments such as the pharmaceutical industry or food industry, etc. The exhaust fumes can leave an oily film of hydrocarbon particles on surrounding surfaces in extreme cases, where there is not adequate ventilation.
They also have a tendency to stall when turning at full lock if the operator does not maintain enough engine revs. The same can happen when hydraulics reach the full limit of their travel.
When considering a gas forklift, there are some safety concerns to be considered: the dangers of LPG, decreased rear visibility from the operator’s position and the transportation of gas cylinders. LPG is highly explosive and caution must be taken at all stages of its use. The gas tanks on most trucks are secured behind the driver decreasing visibility when moving in a backward direction. Renewing empty cylinders for fresh ones presents the opportunity for the escape of volatile gas. Safety cut off valves are incorporated to prevent gas exposure during an accident; however, the possibility of leakage is still present.
Lifting and carrying LPG cylinders should be a two person operation as they are quite heavy, usually in excess of 25 kilograms when full.
Storage is also an issue with cylinders having to be stored outside, usually in a locked, caged area to prevent unauthorised persons from tampering or removing them. In larger companies they may opt for refilling the LPG tanks on site thus requiring a much larger LPG storage tank. This of course can be a major fire hazard and refilling cylinders should only be done by trained and authorised personnel. Freeze burns are also a risk when refilling cylinders and PPE (personal protective equipment) must be worn when doing this. Thick gloves are recommended.