Power Sources » Internal Combustion

Figure 1. Internal combustion engine used in a forklift.
Figure 1. Internal combustion engine used in a forklift.

Forklifts powered by internal combustion engines run on a variety of fuels, including gasoline, diesel fuel, liquid petroleum gas (LPG), and compressed natural gas. Forklifts with internal combustion engines can be quickly refueled but require regular maintenance checks for leaks of fuel or oil and worn parts to keep systems working properly. Forklifts powered by internal combustion engines are also used indoors, although this may increase exposure to exhaust and noise.

The most widely used forklifts have an internal combustion engine powered by fuels that include gas, liquid petroleum, diesel fuel, and compressed natural gas. Forklifts with internal combustion engines can be quickly refueled but require regular maintenance checks for leaks of fuel or oil, worn parts requiring replacement, and to keep systems working properly. Newer forklifts with internal combustion engines have on-board sensors that monitor and adjust emissions and have catalytic converters that help reduce emissions.

Potential Hazards

A fork that shows any of the following defects shall be withdrawn from service and discarded or properly repaired:

  • Exposure to engine exhaust containing carbon monoxide. If the engine is not properly combusting fuel, the exhaust may contain high levels of carbon monoxide.

  • Exposure to spills and leaks of fuel and oil.

Requirements and Recommended Practices

  • Do not operate in a poorly ventilated area where vapors can concentrate.

  • Carefully wash away or completely evaporate spillage of oil or fuel.

  • As part of the pre-operation inspection, check all fluid levels, including oil, water, and hydraulic.

  • Check for leaks from the hydraulic cylinder, the battery, and the fuel system.

  • Check the exhaust color for incomplete combustion. For example, black smoke may be an indication of incomplete combustion.

  • Check and report unusual noises or excessive vibration.

Forklifts that use gasoline are easy to refuel. However, gasoline is very flammable.

Potential Hazard

  • Exposure to explosive vapors.

Figure 2. Operator refueling diesel-powered forklift.

Requirements and Recommended Practices

  • Refuel only at designated safe locations.

    • A designated safe location outdoors is preferable to a refueling area indoors. Do not refuel trucks in hazardous areas or around heat sources.

  • Stop the engine during refueling.

  • Do not smoke while refueling.

  • Do not allow the forklift to become low on fuel or run out of fuel. Sediment or other impurities in the tank could be drawn into the fuel system causing difficulties in starting and actual damage to the internal components. Fill the fuel tank at the end of each day.

  • Do not fill the tank to the top; it may overflow because fuel expands as it is heated.

  • Follow correct refueling procedures:

    1. Park the forklift in the designated refueling area.

    2. Place the transmission in Neutral.

    3. Lower the forks to the ground.

    4. Engage the parking brake.

    5. Shut off the engine.

    6. Open the filler cap.

    7. Fill the tank slowly (if spillage occurs, wipe off fuel and wash down the area with water).

    8. Close the filler cap.

Liquid petroleum gas (LPG) is a commonly used fuel for forklifts. It is a safe fuel when handled properly. When handled improperly, it can cause serious injury or death.

Potential Hazards

  • LPG vapor is heavier than air and will seek the lowest lying area. If not adequately dissipated, it will collect in pockets and possibly ignite when exposed to a heat source.

  • LPG is extremely flammable.

  • LPG is extremely cold when exposed to the atmosphere. If your skin is exposed to LPG, you can get frostbite.

Requirements and Recommended Practices

Figure 3. Operator changing LPG container.
  • Do not refuel LPG-powered trucks in confined areas where LPG vapors could collect if a leak occurs.

  • Do not leave LPG-powered trucks near heat sources, stairways, exits, or other egress areas.

  • When parking LPG-powered trucks for a long period of time, turn the service valve off.

  • Only trained and authorized personnel should replace LPG containers.

  • Follow proper procedures for storing and handling liquid petroleum gas. [29 CFR 1910.110]