The Forklift

123rf photo 46182800
The forklift is the most common type of powered industrial truck (PIT).

A forklift is a type of "powered industrial truck" (PIT) covered by OSHA standards. Like other powered industrial trucks, its purpose is to move, carry, push, pull, and lift a material load then stack it or place it in a storage rack (tier). Forklifts come in many sizes and capacities. They can be powered by batteries, propane, gasoline, or diesel fuel. Some are designed to be used in a hazardous location or atmosphere where an ordinary forklift might cause a fire or explosion.

NIOSH states that the three most common types of injuries occur when: A forklift overturns; workers are struck, crushed, or pinned by a forklift; and workers fall from a forklift. However, no matter what the task, there is always a great risk of injury or death when a forklift operator:

  • has not been trained in the principles of physics that allows a forklift to lift heavy loads
  • is not familiar with how a particular forklift operates
  • operates the forklift carelessly
  • uses a forklift that is not safe due to malfunctioning or missing parts

1. Which of the following is one of the three most common types of forklift accidents?

a. Overexposure to indoor air pollutants
b. Worker is driving too fast
c. The forklift slides into an obstacle
d. A forklift overturns
safety
The backrest extension protects the operator.
design
Left: "Old design"
Right: "New design"
seat belts
Seat belts save lives!

Forklift Safety Features

Backrest Extension

A backrest extension on the forks prevents part of the load from falling rearward toward the operator. This is required when loads are lifted high and the type of load would allow all or part of it to fall to the rear under conditions such as acceleration, sudden stops or driving on an uneven surface.

Overhead Guard

An overhead guard prevents an object on the forks or on a high rack from falling onto the operator while picking or placing a load at elevation. Overhead guards are required on all forklifts that can lift a load above the operator unless conditions such as clearances would not allow the forklift to be used.

The guard is designed to be effective in deflecting small packages. They are not designed to withstand the impact from a full load.

Mast

The masts on newer forklifts are designed for traveling so that operators have a better view through the center in the direction of travel. The image to the right demonstrates improvements in forklift mast design.

Operator Restraints

Operator restraints will hold you in the seat if you strike an object or if the forklift overturns. Since 1992, forklift manufacturers have been required to equip new forklifts with operator restraints such as seat belts. Many forklift manufacturers offer restraint systems that can be retrofitted on older forklifts.

Failure to wear a seat belt can result in the operator being thrown outside the protective cage in the event of an overturn. If your forklift has a restraint, such as a seat belt or a lap bar, you must use it.

2. Which safety feature on the forklift protects the operator if part of the load falls rearward?

a. The overhead guard
b. The backrest extension
c. The mast
d. Operator restraints

Principles of Lifting Loads

gsg photo fulcrum
Fulcrum Principle

A forklift works on four very important principles that must be understood by all operators:

  1. Fulcrum Principle
  2. Stability Triangle
  3. Center of Gravity
  4. Moment

Fulcrum Principle

The Fulcrum Principle states that a forklift has two weights (load, counterweight), each located on the end of a beam which is balanced on a fulcrum, similar to a playground seesaw. A load is located on the forks and is balanced by the weight of the forklift with counterweight. The forks are supported by a fulcrum point located along the axle of the front wheels.

Stability Triangle

load
Stability Triangle

Operators must also understand the Stability Triangle. All forklifts have a stability triangle with the three sides of the triangle as shown in the illustration to the right. The sides of the triangle are formed by the center of each front wheel and the center of the rear wheel or at the center of the axle if there are two rear wheels.

Just imagine you're riding a tricycle. A tricycle is nothing more than a triangle on wheels. If you peddle around a corner too fast and shift your center of gravity outside the stability triangle, you'll tip over sideways. If you shift your center of gravity over the rear wheels, you are less likely to flip over backwards.

Center of Gravity (CG)

The Center of Gravity (CG) is the point at which the weight on both sides of the fulcrum is equal. The load on the forks is counterbalanced by the weight of the forklift body. Counterweight is built into it. The vehicle-load combination CG must be located inside of the stability triangle to prevent the forklift from tipping forward, falling sideways or dropping its load.

3. Which of the following is the point at which the weight on both sides of the fulcrum is equal?

a. Stable point
b. Center of gravity
c. Stability triangle
d. Moment

Moment

moment
The load moment is the distance from the fulcrum to the CG multiplied by the weight of the load.

A moment is calculated in inch-pounds. It equals the distance (in inches) x weight (in pounds) from a fulcrum to each end of the beam.

There are two important moment calculations that determine the stability of the forklift load.

Forklift Moment

The forklift moment is the distance from the fulcrum at the center of the front wheel to the center of gravity (CG) of the unloaded forklift multiplied by (x) the capacity rating of the forklift.

Forklift moment = distance from fulcrum to CG x capacity of forklift.

Load Moment

The load moment is the distance from the fulcrum to the forklift CG of the load multiplied by (x) the weight of the load in pounds.

load
This forklift can safely lift 5,000 lbs. 173 in. high with a center of gravity 24 in. from the face of the forks. With an attachment labeled "HSS," the safe load drops to 4,500 lbs.
Click to Enlarge

Load moment = distance from fulcrum to load CG x capacity of forklift.

Whether a forklift will safely carry a load or tip over can be determined by comparing the forklift moment and the load moment. To be safe, the load moment must be less than the forklift moment.

Capacity Plates

Forklifts have a capacity plate to tell the user what loads are safe to lift. If the plate says the capacity is 30,000 pounds or less then that capacity is rated for a load with a center of gravity 24” from the face of the forks. Most pallets are 48” x 48” and have a 24” CG if the weight of the load is evenly distributed. If the forklift capacity is greater than 30,000 pounds then the label will rate the load at a 36” or 48” center of gravity since larger forklifts usually lift physically larger loads.

4. Where can the forklift operator find out what loads are safe to lift?

a. In the manufacturer's manual
b. In the glove compartment
c. On the capacity plate
d. In the engine compartment

Examples

Let’s take a look at an example that illustrates what we've been discussing. An evenly distributed 48" wide load on the forks has a center of gravity that is 24” from the face of the forks.

Safe Lift

If the load weighs 4,000 pounds then the load moment will be (24" x 4,000 lb.) = 96,000 inch-pounds.

gsg photo calculation
To be safe, the load moment must be less than the forklift moment.
Click to Enlarge

Using the example and capacity plate in the previous section, a forklift rated at 5,000 pounds at 24 inches would safely lift a load with a moment of up to (24" X 5,000 lb.) = 120,000 inch-pounds.

In this case, the load above would be safe to lift.

Forklift Moment = (24" X 5,000 LBS) = 120,000 inch-pounds

Load Moment= (24" X 4,000 LBS) = 96,000 inch-pounds

The load is safe to lift because load moment is less than forklift moment.

Unsafe Lift

Let’s say the same 4,000 pound load was 66" wide, the load moment would then be 132,000 inch-pounds (33” X 4,000 lb.). Would the load be safe?

Forklift Moment = (24" X 5,000 LBS) = 120,000 inch-pounds

Load Moment= (33" X 4,000 LBS) = 132,000 inch-pounds

In this example, the load moment is greater than forklift moment, so the load is too heavy for the forklift and it would tip forward.

5. When would a forklift load be safe to lift?

a. When the load moment is less than the forklift moment
b. When the forklift moment is less than the load moment
c. When the forklift moment is at least twice the load moment
d. When the load moment is less than half the forklift moment
gsg image stability
As the load is raised, it becomes possible for the forklift to fall to the side.
Click to Enlarge

Raising the Load Can Create Instability

As the load is raised, it becomes possible for the forklift to fall to the side as well as tip forward because the combined CG might move outside the stability triangle. The operator must consider the CG of the forklift and load together.

  • This combined CG moves forward as the forklift is loaded.
  • The combined CG also moves as the load is moved and as the forklift travels over surfaces that are rough or inclined.

The combined CG can move outside the stability triangle if:

  • The load is picked up on the tip of the forks.
  • The load is tilted forward.
  • gsg image Load CD
    If the load CG moves outside the Safety Triangle, the forklift may tip forward.
    Click to Enlarge
  • The load is tilted too far back when raised.
  • The load is wide.
  • Forklift movement causes the center of gravity to shift.

These actions will have the following effects:

  • Tilting the load forward moves the combined CG toward the front axle.
  • Tilting the load back moves the combined CG toward the rear axle.
  • Driving across an inclined surface moves the combined CG toward the downhill side of the triangle.
  • Driving across rough or uneven surfaces moves the combined CG toward the rut or low side of the triangle.
  • Turning moves the combined CG toward the side now facing the original direction of travel.

6. Tilting the load back moves the combined center of gravity (CG) _____.

a. toward the front axle
b. toward the rear axle
c. toward the side now opposite the original direction of travel
d. toward the rut or low side of the stability triangle

Driving on an Incline

 gsg image stability
Keep the load uphill to maintain control of the forklift.
Click to Enlarge

If you drive a forklift on an incline, you must keep the load on the uphill side. Otherwise, you may have no weight on the wheels that steer and can lose control. The load could also fall off or cause the forklift to tip.

Operator procedures that reduce the risk of overturn, collision or loss of the load use the following procedures:

  • Make sure the load is stable and safely arranged on the forks.
  • Do not tilt the forks forward except when picking up or depositing a load.
  • Tilt the load backward only enough to stabilize the load.
  • Keep the load low just above the pavement with forks tilted back when traveling.
  • Cross railroad tracks diagonally when possible.
  • Enter elevators squarely.
  • Keep the load uphill when going up or down an incline.
  • Drive at a speed that will allow you to stop safely within the stability triangle.
  • Slow down on wet or slippery surfaces.
  • Slow down to make turns.
  • Avoid driving over loose objects or on surfaces with ruts and holes.

7. Where must the load be positioned when traveling on an incline?

a. Always on the downhill side
b. On the downhill side when traveling up the incline
c. On the uphill side when traveling down the incline
d. Always the uphill side
power source 1
Forklift power sources are either internal combustion or electric.

Power Sources

The two main power sources for powered industrial trucks are:

  1. internal combustion, which uses a traditional engine that runs on liquid petroleum gas (LPG), compressed natural gas (CNG), gasoline, diesel, or other fuel; and
  2. electric, which uses an on-board battery.

Other power sources that may become more widespread in the future include fuel cells and hybrid systems. Hydrogen fuel cells will have zero emissions and quiet operation plus the ability to be refueled as quickly as gasoline engines. Hybrid systems will use a combination of fuel cells and batteries.

Check out this short video by Ted Johnson Propane on Forklift Fuel Filling.
Click to View

Liquid Petroleum Gas

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. Here are some important points to remember about using LPG forklifts:

  • 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.
  • 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.

8. The two main power sources for powered industrial trucks are ____ and _____.

a. fuel cells, diesel
b. LPG, hybrid LPG-Electric
c. internal combustion, electric
d. hydrogen, compressed natural gas
refueling
Electric forklift maintenance.

Electric Forklifts

Electric-powered forklifts are most commonly used indoors in warehouses. They produce zero emissions, virtually eliminate the hazard of carbon monoxide poisoning, and run more quietly than internal combustion forklifts. However, they present other serious hazards that must be addressed. Electric forklifts are powered by large lead-acid batteries, which must be routinely charged. The hazards and recommended practices for charging and changing batteries are reviewed below.

Requirements and recommended practices include:

  • Designate an area for the purpose of battery charging.
  • Make sure that the forklift is charged before using.
  • Recognize that heavy loads drain the battery more.

Battery Maintenance

battery discharge
Discharging a battery beyond recommended levels may ruin or damage the battery.
Click to Enlarge

Under normal operating conditions, power industrial truck forklift batteries can be expected to remain in service for 2,000 work shifts or charge/discharge cycles. Implementing a proper battery maintenance program can increase the life of the batteries and help protect employees. Battery failure could lead to mechanical breakdowns and possible accidents involving forklift operators and/or other personnel.

When working with batteries, be sure to do the following:

  • Do not exceed the service hours in the manufacturer's recommendations.
  • Do not over charge or under charge batteries.
  • Avoid discharging batteries beyond the manufacturer’s discharge level. This can result in permanent battery damage and shorten battery life considerably.
  • Warning signs of a low battery include slow starting, dim headlights, and the ammeter indicating discharge at high RPM.
  • Recycle or properly dispose of batteries. Spent batteries are a hazardous waste unless they are properly reclaimed at a lead smelter or battery recycler.

9. What is an advantage of using electric-powered forklifts?

a. Fuel must be replaced regularly
b. They are more useful for outside work
c. They produce zero emissions
d. They produce less hydrogen dioxide
attachments
Forklift Attachment Examples
Click to Enlarge

Attachments

Sometimes special attachments are installed onto the forks to extend the reach, clamp a barrel, act as a hoist, lift odd-shaped items (e.g., a roll of carpet), or even lift people. Attachments include:

  • jib crane attachment
  • hoist attachment
  • drum grabber attachment
  • carpet lifting attachment
  • personnel platform

Whenever an attachment is used that could affect the capacity or safe operation of a forklift, its use must be approved by the forklift manufacturer.

The employer must mark the forklift to show the new weight with attachment. The maximum capacity at the highest elevation must also be shown.

10. What is required when using an attachment on a forklift?

a. It must have been used before without incident
b. It must be approved by the safety manager
c. It must be approved by the manufacturer
d. It must be rated for the job by OSHA

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