Friday, June 27, 2014

Load Composition Part 2

Safe Load Capacity
Improperly distributed loads may tip the forklift if the operator exceeds the stated capacity of the truck. This forklift can carry 4,000 pounds at a 24 inches load center, but only 2,666 pounds at a 36 inches load center.
Figure 4. Improperly distributed loads may tip the forklift if the operator exceeds the stated capacity of the truck. This forklift can carry 4,000 pounds at a 24 inches load center, but only 2,666 pounds at a 36 inches load center.
Requirements and Recommended Practices:
  • Estimate the safe load capacity with oversized loads.

  • If the stated load center is exceeded, compensate by reducing the weight of the load.

  • Consult the forklift manufacturer’s instructions when handling large or unusually configured loads.

  • Tip: Use field calculations to estimate the reduced lifting capacity if manufacturer’s instructions are not available. This calculation method will not produce exact load reduction figures. Use this method only as a guideline. The forklift manufacturer is the source of more precise information.
Field Calculation of Safe Load Capacity

Assume a situation where a forklift truck that has a 5,000 pound capacity at a 24 inch load center needs to handle a load whose center is 28 inches from the front face of the forks in the horizontal direction. The first thing to recognize is that the actual load center distance of 28 inches exceeds the standard load center distance of 24 inches on which the 5000 pound capacity is based, so the safe load capacity is actually less than 5000 pounds.

To estimate the truck's safe load capacity at a 28-inch load center, take the rated load center and divide it by the actual load center. Then multiply this number by the stated capacity to get the new approximate safe load capacity:

24 in/28 in x 5,000 lb = 4,285 lb (approximate safe load capacity)

Using the example in Figure 4, take the stated standard load center of 24 inches and divide it by the actual load center of 36 inches. Multiply this number by the stated capacity of 4,000 lb to get the new approximate safe load capacity:

24 in/36 in x 4,000 lb = 2,666 (approximate safe load capacity)

Monday, June 23, 2014

Load Composition

As the center of gravity for the load moves forward, the lifting capacity for the forklift decreases.
Figure 1. As the center of gravity for the load moves forward, the lifting capacity for the forklift decreases.
The stated capacity of a forklift only applies to the load center indicated on the data plate. If the load is not centered at the specified position, the forklift's capacity will be reduced. Loads come in all shapes and sizes, not just symmetrical boxes. The load size, position, and weight distribution critically affect the forklift's capacity and the stability of the truck. Consider the following factors before engaging a load:
  • Weight, Size, and Position
  • Safe Load Capacity
  • Maximum Load Moment
  • Balance
  • Stability
Weight, Size, and Position
The same 4500 pounds weight loaded properly (top) will exceed the rated capacity of 4500 pounds if the rectangular box is positioned lengthwise (bottom).
Figure 2. The same 4500 pounds weight loaded properly (top) will exceed the rated capacity of 4500 pounds if the rectangular box is positioned lengthwise (bottom).
Load weight, weight distribution, size, shape, and position are key factors affecting the stability of the forklift. Forklifts are designed to carry a capacity load at a standard load center, commonly 24 inches. This means that the forklift’s capacity was determined as if the load were a cube whose weight is evenly distributed (i.e., whose center of gravity is exactly in the center of the cube) and which is resting on a standard pallet having dimensions of 48 inches by 48 inches. With such a load, the horizontal distance from the center of the load to the vertical part of the forks would be 24 inches. Of course, most loads are not perfectly shaped cubes having their center of gravity exactly in the middle of the cube. To the extent that the load differs from this theoretical load — such as if it is irregularly shaped, has unbalanced weight distribution, or is not centered on the forks — the capacity may be reduced.

Potential Hazards:

While arranging a load, be aware of the following:
  • tipover
  • Loss of steering control (Shifting too much weight forward raises the rear wheels.)
  • Falling load
  • Collision
Requirements and Recommended Practices:
  • Do not exceed the capacity of the forklift that appears on the forklift's data plate (sometimes called the "nameplate"). If the load is oversized, irregularly shaped, or loaded incorrectly, the actual load center distance could exceed the stated load center distance, causing the truck's capacity to be exceeded. (Figure 2).

  • Always minimize the distance from the front wheels to the load center. Load a large rectangular box widthwise across the forks of the truck as in Figure 2. Placing a large rectangular load lengthwise causes the load center to shift forward further away from the front wheels, exceeding the truck's capacity and lifting the rear wheels off the ground.

    The heaviest weight should be loaded as close to the masts as possible.
    Figure 3. The heaviest weight should be loaded as close to the masts as possible.
  • Load as close to the front wheels as possible to minimize the load center distance. Load the heaviest part toward the mast. (Figure 3)

  • Position the load in a way that will shorten the load center distance.




Monday, June 16, 2014

Truck Trailers and Railroad Cars

Truck Trailers and Railroad Cars
Wheels are chocked prior to boarding.
Figure 14. Wheels are chocked prior to boarding.

Use positive protection to prevent railroad cars from being moved.
Figure 15. Use positive protection to prevent railroad cars from being moved.

Operator using warning light and looking in the direction of travel when exiting a truck trailer.
Figure 16. Operator using warning light and looking in the direction of travel when exiting a truck trailer.

Entering a truck trailer with adequate overhead clearance.
Figure 17. Entering a truck trailer with adequate overhead clearance.

Manual dock plate is secured into position. Always walk and inspect trailer floor before boarding.
Figure 18. Manual dock plate is secured into position. Always walk and inspect trailer floor before boarding.
Potential Hazards:

While entering and leaving truck trailers or railroad cars, be aware of the following:
  • Falling off loading dock.
     
  • Moving trucks or railroad cars during loading and unloading.
     
  • Slipping or inadequate dockboards.
Requirements and Recommended Practices:

The OSHA Powered Industrial Trucks standard [29 CFR 1910.178] lists a number of situations in which special procedures must be followed before starting entry:
  • The brakes of highway trucks shall be set and wheel chocks placed under the rear wheels to prevent the trucks from rolling while they are boarded with powered industrial trucks. [29 CFR 1910.178(k)(1)]

  • Wheel stops or other recognized positive protection shall be provided to prevent railroad cars from moving during loading or unloading operations. [29 CFR 1910.178(k)(2)]
     
  • Fixed jacks may be necessary to support a semitrailer and prevent upending during the loading or unloading when the trailer is not coupled to a tractor. [29 CFR 1910.178(k)(3)]
     
  • Positive protection shall be provided to prevent railroad cars from being moved while dockboards or bridge plates are in position. [29 CFR 1910.178(k)(4)]
The OSHA Walking-Working Surfaces standard [29 CFR 1910.30(a)] contains requirements for dockboards (bridge plates).
  • Portable and powered dockboards shall be strong enough to carry the load imposed on them. [29 CFR 1910.30(a)(1)]
     
  • Portable dockboards shall be secured in position, either by being anchored or equipped with devices which will prevent their slipping. [29 CFR 1910.30(a)(2)]
     
  • Powered dockboards shall be designed and constructed in accordance with Commercial Standard CS202-56 (1961) "Industrial Lifts and Hinged Loading Ramps" published by the U.S. Department of Commerce, which is incorporated by reference as specified in Sec. 1910.6. [29 CFR 1910.30(a)(3)]
     
  • Handholds, or other effective means, shall be provided on portable dockboards to permit safe handling. [29 CFR 1910.30(a)(4)]
     
  • Positive protection shall be provided to prevent railroad cars from being moved while dockboards or bridge plates are in position. [29 CFR 1910.30(a)(5)]
Additional Trailer Loading and Unloading Procedures
  • Inspect the floor of the trailer to be sure that it will support the forklift and load.
     
  • Ensure that the height of the entry door is adequate to clear the height of your vehicle, taking into consideration the height of the loading platform.
     
  • Drive straight across the bridge plates when entering or exiting the truck trailer or railroad car.
     
  • Use dock lights and headlights when working in a dark trailer.
     
  • Sound the horn when entering or exiting the trailer.
     
  • In determining the capacity of the trailer floor to support a forklift, consider various factors, including floor thickness and cross-member spacing or unsupported floor area. In general, the larger the unsupported area, the lower the forklift capacity the trailer will have for the same floor thickness.
     
  • Never use the forklift to open railroad car doors unless:

Friday, June 6, 2014

High Tiering

High Tiering
Reach trucks are often used for high tiering, which involves storing material in multiple tiers high off the ground.

Potential Hazard:
  • Overloading
     
  • Tipover
Requirements and Recommended Practices:
  • Set the heaviest loads on the bottom tier.
     
  • Set the lightest loads on the top tier.
     
  • Reduce the load below the capacity of the reach truck as the mast is fully extended.
     
  • Slowly and carefully extend the reach mechanism forward when depositing the load on the top tier.
     
  • Use extreme care when tilting a load forward or backward, particularly when high tiering. [29 CFR 1910.178(o)(6)]
Reach trucks maximize maneuverability in narrow aisle.
Figure 11. Reach trucks maximize maneuverability in narrow aisle.

Triple reach extends 23 feet high. The lightest loads are placed on the top tiers.
Figure 12. Triple reach extends 23 feet high. The lightest loads are placed on the top tiers.

Reach mechanism extends forward to deposit load on top tier.
Figure 13. Reach mechanism extends forward to deposit load on top tier.

Monday, June 2, 2014

Lowering the Load


Tilt the mast backward to stabilize the load.
Figure 10. Tilt the mast backward to stabilize the load.
Potential Hazards:

While lowering the load, be aware of the following:
  • Falling loads.
     
  • Striking objects.
Requirements and Recommended Practices:

The mast must be carefully tilted backward to stabilize the load.
  1. Ensure the load is secured before moving.
     
  2. Carefully tilt the mast backward to stabilize the load.  [29 CFR 1910.178(o)(5)]
     
  3. Slowly move the truck to 20 to 30 cm (8 to 12 inches) away from the stack.
     
  4. Stop the truck.
     
  5. Return the mast to the vertical position before lowering the load.
     
  6. Lower the load so that its lowest point is 15 to 20 cm (6 to 8 inches) from the floor.
     
  7. While traveling, keep the load at a safe travel height. See Traveling & Maneuvering.