The use of hand carts to transport loads instead of carrying them saves workers a lot of effort. It decreases the risk of overexertion injury in jobs that include manual materials handling.
However, pushing, pulling, and maneuvering hand carts still involve some of the old hazards (overexertion), while creating new ones. The most common injuries that result from hand cart operations are:
It is difficult to outline how much weight can be transported using a hand cart. Many factors affect how much force is needed to move a given weight. The main three factors are:
1. Workplace Characteristics:
a. Aisle width - aisles should be wide enough for the operator's body to safely stand behind the cart at all times and apply the force necessary to move it. Load weight may need to be reduced in tight aisles or corners.
b.Ramps - more force is required to move the same weight up ramps, as well as to slow down a fully loaded cart while moving down ramps.
c. Floor characteristics - damaged, uneven, or etched floors create hazards in that they can catch wheels or castors in them. Floors that are dusty, dirty, oily, or wet will reduce the ability of the handler to maintain traction. Without friction, the worker will need to exert excessive force to move the load, and may slip and trip.
2. Cart Characteristics:
a. wheel/castor size and number of wheels or castors
b. handle orientation/height, handle diameter
c. overall cart size.
3. Operator knowledge and training - training in how to move the cart safely has been shown in some studies to lower the force on the body
Good design of the workplace and the selection of a hand cart suitable for the task can reduce the risk of injury. Points to consider when selecting carts include:
There are currently no numerical standards on acceptable loads or forces required while operating hand carts. Recommendations presented in Table 1 are adopted from guidelines developed by the Ergonomics Group of Eastman Kodak Co. who compiled data from various studies.
General recommendations for selection are:
Where there is a need to move heavier loads over longer distances, using powered trucks or a powered conveyor system should be considered.
Recommended Limits in the Selection of Hand and Powered Trucks and Carts
|Type of Truck or Cart||Maximum Load||Maximum Transport Distance||Maximum Frequency Units|
(per 8 hr - shift)
|Minimum Aisle Width||Type of Transfer to and from Truck+|
|2-wheeled hand cart||114||250||16||50||200||1.0||3||Ma, P|
|3-wheeled hand cart||227||500||16||50||200||1.0||3||Ma, P|
|4-wheeled hand cart||227||500||33||100||200||1.3||4||Ma, P|
|Hand pallet truck||682||1500||33||100||200||1.3||4||Me, UL|
|Electric pallet truck||2273||5000||82||250||400||1.3||4||Me, UL|
|Electric hand-jack lift truck||2273||5000||33||100||400||1.3||4||Me, UL|
|Power low lift truck||2273||5000||328||1000||400||2.0||6||Me, P, UL|
|Electric handstacking truck||682||1500||82||250||400||1.3||4++||Me, UL|
|Power fork truck||2273||5000||164||500||400||2.0||6++||Me, UL|
+ Ma = Manual; Me = Mechanical; P = Parts; UL = Unit Load
++ These trucks have tiering capability. In order to use it, ceiling must be more than 4 m (12 ft) high.
Adapted from: Ergonomic Design for People at Work: Vol. 2, by Eastman Kodak Company. Van Nostrand Reinhold, 1986.
Modifying force limits for pushing, pulling or maneuvering for any given work situation is essential not only for the safety of the operator but also for other workers within the work area.
Simple actions can be taken to ensure the risks associated with using hand carts are minimized:
1. Workplace characteristics:
a. Aisle Conditions:
i. Keep aisles clear of clutter.
ii. Aisles that are wide enough to allow the worker to stand behind the cart and push.
iii. Corners that will accommodate the moving cart without stopping and starting.
i. Use winches for large ramps.
ii. Use Power assists (a battery powered pushing device).
iii. If multiple ramps are present, include a hand or foot brake on the cart to help the operator control heavy loads.
iv. If multiple ramps are present, consider using powered carts.
c. Floor Condition
i. Keep floors in good repair.
ii. Ensure floors are clean, free of debris, dirt, dust, miscellaneous liquids, or spills.
iii. If floors are very uneven, consider using powered carts.
2. Cart Characteristics:
i. (Use a larger diameter wheel. Increasing the diameter of the wheels generally decreases force requirements).
ii. A harder caster/tire generally decreases force requirements.
iii. A wider tread generally increases force requirements.
Note: pneumatic wheels should not be used for heavy loads as they may compress and substantially increase the force requirements.
i. Use swivel castors on the same end of the cart as the handle (Figure 1).
ii. Handles on pallet trucks should be long enough to prevent worker's feet from being struck by body of pallet truck (Figure 2).
iii. Fixed horizontal handles should be at a height between 91 cm and 112 cm above the floor (Figure 3).
iv. Vertical handles allow a worker to place hands at comfortable positions for their height (usually used for narrow carts) (Figure 4).
v. For handles fixed to the cart's surface, the handles should not be more than 46 cm apart. Wider separations increase the load on smaller shoulder muscles.
vi. Handles should be thick enough to grip easily - 2.5 cm to 3.8 cm.
vii. Fixed handles mounted in the horizontal direction should have a minimum length of 20 cm.
c. Cart size
i. Large carts (longer than 1.3 m and/or wider than 1 m) are difficult to maneuver and should not be used in workplaces with narrow aisles.
3. Operator Training/Experience:
a. Operators should be trained on appropriate body positioning for the type of cart and load being handled.
b. Operators should receive training on how to maneuver heavy loads.
c. Operators should walk at an appropriate cart speed - recommended speeds should match a typical walking pace (3-4 km/h).
Document last updated on June 18, 2010