One of the most serious hazards that cranes present is collapse of the equipment caused by exceeding the crane's rated capacity. The term "rated capacity" is defined as:
"the maximum working load permitted by the manufacturer under specified working conditions. Such working conditions typically include a specific combination of factors such as equipment configuration, radii, boom length, and other parameters of use."
The combination of factors that determine rated capacity is set forth in a load chart that must be on the equipment. In general, the load chart states the weight of the load that the crane can lift at different boom radii. The longer the radius at which the lift occurs, the smaller amount of weight the crane can lift.
Employees must not operate a crane in excess of its rated capacity. Because variable worksite conditions on worksites, such as swinging of the load caused by wind or other factors, the capacity of the crane may be less than that which exists under ideal conditions.
To comply with the rated capacity, the weight of the load must be known. Before beginning a lift, the operator must determine the load weight by using a reliable means.
1. To comply with crane's rated capacity, _____ must be known.
a. the model of the craneEmployers must permit only thoroughly trained and competent workers to operate cranes. Operators should know what they are lifting and what it weighs.
For example, the rated capacity of mobile cranes varies with the length of the boom and the boom radius. When a crane has a telescoping boom, a load may be safe to lift at a short boom length or a short boom radius, but may overload the crane when the boom is extended and the radius increases.
To reduce the severity of an injury, employers must take the following precautions:
2. What must crane operators do to make sure the crane will not be overloaded by operating conditions?
a. Check capacity rating of slingsOSHA regulation 1926.1425 seeks to protect employees against being struck by a moving or falling load.
Where available, hoisting routes that minimize the exposure of employees to hoisted loads must be used, to the extent consistent with public safety.
While the operator is not moving a suspended load, no employee may be within the fall zone, except for employees:
When employees in the fall zone are engaged in hooking, unhooking, or guiding the load, or are connecting a load to a component or structure, all of the following criteria must be met:
Only employees needed to receive a load are permitted to be within the fall zone when a load is being landed.
3. Who may be within the fall zone of a suspended stationary load?
a. An employee conducting load inspectionThe operator must not engage in any practice or activity that diverts their attention while engaged in operating the equipment, such as the use of a cell phone (except when used for signal communications).
The operator must not leave the controls while the load is suspended except where ALL of the following criteria are met:
The four criteria immediately above do not apply to working gear (such as slings, spreader bars, ladders, and welding machines) where:
4. Which of the following is NOT one of the four criteria that must be met before a crane operator may leave the controls while a load is suspended?
a. A competent person must determine it is safe and implements safety measures.The operator must test the brakes each time a load that is 90% or more of the maximum line pull. The test is handled by lifting the load a few inches and applying the brakes. In duty cycle and repetitive lifts where each lift is 90% or more of the maximum line pull, this requirement applies to the first lift but not to successive lifts.
To prevent rope from becoming detached from a drum, neither the load nor the boom must be lowered below the point where less than two full wraps of rope remain on their respective drums.
Traveling with a load is prohibited if the practice is prohibited by the manufacturer. Where it is not prohibited, you must take precautions to prevent hazardous movement of the load and avoid excessive movement of the load that could overload the crane.
OSHA regulation 1926.1418 provides that, whenever there is a concern about safety, the operator must have the authority to stop and refuse to handle loads until a qualified person has determined that safety has been assured.
5. The operator must perform a brake test _____.
a. each time the load is 90% of maximum line pullA crane operator often needs a second set of eyes - a signal person - to be able to operate safely. A signal person that uses hand, voice, or audible (bells, whistles, horn, etc.) signals must be provided:
During operations requiring signals, the ability to transmit signals between the operator and signal person must be maintained. If that ability is interrupted at any time, the operator must safely stop operations until signal transmission is reestablished and a proper signal is given and understood.
Only one person may give signals to a crane/derrick at a time, though any person may give an emergency stop signal.
6. What must the crane operator do if the ability to transmit signals between the operator and signal person is interrupted?
a. Continue operationsOSHA regulation 1926.1424 is designed to protect employees who work near a crane from being struck or crushed by the crane's rotating superstructure. To prevent employees from entering an area where they could be struck/crushed, you must:
Before an employee goes to a location in the hazard area that is out of view of the operator, the employee (or someone instructed by the employee) must ensure the operator is informed he/she is going to that location.
Where the operator knows an employee went to such a location, the operator must not rotate the superstructure until the operator is informed in accord with a pre-arranged system of communication the employee is in a safe position.
7. What must be done if it can be demonstrated it is neither feasible to erect hazard area barriers on the ground nor on the equipment?
a. Conduct operations without rotating the superstructureThe dominant characteristics of a sling are determined by the components of that sling. For example, the strengths and weaknesses of a wire rope sling are essentially the same as the strengths and weaknesses of the wire rope of which it is made.
Slings are generally one of the following types:
8. Which of the following sling types is used because of its strength and ability to adapt to the shape of the load?
a. Fiber ropeSlings should be selected based upon the characteristics of the load and the environmental conditions surrounding the lift. Be sure to inspect slings prior to each use and that you know how to use it safely. There are four primary factors to consider when safely lifting a load. They are:
The center of gravity of an object is that point at which the entire weight may be considered as concentrated. To make a level lift, the crane hook must be directly above this point. While slight variations are usually permissible, if the crane hook is too far to one side of the center of gravity, dangerous tilting will result causing unequal stresses in the different sling legs. This imbalance must be compensated for at once.
As the angle formed by the sling leg and the horizontal line decreases, the rated capacity of the sling also decreases. In other words, the smaller the angle between the sling leg and the horizontal, the greater the stress on the sling leg and the smaller (lighter) the load the sling can safely support. Larger (heavier) loads can be safely moved if the weight of the load is distributed among more sling legs.
The rated capacity of a sling varies depending upon the type of sling, the size of the sling, and the type of hitch. Operators must know the capacity of the sling. Charts or tables that contain this information generally are available from sling manufacturers. The values given are for new slings. Older slings must be used with additional caution. Under no circumstances shall a sling's rated capacity be exceeded.
Mishandling and misusing slings are the leading cause of sling-related accidents. Most injuries and accidents, however, can be avoided by becoming familiar with the essentials of proper sling care and use. Be sure to check this history of the sling to be used and that it has passed inspections.
9. When calculating sling rated capacity, as the angle formed by the sling leg and the horizontal line _____, the rated capacity of the sling _____.
a. decreases, remains the sameProper care and use are essential for maximum service and safety. Slings must be protected with cover saddles, burlap padding, or wood blocking as well as from unsafe lifting procedures such as overloading to prevent sharp bends and cutting edges. Follow these safe practices when working with slings:
After the sling is properly attached to the load, there are a number of good lifting techniques that are common to all slings.
Once the lift has been completed, clean the sling, check it for damage, and store it in a clean, dry airy place. It is best to hang it on a rack or wall.
Remember, damaged slings cannot lift as much weight as new or older well-cared for slings. Proper and safe use and storage of slings will increase their service life.
10. When lifting a load, where should the hook be positioned over the load to give maximum lifting efficiency?
a. As determined by the load chart on the capacity plateClick on the "Check Quiz Answers" button to grade your quiz and see your score. You will receive a message if you forgot to answer one of the questions. After clicking the button, the questions you missed will be listed below. You can correct any missed questions and check your answers again.