Free NCCCO Dynamic Loading and Environmental Effects Questions and Answers — Questions and Answers
Question 1: What is the primary danger of 'shock loading' a crane?
- It can cause the engine to stall.
- It can create forces far exceeding the crane's rated capacity. (Correct answer)
- It can damage the crane's paint.
- It can cause the radio to malfunction.
Correct answer: It can create forces far exceeding the crane's rated capacity.
Shock loading occurs from sudden starts or stops, such as snatching a load or having a load slip and be caught by the hoist line. This dynamic event can generate forces that are many times greater than the static weight of the load, potentially causing catastrophic structural failure or loss of stability.
Question 2: How does high wind primarily affect a suspended load and the crane's stability?
- It cools the engine more effectively.
- It decreases the weight of the load.
- It can increase the load radius and cause side loading. (Correct answer)
- It makes the wire rope stronger.
Correct answer: It can increase the load radius and cause side loading.
Wind exerts force on both the load and the crane itself. It can push a suspended load, causing it to swing outward, which increases the load radius. This increased radius can overload the crane and lead to a tipping incident. This effect is known as side loading on the boom.
Question 3: Side loading of a crane boom is extremely hazardous because:
- It can scratch the boom's surface.
- Booms are not designed to withstand lateral (sideways) forces. (Correct answer)
- It causes the crane to use more fuel.
- It puts extra stress on the crane's tires.
Correct answer: Booms are not designed to withstand lateral (sideways) forces.
Crane booms are engineered to withstand compressive forces along their length (axially). They have very little strength against forces applied from the side (laterally). Side loading, caused by wind, dragging a load, or rapid swinging, can easily bend and buckle the boom, leading to structural failure.
Question 4: When lifting a load out of water, the operator must anticipate that:
- The load's weight will decrease as it leaves the water.
- The load's weight will suddenly increase as it breaks the surface. (Correct answer)
- The water will lubricate the wire rope.
- The crane's capacity is higher when lifting from water.
Correct answer: The load's weight will suddenly increase as it breaks the surface.
A submerged object is partially supported by the water's buoyancy, making it seem lighter. As the object is lifted clear of the surface, this buoyant force is lost, and the crane suddenly feels the full, unsupported weight of the load, plus any water trapped inside it. This can cause a shock load if not anticipated.
Question 5: Rapidly swinging a load can cause which dangerous effect?
- An increase in load radius due to centrifugal force. (Correct answer)
- A decrease in the weight of the load.
- The boom to automatically retract.
- The crane's counterweight to become heavier.
Correct answer: An increase in load radius due to centrifugal force.
When a crane swings quickly, centrifugal force acts on the suspended load, causing it to swing outward and away from the crane. This movement increases the load's effective radius. Since capacity decreases as radius increases, this can easily move the crane from a safe operating condition to an overload situation.
Question 6: Crane operations must be shut down when wind speeds exceed the limits specified by:
- The site supervisor's best judgment.
- A national standard of 50 mph.
- The crane manufacturer. (Correct answer)
- The local weather forecast.
Correct answer: The crane manufacturer.
While there are general rules of thumb (like 30 mph), the absolute authority on operational limits, including wind speed, is the crane's manufacturer. The manufacturer's operation manual and load charts will specify the maximum allowable wind speed for that specific crane model, which must always be followed.
Question 7: How can extremely cold weather affect a crane's steel components?
- It makes the steel stronger and more flexible.
- It can make the steel more brittle and prone to fracture. (Correct answer)
- It causes the steel to expand, increasing capacity.
- It has no significant effect on the crane's structural integrity.
Correct answer: It can make the steel more brittle and prone to fracture.
At very low temperatures, the molecular structure of steel can change, causing it to lose its ductility and become brittle. This phenomenon, known as brittle fracture, means the steel is more likely to crack or shatter under a load that it could easily handle at normal temperatures.
Free NCCCO Dynamic Loading and Environmental Effects Questions and Answers
What is the primary danger of 'shock loading' a crane?