Dynamic Loading and Environmental Effects Flashcards
7 cards from real NCCCO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Dynamic Loading and Environmental Effects flashcards as text
What is the primary danger of 'shock loading' a crane?
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.
How does high wind primarily affect a suspended load and the crane's stability?
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.
Side loading of a crane boom is extremely hazardous because:
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.
When lifting a load out of water, the operator must anticipate that:
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.
Rapidly swinging a load can cause which dangerous effect?
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.
Crane operations must be shut down when wind speeds exceed the limits specified by:
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.
How can extremely cold weather affect a crane's steel components?
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.