Light duty cranes are generally used in

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Examoogle · Accepted Answer

All of these

Explanation: Light duty cranes are defined as hoisting equipment designed for intermittent, low-frequency operation, typically handling loads significantly lower than their rated capacity. They are selected for environments where the operational demand is sporadic rather than continuous, ensuring cost-effectiveness in installation and maintenance.

Working Principle: The operational duty cycle of a crane, classified as light, medium, heavy, or extra-heavy, depends on the 'Class of Mechanism' determined by the frequency of usage and the load spectrum. Light duty cranes utilize smaller motor ratings and lighter structural frameworks because they are designed for fewer stress cycles over their service life, minimizing the required fatigue resistance compared to heavy-duty industrial cranes.

Key Formulas: $U_d = \frac{n}{N} 	imes 100$ — Duty factor calculation, where $n$ is operating time and $N$ is total time; $L_{avg} = \sqrt[3]{\frac{\sum P_i^3 t_i}{\sum t_i}}$ — Cubic mean load for duty cycle assessment

Key Points: Light duty cranes are classified under FEM or ISO standards based on low utilization rates.; Commonly found in maintenance shops or service areas where repairs are infrequent.; Energy consumption and mechanical wear are minimized by appropriate duty-class selection.; Power houses and pumping stations use them primarily for occasional equipment maintenance (e.g., turbine or pump motor assembly).

Advantages: Reduced capital investment due to lighter structural requirements.; Lower maintenance costs for intermittent operation profiles.

Disadvantages: Not suitable for continuous production lines or high-throughput logistics.; Risk of thermal overload if operated beyond the specified duty cycle.

Applications: Maintenance of heavy pumping station motors.; Assembly and repair of automobile components.; Periodic servicing of power house electrical machinery.

Additional Info: Light duty usually corresponds to ISO classification M1 to M3.. Selecting a crane with a duty cycle higher than the actual requirement increases installation costs unnecessarily, while choosing a lower class leads to premature mechanical failure.

Answer: D is correct — Light duty cranes are versatile machines ideal for intermittent maintenance tasks found in power houses, pumping stations, and workshops.

Exam Tip: Always verify the duty cycle of electrical motors and mechanical hoists before selection; over-specifying equipment leads to wasted capital expenditure (CapEx), while under-specifying leads to excessive operational expenditure (OpEx) due to downtime.

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