The rated lifting capacity of overhead and gantry cranes is fundamentally determined by the most vulnerable component within their integrated system, governed by non-negotiable safety margins. This capacity isn't an arbitrary value but represents the maximum safe load the entire crane structure – including mechanical, electrical, and foundational elements – can bear before risking critical failure under strict design standards (ISO, FEM, GB/T). Safety factors (e.g., 1.48× for structures) are systematically applied to all components to absorb dynamic loads, material flaws, and operational degradation over time.

Concretely, capacity is constrained by three core systems:

1：Structural Integrity – Main girders (governed by strength, stiffness limits like ≤ span/700), end-carrier beams, and especially gantry legs resisting overturning moments;

2：Mechanical Capability – Hoisting mechanism limits (wire rope safety factors ≥5.6×, drum/sheave strength, brake torque) and trolley frame load transfer capacity;

3：Foundation & Stability – Building support/runway rails for overhead cranes, and mission-critical ground foundations/rails for ganties, where settlement or inadequate load distribution poses collapse risks.