The minimum height under boom equals the height of the load, plus the maximum distance the load is to be lifted, plus the headroom required for the hoist, trolley, and attachments.

• 推力指施加在支撑结构上推向（或压向）的力，而拉力是拉伸的力。推力和拉力是相等的（但方向相反）。当起重机处于满负荷状态时，推力和拉力出现最大值。