Lifting load, rated lifting capacity, maximum reach, and maximum lifting height—these parameters serve as the critical basis for formulating hoisting crane technical solutions.
1. Components of Hoisting Crane Lifting Load
The weight of the lifted object (equipment or component) in the hoisting state, plus the weight of the lifting and rigging equipment (for mobile hoisting cranes, this generally also includes the weight of the hook and the hoisting wire rope hanging from the boom tip to the hook). For example, the lifting load of a crawler hoisting crane comprises the sum of the lifted equipment (including reinforcements, lifting lugs, etc.), the weight of the lifting slings (rope loops), the weight of the hook block, and the weight of the hoisting wire rope hanging from the boom tip.
2. Calculation of Loads about Hoisting Crane
(1) Dynamic Load Factor
A coefficient accounting for the impact of loads generated during the movement of a hoisting crane lifting a load on the lifting equipment. In lifting engineering calculations, this impact is incorporated via the dynamic load factor. Typically, the dynamic load factor K1 is taken as 1.1.
(2) Uneven Load Factor
When two or more hoisting cranes (multiple cranes, pulley blocks, etc.) jointly lift a load, additional loads may act on the lifting machinery, load, and slings due to relative motion between the hoisting cranes. Alternatively, due to asynchronous operation, individual branches often cannot bear loads exactly according to the set proportion. In lifting projects, this effect is accounted for using the uneven load factor. Typically, the unbalanced load factor K2 is set between 1.1 and 1.25.
(3) Lifting Calculation Load
The lifting calculation load (abbreviated as calculation load): equals the dynamic load factor multiplied by the lifting load. In lifting operations, the calculation load is commonly used as the basis for calculations. In crane project designs involving multiple cranes lifting equipment jointly, the calculated load borne by one crane is further adjusted for load motion and imbalance effects. The general formula for the calculated load is: Qj = k1 × k2 × Q
Where:
Qj — Calculated load;
k₁ — Dynamic load factor;
k₂ — load imbalance coefficient;
Q — lifting load allocated to a single crane, including equipment and sling/hoist weight.
3. Rated Lifting Capacity
(1) The maximum lifting capacity of the crane at the selected boom length and slewing radius shall exceed the calculated load for the lifting operation.
(2) When two cranes lift a single load simultaneously, cranes of the same type or similar performance should be selected. Load distribution must be reasonable based on the cranes’ lifting capacities; the total lifted weight should not exceed 75% of the combined allowable lifting capacity of both cranes. The load on each hoisting crane should not exceed 80% of its safe working load.
(3) Maximum Radius：The maximum radius is the crane’s maximum lifting swing radius, defined as the swing radius under rated load conditions.
(4) Maximum Lifting Height
The maximum lifting height must satisfy the following requirement about hoisting crane:
Hm > H1 + H2 + H3 + H4
Hm — Lifting height at the lower pulley of the hoisting crane boom tip (m);
H1 — Equipment height (m); H2—Height from the top surface of the equipment to the hook’s rigging (including wire rope, counterweight beam, shackles, etc.) (m); H3—Height from the top surface of the foundation or anchor bolts to the bottom surface of the equipment when positioned (m); H4—Height of the top surface of the foundation or anchor bolts (m).
