What Are The Loads Of Commonly Used Cranes?
Mar 22, 2023
What Are The Loads Of Commonly Used Cranes?
During the operation of the 20 ton bridge crane, it must bear various loads (such as static load, dynamic load, alternating load, impact load, vibration load, etc.), and the bearing parts and structural parts will produce corresponding stress and deformation. , if it exceeds a certain limit, it will lose its function or even be damaged, thus causing danger.
During the operation of the 20 ton bridge crane, the complexity of the load is not only reflected in the diversity of the load types, but also shows the changeable characteristics with the different working conditions of the crane operation.
The load is the original basis for the normal working force analysis of the 20 ton bridge crane and its component parts, and also the basis for the judgment and analysis of the scrapped parts or the cause of the accident. Whether the load is determined accurately will directly affect the safety of the calculation results and the accident conclusion correctness.
1. Static Load
When the 20 ton bridge crane is in a static state or a stable operating state, the 20 ton bridge crane is only subjected to the static load of its own weight load and lifting load.
(1) Self-weight load PG
It includes the metal structure of the 20 ton bridge crane, mechanical equipment, electrical equipment, and the gravity of the storage or conveyor attached to the crane and the materials on it (except for the gravity of the lifting load).
The action mode of the load can be considered separately. Generally, the load of mechanical equipment and electrical equipment is regarded as concentrated load;
(2) Lifting load PQ
This refers to the gravity of all starting masses. Including the maximum effective items allowed to be lifted, pick-up devices (such as pulley blocks, hooks, beams, grabs, containers, lifting electromagnets, etc.), suspension coils, and the gravity of other spare parts during lifting.
The weight of the hoisting wire rope whose hoisting height is less than 50 m can be ignored.
2. Dynamic load
The dynamic load is the dynamic load effect produced by the 20 ton bridge crane when the state of motion changes.
It is an important basis for strength calculation and also affects fatigue calculation.
When the 20 ton bridge crane is not working or the hoisting load is still in the air, its self-weight load and hoisting load are in a static state.
When the 20 ton bridge crane is working, the motion state changes, and the dynamic load effect increases the original static load value. The increased part is the dynamic load.
The dynamic load includes the inertial load generated by the self-weight of the structure and the lifting load during the variable speed movement; the impact load caused by the impact of the wheel passing through the uneven track joint or the moving part on the buffer; the inertial load and impact load make the metal structure and mechanism elastic. Vibration loads that vibrate the system.
The dynamic load is related to the direction of motion and working speed (acceleration), related to structural factors (such as the distribution of system mass, stiffness and damping of the system, etc.), and related to service conditions (such as the size of the external load and its variation. With or without impact etc.) related.
For the convenience of calculation, it is usually expressed by dynamic coefficient (the ratio of dynamic load to static load). When using, generally refer to the 20 ton bridge crane design specifications and relevant manuals for selection according to the actual situation.
