1. Basic concepts and mutual influence
The lifting capacity refers to the maximum weight that the portal crane can safely lift, and the working range refers to the horizontal distance from the center of rotation of the crane to the center of the hook. These two parameters are interrelated and jointly affect the working performance of the crane. Generally speaking, under the condition of certain crane structure and performance, the lifting capacity and working range are inversely proportional.
When the working range increases, the moment borne by the crane will also increase. Because the moment is equal to the force (lifting capacity) multiplied by the arm (working range). In order to ensure the stability and safety of the crane, the lifting capacity needs to be reduced accordingly. For example, in port loading and unloading operations, if the working range of the crane extends from the closer ship position to the farther shore yard, as the working range increases, in order to avoid dangerous situations such as the crane tipping over, the weight of the cargo that can be lifted must be reduced.
2. Restrictions on the relationship by structural factors
The structural design of the portal crane has a key restrictive effect on the relationship between the lifting capacity and the working range. The strength and stiffness of the structural components of the crane such as the main beam and outriggers determine the maximum moment it can withstand. Factors such as the cross-sectional shape of the main beam, material properties, and the spacing and stability of the outriggers will affect this relationship.
For example, a main beam made of high-strength steel and with a reasonable cross-sectional shape (such as a box-type structure) can withstand greater bending moments, and to a certain extent, can allow a relatively high lifting capacity to be maintained at a larger working range. The good stability and appropriate spacing of the outriggers also help to maintain the balance of the crane when the working range is increased, thereby achieving a better lifting capacity-working range combination within the design allowable range.
3. Relationship between safety factor and actual operation
In actual operation, the safety factor is an important factor that must be considered. In order to ensure the safe operation of the portal crane, a safety factor is introduced when determining the relationship between the lifting capacity and the working range. The size of the safety factor depends on many factors such as the use environment, working frequency, and importance of the crane.
Usually, the safety factor is set higher in high-risk working environments or frequent use occasions. This means that the actual allowable lifting capacity will be lower than the theoretical calculated value under a given working range. For example, for Portal Cranes used in dangerous places such as chemical enterprises, the lifting capacity-working range relationship specified in the operation manual will be more conservative, considering the serious consequences that may be caused in the event of an accident, so as to maximize the safety of personnel and equipment.
4. Balance between application scenarios and relationships
Different application scenarios have different requirements for lifting capacity and working range, and these two parameters need to be balanced according to actual conditions. On construction sites, more emphasis may be placed on lifting heavier building materials, such as prefabricated components, at a smaller working range; while in port operations, due to the need to lift goods between docks and ships and between different yard locations, the working range requirements are relatively high, and the lifting capacity varies according to the type of goods (such as containers, bulk cargo, etc.).
In order to meet these different needs, the design and operation of Portal Cranes need to comprehensively consider the relationship between lifting capacity and working range. Through reasonable structural design, precise calculations and strict operating specifications, the working efficiency of the crane in various working scenarios can be improved as much as possible while ensuring safety.
